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J.P. Magué & B. Ménard



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[1]  arXiv:1608.08626 [pdf, other]
Title: The Afterglow and Early-Type Host Galaxy of the Short GRB 150101B at z=0.1343
Comments: 13 pages, 7 figures, 2 tables. Submitted to ApJ
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

We present the discovery of the X-ray and optical afterglows of the short-duration GRB 150101B, pinpointing the event to an early-type host galaxy at z=0.1343 +/- 0.0030. This makes GRB 150101B the most nearby short GRB with an early-type host galaxy discovered to date. Fitting the spectral energy distribution of the host galaxy results in an inferred stellar mass of ~7x10^10 M_sol, stellar population age of ~2-2.5 Gyr, and star formation rate of <0.4 M_sol yr^-1. The host of GRB 150101B is one of the largest and most luminous short GRB host galaxies, with a B-band luminosity of ~4.3L* and half-light radius of ~8 kpc. GRB 150101B is located at a projected distance of 7.35 +/- 0.07 kpc from its host center, and lies on a faint region of its host rest-frame optical light. Its location, combined with the lack of associated supernova, is consistent with a NS-NS/NS-BH merger progenitor. From modeling the evolution of the broad-band afterglow, we calculate isotropic-equivalent gamma-ray and kinetic energies of ~1.3x10^49 erg and ~(6-14)x10^51 erg, respectively, a circumburst density of ~(0.8-4)x10^-5 cm^-3, and a jet opening angle of >9 deg. Using observations extending to ~30 days, we place upper limits of <(2-4)x10^41 erg s^-1 on associated kilonova emission. We compare searches following previous short GRBs to existing kilonova models, and demonstrate the difficulty of performing effective kilonova searches from cosmological short GRBs using current ground-based facilities. We show that at the Advanced LIGO/VIRGO horizon distance of 200 Mpc, searches reaching depths of ~23-24 AB mag are necessary to probe a meaningful range of kilonova models.

[2]  arXiv:1608.08627 [pdf, other]
Title: Double Compton and Cyclo-Synchrotron in Super-Eddington Disks, Magnetized Coronae, and Jets
Authors: Jonathan C. McKinney (1), Jens Chluba (2), Maciek Wielgus (3), Ramesh Narayan, (4) Aleksander Sadowski (5) ((1) University of Maryland at College Park, Dept. of Physics, Joint Space-Science Institute, (2) Jodrell Bank Centre for Astrophysics, University of Manchester, (3) Copernicus Astronomical Center, (4) Harvard-Smithsonian Center for Astrophysics, (5) MIT Kavli Institute for Astrophysics and Space Research)
Comments: 24 pages, 14 figures, 3 tables, submitted to MNRAS
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc)

We present an extension to the general relativistic radiation magnetohydrodynamic code HARMRAD to account for emission and absorption by thermal cyclo-synchrotron, double Compton, bremsstrahlung, low-temperature OPAL opacities as well as Thomson and Compton scattering. We approximate the radiation field as a Bose-Einstein distribution and evolve it using the radiation number-energy-momentum conservation equations in order to track photon hardening. We perform various simulations to study how these extensions affect the radiative properties of magnetically-arrested disks accreting at Eddington to super-Eddington rates. We find that double Compton dominates bremsstrahlung in the disk within a radius of $r\sim 15r_g$ (gravitational radii) at a hundred times the Eddington accretion rate, and within smaller radii at lower accretion rates. Double Compton and cyclo-synchrotron regulate radiation and gas temperatures in the corona, while cyclo-synchrotron regulates temperatures in the jet. Interestingly, as the accretion rate drops to Eddington, an optically thin corona develops whose gas temperature of $T\sim 10^9$K is $\sim 100$ times higher than the disk's black body temperature. Our results show the importance of double Compton and synchrotron in super-Eddington disks, magnetized coronae, and jets.

[3]  arXiv:1608.08628 [pdf, other]
Title: New Constraints on a complex relation between globular cluster colors and environment
Comments: 7 pages, 5 figures, accepted for publication in ApJ-Letters
Subjects: Astrophysics of Galaxies (astro-ph.GA)

We present an analysis of high-quality photometry for globular clusters (GCs) in the Virgo cluster core region, based on data from the Next Generation Virgo Cluster Survey (NGVS) pilot field, and in the Milky Way (MW) based on VLT/X-Shooter spectrophotometry. We find significant discrepancies in color-color diagrams between sub-samples from different environments, confirming that the environment has a strong influence on the integrated colors of GCs. GC color distributions along a single color are not sufficient to capture the differences we observe in color-color space. While the average photometric colors become bluer with increasing radial distance to the cD galaxy M87, we also find a relation between the environment and the slope and intercept of the color-color relations. A denser environment seems to produce a larger dynamic range in certain color indices. We argue that these results are not due solely to differential extinction, IMF variations, calibration uncertainties, or overall age/metallicity variations. We therefore suggest that the relation between the environment and GC colors is, at least in part, due to chemical abundance variations, which affect stellar spectra and stellar evolution tracks. Our results demonstrate that stellar population diagnostics derived from model predictions which are calibrated on one particular sample of GCs may not be appropriate for all extragalactic GCs. These results advocate a more complex model of the assembly history of GC systems in massive galaxies that goes beyond the simple bimodality found in previous decades.

[4]  arXiv:1608.08629 [pdf, ps, other]
Title: Confronting semi-analytic galaxy models with galaxy-matter correlations observed by CFHTLenS
Comments: 9 pages, 10 figures, submitted to A&A. Comments welcome
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)

Testing predictions of semi-analytic models of galaxy evolution against observations help to understand the complex processes that shape galaxies. We compare predictions from the Garching and Durham models implemented on the Millennium Run with observations of galaxy-galaxy lensing (GGL) and galaxy-galaxy-galaxy lensing (G3L) for various galaxy samples with stellar masses in the range 0.5 < (M_* / 10^10 M_Sun) < 32 and photometric redshift range 0.2 < z < 0.6 in the Canada-France-Hawaii Telescope Lensing Survey (CFHTLenS). We find that the predicted GGL and G3L signals are in qualitative agreement with CFHTLenS data. Quantitatively, the models succeed in reproducing the observed signals in the highest stellar mass bin 16 < ( M_* / 10^10 M_Sun) < 32 but show different degrees of tension for the other stellar mass samples. The Durham model is strongly excluded on a 95% confidence level by the observations as it largely over-predicts the amplitudes of GGL and G3L signals, probably owing to a larger number of satellite galaxies in massive halos.

[5]  arXiv:1608.08630 [pdf, other]
Title: In the Wake of Dark Giants: New Signatures of Dark Matter Self Interactions in Equal Mass Mergers of Galaxy Clusters
Comments: 30 pages, 18 figures, and 2 tables; key results are summarized in Figures 12 and 13. Submitted to MNRAS. For a brief video describing the main results of this paper, please see this https URL Comments welcome!
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)

Merging galaxy clusters have been touted as one of the best probes for constraining self-interacting dark matter, but few simulations exist to back up this claim. We simulate equal mass mergers of 10$^{15}$ M$_\odot$ halos, like the El Gordo and Sausage clusters, with cosmologically-motivated halo and merger parameters, and with velocity-independent dark-matter self-interactions. Although the standard lore for merging clusters is that self-interactions lead to large separations between the galaxy and dark-matter distributions, we find that maximal galaxy-dark matter offsets of $\lesssim~20$~kpc form for a self-interaction cross section of $\sigma_\text{SI}/m_\chi$ = 1 cm$^2$/g. This is an order of magnitude smaller than those measured in observed equal mass and near equal mass mergers, and is likely to be even smaller for lower-mass systems. While competitive cross-section constraints are thus unlikely to emerge from offsets, we find other signatures of self-interactions which are more promising. Intriguingly, we find that after dark matter halos coalesce, the collisionless galaxies (and especially the Brightest Cluster Galaxy [BGC]) oscillate around the center of the merger remnant on stable orbits of 100 kpc for $\sigma_\text{SI}/m_\chi = 1$~cm$^2$/g for at least several Gyr, well after the clusters have relaxed. If BCG miscentering in relaxed clusters remains a robust prediction of SIDM under the addition of gas physics, substructure, merger mass ratios (e.g., 10:1 like the Bullet Cluster), and complex cosmological merger histories, the observed BCG offsets may constrain $\sigma_\text{SI}/m_\chi \lesssim$ 0.1 cm$^2$/g---the tightest constraint yet.

[6]  arXiv:1608.08631 [pdf, other]
Title: Bolometric Lightcurves of Peculiar Type II-P Supernovae
Comments: 27 pages, 11 figures, 5 tables, submitted to PASP
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); High Energy Astrophysical Phenomena (astro-ph.HE)

We examine the bolometric lightcurves of five Type II-P supernovae (SNe 1998A, 2000cb, 2006V, 2006au and 2009E) which are thought to originate from blue supergiant progenitors using a new python package named SuperBoL. With this code, we calculate SNe lightcurves using three different techniques common in the literature: the quasi-bolometric method, which integrates the observed photometry, the direct integration method, which additionally corrects for unobserved flux in the UV and IR, and the bolometric correction method, which uses correlations between observed colors and V-band bolometric corrections. We present here the lightcurves calculated by SuperBoL along with previously published lightcurves, as well as peak luminosities and Ni-56 yields. We find that the direct integration and bolometric correction lightcurves largely agree with previously published lightcurves, but with what we believe to be more robust error calculations, with $0.2 \leq \delta L_{bol}/L_{bol} \leq 0.5$. Peak luminosities and Ni-56 masses are similarly comparable to previous work. SN 2000cb remains an unusual member of this sub-group, owing to the faster rise and flatter plateau than the other supernovae in the sample. Initial comparisons with the NLTE atmosphere code PHOENIX show that the direct integration technique re-produces the luminosity of a model supernova spectrum to ~5% when given synthetic photometry of the spectrum as input. Our code is publicly available. The ability to produce bolometric lightcurves from observed sets of broad-band light curves should be helpful in the interpretation of other types of supernovae, particularly those that are not well characterized, such as extremely luminous supernovae and faint fast objects.

[7]  arXiv:1608.08634 [pdf, other]
Title: The intermediate neutron-capture process and carbon-enhanced metal-poor stars
Comments: 16 pages, 28 figures. Accepted for publication in ApJ
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

Carbon-enhanced metal-poor (CEMP) stars in the Galactic Halo display enrichments in heavy elements associated with either the s (slow) or the r (rapid) neutron-capture process (e.g., barium and europium respectively), and in some cases they display evidence of both. The abundance patterns of these CEMP-s/r stars, which show both Ba and Eu enrichment, are particularly puzzling since the s and the r processes require neutron densities that are more than ten orders of magnitude apart, and hence are thought to occur in very different stellar sites with very different physical conditions. We investigate whether the abundance patterns of CEMP-s/r stars can arise from the nucleosynthesis of the intermediate neutron-capture process (the i process), which is characterised by neutron densities between those of the s and the r processes. Using nuclear network calculations, we study neutron capture nucleosynthesis at different constant neutron densities n ranging from $10^7$ to $10^{15}$ cm$^{-3}$. With respect to the classical s process resulting from neutron densities on the lowest side of this range, neutron densities on the highest side result in abundance patterns that show an increased production of heavy s-process and r-process elements but similar abundances of the light s-process elements. Such high values of n may occur in the thermal pulses of asymptotic giant branch (AGB) stars due to proton ingestion episodes. Comparison to the surface abundances of 20 CEMP-s/r stars show that our modelled i-process abundances successfully reproduce observed abundance patterns that could not be previously explained by s-process nucleosynthesis. Because the i-process models fit the abundances of CEMP-s/r stars so well, we propose that this class should be renamed as CEMP-i.

[8]  arXiv:1608.08636 [pdf, other]
Title: Merger of a White Dwarf-Neutron Star Binary to $10^{29}$ Carat Diamonds: Origin of the Pulsar Planets
Comments: 15 pages, 6 figures, submitted to MNRAS
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

We show that the merger and tidal disruption of a C/O white dwarf (WD) by a neutron star (NS) binary companion provides a natural formation scenario for the PSR B1257+12 planetary system. Starting with initial conditions for the debris disk produced of the disrupted WD, we model its long term viscous evolution, including for the first time the effects of mass and angular momentum loss during the early radiatively inefficient accretion flow (RIAF) phase and accounting for the unusual C/O composition on the disk opacity. For plausible values of the disk viscosity $\alpha \sim 10^{-3}-10^{-2}$ and the RIAF mass loss efficiency, we find that the disk mass remaining near the planet formation radius at the time of solid condensation is sufficient to explain the pulsar planets. Rapid rocky planet formation via gravitational instability of the solid carbon-dominated disk is facilitated by the suppression of vertical shear instabilities due to the high solid-to-gas ratio. Additional evidence supporting a WD-NS merger scenario includes (1) the low observed occurrence rate of pulsar planets ($\lesssim 1\%$ of NS birth), comparable to the expected WD-NS merger rate; (2) accretion by the NS during the RIAF phase is sufficient to spin PSR B1257+12 up to its observed 6 ms period; (3) similar models of `low angular momentum' disks, such as those produced from supernova fallback, find insufficient mass reaching the planet formation radius. The unusually high space velocity of PSR B1257+12 of $\gtrsim 326\,{\rm km\,s}^{-1}$ suggests a possible connection to the Calcium-rich transients, dim supernovae which occur in the outskirts of their host galaxies and were proposed to result from mergers of WD-NS binaries receiving SN kicks. The C/O disk composition implied by our model likely results in carbon-rich planets with diamond interiors.

[9]  arXiv:1608.08638 [pdf, other]
Title: A detection of the integrated Sachs-Wolfe imprint of cosmic superstructures using a matched-filter approach
Comments: 7 pages, 3 figures. Catalogue data and information on parameter fits used are available from this http URL
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)

We present a new method for detection of the integrated Sachs-Wolfe (ISW) imprints of cosmic superstructures on the cosmic microwave background, based on a matched filtering approach. The expected signal-to-noise ratio for this method is comparable to that obtained from the full cross-correlation, and unlike other stacked filtering techniques it is not subject to an a posteriori bias. We apply this method to Planck CMB data using voids and superclusters identified in the CMASS galaxy data from the Sloan Digital Sky Survey Data Release 12, and measure the ISW amplitude to be $A_\mathrm{ISW}=1.64\pm0.53$ relative to the $\Lambda$CDM expectation, corresponding to a $3.1\sigma$ detection. In contrast to some previous measurements of the ISW effect of superstructures, our result is in agreement with the $\Lambda$CDM model.

[10]  arXiv:1608.08639 [pdf, other]
Title: The impact of stellar feedback on the density and velocity structure of the interstellar medium
Comments: 18 pages, 12 figures, 2 Tables, submitted to MNRAS
Subjects: Astrophysics of Galaxies (astro-ph.GA)

We study the role of stellar feedback in shaping the density and velocity structure of neutral hydrogen (HI) in disc galaxies. For our analysis, we carry out $\sim 4.6$ pc resolution $N$-body+adaptive mesh refinement (AMR) hydrodynamic simulations of isolated galaxies, set up to mimic a Milky Way (MW), and a Large and Small Magellanic Cloud (LMC, SMC). We quantify the density and velocity structure of the interstellar medium using power spectra and compare the simulated galaxies to observed HI in local spiral galaxies from THINGS (The HI Nearby Galaxy Survey). We find that observed HI density power spectra is only reproduced by simulations with efficient stellar feedback, which influences the gas density field up to large (kpc) scales. Furthermore, the kinetic energy power spectra in feedback regulated galaxies, regardless of galaxy mass and size, show scalings in excellent agreement with super-sonic turbulence ($E(k)\propto k^{-2})$ on scales below the thickness of the HI layer. This is in stark contrast to models without feedback that feature only large scale galactic turbulence driving. Analysed face-on, the line-of-sight $E(k)$ in simulated galaxies shows strong signatures of stellar feedback on all scales. This matches observations on scales $< 1$ kpc, in contrast to models without feedback (although inclination effects must carefully be accounted for). We conclude that the neutral gas content of galaxies carries signatures of stellar feedback on all scales, providing us with a new benchmark for stellar feedback models in galaxy formation simulations.

[11]  arXiv:1608.08642 [pdf, other]
Title: Resolving the planet-hosting inner regions of the LkCa 15 disk
Comments: 6 pages, 4 figures, 1 table; accepted for publication in ApJ Letters
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Earth and Planetary Astrophysics (astro-ph.EP)

LkCa 15 hosts a pre-transitional disk as well as at least one accreting protoplanet orbiting in its gap. Previous disk observations have focused mainly on the outer disk, which is cleared inward of ~50 au. The planet candidates, on the other hand, reside at orbital radii around 15 au, where disk observations have been unreliable until recently. Here we present new J-band imaging polarimetry of LkCa 15 with SPHERE IRDIS, yielding the most accurate and detailed scattered-light images of the disk to date down to the planet-hosting inner regions. We find what appear to be persistent asymmetric structures in the scattering material at the location of the planet candidates, which could be responsible at least for parts of the signals measured with sparse-aperture masking. These images further allow us to trace the gap edge in scattered light at all position angles and search the inner and outer disks for morphological substructure. The outer disk appears smooth with slight azimuthal variations in polarized surface brightness, which may be due to shadowing from the inner disk or a two-peaked polarized phase function. We find that the near-side gap edge revealed by polarimetry matches the sharp crescent seen in previous ADI imaging very well. Finally, the ratio of polarized disk to stellar flux is more than six times larger in J-band than in the RI bands.

[12]  arXiv:1608.08643 [pdf, other]
Title: On the Composition of Young, Directly Imaged Giant Planets
Comments: Accepted in The Astrophysical Journal
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

The past decade has seen significant progress on the direct detection and characterization of young, self-luminous giant planets at wide orbital separations from their host stars. Some of these planets show evidence for disequilibrium processes like transport-induced quenching in their atmospheres; photochemistry may also be important, despite the large orbital distances. These disequilibrium chemical processes can alter the expected composition, spectral behavior, thermal structure, and cooling history of the planets, and can potentially confuse determinations of bulk elemental ratios, which provide important insights into planet-formation mechanisms. Using a thermo/photochemical kinetics and transport model, we investigate the extent to which disequilibrium chemistry affects the composition and spectra of directly imaged giant exoplanets. Results for specific "young Jupiters" such as HR 8799 b and 51 Eri b are presented, as are general trends as a function of planetary effective temperature, surface gravity, incident ultraviolet flux, and strength of deep atmospheric convection. We find that quenching is very important on young Jupiters, leading to CO/CH4 and N2/NH3 ratios much greater than, and H2O mixing ratios a factor of a few less than, chemical-equilibrium predictions. Photochemistry can also be important on such planets, with CO2 and HCN being key photochemical products. Carbon dioxide becomes a major constituent when stratospheric temperatures are low and recycling of water via the H2 + OH reaction becomes kinetically stifled. Young Jupiters with effective temperatures <~ 700 K are in a particularly interesting photochemical regime that differs from both transiting hot Jupiters and our own solar-system giant planets.

[13]  arXiv:1608.08650 [pdf, ps, other]
Title: r-process Production Sites as inferred from Eu Abundances in Dwarf Galaxies
Comments: 27 pages, 3 figures. Submitted
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

Recent observations of $r$-process material in ultra-faint dwarf galaxies (UFDs) shed light on the sources of these elements. Strong upper limits on the Eu mass in some UFDs combined with detections of much larger masses in a UFD, Reticulum II, and other dwarf galaxies imply that Eu production is dominated by rare events, and that the minimal Eu mass observed in any UFD is approximately the amount of Eu mass produced per event. This is consistent with other independent observations in the Galaxy. We estimate, using a model independent likelihood analysis, the rate and Eu (Fe) mass produced per $r$-process (Fe production) event in dwarf galaxies including classical dwarfs and UFDs. The mass and rate of the Fe production events are consistent with the normal core-collapse supernova~(ccSN) scenario. The Eu mass per event is $3\times 10^{-5}M_{\odot}<\tilde{m}_{\rm Eu}<2\times 10^{-4}M_{\odot}$, corresponding to a total $r$-process mass per event of $6\times 10^{-3}M_{\odot}<\tilde{m}_{r-process}<4\times 10^{-2}M_{\odot}$. The rate of $r$-process events is $2.5\times 10^{-4}<R_{rp/SN}<1.4\times 10^{-3}$ as compared with the ccSNe rate. These values are consistent with the total Eu mass observed in our own Galaxy, suggesting that the same mechanism is behind the production of $r$-process events in both dwarf galaxies and the Milky Way, and that it may be the dominant mechanism for production of $r$-process elements in the Universe. The results are consistent with neutron star mergers estimates, but cannot rule out other rare core collapse scenarios, provided that they produce a significant amounts of $r$-process material per event.

[14]  arXiv:1608.08677 [pdf, other]
Title: Connecting low- and high-mass star formation: the intermediate-mass protostar IRAS 05373+2349 VLA 2
Comments: 11 pages, 7 figures and 4 tables. Accepted by MNRAS
Subjects: Astrophysics of Galaxies (astro-ph.GA)

Until recently, there have been few studies of the protostellar evolution of intermediate-mass (IM) stars, which may bridge the low- and high-mass regimes. This paper aims to investigate whether the properties of an IM protostar within the IRAS 05373+2349 embedded cluster are similar to that of low- and/or high-mass protostars. We carried out Very Large Array as well as Combined Array for Research in Millimeter Astronomy continuum and 12CO(J=1-0) observations, which uncover seven radio continuum sources (VLA 1-7). The spectral index of VLA 2, associated with the IM protostar is consistent with an ionised stellar wind or jet. The source VLA 3 is coincident with previously observed H2 emission line objects aligned in the north-south direction (P.A. -20 to -12 deg), which may be either an ionised jet emanating from VLA 2 or (shock-)ionised cavity walls in the large-scale outflow from VLA 2. The position angle between VLA 2 and 3 is slightly misaligned with the large-scale outflow we map at ~5-arcsec resolution in 12CO (P.A. ~30 deg), which in the case of a jet suggests precession. The emission from the mm core associated with VLA 2 is also detected; we estimate its mass to be 12-23 Msun, depending on the contribution from ionised gas. Furthermore, the large-scale outflow has properties intermediate between outflows from low- and high-mass young stars. Therefore, we conclude that the IM protostar within IRAS 05373+2349 is phenomenologically as well as quantitatively intermediate between the low- and high-mass domains.

[15]  arXiv:1608.08694 [pdf, ps, other]
Title: A Multi-Line Ammonia Survey of the Galactic Center Region with the Tsukuba 32-m Telescope - I. Observations and Data
Comments: 19 pages, 11 figures
Subjects: Astrophysics of Galaxies (astro-ph.GA)

We present survey data of the NH3 (J, K) = (1, 1)--(6, 6) lines, simultaneously observed with the Tsukuba 32-m telescope, in the main part of the central molecular zone of the Galaxy. The total number of on-source positions was 2655. The lowest three transitions were detected with S/N > 3 at 2323 positions (93% of all the on-source positions). Among 2323, the S/N of (J, K ) = (4, 4), (5, 5), and (6, 6) exceeded 3.0 at 1426 (54%), 1150 (43%), and 1359 (51%) positions, respectively. Simultaneous observations of the lines enabled us to accurately derive intensity ratios with less systematic errors. Boltzmann plots indicate there are two temperature components: cold ($\sim$ 20 K) and warm ($\sim$ 100 K). Typical intensity ratios of Tmb(2,2)/Tmb(1,1), Tmb(4,4)/Tmb(2,2), Tmb(5,5)/Tmb(4,4), and Tmb(6,6)/Tmb(3,3) were 0.71, 0.45, 0.65, and 0.17, respectively. These line ratios correspond to diversity of rotational temperature, which results from mixing of the two temperature components.

[16]  arXiv:1608.08703 [pdf, ps, other]
Title: SEEDS direct imaging of the RV-detected companion to V450 Andromedae, and characterization of the system
Comments: 15 pages, 9 figures, 7 tables, to appear in ApJ
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Earth and Planetary Astrophysics (astro-ph.EP)

We report the direct imaging detection of a low-mass companion to a young, moderately active star V450 And, that was previously identified with the radial velocity method. The companion was found in high-contrast images obtained with the Subaru Telescope equipped with the HiCIAO camera and AO188 adaptive optics system. From the public ELODIE and SOPHIE archives we extracted available high-resolution spectra and radial velocity (RV) measurements, along with RVs from the Lick planet search program. We combined our multi-epoch astrometry with these archival, partially unpublished RVs, and found that the companion is a low-mass star, not a brown dwarf, as previously suggested. We found the best-fitting dynamical masses to be $m_1=1.141_{-0.091}^{+0.037}$ and $m_2=0.279^{+0.023}_{-0.020}$ M$_\odot$. We also performed spectral analysis of the SOPHIE spectra with the iSpec code. The Hipparcos time-series photometry shows a periodicity of $P=5.743$ d, which is also seen in SOPHIE spectra as an RV modulation of the star A. We interpret it as being caused by spots on the stellar surface, and the star to be rotating with the given period. From the rotation and level of activity, we found that the system is $380^{+220}_{-100}$ Myr old, consistent with an isochrone analysis ($220^{+2120}_{-90}$ Myr). This work may serve as a test case for future studies of low-mass stars, brown dwarfs and exoplanets by combination of RV and direct imaging data.

[17]  arXiv:1608.08707 [pdf, ps, other]
Title: The BOSS Emission-Line Lens Survey. IV. : Smooth Lens Models for the BELLS GALLERY Sample
Comments: 14 pages, 4 figures, submitted to the ApJ
Subjects: Astrophysics of Galaxies (astro-ph.GA)

We present \textsl{Hubble Space Telescope} (\textsl{HST}) F606W-band imaging observations of 21 galaxy-Ly$\alpha$ emitter lens candidates in the Baryon Oscillation Spectroscopic Survey (BOSS) Emission-Line Lens Survey (BELLS) for GALaxy-Ly$\alpha$ EmitteR sYstems (BELLS GALLERY) survey. 17 systems are confirmed to be definite lenses with unambiguous evidence of multiple imaging. The lenses are primarily massive early-type galaxies (ETGs) at redshifts of approximately $0.55$, while the lensed sources are Ly$\alpha$ emitters (LAEs) at redshifts from 2 to 3. Although the \textsl{HST} imaging data are well fit by smooth lens models consisting of singular isothermal ellipsoids in an external shear field, a thorough exploration of dark substructures in the lens galaxies is required. The Einstein radii of the BELLS GALLERY lenses are on average $60\%$ larger than those of the BELLS lenses because of the much higher source redshifts which will allow a detailed investigation of the radius evolution of the mass profile in ETGs. With the aid of the average $\sim 13 \times$ lensing magnification, the LAEs are resolved to comprise individual star-forming knots of a wide range of properties with characteristic sizes from less than 100 pc to several kpc, rest-frame far UV apparent AB magnitudes from 29.6 to 24.2, and typical projected separations of 500 pc to 2 kpc.

[18]  arXiv:1608.08713 [pdf, other]
Title: The systematics of strong lens modeling quantified: the effects of constraint selection and redshift information on magnification, mass, and multiple image predictability
Authors: Traci L. Johnson (University of Michigan), Keren Sharon (University of Michigan)
Comments: 20 pages, 10 figures, 2 tables, submitted to ApJ
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); Astrophysics of Galaxies (astro-ph.GA)

Until now, systematic errors in strong gravitational lens modeling have been acknowledged but never been fully quantified. Here, we launch an investigation into the systematics induced by constraint selection. We model the simulated cluster Ares 362 times using random selections of image systems with and without spectroscopic redshifts and quantify the systematics using several diagnostics: image predictability, accuracy of model-predicted redshifts, enclosed mass, and magnification. We find that for models with $>15$ image systems, the image plane rms does not decrease significantly when more systems are added; however the rms values quoted in the literature may be misleading as to the ability of a model to predict new multiple images. The mass is well constrained near the Einstein radius in all cases, and systematic error drops to $<2\%$ for models using $>10$ image systems. Magnification errors are smallest along the straight portions of the critical curve, and the value of the magnification is systematically lower near curved portions. For $>15$ systems, the systematic error on magnification is $\sim2\%$. We report no trend in magnification error with fraction of spectroscopic image systems when selecting constraints at random; however, when using the same selection of constraints, increasing this fraction up to $\sim0.5$ will increase model accuracy. The results suggest that the selection of constraints, rather than quantity alone, determines the accuracy of the magnification. We note that spectroscopic follow-up of at least a few image systems is crucial, as models without any spectroscopic redshifts are inaccurate across all of our diagnostics.

[19]  arXiv:1608.08714 [pdf, other]
Title: ALMA View of the Galactic Center Mini-spiral: Ionized Gas Flows around Sagittarius A*
Comments: 25 pages, 8 figures, submitted to APJ
Subjects: Astrophysics of Galaxies (astro-ph.GA)

We have performed the observation of the "Galactic Center Mini-spiral(GCMS)" in H42alpha recombination line as a part of the first large-scale mosaic observation in the Sagittarius A complex using Atacama Millimeter/sub-millimeter Array (ALMA). We revealed the kinematics of the ionized gas streamers of the GCMS. Especially we found that the streamer corresponding to the Bar of the GCMS has a Keplerian orbit with high eccentricity which is independent from the Keplerian orbits of the other streamers of the GCMS. The periastron is probably located within the Bondi accretion radius derived from X-ray observation. In addition, we estimated the LTE electron temperature in the sub-structures of the GCMS from the line-continuum flux density ratio. The electron temperatures are in the range of T* e=(6-13)x10^3 K. We confirmed the previously claimed tendency that the electron temperatures increase toward Sgr A*. We also found that the electron temperature at the positive velocity end of the Bar is twice as high as that at the negative velocity end. This may be caused by the positional difference on the Keplarian orbit. There is a good positional correlation between the protostar candidates detected by JVLA at 34 GHz and the ionized gas streamer found by our H42alpha recombination line observation. This suggests that the candidates have been formed in the streamer and they were brought to near Sgr A* as the streamer falls.

[20]  arXiv:1608.08735 [pdf, ps, other]
Title: Preliminary results of CCD observations of Himalia at Yunnan Observatories in 2015
Comments: 9 pages, 3 figures
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

In order to study the potential in high precision CCD astrometry of irregular satellites, we have made experimental observations for Himalia, the sixth and irregular satellite of Jupiter. A total of 185 CCD observations were obtained by using the 2.4 m telescope and 1 m telescope at Yunnan Observatories over ten nights. Preliminary analysis for the observations were made, including the geometric distortion, the atmospheric refraction, and also the phase effect. All positions of Himalia are measured relative to the reference stars from the catalogue UCAC4 in each CCD field of view. The theoretical positions of Himalia were retrieved from the IMCCE, while the positions of Jupiter were obtained based on the planetary theory INPOP13C. The results show that the mean (O-C) (observed minus computed) residuals are -0.004 and -0.002 arcsec in right ascension and declination, respectively. The standard deviation of (O-C) residuals are estimated at about 0.04 arcsec in each direction.

[21]  arXiv:1608.08739 [pdf, ps, other]
Title: Subdwarf B stars from the common envelope ejection channel
Comments: 10 pages, 11 figures
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

From the canonical binary scenario, the majority of sdBs are produced from low-mass stars with degenerate cores where helium is ignited in a way of flashes. Due to numerical difficulties, the models of produced sdBs are generally constructed from more massive stars with non-degenerate cores, leaving several uncertainties on the exact characteristics of sdB stars. Employing MESA, we systematically studied the characteristics of sdBs produced from the common envelope (CE) ejection channel, and found that the sdB stars produced from the CE ejection channel appear to form two distinct groups on the effective temperature-gravity diagram. One group (the flash-mixing model) almost has no H-rich envelope and crows at the hottest temperature end of the extremely horizontal branch (EHB), while the other group has significant H-rich envelope and spreads over the whole canonical EHB region. The key factor for the dichotomy of the sdB properties is the development of convection during the first helium flash, which is determined by the interior structure of the star after the CE ejection. For a given initial stellar mass and a given core mass at the onset of the CE, if the CE ejection stops early, the star has a relatively massive H-rich envelope, resulting in a canonical sdB generally. The fact of only a few short-orbital-period sdB binaries being in the flash-mixing sdB region and the lack of He-rich sdBs in short-orbital-period binaries indicate that the flash mixing is not very often in the products of the CE ejection. A falling back process after the CE ejection, similar to that happened in nova, is an appropriate way of increasing the envelope mass, then prevents the flash mixing.

[22]  arXiv:1608.08741 [pdf, other]
Title: Chandra View of Magnetically Confined Wind in HD191612: Theory versus Observations
Authors: Yael Naze (ULg, Belgium), Asif ud-Doula (Penn State, USA), Svetozar A. Zhekov (Inst. of Astro, Bulgaria)
Comments: accepted for publication in ApJ
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); High Energy Astrophysical Phenomena (astro-ph.HE)

High-resolution spectra of the magnetic star HD191612 were acquired using the Chandra X-ray observatory at both maximum and minimum emission phases. We confirm the flux and hardness variations previously reported with XMM-Newton, demonstrating the great repeatability of the behavior of HD191612 over a decade. The line profiles appear typical for magnetic massive stars: no significant line shift, relatively narrow lines for high-Z elements, and formation radius at about 2R*. Line ratios confirm the softening of the X-ray spectrum at the minimum emission phase. Shift or width variations appear of limited amplitude at most (slightly lower velocity and slightly increased broadening at minimum emission phase, but within 1--2 sigma of values at maximum). In addition, a fully self-consistent 3D magnetohydrodynamic (MHD) simulation of the confined wind in HD191612 was performed. The simulation results were directly fitted to the data leading to a remarkable agreement overall between them.

[23]  arXiv:1608.08745 [pdf, other]
Title: Search for Neutrinos in Super-Kamiokande associated with Gravitational Wave Events GW150914 and GW151226
Comments: 8 pages, 4 figures
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics - Experiment (hep-ex)

We report the results from a search in Super-Kamiokande for neutrino signals coincident with the first detected gravitational wave events, GW150914 and GW151226, using a neutrino energy range from 3.5 MeV to 100 PeV. We searched for coincident neutrino events within a time window of $\pm$500 seconds around the gravitational wave detection time. Four neutrino candidates are found for GW150914 and no candidates are found for GW151226. The remaining neutrino candidates are consistent with the expected background events. We calculated the 90\% confidence level upper limits on the combined neutrino fluence for both gravitational wave events, which depends on event energy and topologies. Considering the upward going muon data set (1.6 GeV - 100 PeV) the neutrino fluence limit for each gravitational wave event is 14 - 37 (19 - 50) cm$^{-2}$ for muon neutrinos (muon antineutrinos), depending on the zenith angle of the event. In the other data sets, the combined fluence limits for both gravitational wave events range from 2.4$\times 10^{4}$ to 7.0$\times 10^{9}$ cm$^{-2}$.

[24]  arXiv:1608.08748 [pdf, ps, other]
Title: A New Code for Numerical Simulation of MHD Astrophysical Flows With Chemistry
Comments: 13 pages, 10 figures; submitted to ApJS
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM)

The new code for numerical simulation of magnetic hydrodynamical astrophysical flows with consideration of chemical reactions is given in the paper. At the heart of the code - the new original low-dissipation numerical method based on a combination of operator splitting approach and piecewise-parabolic method on the local stencil. The details of the numerical method are described; the main tests and the scheme of parallel implementation are shown. The chemodynamics of the hydrogen while the turbulent formation of molecular clouds is modeled.

[25]  arXiv:1608.08751 [pdf, ps, other]
Title: The complex evolutionary paths of local infrared bright galaxies: a high angular resolution mid-infrared view
Comments: Accepted for publication in MNRAS
Subjects: Astrophysics of Galaxies (astro-ph.GA)

We investigate the evolutionary connection between local IR-bright galaxies ($\log L_{\rm IR}\ge 11.4\,L_\odot$) and quasars. We use high angular resolution ($\sim$ 0.3-0.4 arcsec $\sim$ few hundred parsecs) $8-13\,\mu$m ground-based spectroscopy to disentangle the AGN mid-IR properties from those of star formation. The comparison between the nuclear $11.3\,\mu$m PAH feature emission and that measured with Spitzer/IRS indicates that the star formation is extended over a few kpc in the IR-bright galaxies. The AGN contribution to the total IR luminosity of IR-bright galaxies is lower than in quasars. Although the dust distribution is predicted to change as IR-bright galaxies evolve to IR-bright quasars and then to optical quasars, we show that the AGN mid-IR emission of all the quasars in our sample is not significantly different. In contrast, the nuclear emission of IR-bright galaxies with low AGN contributions appears more heavily embedded in dust although there is no clear trend with the interaction stage or projected nuclear separation. This suggests that the changes in the distribution of the nuclear obscuring material may be taking place rapidly and at different interaction stages washing out the evidence of an evolutionary path. When compared to normal AGN, the nuclear star formation activity of quasars appears to be dimming whereas it is enhanced in some IR-bright nuclei, suggesting that the latter are in an earlier star-formation dominated phase.

[26]  arXiv:1608.08756 [pdf, ps, other]
Title: Migration of accreting planets in radiative discs from dynamical torques
Comments: accepted in MNRAS
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

We present the results of hydrodynamical simulations of the orbital evolution of planets undergoing runaway gas accretion in radiative discs. We consider accreting disc models with constant mass flux through the disc, and where radiative cooling balances the effect of viscous heating and stellar irradiation. We assume that 20-30 $M_\oplus$ giant planet cores are formed in the region where viscous heating dominates and migrate outward under the action of a strong corotation torque. In the case where gas accretion is neglected, we find evidence for strong dynamical torques in accreting discs with accretion rates ${\dot M}\gtrsim 7\times 10^{-8} \;M_\odot/yr$. Their main effect is to increase outward migration rates by a factor of $\sim 2$ typically. In the presence of gas accretion, however, runaway outward migration is observed with the planet passing through the zero-torque radius and the transition between the viscous heating and stellar heating dominated regimes. The ability for an accreting planet to enter a fast migration regime is found to depend strongly on the planet growth rate, but can occur for values of the mass flux through the disc of ${\dot M}\gtrsim 5\times 10^{-8} \;M_\odot/yr$. We find that an episode of runaway outward migration can cause an accreting planet formed in the 5-10 AU region to temporarily orbit at star-planet separations as large as $\sim$60-70 AU. However, increase in the amplitude of the Lindblad torque associated with planet growth plus change in the streamline topology near the planet systematically cause the direction of migration to be reversed. Our results indicate that a planet can reach large orbital distances under the combined effect of dynamical torques and gas accretion, but an alternative mechanism is required to explain the presence of massive planets on wide orbits.

[27]  arXiv:1608.08772 [pdf, ps, other]
Title: New Extreme Trans-Neptunian Objects: Towards a Super-Earth in the Outer Solar System
Comments: Accepted Astronomical Journal
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Instrumentation and Methods for Astrophysics (astro-ph.IM); Solar and Stellar Astrophysics (astro-ph.SR)

We are conducting a wide and deep survey for extreme distant solar system objects. Our goal is to understand the high perihelion objects Sedna and 2012 VP113 and determine if an unknown massive planet exists in the outer solar system. The discovery of new extreme objects from our survey of some 1080 square degrees of sky to over 24th magnitude in the r-band are reported. Two of the new objects, 2014 SR349 and 2013 FT28, are extreme detached trans-Neptunian objects, which have semi-major axes greater than 150 AU and perihelia well beyond Neptune (q>40 AU). Both new objects have orbits with arguments of perihelia within the range of the clustering of this angle seen in the other known extreme objects. One of these objects, 2014 SR349, has a longitude of perihelion similar to the other extreme objects, but 2013 FT28, which may have more significant Neptune interactions, is about 180 degrees away or anti-aligned in its longitude of perihelion. We also discovered the first outer Oort cloud object with a perihelion beyond Neptune, 2014 FE72. We discuss these and other interesting objects discovered in our ongoing survey. All the high semi-major axis (a>150 AU) and high perihelion (q>35 AU) bodies follow the previously identified argument of perihelion clustering between 290 and 40 degrees as first reported and explained as being from an unknown massive planet by Trujillo and Sheppard (2014), which some have called Planet X or Planet 9. We also report objects with lower perihelia (q<35 AU) and a>200 AU show arguments of perihelia clustering at the opposite angles between 100 and 200 degrees. Finally, we find that the longitude of perihelion is significantly correlated with the argument of perihelion for all extreme objects.

[28]  arXiv:1608.08774 [pdf, ps, other]
Title: Sublimation of icy aggregates in the coma of comet 67P/Churyumov-Gerasimenko detected with the OSIRIS cameras onboard Rosetta
Comments: 11 pages, 7 figures, 3 tables, special issue "The ESLAB 50 Symposium - spacecraft at comets from 1P/Halley to 67P/Churyumov-Gerasimenko" in the Monthly Notices of the Royal Astronomical Society
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

Beginning in March 2014, the OSIRIS (Optical, Spectroscopic, and Infrared Remote Imaging System) cameras began capturing images of the nucleus and coma (gas and dust) of comet 67P/Churyumov-Gerasimenko using both the wide angle camera (WAC) and the narrow angle camera (NAC). The many observations taken since July of 2014 have been used to study the morphology, location, and temporal variation of the comet's dust jets. We analyzed the dust monitoring observations shortly after the southern vernal equinox on May 30 and 31, 2015 with the WAC at the heliocentric distance Rh = 1.53 AU, where it is possible to observe that the jet rotates with the nucleus. We found that the decline of brightness as a function of the distance of the jet is much steeper than the background coma, which is a first indication of sublimation. We adapted a model of sublimation of icy aggregates and studied the effect as a function of the physical properties of the aggregates (composition and size). The major finding of this article was that through the sublimation of the aggregates of dirty grains (radius a between 5 microm and 50 microm) we were able to completely reproduce the radial brightness profile of a jet beyond 4 km from the nucleus. To reproduce the data we needed to inject a number of aggregates between 8.5 x $10^{13}$ and 8.5 x $10^{10}$ for a = 5 microm and 50 microm respectively, or an initial mass of $H_2O$ ice around 22kg.

[29]  arXiv:1608.08776 [pdf, ps, other]
Title: Structure and kinematics of the clouds surrounding the Galactic mini-starburst W43 MM1
Subjects: Astrophysics of Galaxies (astro-ph.GA)

Massive stars have a major influence on their environment yet their formation is difficult to study. W43 is a highly luminous galactic massive star forming region at a distance of 5.5 kpc and the MM1 part hosts a very massive dense core (1000 M$_{\odot}$ within 0.05 pc). We present new Herschel HIFI maps of the W43 MM1 region covering the main low-energy water lines at 557, 987, and 1113 GHz, their H$_2^{18}$O counterparts, and other lines such as $^{13}$CO(10-9) and C$^{18}$O(9-8) which trace warm gas. These water lines are, with the exception of line wings, observed in absorption. Herschel SPIRE and JCMT 450 $\mu$m data have been used to make a model of the continuum emission at these wavelengths. Analysis of the maps, and in particular the optical depth maps of each line and feature, shows that a velocity gradient, possibly due to rotation, is present in both the envelope and the protostellar core. Velocities increase in both components from SW to NE, following the general source orientation. While the H$_2$O lines trace essentially the cool envelope, we show that the envelope cannot account for the H$_2^{18}$O absorption, which traces motions close to the protostar. The core has rapid infall, 2.9 kms, as manifested by the H$_2^{18}$O absorption features which are systematically red-shifted with respect to the $^{13}$CO(10-9) emission line which also traces the inner material with the same angular resolution. Some H$_2^{18}$O absorption is detected outside the central core and thus outside the regions expected to be above 100 K - we attribute this to warm gas associated with the other massive dense cores in W43 MM1. Using the maps to identify absorption from cool gas on large scales, we subtract this component to model spectra for the inner envelope. Modeling the new spectra results in a lower water abundance, decreased from $8 10^{-8}$ to $8 10^{-9}$ , with no change in infall rate.

[30]  arXiv:1608.08801 [pdf, other]
Title: Non-Gaussianity in multi-sound-speed disformally coupled inflation
Comments: 24 pages, 2 figures
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc)

Most, if not all, scalar-tensor theories are equivalent to General Relativity with a disformally coupled matter sector. In extra-dimensional theories such a coupling can be understood as a result of induction of the metric on a brane that matter is confined to. This article presents a first look at the non-Gaussianities in disformally coupled inflation, a simple two-field model that features a novel kinetic interaction. Cases with both canonical and Dirac-Born-Infeld (DBI) kinetic terms are taken into account, the latter motivated by the possible extra-dimensional origin of the disformality. The computations are carried out for the equilateral configuration in the slow-roll regime, wherein it is found that the non-Gaussianity is typically rather small and negative. This is despite the fact that the new kinetic interaction causes the perturbation modes to propagate with different sounds speeds, which may both significantly deviate from unity during inflation.

[31]  arXiv:1608.08802 [pdf, ps, other]
Title: Hard X-ray variability of V404 Cyg during the 2015 outburst
Comments: Submitted to A&A
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

Aims. Hard X-ray spectra of black hole binaries (BHB) are produced by Comptonization of soft seed photons by hot electrons near the black hole. The slope of the resulting energy spectra is governed by two main parameters: the electron temperature and the optical depth of the emitting plasma. Given the extreme brightness of V404 Cyg during the 2015 outburst, we aim to constraint the source spectral properties using an unprecedented time resolution in hard X-rays, and to monitor their evolution over the whole outburst. Methods. We have extracted and analyzed 602 X-ray spectra of V404 Cyg obtained during the 2015 June outburst by the IBIS/ISGRI instrument onboard INTEGRAL. We have performed time-resolved spectral analysis, using a time resolution ranging between 64 and 176000 seconds. The spectra were fitted in the 20-200 keV energy range. Results. We find that while the V404 Cyg light curve and soft X-ray spectra are remarkably different from other BHBs light curves, the spectral evolution of V404 Cyg in hard X-rays and the relations between the spectral parameters are consistent with those observed in other BHBs.We identify a hard branch where the electron temperature is anti-correlated with the hard X-ray flux, and a soft flaring branch where the relation reverses. In addition, we find that during the long X-ray plateaus detected at intermediate fluxes, the thermal Comptonization models fail to describe the spectra. Conclusions. We conclude that the hard branch in V404 Cyg is analogous to the canonical hard state of BHBs. V404 Cyg never seems to enter the canonical soft state, although the soft flaring branch bears resemblance to the BHB intermediate state and very high state. The X-ray plateaus are likely produced by absorption in a Compton-thick outflow, where the extreme absorption columns reduce the observed flux by a factor of about 10. [abridged]

[32]  arXiv:1608.08806 [pdf, other]
Title: Post fall-back evolution of multipolar magnetic fields and radio pulsar activation
Comments: 15 pages, 17 figures, accepted to the MNRAS 28 July 2016
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

It has long been unclear if the small-scale magnetic structures on the neutron star (NS) surface could survive the fall-back episode. The study of the Hall cascade (Cumming, Arras and Zweibel 2004; Wareing and Hollerbach 2009) hinted that energy in small scales structures should dissipate on short timescales. Our new 2D magneto-thermal simulations suggest the opposite. For the first $\sim$10 kyrs after the fall-back episode with accreted mass $10^{-3} M_\odot$, the observed NS magnetic field appears dipolar, which is insensitive to the initial magnetic topology. In framework of the Ruderman & Sutherland (1975) vacuum gap model during this interval, non-thermal radiation is strongly suppressed. After this time the initial (i.e. multipolar) structure begins to re-emerge through the NS crust. We distinguish three evolutionary epochs for the re-emergence process: the growth of internal toroidal field, the advection of buried poloidal field, and slow Ohmic diffusion. The efficiency of the first two stages can be enhanced when small-scale magnetic structure is present. The efficient re-emergence of high order harmonics might significantly affect the curvature of the magnetospheric field lines in the emission zone. So, only after few $10^4$ yrs would the NS starts shining as a pulsar again, which is in correspondence with radio silence of central compact objects (CCOs). In addition, these results can explain the absence of good candidates for thermally emitting NSs with freshly re-emerged field among radio pulsars (Bogdanov, Ng and Kaspi 2014), as NSs have time to cool down, and supernova remnants can already dissipate.

[33]  arXiv:1608.08808 [pdf, other]
Title: Characterizing the \lyaf\ flux probability distribution function using Legendre polynomials
Comments: 8 pages, 6 figures
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)

The Lyman-$\alpha$ forest is a highly non-linear field with a lot of information available in the data beyond the power spectrum. The flux probability distribution function (PDF) has been used as a successful probe of small-scale physics. In this paper we argue that measuring coefficients of the Legendre polyonomial expansion of the PDF offers several advantages over measuring the binned values as is commonly done. In particular, $n$-th coefficient can be expressed as a linear combination of the first $n$ moments, allowing these coefficients to be measured in the presence of noise and allowing a clear route for marginalisation over mean flux. Moreover, in the presence of noise, our numerical work shows that a finite number of coefficients are well measured with very sharp transition into noise dominance. This compresses the available information into a small number of well-measured quantities.

[34]  arXiv:1608.08816 [pdf]
Title: NEOPROP: a NEO Propagator for Space Situational Awareness
Comments: Proceeding of the 6th IAASS Conference "Safety is Not an Option", held 21-23 May 2013 in Montreal, Canada, this http URL
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

The overall aim of the Space Situational Awareness (SSA) Preparatory Programme is to support the European independent utilisation of and access to space for research or services, through providing timely and quality data, information, services and knowledge regarding the environment, the threats and the sustainable exploitation of the outer space surrounding our planet Earth. The SSA system will comprise three main segments: Space Weather (SWE) monitoring and forecast Near-Earth Objects (NEO) survey and follow-up Space Surveillance and Tracking (SST) of man-made space objects. There already exist different algorithms to predict orbits for NEOs. The objective of this activity is to come up with a different trajectory prediction algorithm, which allows an independent validation of the current algorithms within the SSA-NEO segment (e.g. NEODyS, JPL Sentry System). The key objective of this activity was to design, develop, test, verify, and validate trajectory prediction algorithm of NEOs in order to be able to compute analytically and numerically the minimum orbital intersection distances (MOIDs). The NEOPROP software consists of two separate modules/tools: (i) the Analytical Module makes use of analytical algorithms in order to rapidly assess the impact risk of a NEO. (ii) The Numerical Module makes use of numerical algorithms in order to refine and to better assess the impact probabilities.

[35]  arXiv:1608.08824 [pdf, other]
Title: Cosmological constraints on the radiation released during structure formation
Authors: David Camarena Torres (Espirito Santo U.), Valerio Marra (Espirito Santo U.)
Comments: 10 pages, 3 figures
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)

During the process of structure formation in the universe matter is converted into radiation through a variety of processes such as light from stars, infrared radiation from cosmic dust and gravitational waves from binary black holes/neutron stars and supernova explosions. The production of this astrophysical radiation background (ARB) could affect the expansion rate of the universe and the growth of perturbations. Here, we aim at understanding to which level one can constraint the ARB using future cosmological observations. We model the energy transfer from matter to radiation through an effective interaction between matter and astrophysical radiation. Using future supernova data from LSST and growth-rate data from Euclid we find that the ARB density parameter is constrained, at the 95% confidence level, to be $\Omega_{ar_0}<0.008$. Estimates of the energy density produced by well-known astrophysical processes give roughly $\Omega_{ar_0}\sim 10^{-6}$. Therefore, we conclude that cosmological observations will only be able to constrain exotic or not-well understood sources of radiation.

[36]  arXiv:1608.08833 [pdf, other]
Title: QuickPol: Fast effective beam matrices calculation for CMB polarization
Comments: 22 pages, 5 figures; submitted to A&A
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)

Current and planned observations of the Cosmic Microwave Background (CMB) polarization anisotropies, with their ever increasing number of detectors, have reached a potential accuracy that requires a very demanding control of systematic effects. While some of these systematics can be reduced in the design of the instruments, others will be have to be modeled and hopefully accounted for or corrected a posteriori. We propose QuickPol, a quick and accurate calculation of the full effective beam transfer function and of temperature to polarization leakage at the power spectra level, as induced by beam imperfections and mismatches between detector optical and electronic responses. All the observation details such as exact scanning strategy, imperfect polarization measurements and flagged samples are accounted for. Our results are validated on Planck-HFI simulations. We show how the pipeline can be used to propagate instrumental uncertainties up to the final science products, and could be applied to experiments with rotating half wave plates.

[37]  arXiv:1608.08837 [pdf, other]
Title: Tracing the reionization epoch with ALMA: [CII] emission in z~7 galaxies
Comments: To appear in ApJL
Subjects: Astrophysics of Galaxies (astro-ph.GA)

We present new results on [CII]158$\mu$ m emission from four galaxies in the reionization epoch. These galaxies were previously confirmed to be at redshifts between 6.6 and 7.15 from the presence of the Ly$\alpha$ emission line in their spectra. The Ly$\alpha$ emission line is redshifted by 100-200 km/s compared to the systemic redshift given by the [CII] line. These velocity offsets are smaller than what is observed in z~3 Lyman break galaxies with similar UV luminosities and emission line properties. Smaller velocity shifts reduce the visibility of Ly$\alpha$ and hence somewhat alleviate the need for a very neutral IGM at z~7 to explain the drop in the fraction of Ly$\alpha$ emitters observed at this epoch.
The galaxies show [CII] emission with L[CII]=0.6-1.6 x10$^8 L_\odot$: these luminosities place them consistently below the SFR-L[CII] relation observed for low redshift star forming and metal poor galaxies and also below z =5.5 Lyman break galaxies with similar star formation rates. We argue that previous undetections of [CII] in z~7 galaxies with similar or smaller star formation rates are due to selection effects: previous targets were mostly strong Ly$\alpha$ emitters and therefore probably metal poor systems, while our galaxies are more representative of the general high redshift star forming population .

[38]  arXiv:1608.08840 [pdf, other]
Title: Stacked search for time shifted high energy neutrinos from gamma ray bursts with the \ANTARES neutrino telescope
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

A search for high-energy neutrino emission correlated with gamma-ray bursts outside the electromagnetic prompt-emission time window is presented. Using a stacking approach of the time delays between reported gamma-ray burst alerts and spatially coincident muon-neutrino signatures, data from the Antares neutrino telescope recorded between 2007 and 2012 are analysed. One year of public data from the IceCube detector between 2008 and 2009 have been also investigated. The respective timing pro?les are scanned for statistically significant accumulations within 40 days of the Gamma Ray Burst, as expected from Lorentz Invariance Violation effects and some astrophysical models. No significant excess over the expected accidental coincidence rate could be found in either of the two data sets. The average strength of the neutrino signal is found to be fainter than one detectable neutrino signal per hundred gamma-ray bursts in the Antares data at 90% confidence level.

[39]  arXiv:1608.08842 [pdf, other]
Title: On the properties of dust and gas in the environs of V838 Monocerotis
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Astrophysics of Galaxies (astro-ph.GA)

Herschel FIR imaging and spectroscopy were taken at several epochs to probe the central point source and the extended environment of V838 Mon. PACS and SPIRE maps were used to obtain photometry of the near and far dust around V838 Mon. Fitting reveals 0.5-0.6 solar masses of ~19K dust in the environs (~2.7pc) surrounding the star. The surface-integrated infrared flux (signifying the thermal light echo) and derived dust properties do not vary significantly between the epochs. We also fit the SED of the point source. As the peak of the SED lies outside the Herschel spectral range, it is only by incorporating data from other observatories and epochs that we can perform useful fitting; with this we explicitly assume no evolution of the point source between the epochs. We find warm dust with a temperature of ~300K distributed over a radius of 150-200AU. PACS and SPIRE spectra were also used to detect emission lines from the extended environment around the star. We fit the far-infrared lines of CO arising from the point source, from an extended environment around V838 Mon. Assuming a model of a spherical shell for this gas, we find that the CO appears to arise from two temperature zones: a cold zone (Tkin ~18K) that could be associated with the ISM or possibly with a cold layer in the outermost part of the shell, and a warm (Tkin ~400K) zone that is associated with the extended environment of V838 Mon within a region of radius of ~210AU. The SiO lines arise from a warm/hot zone. We did not fit the lines of H2O as they are far more dependent on the model assumed.

[40]  arXiv:1608.08847 [pdf]
Title: Thermodynamic Explanation for the Cosmic Ubiquity of Organic Pigments
Comments: 23 pages, no figures
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Biological Physics (physics.bio-ph)

There is increasingly more evidence being accumulated for the occurrence of large amounts of organic material in the cosmos, particularly in the form of aromatic compounds. These molecules can be found on the surface of Earth and Mars, in the atmospheres of the larger planets and on many of their satellites, on asteroids, comets, meteorites, the atmospheres of red giant stars, interstellar nebulae, and in the spiral arms of galaxies. Many of these environments are expected to be of low temperature and pressure, implying that the Gibbs free energy for the formation of these complex molecules should be positive and large, suggesting that their existence could only be attributed to non-equilibrium thermodynamic processes. In this article we first review the evidence for the abundance of these molecules in the cosmos and then describe how the ubiquity can be explained from within the framework of non-equilibrium thermodynamics on the basis of the catalytic properties of these pigment molecules in dissipating photons of the ultraviolet and visible emission spectra of neighboring stars, leading to greater local entropy production. A relation between the maximum wavelength of absorption of these organic pigments and the corresponding stellar photon environment, provides a guide to determining which aromatic compounds are most probable in a given stellar neighborhood, a postulate that can be verified on Earth. It is suggested that at least some of the baryonic dark matter may be associated with these molecules which emit in the extreme infrared with many, but weak, emission lines, thus so far escaping detection. This thermodynamic explanation for the ubiquity of these organic molecules also has relevance to the possibility of life, both as we know it, and as we may not know it, throughout the universe.

[41]  arXiv:1608.08853 [pdf, other]
Title: Estimating sizes of faint, distant galaxies in the submillimetre regime
Comments: Accepted for publication in MNRAS
Subjects: Astrophysics of Galaxies (astro-ph.GA)

We measure the sizes of redshift ~2 star-forming galaxies by stacking data from the Atacama Large Millimeter/submillimeter Array (ALMA). We use a uv-stacking algorithm in combination with model fitting in the uv-domain and show that this allows for robust measures of the sizes of marginally resolved sources. The analysis is primarily based on the 344 GHz ALMA continuum observations centred on 88 sub-millimeter galaxies in the LABOCA ECDFS Submillimeter Survey (ALESS). We study several samples of galaxies at z~2 with $M_* \sim{} 5\times{}10^{10} $ M$_\odot$ , selected using near-infrared photometry (distant red galaxies, extremely red objects, sBzK-galaxies, and galaxies selected on photometric redshift).
We find that the typical sizes of these galaxies are ~0.6 arcsec which corresponds to ~5 kpc at z~2, this agrees well with the median sizes measured in the near-infrared z-band (~0.6 arcsec). We find errors on our size estimates of ~0.1-0.2 arcsec, which agree well with the expected errors for model fitting at the given signal-to-noise ratio. With the uv-coverage of our observations (18-160 m), the size and flux density measurements are sensitive to scales out to 2 . We compare this to a simulated ALMA Cycle 3 dataset with intermediate length baseline coverage, and we find that, using only these baselines, the measured stacked flux density would be an order of magnitude fainter. This highlights the importance of short baselines to recover the full flux density of high-redshift galaxies.

[42]  arXiv:1608.08860 [pdf, ps, other]
Title: The RINGO2 and DIPOL Optical Polarisation Catalogue of Blazars
Comments: 34 pages, 23 figures
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Astrophysics of Galaxies (astro-ph.GA)

We present ~2000 polarimetric and ~3000 photometric observations of 15 gamma-ray bright blazars over a period of 936 days (11/10/2008 - 26/10/2012) using data from the Tuorla blazar monitoring program (KVA DIPOL) and Liverpool Telescope (LT) RINGO2 polarimeters (supplemented with data from SkyCamZ (LT) and Fermi-LAT gamma-ray data). In 11 out of 15 sources we identify a total of 19 electric vector position angle (EVPA) rotations and 95 flaring episodes. We group the sources into subclasses based on their broadband spectral characteristics and compare their observed optical and gamma-ray properties. We find that (1) the optical magnitude and gamma-ray flux are positively correlated, (2) EVPA rotations can occur in any blazar subclass, 4 sources show rotations that go in one direction and immediately rotate back, (3) we see no difference in the gamma-ray flaring rates in the sample; flares can occur during and outside of rotations with no preference for this behaviour, (4) the average degree of polarisation (DoP), optical magnitude and gamma-ray flux are lower during an EVPA rotation compared with during non-rotation and the distribution of the DoP during EVPA rotations is not drawn from the same parent sample as the distribution outside rotations, (5) the number of observed flaring events and optical polarisation rotations are correlated, however we find no strong evidence for a temporal association between individual flares and rotations and (6) the maximum observed DoP increases from ~10% to ~30% to ~40% for subclasses with synchrotron peaks at high, intermediate and low frequencies respectively.

[43]  arXiv:1608.08862 [pdf, other]
Title: Towards generating a new supernova equation of state: A systematic analysis of cold hybrid stars
Comments: 14 pages, 11 figures
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)

The hadron-quark phase transition in core-collapse supernovae (CCSNe) has the potential to trigger explosions in otherwise non-exploding models. However, those hybrid supernova equations of state (EOS) shown to trigger an explosion do not support the observational 2 M_sun neutron star maximum mass constraint. In this work, we analyze cold hybrid stars by the means of a systematic parameter scan for the phase transition properties, with the aim to develop a new hybrid supernova EOS. The hadronic phase is described with the state-of-the-art supernova EOS HS(DD2), and quark matter by an EOS with a constant speed of sound ("CSS"). We find promising cases which meet the 2 M_sun criterion and are interesting for CCSN explosions. We show that the very simple CSS EOS is transferable into the well known thermodynamic bag model, important for future application in CCSN simulations. In the second part, the occurrence of reconfinement and multiple phase transitions is discussed. In the last part, the influence of hyperons in our parameter scan is studied. Including hyperons no change in the general behavior is found, except for overall lower maximum masses. In both cases (with and without hyperons) we find that quark matter can increase the maximum mass only if reconfinement is suppressed or if quark matter is absolutely stable.

[44]  arXiv:1608.08869 [pdf, other]
Title: Ultimate precision in cosmic-ray radio detection --- the SKA
Comments: To be published in the Proceedings of the ARENA2016 conference, Groningen, The Netherlands
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); High Energy Physics - Experiment (hep-ex)

As of 2023, the low-frequency part of the Square Kilometre Array will go online in Australia. It will constitute the largest and most powerful low-frequency radio-astronomical observatory to date, and will facilitate a rich science programme in astronomy and astrophysics. With modest engineering changes, it will also be able to measure cosmic rays via the radio emission from extensive air showers. The extreme antenna density and the homogeneous coverage provided by more than 60,000 antennas within an area of one km$^2$ will push radio detection of cosmic rays in the energy range around 10$^{17}$ eV to ultimate precision, with superior capabilities in the reconstruction of arrival direction, energy, and an expected depth-of-shower-maximum resolution of 6~g/cm${^2}$.

[45]  arXiv:1608.08877 [pdf]
Title: Quantum Tunneling Enhancement of the C + H2O and C + D2O Reactions at Low Temperature
Comments: Accepted to the Journal of Physical Chemistry Letters
Subjects: Astrophysics of Galaxies (astro-ph.GA)

Recent studies of neutral gas-phase reactions characterized by barriers show that certain complex forming processes involving light atoms are enhanced by quantum mechanical tunneling at low temperature. Here, we performed kinetic experiments on the activated C(3P) + H2O reaction, observing a surprising reactivity increase below 100 K, an effect which is only partially reproduced when water is replaced by its deuterated analogue. Product measurements of H- and D-atom formation allowed us to quantify the contribution of complex stabilization to the total rate while confirming the lower tunneling efficiency of deuterium. This result, which is validated through statistical calculations of the intermediate complexes and transition states has important consequences for simulated interstellar water abundances and suggests that tunneling mechanisms could be ubiquitous in cold dense clouds.

[46]  arXiv:1608.08880 [pdf, other]
Title: Timing of Five PALFA-Discovered Millisecond Pulsars
Comments: 8 pages, 5 figures, 1 table, submitted to ApJ
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

We report the discovery and timing results for five millisecond pulsars (MSPs) from the Arecibo PALFA survey: PSRs J1906+0055, J1914+0659, J1933+1726, J1938+2516, and J1957+2516. Timing observations of the 5 pulsars were conducted with the Arecibo and Lovell telescopes for time spans ranging from 1.5 to 3.3 yr. All of the MSPs except one (PSR J1914+0659) are in binary systems with low eccentricities. PSR J1957+2516 is likely a redback pulsar, with a ~0.1 $M_\odot$ companion and possible eclipses that last ~10% of the orbit. The position of PSR J1957+2516 is also coincident with a NIR source. All 5 MSPs are distant (>3.1 kpc) as determined from their dispersion measures, and none of them show evidence of $\gamma$-ray pulsations in a search of Fermi Gamma-Ray Space Telescope data. These 5 MSPs bring the total number of MSPs discovered by the PALFA survey to 26 and further demonstrate the power of this survey in finding distant, highly dispersed MSPs deep in the Galactic plane.

[47]  arXiv:1608.08881 [pdf, other]
Title: The Crab Pulsar at Centimeter Wavelengths II: Single Pulses
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR)

We have carried out new, high-frequency, high-time-resolution observations of the Crab pulsar. Combining these with our previous data, we characterize bright single pulses associated with the Main Pulse, both the Low-Frequency and High-Frequency Interpulses, and the two High-Frequency Components. Our data include observations at frequencies ranging from 1 to 43 GHz with time resolution down to a fraction of a nanosecond. We find at least two types of emission physics are operating in this pulsar. Both Main Pulses and Low-Frequency Interpulses, up to about 10 GHz, are characterized by nanoshot emission - overlapping clumps of narrow-band nanoshots, each with its own polarization signature. High-Frequency Interpulses, between 5 and 30 GHz, are characterized by spectral band emission - linearly polarized emission containing about 30 proportionately spaced spectral bands. We cannot say whether the longer-duration High-Frequency Component pulses are due to a scattering process, or if they come from yet another type of emission physics.

[48]  arXiv:1608.08884 [pdf, ps, other]
Title: Very Bright Prompt and Reverse Shock Emission of GRB 140512A
Comments: 11 pages in emulateapj style, 5 figures, 4 tables. Accepted for publication in ApJ
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

We report our observations of very bright prompt optical and reverse shock (RS) optical emission of GRB 140512A and analyze its multi-wavelength data observed with the {\em Swift} and {\em Fermi} missions. It is found that the joint optical-X-ray-gamma-ray spectrum with our first optical detection (R=13.09 mag) at $T_0+136$ seconds during the second episode of the prompt gamma-rays can be fit by a single power-law with index $-1.32\pm 0.01$. Our empirical fit to the afterglow lightcurves indicates that the observed bright optical afterglow with R=13.00 mag at the peak time is consistent with predictions of the RS and forward shock (FS) emission of external shock models. Joint optical-X-ray afterglow spectrum is well fit with an absorbed single power-law, with an index evolving with time from $-1.86\pm 0.01$ at the peak time to $-1.57\pm 0.01$ at late epoch, which could be due to the evolution of the ratio of the RS to FS emission fluxes. We fit the lightcurves with standard external models, and derive the physical properties of the outflow. It is found that the ratio $R_B\equiv\epsilon_{\rm B, r}/\epsilon_{\rm B, f}$ is 8187, indicating a high magnetization degree in the RS region. Measuring the relative radiation efficiency with $R_e\equiv\epsilon_{\rm e, r}/\epsilon_{\rm e, f}$, we have $R_e= 0.02$, implying the radiation efficiency of the RS is much lower than that in FS. We also show that the $R_B$ of GRBs 990123, 090102, and 130427A are similar to that of GRB 140512A and their apparent difference may be mainly attributed to the difference of the jet kinetic energy, initial Lorentz factor, and medium density among them.

[49]  arXiv:1608.08891 [pdf, other]
Title: Silicon-Based Antenna-Coupled Polarization-Sensitive Millimeter-Wave Bolometer Arrays for Cosmic Microwave Background Instruments
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Cosmology and Nongalactic Astrophysics (astro-ph.CO)

We describe feedhorn-coupled polarization-sensitive detector arrays that utilize monocrystalline silicon as the dielectric substrate material. Monocrystalline silicon has a low-loss tangent and repeatable dielectric constant, characteristics that are critical for realizing efficient and uniform superconducting microwave circuits. An additional advantage of this material is its low specific heat. In a detector pixel, two Transition-Edge Sensor (TES) bolometers are antenna-coupled to in-band radiation via a symmetric planar orthomode transducer (OMT). Each orthogonal linear polarization is coupled to a separate superconducting microstrip transmission line circuit. On-chip filtering is employed to both reject out-of-band radiation from the upper band edge to the gap frequency of the niobium superconductor, and to flexibly define the bandwidth for each TES to meet the requirements of the application. The microwave circuit is compatible with multi-chroic operation. Metalized silicon platelets are used to define the backshort for the waveguide probes. This micro-machined structure is also used to mitigate the coupling of out-of-band radiation to the microwave circuit. At 40 GHz, the detectors have a measured efficiency of 90%. In this paper, we describe the development of the 90 GHz detector arrays that will be demonstrated using the Cosmology Large Angular Scale Surveyor (CLASS) ground-based telescope.

[50]  arXiv:1608.08893 [pdf, other]
Title: High surface magnetic field in red giants as a new signature of planet engulfment?
Comments: 5 pages, abstract abridged for arXiv submission, accepted for publication in A&A Letters
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Earth and Planetary Astrophysics (astro-ph.EP)

Context. Red-giant stars may engulf planets. This may increase the rotation rate of their convective envelope, which could lead to strong dynamo-triggered magnetic fields. Aims. We explore the possibility of generating magnetic fields in red giants that have gone through the process of a planet engulfment. We compare them with similar models that evolve without any planets. We discuss the impact of stellar wind magnetic braking on the evolution of the surface velocity of the parent star. Methods. With rotating stellar models with and without planets and an empirical relation between the Rossby number and the surface magnetic field, we deduce the evolution of the surface magnetic field along the red-giant branch. The effects of wind magnetic braking is explored using a relation deduced from MHD simulations. Results. The stellar evolution model of a 1.7 M$_\odot$ without planet engulfment and that has a time-averaged rotation velocity during the Main-Sequence equal to 100 km s$^{-1}$, shows a surface magnetic field triggered by convection larger than 10 G only at the base of the red giant branch, that means for gravities log $g > 3$. When a planet engulfment occurs, such magnetic field can also appear at much lower gravities, i.e. at much higher luminosities along the red giant branch. Typically the engulfment of a 15 M$_J$ planet produces a dynamo triggered magnetic field larger than 10 G for gravities between 2.5 and 1.9. We show that for reasonable wind magnetic braking laws, the high surface velocity reached after a planet engulfment may be maintained sufficiently long for being observable. Conclusions. High surface magnetic fields for red giants in the upper part of the red giant branch is a strong indication of a planet engulfment or of an interaction with a companion. Our theory can be tested by observing fast rotating red giants and check whether they show magnetic fields.

[51]  arXiv:1608.08928 [pdf, other]
Title: Hierarchical follow-up of sub-threshold candidates of an all-sky Einstein@Home search for continuous gravitational waves on LIGO sixth science run data
Comments: 14 pages, 11 figures, extensive tables in the appendixes on pages 10-13
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); General Relativity and Quantum Cosmology (gr-qc)

We report results of an all-sky search for periodic gravitational waves with frequency between 50 and 510 Hz from isolated compact objects, i.e. neutron stars. A new hierarchical multi-stage approach is taken, supported by the computing power of the Einstein@Home project, allowing to probe more deeply than ever before. 16 million sub-threshold candidates from the initial search [LVC,arXiv:1606.09619] are followed up in three stages. None of those candidates is consistent with an isolated gravitational wave emitter, and 90% confidence level upper limits are placed on the amplitudes of continuous waves from the target population. Between 170.5 and 171 Hz we set the most constraining 90% confidence upper limit on the strain amplitude h0 at 4.3x10-25 , while at the high end of our frequency range we achieve an upper limit of 7.6x10-25. These are the most constraining all-sky upper limits to date and constrain the ellipticity of rotating compact objects emitting at 300 Hz at a distance D to less than 6x10-7 [d/100pc].

[52]  arXiv:1608.08939 [pdf, other]
Title: Pulsational-Pair Instability Supernovae
Authors: S. E. Woosley
Comments: 31 pages, 25 figures, submitted to Astrophysical Journal, Aug. 31, 2016
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

The final evolution of stars in the mass range 60 - 150 solar masses is explored. Depending upon their mass loss and rotation rates, many of these stars will end their lives as pulsational pair-instability supernovae. Even a non-rotating 70 solar mass star is pulsationally unstable during oxygen shell burning and can power a sub-luminous supernova. Rotation decreases the limit further. For more massive stars, the pulsations are less frequent, span a longer time, and are more powerful. Violent pulsations eject not only any residual low density envelope, but also that fraction of the helium core mass outside about 35 - 50 solar masses. The remaining core of helium and heavy elements continues to evolve, ultimately forming an iron core of about 2.5 solar masses that probably collapses to a black hole. A variety of observational transients result with total durations ranging from days to 10,000 years, and luminosities from 10$^{41}$ to 10$^{44}$ erg s$^{-1}$. Many transients resemble ordinary Type IIp supernovae, but others can recur on time scales of years or longer, with highly structured light curves. Some high mass supernova remnants will contain Wolf-Rayet stars for thousands of years. The relevance of PPISN to supernova impostors like Eta Carinae, to ultra-luminous supernovae, and to sources of gravitational radiation like GW 150914 is discussed. No black holes between 52 and 133 solar masses are expected from stellar evolution in close binaries.

[53]  arXiv:1608.08947 [pdf, other]
Title: H, He-like recombination spectra II: $l$-changing collisions for He Rydberg states
Comments: 9 pages, $ figures, 2 tables, accepted for publication in MNRAS
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); Astrophysics of Galaxies (astro-ph.GA); Atomic Physics (physics.atom-ph)

Cosmological models can be constrained by determining primordial abundances. Accurate predictions of the He I spectrum are needed to determine the primordial helium abundance to a precision of $< 1$% in order to constrain Big Bang Nucleosynthesis models. Theoretical line emissivities at least this accurate are needed if this precision is to be achieved. In the first paper of this series, which focused on H I, we showed that differences in $l$-changing collisional rate coefficients predicted by three different theories can translate into 10% changes in predictions for H I spectra. Here we consider the more complicated case of He atoms, where low-$l$ subshells are not energy degenerate. A criterion for deciding when the energy separation between $l$ subshells is small enough to apply energy-degenerate collisional theories is given. Moreover, for certain conditions, the Bethe approximation originally proposed by Pengelly & Seaton (1964) is not sufficiently accurate. We introduce a simple modification of this theory which leads to rate coefficients which agree well with those obtained from pure quantal calculations using the approach of Vrinceanu et al. (2012). We show that the $l$-changing rate coefficients from the different theoretical approaches lead to differences of $\sim 10$% in He I emissivities in simulations of H II regions using spectral code Cloudy.

[54]  arXiv:1608.08959 [pdf, other]
Title: On the Origin of Earth's Moon
Authors: Amy C. Barr
Comments: 57 pages, 8 figures, 7 tables, 2 appendices; Journal of Geophysical Research -- Planets, in press 2016
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

The Giant Impact is currently accepted as the leading theory for the formation of Earth's Moon. Successful scenarios for lunar origin should be able to explain the chemical composition of the Moon (volatile content and stable isotope ratios), the Moon's initial thermal state, and the system's bulk physical and dynamical properties. Hydrocode simulations of the formation of the Moon have long been able to match the bulk properties, but recent, more detailed work on the evolution of the protolunar disk has yielded great insight into the origin of the Moon's chemistry, and its early thermal history. Here, I show that the community has constructed the elements of an end-to-end theory for lunar origin that matches the overwhelming majority of observational constraints. In spite of the great progress made in recent years, new samples of the Moon, clarification of processes in the impact-generated disk, and a broader exploration of impact parameter space could yield even more insights into this fundamental and uniquely challenging geophysical problem.

[55]  arXiv:1608.08963 [pdf, other]
Title: SPIDERS: the spectroscopic follow-up of X-ray selected clusters of galaxies in SDSS-IV
Comments: 27 pages, 31 figures, 9 tables. Tables in electronic format are available from this http URL Submitted to MNRAS
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)

SPIDERS (The SPectroscopic IDentification of eROSITA Sources) is a program dedicated to the homogeneous and complete spectroscopic follow-up of X-ray AGN and galaxy clusters over a large area ($\sim$7500 deg$^2$) of the extragalactic sky. SPIDERS is part of the SDSS-IV project, together with the Extended Baryon Oscillation Spectroscopic Survey (eBOSS) and the Time-Domain Spectroscopic Survey (TDSS). This paper describes the largest project within SPIDERS before the launch of eROSITA: an optical spectroscopic survey of X-ray selected, massive ($\sim 10^{14}$ to $10^{15}~M_{\odot}$) galaxy clusters discovered in ROSAT and XMM-Newton imaging. The immediate aim is to determine precise ($\Delta_z \sim 0.001$) redshifts for 4,000-5,000 of these systems out to $z \sim 0.6$. The scientific goal of the program is precision cosmology, using clusters as probes of large-scale structure in the expanding Universe. We present the cluster samples, target selection algorithms and observation strategies. We demonstrate the efficiency of selecting targets using a combination of SDSS imaging data, a robust red-sequence finder and a dedicated prioritization scheme. We describe a set of algorithms and work-flow developed to collate spectra and assign cluster membership, and to deliver catalogues of spectroscopically confirmed clusters. We discuss the relevance of line-of-sight velocity dispersion estimators for the richer systems. We illustrate our techniques by constructing a catalogue of 230 spectroscopically validated clusters ($0.031 < z < 0.658$), found in pilot observations. We discuss two potential science applications of the SPIDERS sample: the study of the X-ray luminosity-velocity dispersion ($L_X-\sigma$) relation and the building of stacked phase-space diagrams.

[56]  arXiv:1608.08973 [pdf, ps, other]
Title: Detection relic gravitational waves in thermal case
Authors: Basem Ghayour
Comments: 10 pages, 4 figures
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)

The thermal spectrum of relic gravitational waves causes the new amplitude that called `modified amplitude'. Our analysis shows that, there exist some chances for detection of the thermal spectrum in addition to the usual spectrum by Adv.LIGO and Dml detectors. The behaviour of the inflation and reheating stages are often known as power law expansion like $S(\eta)\propto \eta^{1+\beta}$, $S(\eta)\propto \eta^{1+\beta_s}$ respectively. The $\beta$ and $\beta_s$ have an unique effect on the shape of the spectrum. We find some upper bounds on the $\beta$ and $\beta_s$ by comparison the usual and thermal spectrum with the Adv.LIGO and Dml. As this result gives us more information about the nature of the evolution of inflation and reheating stages.

[57]  arXiv:1608.08978 [pdf, other]
Title: The NuSTAR X-ray Spectrum of Hercules X-1: A Radiation-Dominated Radiative Shock
Comments: Accepted for publication in the Astrophysical Journal
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

We report new spectral modeling of the accreting X-ray pulsar Hercules X- 1. Our radiation-dominated radiative shock model is an implementation of the analytic work of Becker & Wolff on Comptonized accretion flows onto magnetic neutron stars. We obtain a good fit to the spin-phase averaged 4 to 78 keV X-ray spectrum observed by the Nuclear Spectroscopic Telescope Array during a main- on phase of the Her X-1 35-day accretion disk precession period. This model allows us to estimate the accretion rate, the Comptonizing temperature of the radiating plasma, the radius of the magnetic polar cap, and the average scattering opacity parameters in the accretion column. This is in contrast to previous phenomenological models that characterized the shape of the X-ray spectrum but could not determine the physical parameters of the accretion flow. We describe the spectral fitting details and discuss the interpretation of the accretion flow physical parameters.

[58]  arXiv:1608.08981 [pdf, ps, other]
Title: Disentangling the Virgo Overdensity with RR Lyrae stars
Authors: A. Katherina Vivas (CTIO), Robert Zinn (Yale), John Farmer (U. of Chicago), Sonia Duffau (PUC), Yiding Ping (Yale)
Comments: Accepted for publication in ApJ
Subjects: Astrophysics of Galaxies (astro-ph.GA)

We use a combination of spatial distribution and radial velocity to search for halo sub-structures in a sample of 412 RR Lyrae stars (RRLS) that covers a $\sim 525$ square degrees region of the Virgo Overdensity (VOD) and spans distances from the Sun from 4 to 75 kpc. With a friends-of-friends algorithm we identified six high significance groups of RRLS in phase space, which we associate mainly with the VOD and with the Sagittarius stream. Four other groups were also flagged as less significant overdensities. Three high significance and 3 lower significance groups have distances between $\sim 10$ and 20 kpc, which places them with the distance range attributed by others to the VOD. The largest of these is the Virgo Stellar Stream (VSS) at 19 kpc, which has 18 RRLS, a factor of 2 increase over the number known previously. While these VOD groups are distinct according to our selection cirteria, their overlap in position and distance, and, in a few cases, similarity in radial velocity are suggestive that they may not all stem separate accretion events. Even so, the VOD appears to be caused by more than one overdensity. The Sgr stream is a very obvious feature in the background of the VOD at a mean distance of 44 kpc. Two additional high significant groups were detected at distances $>40$ kpc. Their radial velocities and locations differ from the expected path of the Sgr debris in this part of the sky, and they are likely to be remnants of other accretion events.

[59]  arXiv:1608.08983 [pdf, other]
Title: Search for Blazar Flux-Correlated TeV Neutrinos in IceCube 40-String Data
Comments: 10 Pages, 4 tables, 3 figures. Bulk of table 2 provided in machine readable format
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

We present a targeted search for blazar flux-correlated high-energy ($\varepsilon_\nu > 1$ TeV) neutrinos from six bright northern blazars, using the public database of northern-hemisphere neutrinos detected during "IC40" 40-string operations of the IceCube neutrino observatory (April 2008 to May 2009). Our six targeted blazars are subjects of long-term monitoring campaigns by the VERITAS TeV gamma-ray observatory. We use the publicly-available VERITAS lightcurves to identify periods of excess and flaring emission. These predefined intervals serve as our "active temporal windows" in a search for an excess of neutrinos, relative to Poisson fluctuations of the near-isotropic atmospheric neutrino background which dominates at these energies. After defining the parameters of an optimized search, we confirm the expected Poisson behavior with Monte Carlo simulations prior to testing for excess neutrinos in the actual data. We make two searches: One for excess neutrinos associated with the bright flares of Mrk 421 that occurred during the IC40 run, and one for excess neutrinos associated with the brightest emission periods of five other blazars (Mrk 501, 1ES 0805+524, 1ES 1218+304, 3C66A, and W Comae), all significantly fainter than the Mrk 421 flares. We find no significant excess of neutrinos from the preselected blazar directions during the selected temporal windows. We derive 90%-confidence upper limits on the number of expected flux-associated neutrinos from each search. The upper limits are sufficiently close to the physically-interesting regime that we anticipate future analyses using already-collected data will either constrain models or yield discovery of the first blazar-associated high-energy neutrinos.

[60]  arXiv:1608.08986 [pdf, ps, other]
Title: ALFALFA and WSRT Imaging of Extended HI Features in the Leo Cloud of Galaxies
Comments: 17 pages, 9 figures, accepted for publication in MNRAS
Subjects: Astrophysics of Galaxies (astro-ph.GA)

We present ALFALFA HI observations of a well studied region of the Leo Cloud, which includes the NGC 3227 group and the NGC 3190 group. We detect optically dark HI tails and plumes with extents potentially exceeding 600 kpc, well beyond the field of view of previous observations. These HI features contain approximately 40% of the total HI mass in the NGC~3227 group and 10% in the NGC~3190 group. We also present WSRT maps which show the complex morphology of the extended emission in the NGC~3227 group. We comment on previously proposed models of the interactions in these groups and the implications for the scale of group processing through interactions. Motivated by the extent of the HI plumes, we place the HI observations in the context of the larger loose group, demonstrating the need for future sensitive, wide field HI surveys to understand the role of group processing in galaxy evolution.

[61]  arXiv:1608.08991 [pdf, other]
Title: Modelling resonances and orbital chaos in disk galaxies. Application to a Milky Way spiral model
Comments: 17 pages, 14 figures. Submitted to A&A
Subjects: Astrophysics of Galaxies (astro-ph.GA); Chaotic Dynamics (nlin.CD)

Context: Resonances in the stellar orbital motion under perturbations from spiral arms structure play an important role in the evolution of the disks of spiral galaxies. The epicyclic approximation allows the determination of the corresponding resonant radii on the equatorial plane (for nearly circular orbits), but is not suitable in general.
Aims: To expand the study of resonant orbits by analysing stellar motions perturbed by spiral arms with Gaussian-shaped profiles, without any restriction on the stellar orbital configurations, and expand the concept of Lindblad (epicyclic) resonances for orbits with large radial excursions.
Methods: We define a representative plane of initial conditions, which covers the whole phase space of the system. Dynamical maps on representative planes are constructed numerically, in order to characterize the phase-space structure and identify the precise location of the resonances. The study is complemented by the construction of dynamical power spectra, which provide the identification of fundamental oscillatory patterns in the stellar motion.
Results: Our approach allows a precise description of the resonance chains in the whole phase space, giving a broader view of the dynamics of the system when compared to the classical epicyclic approach, even for objects in retrograde motion. The analysis of the solar neighbourhood shows that, depending on the current azimuthal phase of the Sun with respect to the spiral arms, a star with solar kinematic parameters may evolve either inside the stable co-rotation resonance or in a chaotic zone.
Conclusions: Our approach contributes in quantifying the domains of resonant orbits and the degree of chaos in the whole Galactic phase-space structure. It may serve as a starting point to apply these techniques to the investigation of clumps in the distribution of stars in the Galaxy, such as kinematic moving groups.

[62]  arXiv:1608.08993 [pdf, other]
Title: Transmission spectroscopy of the inflated exoplanet WASP-52b, and evidence for a bright region on the stellar surface
Comments: Accepted for publication in MNRAS. 11 pages, 6 figures, 2 tables
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

We have measured the transmission spectrum of the extremely inflated hot Jupiter WASP-52b using simultaneous photometric observations in SDSS u', g' and a filter centred on the sodium doublet (NaI) with the ULTRACAM instrument mounted on the 4.2m William Herschel Telescope. We find that Rayleigh scattering is not the dominant source of opacity within the planetary atmosphere and find a transmission spectrum more consistent with wavelength-independent opacity such as from clouds. We detect an in-transit anomaly that we attribute to the presence of stellar activity and find that this feature can be more simply modelled as a bright region on the stellar surface akin to Solar faculae rather than spots. A spot model requires a significantly larger planet/star radius ratio than that found in previous studies. Our results highlight the precision that can be achieved by ground-based photometry with errors in the scaled planetary radii of less than one atmospheric scale height, comparable to HST observations.

[63]  arXiv:1608.09007 [pdf, ps, other]
Title: Timing of 29 Pulsars Discovered in the PALFA Survey
Comments: 30 pages, 8 Figures, submitted to ApJ
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

We report on the discovery and timing observations of 29 distant long-period pulsars discovered in the ongoing Arecibo PALFA pulsar survey. Following discovery with the Arecibo Telescope, confirmation and timing observations of these pulsars over several years at Jodrell Bank Observatory have yielded high-precision positions and measurements of rotation and radiation properties. We have used multi-frequency data to measure the interstellar scattering properties of some of these pulsars. Most of the pulsars have properties that mirror those of the previously known pulsar population, although four show some notable characteristics. PSRs J1907+0631 and J1925+1720 are young and are associated with supernova remnants or plerionic nebulae: J1907+0631 lies close to the center of SNR G40.5-0.5, while J1925+1720 is coincident with a high-energy Fermi gamma-ray source. One pulsar, J1932+1500, is in a surprisingly eccentric, 199-day binary orbit with a companion having a minimum mass of 0.33 solar masses. Several of the sources exhibit timing noise, and two, PSRs J0611+1436 and J1907+0631, have both suffered large glitches, but with very different post-glitch rotation properties. In particular, the rotational period of PSR J0611+1436 will not recover to its pre-glitch value for about 12 years, a far greater recovery timescale than seen following any other large glitches.

[64]  arXiv:1608.09008 [pdf, ps, other]
Title: Two long-term intermittent pulsars discovered in the PALFA Survey
Comments: 21 pages, 7 figures, submitted to ApJ
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

We report the discovery of two long-term intermittent radio pulsars in the ongoing Arecibo PALFA pulsar survey. Following discovery with the Arecibo Telescope, extended observations of these pulsars over several years at Jodrell Bank Observatory have revealed the details of their rotation and radiation properties. PSRs J1910+0517 and J1929+1357 show long-term extreme bi-modal intermittency, switching between active (ON) and inactive (OFF) emission states and indicating the presence of a large, hitherto unrecognised, underlying population of such objects. For PSR J1929+1357, the initial duty cycle was fON=0.008, but two years later this changed, quite abruptly, to fON=0.16. This is the first time that a significant evolution in the activity of an intermittent pulsar has been seen and we show that the spin-down rate of the pulsar is proportional to the activity. The spin-down rate of PSR J1929+1357 is increased by a factor of 1.8 when it is in active mode, similar to the increase seen in the other three known long-term intermittent pulsars.