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J.P. Magué & B. Ménard



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[1]  arXiv:1707.08119 [pdf, other]
Title: Cosmological forecasts from current observations of LIGO
Comments: 6 pages, 7 figures
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Phenomenology (hep-ph)

We use the simulated gravitational-wave data to explore the evolution of the universe in light of current observations of the Laser Interferometer Gravitational-Wave Observatory (LIGO). Taking advantage of state-of-the-art Markov Chain Monte Carlo technique to constrain the basic cosmological parameters, the Hubble constant, present matter density parameter and equation of state of dark energy, we find that LIGO needs about, at least 5-year data accumulation, namely about 1000 events, to achieve the accuracy comparable to the Planck result. We also find that, from a new information channel, the constrained value of the Hubble constant from 1000 simulated events is more consistent with the direct local observation by Riess et al. than the indirect global measurement by the Planck Collaboration at the $2\sigma$ confidence level. The combination of gravitational waves and electromagnetic signals is very prospective to reveal the underlying physics of the universe.

[2]  arXiv:1707.08121 [pdf, ps, other]
Title: An improved model of redshift-space distortions around voids: application to quintessence dark energy
Authors: Ixandra Achitouv
Comments: 12 pages, 11 figures
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc)

Using cosmic voids to probe the growth rate of cosmic structure, and hence the nature of dark energy, is particularly interesting in the context of modified gravity theories that rely on the screening mechanism. In this work we improve the modelling of redshift-space distortions around voids in the dark matter density field, and thus reduce systematic errors in the derivation of cosmological parameters. We also show how specific types of voids can be used to better probe the growth rate, using a flexible void finder. We apply our results to test for a quintessence type of dark energy vs. a LCDM model, and find a good agreement with the fiducial cosmology after implementing an analytical correction to the radial velocity profiles around voids. We additionally outline characteristic imprints of dark energy in the dark matter velocity distributions around voids.

[3]  arXiv:1707.08122 [pdf, other]
Title: Alignment Between Protostellar Outflows and Filamentary Structure
Comments: Accepted to ApJ
Subjects: Astrophysics of Galaxies (astro-ph.GA); Solar and Stellar Astrophysics (astro-ph.SR)

We present new Submillimeter Array (SMA) observations of CO(2-1) outflows toward young, embedded protostars in the Perseus molecular cloud as part of the Mass Assembly of Stellar Systems and their Evolution with the SMA (MASSES) survey. For 57 Perseus protostars, we characterize the orientation of the outflow angles and compare them with the orientation of the local filaments as derived from $Herschel$ observations. We find that the relative angles between outflows and filaments are inconsistent with purely parallel or purely perpendicular distributions. Instead, the observed distribution of outflow-filament angles are more consistent with either randomly aligned angles or a mix of projected parallel and perpendicular angles. A mix of parallel and perpendicular angles requires perpendicular alignment to be more common by a factor of $\sim$3. Our results show that the observed distributions probably hold regardless of the protostar's multiplicity, age, or the host core's opacity. These observations indicate that the angular momentum axis of a protostar may be independent of the large-scale structure. We discuss the significance of independent protostellar rotation axes in the general picture of filament-based star formation.

[4]  arXiv:1707.08123 [pdf, other]
Title: BAT AGN Spectroscopic Survey I: Spectral Measurements, Derived Quantities, and AGN Demographics
Comments: Accepted ApJ, see www.bass-survey.com for data
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Astrophysics of Galaxies (astro-ph.GA)

We present the first catalog and data release of the Swift-BAT AGN Spectroscopic Survey (BASS). We analyze optical spectra of the majority of AGN (77%, 641/836) detected based on their 14-195 keV emission in the 70-month Swift BAT all-sky catalog. This includes redshift determination, absorption and emission line measurements, and black hole mass and accretion rate estimates for the majority of obscured and un-obscured AGN (74%, 473/641) with 340 measured for the first time. With ~90% of sources at z<0.2, the survey represents a significant census of hard-X-ray selected AGN in the local universe. In this first catalog paper, we describe the spectroscopic observations and datasets, and our initial spectral analysis. The FWHM of the emission lines show broad agreement with the X-ray obscuration (~94%), such that Sy 1-1.8 have NH<10^21.9 cm^-2, and Seyfert 2, have NH>10^21.9 cm^-2. Seyfert 1.9 show a range of column densities. Compared to narrow line AGN in the SDSS, the X-ray selected AGN have a larger fraction of dusty host galaxies suggesting these types of AGN are missed in optical surveys. Using the most sensitive [OIII]/Hbeta and [NII]/Halpha emission line diagnostic, about half of the sources are classified as Seyferts, ~15% reside in dusty galaxies that lack an Hbeta detection, but for which the line upper limits imply either a Seyfert or LINER, ~15% are in galaxies with weak or no emission lines despite high quality spectra, and a few percent each are LINERS, composite galaxies, HII regions, or in known beamed AGN.

[5]  arXiv:1707.08126 [pdf, ps, other]
Title: Detection of Extraplanar Diffuse Ionized Gas in M83
Comments: 19 pages, 11 figures, accepted for publication in the Astrophysical Journal
Subjects: Astrophysics of Galaxies (astro-ph.GA)

We present the first kinematic study of extraplanar diffuse ionized gas (eDIG) in the nearby, face-on disk galaxy M83 using optical emission-line spectroscopy from the Robert Stobie Spectrograph on the Southern African Large Telescope. We use a Markov Chain Monte Carlo method to decompose the [NII]$\lambda\lambda$6548, 6583, H$\alpha$, and [SII]$\lambda\lambda$6717, 6731 emission lines into HII region and diffuse ionized gas emission. Extraplanar, diffuse gas is distinguished by its emission-line ratios ([NII]$\lambda$6583/H$\alpha \gtrsim 1.0$) and its rotational velocity lag with respect to the disk ($\Delta v = -24$ km/s in projection). With interesting implications for isotropy, the velocity dispersion of the diffuse gas, $\sigma = 96$ km/s, is a factor of a few higher in M83 than in the Milky Way and nearby, edge-on disk galaxies. The turbulent pressure gradient is sufficient to support the eDIG layer in dynamical equilibrium at an electron scale height of $h_{z} = 1$ kpc. However, this dynamical equilibrium model must be finely tuned to reproduce the rotational velocity lag. There is evidence of local bulk flows near star-forming regions in the disk, suggesting that the dynamical state of the gas may be intermediate between a dynamical equilibrium and a galactic fountain flow. As one of the first efforts to study eDIG kinematics in a face-on galaxy, this study demonstrates the feasibility of characterizing the radial distribution, bulk velocities, and vertical velocity dispersions in low-inclination systems.

[6]  arXiv:1707.08127 [pdf, ps, other]
Title: Formation of wide-orbit gas giant near the stability limit in multi-stellar systems
Comments: accepted for publication in AJ
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

We have investigated the formation of a circumstellar wide-orbit gas giant planet in a multiple stellar system. We consider a model of orbital circularization of a core of the giant planet after it is scattered from an inner disk region by a more massive planet, which was proposed by Kikuchi et al (2014). We extend their model for single star systems to binary (multiple) star systems, by taking into account tidal truncation of the protoplanetary gas disk by a binary companion. As an example, we consider wide-orbit gas giant in a hierarchical triple system, HD131399Ab. The best-fit orbit of the planet is that with semimajor axis $\sim 80$ au and eccentricity $\sim 0.35$. Since the binary separation is $\sim 350$ au, it is very close to the stability limit, which is puzzling. With the original core location $\sim 20$-30 au, the core (planet) mass $\sim 50 M_{\rm E}$ and the disk truncation radius $\sim 150$ au, our model reproduces the best-fit orbit of HD131399Ab. We find that the orbit after the circularization is usually close to the stability limit against the perturbations from the binary companion, since the scattered core accretes gas from the truncated disk. Our conclusion can also be applied for wider or more compact binary systems if the separation is not too large and another planet with $> \sim$ 20-30 earth masses that scattered the core existed in inner region of the system.

[7]  arXiv:1707.08129 [pdf, other]
Title: Reconstruction of the remote dipole and quadrupole fields from the kinetic Sunyaev Zel'dovich and polarized Sunyaev Zel'dovich effects
Comments: 24 pages, 7 figures
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Phenomenology (hep-ph); High Energy Physics - Theory (hep-th)

The kinetic Sunyaev Zel'dovich (kSZ) and polarized Sunyaev Zel'dovich (pSZ) effects are temperature and polarization anisotropies induced by the scattering of CMB photons from structure in the post-reionization Universe. In the case of the kSZ effect, small angular scale anisotropies in the optical depth are modulated by the cosmic microwave background (CMB) dipole field, e.g. the CMB dipole observed at each spacetime point. In the case of the pSZ effect, similar small-scale anisotropies are modulated by the CMB quadrupole field, which receives contributions from both scalar and tensor modes. Statistical anisotropies in the cross correlations of CMB temperature and polarization with tracers of the inhomogeneous distribution of electrons provide a means of isolating and reconstructing the dipole and quadrupole fields. In this paper, we present a set of unbiased minimum variance quadratic estimators for the reconstruction of the dipole and quadrupole fields, and forecast the ability of future CMB experiments and large scale structure surveys to perform this reconstruction in the cosmic variance limit. Consistent with previous work, we find that a high fidelity reconstruction of the dipole and quadrupole fields over a variety of scales is indeed possible, and demonstrate the sensitivity of the pSZ effect to primordial tensor modes. Using a principle component analysis, we estimate how many independent modes could be accessed in such a reconstruction. We also comment on a few first applications of a detection of the dipole and quadrupole fields, including a reconstruction of the primordial contribution to our locally observed CMB dipole, a test of statistical homogeneity on large scales from the first modes of the quadrupole field, and a reconstruction technique for the primordial potential on the largest scales.

[8]  arXiv:1707.08132 [pdf, other]
Title: Theoretical Models of Optical Transients. I. A Broad Exploration of the Duration-Luminosity Phase Space
Comments: 30 pages, 20 figures, submitted to ApJ; interactive figure: ashleyvillar.com/dlps
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR)

The duration-luminosity phase space of optical transients is used, mostly heuristically, to compare various classes of transient events, to explore the origin of new transients, and to influence optical survey observing strategies. For example, several observational searches have been guided by intriguing voids and gaps in this phase space. However we should ask: Do we expect to find transients in these voids given our understanding of the various heating sources operating in astrophysical transients? In this work, we explore a broad range of theoretical models and empirical relations to generate optical light curves and to populate the duration-luminosity phase space (DLPS). We explore transients powered by adiabatic expansion, radioactive decay, magnetar spin-down, and circumstellar interaction. For each heating source, we provide a concise summary of the basic physical processes, a physically motivated choice of model parameter ranges, an overall summary of the resulting light curves and their the occupied range in the DLPS, and how the various model input parameters affect the light curves. We specifically explore the key voids discussed in the literature: the intermediate luminosity gap between classical novae and supernovae, and short-duration transients (<10 days). We find that few physical models lead to transients that occupy these voids. Moreover, we find that only relativistic expansion can produce fast and luminous transients, while for all other heating sources, events with durations <10 days are dim (> -15 mag). Finally, we explore the detection potential of optical surveys (e.g., LSST) in the DLPS and quantify the notion that short-duration and dim transients are exponentially more difficult to discover in untargeted surveys.

[9]  arXiv:1707.08153 [pdf, other]
Title: Parameter constraints from weak lensing tomography of galaxy shapes and cosmic microwave background fluctuations
Authors: Philipp M. Merkel (1), Bjoern Malte Schaefer (1) ((1) ZAH/Heidelberg)
Comments: 11 pages, 6 figures, MNRAS accepted
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)

Recently, it has been shown that cross-correlating CMB lensing and 3D cosmic shear allows to considerably tighten cosmological parameter constraints. We investigate whether similar improvement can be achieved in a conventional tomographic setup. We present Fisher parameter forecasts for a Euclid-like galaxy survey in combination with different ongoing and forthcoming CMB experiments. In contrast to a fully three-dimensional analysis we find only marginal improvement. Assuming Planck-like CMB data we show that including the full covariance of the combined CMB and cosmic shear data improves the dark energy figure of merit by only three per cent. The marginalized error on the sum of neutrino masses is reduced at the same level. For a next generation CMB satellite mission such as Prism the predicted improvement of the dark energy figure of merit amounts to approximately 25 per cent. Furthermore, we show that the small improvement is contrasted by an increased bias in the dark energy parameters when the intrinsic alignment of galaxies is not correctly accounted for in the full covariance matrix.

[10]  arXiv:1707.08156 [pdf, ps, other]
Title: Partially chaotic orbits in a perturbed cubic force model
Authors: J.C. Muzzio
Comments: Accepted for publication by the Monthly Notices of the Royal Astronomical Society, July 23, 2017
Subjects: Astrophysics of Galaxies (astro-ph.GA); Chaotic Dynamics (nlin.CD)

Three types of orbits are theoretically possible in autonomous Hamiltonian systems with three degrees of freedom: fully chaotic (they only obey the energy integral), partially chaotic (they obey an additional isolating integral besides energy) and regular (they obey two isolating integrals besides energy). The existence of partially chaotic orbits has been denied by several authors, however, arguing either that there is a sudden transition from regularity to full chaoticity, or that a long enough follow up of a supposedly partially chaotic orbit would reveal a fully chaotic nature. This situation needs clarification, because partially chaotic orbits might play a significant role in the process of chaotic diffusion. Here we use numerically computed Lyapunov exponents to explore the phase space of a perturbed three dimensional cubic force toy model, and a generalization of the Poincar\'e maps to show that partially chaotic orbits are actually present in that model. They turn out to be double orbits joined by a bifurcation zone, which is the most likely source of their chaos, and they are encapsulated in regions of phase space bounded by regular orbits similar to each one of the components of the double orbit.

[11]  arXiv:1707.08159 [pdf, other]
Title: Modelling the thermal X-ray emission around the Galactic centre from colliding Wolf-Rayet winds
Comments: 1 page, 1 figure; to appear in Proceedings of IAU Symposium 329, "The Lives and Death-Throes of Massive Stars"
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

We compute the thermal X-ray emission from hydrodynamic simulations of the 30 Wolf-Rayet (WR) stars orbiting within a parsec of Sgr A$^*$, with the aim of interpreting the Chandra X-ray observations of this region. The model well reproduces the spectral shape of the observations, indicating that the shocked WR winds are the dominant source of this thermal emission. The model X-ray flux is tied to the strength of the Sgr A$^*$ outflow, which clears out hot gas from the vicinity of Sgr A$^*$. A moderate outflow best fits the present-day observations, even though this supermassive black hole (SMBH) outflow ended $\sim$100 yr ago.

[12]  arXiv:1707.08193 [pdf]
Title: SOLARIS: Solar Sail Investigation of the Sun
Journal-ref: Macdonald M. (eds) Advances in Solar Sailing, pp 259-268, Feb 2014
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

In this paper, we detail the scientific objectives and outline a strawman payload of the SOLAR sail Investigation of the Sun (SOLARIS). The science objectives are to study the 3D structure of the solar magnetic and velocity field, the variation of total solar irradiance with latitude, and the structure of the corona. We show how we can meet these science objective using solar-sail technologies currently under development. We provide a tentative mission profile considering several trade-off approaches. We also provide a tentative mass budget breakdown and a perspective for a programmatic implementation.

[13]  arXiv:1707.08223 [pdf, other]
Title: NGC 6819: testing the asteroseismic mass scale, mass loss, and evidence for products of non-standard evolution
Comments: 21 pages, 11 figures
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

We present an extensive peakbagging effort on Kepler data of $\sim$50 red giant stars in the open star cluster NGC 6819. By employing sophisticated pre-processing of the time series and Markov Chain Monte Carlo techniques we extracted individual frequencies, heights and linewidths for hundreds of oscillation modes.
We show that the "average" asteroseismic parameter $\delta\nu_{02}$, derived from these, can be used to distinguish the stellar evolutionary state between the red giant branch (RGB) stars and red clump (RC) stars.
Masses and radii are estimated using asteroseismic scaling relations, both empirically corrected to obtain self-consistency as well as agreement with independent measures of distance, and using updated theoretical corrections. Remarkable agreement is found, allowing the evolutionary state of the giants to be determined exclusively from the empirical correction to the scaling relations. We find a mean mass of the RGB stars and RC stars in NGC 6819 to be $1.61\pm0.02\,\textrm{M}_\odot$ and $1.64{\pm}0.02\,\textrm{M}_\odot$, respectively. The difference $\Delta M=-0.03\pm0.01\,\textrm{M}_\odot$ is almost insensitive to systematics, suggesting very little RGB mass loss, if any.
Stars that are outliers relative to the ensemble reveal overmassive members that likely evolved via mass-transfer in a blue straggler phase. We suggest that KIC 4937011, a low-mass Li-rich giant, is a cluster member in the RC phase that experienced very high mass-loss during its evolution. Such over- and undermassive stars need to be considered when studying field giants, since the true age of such stars cannot be known and there is currently no way to distinguish them from normal stars.

[14]  arXiv:1707.08224 [pdf, other]
Title: How much mass and angular momentum can the progenitors of carbon-enriched stars accrete?
Comments: 8 pages (8 figures) plus a table. Accepted for publication in A&A
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

The chemically peculiar barium stars, CH stars, and most CEMP stars are all believed to be the products of mass transfer in binary systems from a now extinct AGB primary star. The mass of the AGB star and the orbital parameters of the system are the key factors usually considered when determining how much mass is transferred onto the lower-mass main-sequence companion. What is usually neglected, however, is the angular momentum of the accreted material, which should spin up the accreting star. If the star reaches critical rotation, further accretion should cease until the excess angular momentum is somehow dealt with. If the star cannot redistribute or lose the angular momentum while the primary is on the AGB, the amount of mass accreted could be much lower than otherwise expected. Here we present calculations, based on detailed stellar evolution models, of the mass that can be accreted by putative progenitors of Ba and CEMP stars before they reach critical rotation under the assumption that no angular momentum loss occurs during the mass transfer. We consider different accretion rates and values of specific angular momentum. The most stringent limits on the accreted masses result from considering accretion from a Keplerian accretion disk, which is likely present during the formation of most extrinsically-polluted carbon-enriched stars. Our calculations indicate that in this scenario only about 0.05 solar masses of material can be added to the accreting star before it reaches critical rotation, which is much too low to explain the chemical enrichment of many Ba and CEMP stars. Either the specific angular momentum of the accreted material has to effectively be lower by about a factor of ten than the Keplerian value, or significant angular momentum losses must occur for substantial accretion to take place.

[15]  arXiv:1707.08229 [pdf, ps, other]
Title: ALMA Observations of Circumnuclear Disks in Early Type Galaxies: 12CO(2-1) and Continuum Properties
Comments: 20 pages, 10 figures; accepted for publication in ApJ
Subjects: Astrophysics of Galaxies (astro-ph.GA)

We present results from an Atacama Large Millimeter/submillimeter Array (ALMA) Cycle 2 program to map CO(2-1) emission in nearby early-type galaxies (ETGs) that host circumnuclear gas disks. We obtained $\sim0.3''-$resolution Band 6 observations of seven ETGs selected on the basis of dust disks in Hubble Space Telescope images. We detect CO emission in five at high signal-to-noise ratio with the remaining two only faintly detected. All CO emission is coincident with the dust and is in dynamically cold rotation. Four ETGs show evidence of rapid central rotation; these are prime candidates for higher-resolution ALMA observations to measure the black hole masses. In this paper we focus on the molecular gas and continuum properties. Total gas masses and H$_2$ column densities for our five CO-bright galaxies are on average $\sim10^8$ $M_\odot$ and $\sim10^{22.5}$ cm$^{-2}$ over the $\sim$kpc-scale disks, and analysis suggests that these disks are stabilized against gravitational fragmentation. The continuum emission of all seven galaxies is dominated by a central, unresolved source, and in five we also detect a spatially extended component. The $\sim$230 GHz nuclear continua are modeled as power laws ranging from $S_\nu \sim \nu^{-0.4}$ to $\nu^{1.6}$ within the observed frequency band. The extended continuum profiles of the two radio-bright (and CO-faint) galaxies are roughly aligned with their radio jet and suggests resolved synchrotron jets. The extended continua of the CO-bright disks are coincident with optically thick dust absorption and have spectral slopes that are consistent with thermal dust emission.

[16]  arXiv:1707.08230 [pdf, ps, other]
Title: A Dust Twin of Cas A: Cool Dust and Pre-Solar Grain of Silica Revealed in the Supernova Remnant G54.1+0.3
Authors: J. Rho (1, 2), H. L. Gomez (3), A. Boogert (2, 4), M.W.L. Smith (3), P.-O Lagage (5, 6), D. Dowell (7), C.J.R. Clark (3) ((1) SETI Institute (2) SOFIA Science Center/NASA Ames (3) Cardiff U. (4) USRA (5) Paris-Saclay U. (6) CEA (7) NASA/JPL)
Comments: MNRAS, submitted
Subjects: Astrophysics of Galaxies (astro-ph.GA)

We present infrared and submillimeter observations of the Crab-like supernova remnant (SNR) G54.1+0.3 including 350 micron (SHARC-II), 870 micron (LABOCA), 70, 100, 160, 250, 350 and 500 micron (Herschel) and ancillary mid-infrared observations from Spitzer. The distribution of the shell-like ejecta and dust around the pulsar wind nebula in G54.1+0.3 is analogous with the Crab Nebula. In the mid-infrared we detect dust features at 9, 11 and 21 micron and we also reveal a long wavelength continuum dust component. The 21 micron dust feature is particularly strong in the western shell of G54.1+0.3 and coincides with [Ar II] ejecta emission and 9 micron dust feature. The 21 micron feature is remarkably similar to the 21 micron-dust component detected originally in Cas A. The IRAC 8 micron image including Ar ejecta is distributed in a shell-like morphology which is coincident with dust emission, suggesting that dust has formed in the ejecta. We fit the IR-submm spectral energy distribution of the SNR using the continuous distributions of ellipsoidal grain model of pre-solar grain SiO2 that reproduces the 21 and 9 micron dust features, and discuss grains of SiC and PAH that may be responsible for the 11 micron dust feature. To reproduce the long-wavelength continuum, we explore models consisting of different grains including Mg2SiO4, MgSiO3, Al2O3, FeS, carbon and Fe3O4. We also tested a model with a temperature-dependent silicate absorption coefficient. We detect cold dust (27-44 K) in the remnant and the total dust mass ranges from 0.08-0.9 Msun depending on the grain composition, which is comparable to predicted masses from theoretical models. Our estimated dust masses are consistent with the idea that SNe are a significant source of dust in the early Universe.

[17]  arXiv:1707.08246 [pdf, ps, other]
Title: Evidence of Eta Aquariid Outbursts Recorded in the Classic Maya Hieroglyphic Script Using Orbital Integrations
Journal-ref: Planet. Space Sci., 144, 112-125 (2017)
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

No firm evidence has existed that the ancient Maya civilization recorded specific occurrences of meteor showers or outbursts in the corpus of Maya hieroglyphic inscriptions. In fact, there has been no evidence of any pre-Hispanic civilization in the Western Hemisphere recording any observations of any meteor showers on any specific dates.
The authors numerically integrated meteoroid-sized particles released by Comet Halley as early as 1404 BC to identify years within the Maya Classic Period, AD 250-909, when Eta Aquariid outbursts might have occurred. Outbursts determined by computer model were then compared to specific events in the Maya record to see if any correlation existed between the date of the event and the date of the outburst. The model was validated by successfully explaining several outbursts around the same epoch in the Chinese record. Some outbursts observed by the Maya were due to recent revolutions of Comet Halley, within a few centuries, and some to resonant behavior in older Halley trails, of the order of a thousand years. Examples were found of several different Jovian mean motion resonances as well as the 1:3 Saturnian resonance that have controlled the dynamical evolution of meteoroids in apparently observed outbursts.

[18]  arXiv:1707.08251 [pdf, other]
Title: Black Hole Mass Estimation in Type 1 AGN: H$β$ vs. Mg II lines and the role of Balmer continuum
Comments: 9 pages, 3 figures, Accepted for publication in Frontiers in Astronomy and Space Sciences
Journal-ref: Front. Astron. Space Sci. 4:7 (2017)
Subjects: Astrophysics of Galaxies (astro-ph.GA)

Here we investigate the H$\beta$ and Mg II spectral line parameters used for the black hole mass (M$_{\rm BH}$) estimation for a sample of Type 1 Active Galactic Nuclei (AGN) spectra selected from the Sloan Digital Sky Survey (SDSS) database. We have analyzed and compared the virialization of the H$\beta$ and Mg II emission lines, and found that the H$\beta$ line is more confident virial estimator than Mg II. We have investigated the influence of the Balmer continuum emission to the M$_{\rm BH}$ estimation from the UV parameters, and found that the Balmer continuum emission can contribute to the overestimation of the M$_{\rm BH}$ on average for ~ 5% (up to 10%).

[19]  arXiv:1707.08256 [pdf, other]
Title: Cross-Correlation Redshift Calibration Without Spectroscopic Calibration Samples in DES Science Verification Data
Comments: 12 pages, 5 figures. Submitted to MNRAS. Comments welcome!
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)

Galaxy cross-correlations with high-fidelity redshift samples hold the potential to precisely calibrate systematic photometric redshift uncertainties arising from the unavailability of complete and representative training and validation samples of galaxies. However, application of this technique in the Dark Energy Survey (DES) is hampered by the relatively low number density, small area, and modest redshift overlap between photometric and spectroscopic samples. We propose instead using photometric catalogs with reliable photometric redshifts for photo-z calibration via cross-correlations. We verify the viability of our proposal using redMaPPer clusters from the Sloan Digital Sky Survey (SDSS) to successfully recover the redshift distribution of SDSS spectroscopic galaxies. We demonstrate how to combine photo-z with cross-correlation data to calibrate photometric redshift biases while marginalizing over possible clustering bias evolution in either the calibration or unknown photometric samples. We apply our method to DES Science Verification (DES SV) data in order to constrain the photometric redshift distribution of a galaxy sample selected for weak lensing studies, constraining the mean of the tomographic redshift distributions to a statistical uncertainty of $\Delta z \sim \pm 0.01$. We forecast that our proposal can in principle control photometric redshift uncertainties in DES weak lensing experiments at a level near the intrinsic statistical noise of the experiment over the range of redshifts where redMaPPer clusters are available. Our results provide strong motivation to launch a program to fully characterize the systematic errors from bias evolution and photo-z shapes in our calibration procedure.

[20]  arXiv:1707.08263 [pdf, ps, other]
Title: Modeling the GeV emission of HESS J0632+057
Comments: 7pages, 7 figures. Accepted for publication in MNRAS
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

The binary system HESS J0632+057 was recently detected by {Fermi} to possess orbital modulated GeV emission. In this paper, we study the possibility that the compact companion of HESS J0632+057 is a pulsar. Under such a presumption, we focus on the high energy emission mechanism of this system, which is as follows. The pulsar companion travels through the circumstellar disc of the main sequence star twice in each orbit, when some of the matter is gravity-captured. The captured matter develops an accretion disc around the pulsar, and the soft photons from which are inverse Compton scattered by the pulsar wind as the GeV emission from the system. With proper choice of parameters, SED and light curve which are in accordance with observations can be produced. We predict that the light curve of GeV emission has two peaks, the larger one is at around 0.4 after the periastron (or 0.1 after the X-ray maximum), while the smaller one is between phases 0 and 0.1, with integrated flux one forth of the larger one.

[21]  arXiv:1707.08267 [pdf, ps, other]
Title: $^{13}$C isotopic fractionation of HC$_{3}$N in two starless cores: L1521B and L134N (L183)
Comments: Accepted for publication in ApJ, 11pages, 4 figures, 2 tables
Subjects: Astrophysics of Galaxies (astro-ph.GA); Solar and Stellar Astrophysics (astro-ph.SR)

We observed the $J=5-4$ rotational lines of the normal species and three $^{13}$C isotopologues of HC$_{3}$N at the 45 GHz band toward two low-mass starless cores, L1521B and L134N (L183), using the Nobeyama 45 m radio telescope in order to study the main formation pathways of HC$_{3}$N in each core. The abundance ratios of the three $^{13}$C isotopologues in L1521B are derived to be [H$^{13}$CCCN]:[HC$^{13}$CCN]:[HCC$^{13}$CN] = 0.98 (+- 0.14) : 1.00 : 1.52 (+- 0.16) (1 sigma). The fractionation pattern is consistent with that at the cyanopolyyne peak in Taurus Molecular Cloud-1. This fractionation pattern suggests that the main formation pathway of HC$_{3}$N is the neutral-neutral reaction between C$_{2}$H$_{2}$ and CN. On the other hand, their abundance ratios in L134N are found to be [H$^{13}$CCCN]:[HC$^{13}$CCN]:[HCC$^{13}$CN]= 1.5 (+- 0.2) : 1.0 : 2.1 (+- 0.4) (1 sigma), which are different from those in L1521B. From this fractionation pattern, we propose that the reaction between HNC and CCH is a possible main formation pathway of HC$_{3}$N in L134N. We find out that the main formation pathways of the same molecule are not common even in the similar physical conditions. We discuss the possible factors to make a difference in fractionation pattern between L134N and L1521B/TMC-1.

[22]  arXiv:1707.08280 [pdf, ps, other]
Title: Radial Acceleration Relation by Dark Matter and Baryons in the Intermediate Acceleration Regime
Comments: 5 pages, 2 figures, submitted to PRL
Subjects: Astrophysics of Galaxies (astro-ph.GA); Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Theory (hep-th)

We report an empirical relation between the radial accelerations by baryons ($a_{\rm B}$) and dark matter ($a_{\rm DM}$) derived from kinematic analyses of $\sim 7000$ nearly round, pure bulge, non-rotating elliptical galaxies, selected from Sloan Digital Sky Survey DR7. For an acceleration range $a_0 < a_{\rm B} < 30 a_0$ above $a_0 =1.2 \times 10^{-10}$~m~s$^{-2}$, we find $a_{\rm DM}/a_{\rm B} = 10^{p} (a_{\rm B}/a_0)^q$ with $p = -0.08 \pm 0.02$ (stat) $\pm 0.1$ (sys) and $q=-0.93\pm 0.03$ (stat) $\pm 0.1$ (sys). This relation constrains the higher acceleration part of the radial acceleration relation observed for rotating galaxies near or below $a_0$. Our results point to a particular direction in theories of dark matter or modified gravity.

[23]  arXiv:1707.08299 [pdf, other]
Title: Assessing the collision nature of coronal mass ejections in the inner heliosphere
Comments: 38 pages, 13 figures, accepted in ApJ Supplement Series
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

There have been few attempts in the past to understand the collision of individual cases of interacting Coronal Mass Ejections (CMEs). We selected 8 cases of interacting CMEs and estimated their propagation and expansion speeds, direction of impact and masses exploiting coronagraphic and heliospheric imaging observations. Using these estimates with ignoring the errors therein, we find that the nature of collision is perfectly inelastic for 2 cases (e.g., 2012 March and November), inelastic for 2 cases (e.g., 2012 June and 2011 August), elastic for 1 case (e.g., 2013 October) and super-elastic for 3 cases (e.g., 2011 February, 2010 May and 2012 September). Admitting large uncertainties in the estimated directions, angular widths and pre-collision speeds; the probability of perfectly inelastic collision for 2012 March and November cases diverge from 98%-60% and 100%-40%, respectively, reserving some probability for other nature of collision. Similarly, the probability of inelastic collision diverge from 95%-50% for 2012 June case, 85%-50% for 2011 August case, and 75%-15% for 2013 October case. We note that probability of super-elastic collision for 2011 February, 2010 May and 2012 September CMEs diverge from 90%-75%, 60%-45% and 90%-50%, respectively. Although the sample size is small, we find a good dependence of nature of collision on CMEs parameters. The crucial pre-collision parameters of the CMEs responsible for increasing the probability of super-elastic collision, in descending order of priority, are their lower approaching speed, higher expansion speed of the following CME over the preceding one, and longer duration of collision phase.

[24]  arXiv:1707.08317 [pdf, ps, other]
Title: Very Large Array multi-band monitoring observations of M 31*
Comments: 18 pages, 3 figures, 2 tables, accepted for publication in ApJ
Subjects: Astrophysics of Galaxies (astro-ph.GA); High Energy Astrophysical Phenomena (astro-ph.HE)

The Andromeda galaxy (M\,31) hosts one of the nearest and most quiescent super-massive black holes, which provides a rare, but promising opportunity for studying the physics of black hole accretion at the lowest state. We have conducted a multi-frequency, multi-epoch observing campaign, using the Karl G. Jansky Very Large Array (VLA) in its extended configurations in 2011-2012, to advance our knowledge of the still poorly known radio properties of M\,31*. For the first time, we detect M\,31* at 10, 15 and 20 GHz, and measure its spectral index, $\alpha \approx -0.45\pm0.08$ (S$_{\nu}$ $\varpropto$ $\nu^{\alpha}$), over the frequency range of 5-20 GHz. The relatively steep spectrum suggests that the observed radio flux is dominated by the optically-thin part of a putative jet, which is located at no more than a few thousand Schwarzschild radii from the black hole. On the other hand, our sensitive radio images show little evidence for an extended component, perhaps except for several parsec-scale "plumes", the nature of which remains unclear. Our data also reveal significant (a few tens of percent) flux variation of M\,31* at 6 GHz, on timescales of hours to days. Furthermore, a curious decrease of the mean flux density, by $\sim$50\%, is found between VLA observations taken during 2002-2005 and our new observations, which might be associated with a substantial increase in the mean X-ray flux of M\,31* starting in 2006.

[25]  arXiv:1707.08328 [pdf, ps, other]
Title: Near-UV transit photometry of HAT-P-32 b with the LBT: Silicate aerosols in the planetary atmosphere
Comments: accepted for publication in Astronomical Notes (AN)
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

Broad-band exoplanet transit photometry can characterize the planetary atmosphere when observed at multiple selected filters. This observing technique can reveal gradients in the spectra of extrasolar planets, for example the slope of decreasing opacity from short to long optical wavelengths caused by aerosol scattering. In this work we observed a transit of the hot Jupiter HAT-P-32 b in the shortest wavelength possible from the ground using the Large Binocular Telescope (LBT). The data comprise the best-quality ground-based U-band taken so far of an exoplanet transit. Compared to broad-band observations of intermediate and long optical wavelength published previously, a clear scattering slope in the planetary transmission spectrum is revealed. Most likely, the scattering particles are magnesium silicate aerosols larger than 0.1 micrometer. We defined a spectral index to compare this scattering feature of HAT-P-32 b to published results of other exoplanets. It turned out to be very typical in amplitude within the comparison sample. Furthermore, we searched for correlation in this sample of the spectral index with planetary equilibrium temperature, surface acceleration and stellar activity indicator, but could not reveal any.

[26]  arXiv:1707.08344 [pdf, ps, other]
Title: The evolution of Galactic planetary nebula progenitors through the comparison of their nebular abundances with AGB yields
Comments: 15 pages, 2 figures, 3tables, accepted for publication in MNRAS
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Astrophysics of Galaxies (astro-ph.GA)

We study the chemical abundances of a wide sample of 142 Galactic planetary nebulae (PNe) with good quality observations, for which the abundances have been derived more or less homogeneously, thus allowing a reasonable comparison with stellar models. The goal is the determination of mass, chemical composition and formation epoch of their progenitors, through comparison of the data with results from AGB evolution. The dust properties of PNe, when available, were also used to further support our interpretation.
We find that the majority ($\sim60\%$) of the Galactic PNe studied has nearly solar chemical composition, while $\sim40\%$ of the sources investigated have sub-solar metallicities. About half of the PNe have carbon star progenitors, in the $1.5~M_{\odot} < M < 3~M_{\odot}$ mass range, which have formed between 300 Myr and 2 Gyr ago. The remaining PNe are almost equally distributed among PNe enriched in nitrogen, which we interpret as the progeny of $M > 3.5~M_{\odot}$ stars, younger than 250 Myr, and a group of oxygen-rich PNe, descending from old ($> 2$ Gyr) low-mass ($M < 1.5~M_{\odot}$) stars that never became C-stars.
This analysis confirms the existence of an upper limit to the amount of carbon which can be accumulated at the surface of carbon stars, probably due to the acceleration of mass loss in the late AGB phases. The chemical composition of the present sample suggests that in massive AGB stars of solar (or slightly sub-solar) metallicity, the effects of third dredge up combine with hot bottom burning, resulting in nitrogen-rich - but not severely carbon depleted - gaseous material to be ejected.

[27]  arXiv:1707.08395 [pdf, ps, other]
Title: The optical vs. mid-infrared spectral properties of 82 Type 1 AGNs: coevolution of AGN and starburst
Comments: Accepted to MNRAS
Subjects: Astrophysics of Galaxies (astro-ph.GA)

We investigated the connection between the mid-infrared (MIR) and optical spectral characteristics in a sample of 82 Type 1 active galactic nuclei (AGNs), observed with Infrared Spectrometer on Spitzer (IRS) and Sloan Digital Sky Survey (SDSS, DR12). We found several interesting correlations between optical and MIR spectral properties: i) as starburst significators in MIR increase, the EWs of optical lines H$\beta$NLR and FeII, increase as well; ii) as MIR spectral index increases, EW([OIII]) decreases, while fractional contribution of AGN (RAGN) is not connected with EW([OIII]); iii) The log([OIII]5007/$\rm H\beta$NLR) ratio is weakly related to the fractional contribution of polycyclic aromatic hydrocarbons (RPAHs). We compare the two different MIR and optical diagnostics for starburst contribution to the overall radiation (RPAH and BPT diagram, respectively). The significant differences between optical and MIR starburst diagnostics were found. The starburst influence to observed correlations between optical and MIR parameters is discussed.

[28]  arXiv:1707.08397 [pdf, ps, other]
Title: The Magellanic Inter-Cloud Project (MAGIC) III: First spectroscopic evidence of a dwarf stripping a dwarf
Authors: Ricardo Carrera (1,2), Blair C. Conn (3), Noelia E. D. Noël (4), Justin I. Read (4), Ángel R López Sánchez (5,6) ((1) Instituto de Astrofísica de Canarias, Spain, (2) Departamento de Astrofísica, Universidad de La Laguna, Spain, (3) Research School of Astronomy and Astrophysics, Mount Stromlo Observatory, Australia, (4) Department of Physics, University of Surrey, UK, (5) Australian Astronomical Observatory, Australia, (6) Department of Physics and Astronomy, Macquarie University, Australia)
Comments: Accepted for publication in MNRAS: 8 pages, 6 figures
Subjects: Astrophysics of Galaxies (astro-ph.GA)

The Magellanic Bridge (MB) is a gaseous stream that links the Large (LMC) and Small (SMC) Magellanic Clouds. Current simulations suggest that the MB forms from a recent interaction between the Clouds. In this scenario, the MB should also have an associated stellar bridge formed by stars tidally stripped from the SMC by the LMC. There are several observational evidences for these stripped stars, from the presence of intermediate age populations in the MB and carbon stars, to the recent observation of an over-density of RR Lyrae stars offset from the MB. However, spectroscopic confirmation of stripped stars in the MB remains lacking. In this paper, we use medium resolution spectra to derive the radial velocities and metallicities of stars in two fields along the MB. We show from both their chemistry and kinematics that the bulk of these stars must have been tidally stripped from the SMC. This is the first spectroscopic evidence for a dwarf galaxy being tidally stripped by a larger dwarf.

[29]  arXiv:1707.08400 [pdf]
Title: Assessments of Ali, Dome A, and Summit Camp for Mm-wave Observations Using MERRA-2 Reanalysis
Authors: Chao-Lin Kuo (Stanford University, SLAC National Accelerator Laboratory)
Comments: 14 pages, 8 figures
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Cosmology and Nongalactic Astrophysics (astro-ph.CO)

The latest MERRA-2 reanalysis of the modern satellite measurements provides unprecedented uniformity and fidelity for the atmospheric data. In this paper, these data are used to evaluate five sites for millimeter-wave (mm-wave) observations. These include two established sites (South Pole and Chajnantor, Atacama), and three new sites (Ali, Tibet; Dome A, Antarctica; and Summit Camp, Greenland). Atmospheric properties including precipitable water vapor (PWV), sky brightness temperature fluctuations, ice and liquid water paths are derived and compared. Dome A emerges to be the best among those evaluated, with PWV and fluctuations smaller than the second-best site, South Pole, by more than a factor of 2. It is found that the higher site in Ali (6,100 m) is on par with Cerro Chajnantor (5,612 m) in terms of transmission and stability. The lower site in Ali (5,250 m) planned for first stage of observations at 90/150GHz provides conditions comparable to those on the Chajnantor Plateau. These analyses confirm Ali to be an excellent mm-wave site on the Northern Hemisphere that will complement well-established sites on the Southern Hemisphere. It is also found in this analysis that the observing conditions at Summit Camp are comparable to Cerro Chajnantor. Although it is more affected by the presence of liquid water clouds.

[30]  arXiv:1707.08402 [pdf, other]
Title: The SAMI Galaxy Survey: Data Release One with Emission-line Physics Value-Added Products
Comments: Submitted to MNRAS. SAMI DR1 data products available from this http URL
Subjects: Astrophysics of Galaxies (astro-ph.GA)

We present the first major release of data from the SAMI Galaxy Survey. This data release focuses on the emission-line physics of galaxies. Data Release One includes data for 772 galaxies, about 20% of the full survey. Galaxies included have the redshift range 0.004 < z < 0.092, a large mass range (7.6 < log(Mstellar/M$_\odot$) < 11.6), and star-formation rates of 10^-4 to 10^1\ M$_\odot$/yr. For each galaxy, we include two spectral cubes and a set of spatially resolved 2D maps: single- and multi-component emission-line fits (with dust extinction corrections for strong lines), local dust extinction and star-formation rate. Calibration of the fibre throughputs, fluxes and differential-atmospheric-refraction has been improved over the Early Data Release. The data have average spatial resolution of 2.16 arcsec (FWHM) over the 15~arcsec diameter field of view and spectral (kinematic) resolution R=4263 (sigma=30km/s) around Halpha. The relative flux calibration is better than 5\% and absolute flux calibration better than $\pm0.22$~mag, with the latter estimate limited by galaxy photometry. The data are presented online through the Australian Astronomical Observatory's Data Central.

[31]  arXiv:1707.08408 [pdf, ps, other]
Title: A Statistical Spectropolarimetric Study of Herbig Ae/Be Stars
Authors: Karim Ababakr (1), Rene Oudmaijer (1), Jorick Vink (2) ((1) Leeds UK, (2) Armagh UK)
Comments: 17 Pages, accepted for publication in MNRAS
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

We present Halpha linear spectropolarimetry of a large sample of Herbig Ae/Be stars. Together with newly obtained data for 17 objects, the sample contains 56 objects, the largest such sample to date. A change in linear polarization across the Halpha line is detected in 42 (75 %) objects, which confirms the previous finding that the circumstellar environment around these stars on small spatial scales has an asymmetric structure, which is typically identified with a disk. A second outcome of this research is that we confirm that Herbig Ae stars are similar to T Tauri stars in displaying a line polarization effect, while depolarization is more common among Herbig Be stars. This finding had been suggested previously to indicate that Herbig Ae stars form in the same manner than T Tauri stars through magnetospheric accretion. It appears that the transition between these two differing polarization line effects occurs around the B7-B8 spectral type. This would in turn not only suggest that Herbig Ae stars accrete in a similar fashion as lower mass stars, but also that this accretion mechanism switches to a different type of accretion for Herbig Be stars. We report that the magnitude of the line effect caused by electron scattering close to the stars does not exceed 2%. Only a very weak correlation is found between the magnitude of the line effect and the spectral type or the strength of the Halpha line. This indicates that the detection of a line effect only relies on the geometry of the line-forming region and the geometry of the scattering electrons.

[32]  arXiv:1707.08444 [pdf]
Title: Circular Polarization and Coherent Backscattering
Authors: Adrian J. Brown
Comments: 13 pages, 5 figures
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Earth and Planetary Astrophysics (astro-ph.EP)

We extend the work of Mishchenko et al. (2000) regarding the exact results of the polarization effect, using the theory of Amic et al. (1997) to derive a model prediction for the polarization coherent opposition effect at small angles. Our extension is to assess the effect of circular polarized light, thus completing exact derivation of the full M\"uller matrix for the semi infinite slab of Rayleigh sized particles. We find the circular polarization peak is narrower than the coherent backscattering intensity peak, and weaker in intensity.

[33]  arXiv:1707.08445 [pdf, ps, other]
Title: Spectroscopy of very hot plasma in non-flaring parts of a solar limb active region: spatial and temporal properties
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

In this work we investigate the thermal structure of an off-limb active region in various non-flaring areas, as it provides key information on the way these structures are heated. In particular, we concentrate in the very hot component (>3 MK) as it is a crucial element to discriminate between different heating mechanisms. We present an analysis using Fe and Ca emission lines from both SOHO/SUMER and HINODE/EIS. A dataset covering all ionization stages from Fe X to Fe XIX has been used for the thermal analysis (both DEM and EM). Ca XIV is used for the SUMER-EIS radiometric cross-calibration.
We show how the very hot plasma is present and persistent almost everywhere in the core of the limb AR. The off-limb AR is clearly structured in Fe XVIII. Almost everywhere, the EM analysis reveals plasma at 10 MK (visible in Fe XIX emission) which is down to 0.1% of EM of the main 3 MK plasma. We estimate the power law index of the hot tail of the EM to be between -8.5 and -4.4. However, we leave an open question on the possible existence of a small minor peak at around 10 MK. The absence in some part of the AR of Fe XIX and Fe XXIII lines (which fall into our spectral range) enables us to determine an upper limit on the EM at such temperatures. Our results include a new Ca XIV 943.59 \AA~ atomic model.

[34]  arXiv:1707.08471 [pdf, other]
Title: Acceleration and propagation of ultra high energy cosmic rays
Authors: Roberto Aloisio
Comments: Solicited review paper accepted for publication by Progress of Theoretical and Experimental Physics. 40 pages, 20 figures. arXiv admin note: substantial text overlap with arXiv:1707.06147
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

We review the physics of the highest energy cosmic rays. The discovery of their sources, still unknown, will reveal the most energetic astrophysical objects in the universe and could unveil new physics beyond the standard model of particle physics. We discuss the details of propagation of these high energy particles, their interaction with astrophysical photon backgrounds and intergalactic magnetic fields, and the production of secondary cosmogenic particles associated to their transport. We examine different models of acceleration, reviewing the principal astrophysical objects that could energise cosmic rays until the highest energies. Given the uncertainties in the observed mass composition, we review the two alternative scenarios of a composition made only by protons or by protons and heavier nuclei; discussing the consequences of the two scenarios in terms of sources, acceleration mechanisms and production of secondary cosmogenic gamma rays and neutrinos.

[35]  arXiv:1707.08473 [pdf, other]
Title: Hard Cosmic Ray Sea in the Galactic Center: a consistent interpretation of H.E.S.S. and Fermi-LAT $γ$-ray data
Authors: D. Gaggero (1), D. Grasso, A. Marinelli (2), M. Taoso (3), A. Urbano (4), S. Ventura (2) ((1) GRAPPA (2) INFN and Universitá Pisa (3) IFT (4) CERN)
Comments: Oral contribution to the International Cosmic Ray Conference (ICRC 2017), 12-20 July 2017, Bexco, Busan, Korea
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

We present a novel interpretation of the gamma-ray diffuse emission measured by H.E.S.S. in the Galactic Center (GC) region and the Galactic ridge. Our starting base is an updated analysis of PASS8 Fermi-LAT data, which allows to extend down to few GeV the spectra measured by H.E.S.S. and to infer the primary CR radial distribution above 100 GeV. We compare those results with a CR transport model assuming a harder scaling of the diffusion coefficient with rigidity in the inner Galaxy. Such a behavior reproduces the radial dependence of the CR spectral index recently inferred from Fermi-LAT measurements in the inner GP. We find that, in this scenario, the bulk of the Galactic ridge emission can be naturally explained by the interaction of the diffuse, steady-state Galactic CR sea interacting with the gas present in the Central molecular zone. The evidence of a GC PeVatron is significantly weaker than that inferred adopting a conventional (softer) CR sea.

[36]  arXiv:1707.08478 [pdf]
Title: GNSS Differential Interferometer
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM)

Baseline azimuth calculation using GPS carrier phase data can be achieved in a classic way by using two or more geodetic synchronized GPS receivers. Such system includes dedicated expensive components and thus is not applicable to many uses. The development of low cost GPS receivers have come to a point where good quality carrier phase measurements are available and double differencing systems utilizing these receivers have proven feasible. Inexpensive receivers like this, combined with attitude determination algorithm, can make accurate attitude determination using GPS accessible to everyone.
Our project consisted of developing a low cost attitude determination system utilizing 2 Fastrax off-the-shelf receivers. Phase and code data from the receivers is processed, filtered and used for attitude determination using double-difference algorithm. Possible applications for such systems are for example: * Civilian - search and rescue equipment * Industrial - low cost geodetic measurement * Military - inexpensive weapon guidance system

[37]  arXiv:1707.08515 [pdf, ps, other]
Title: Modeling The Most Luminous Supernova Associated with a Gamma-Ray Burst, SN 2011kl
Comments: 9 pages, 2 figures, 1 table
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

We study the most luminous known supernova (SN) associated with a gamma-ray burst (GRB), SN$\sim$2011kl. The photospheric velocity of SN$\sim$2011kl around peak brightness is $21,000\pm7000$ km s$^{-1}$. Owing to different assumptions related to the light-curve (LC) evolution (broken or unbroken power-law function) of the optical afterglow of GRB$\sim$111209A, different techniques for the LC decomposition, and different methods (with or without a near-infrared contribution), three groups derived three different bolometric LCs for SN$\sim$2011kl. Previous studies have shown that the LCs without an early-time excess preferred a magnetar model, a magnetar+$^{56}$Ni model, or a white dwarf tidal disruption event model rather than the radioactive heating model. On the other hand, the LC shows an early-time excess and dip that cannot be reproduced by the aforementioned models, and hence the blue-supergiant model was proposed to explain it. Here, we reinvestigate the energy sources powering SN$\sim$2011kl. We find that the two LCs without the early-time excess of SN$\sim$2011kl can be explained by the magnetar+$^{56}$Ni model, and the LC showing the early excess can be explained by the magnetar+$^{56}$Ni model taking into account the cooling emission from the shock-heated envelope of the SN progenitor, demonstrating that this SN might primarily be powered by a nascent magnetar.

[38]  arXiv:1707.08531 [pdf, ps, other]
Title: Cosmological perturbations in the $Λ$CDM-like limit of a polytropic dark matter model
Comments: 14 pages, 7 figures, accepted for publication in Astronomy & Astrophysics
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)

In a recent article, Kleidis and Spyrou (2015) proposed that both dark matter (DM) and dark energy (DE) can be treated as a single component, if accommodated in the context of a polytropic DM fluid with thermodynamical content. Depending only on the polytropic exponent, $-0.103 < \Gamma \leq 0$, this unified DM model reproduces to high accuracy the distance measurements performed with the aid of the supernovae Type Ia (SNe Ia) standard candles, without suffering either from the age or from the coincidence problem. To demonstrate also its compatibility with current observational data concerning structure formation, in the present article we discuss the evolution of cosmological perturbations in the $\Lambda$ CDM-like (i.e., $\Gamma = 0$) limit of the polytropic DM model. The corresponding results are quite encouraging, since, such a model reproduces every major effect already known from conventional (i.e., pressureless cold dark matter - CDM) structure formation theory, such as the constancy of metric perturbations in the vicinity of recombination and the (late-time) Meszaros effect on their rest-mass density counterparts (Meszaros 1974). The non-zero (polytropic) pressure, on the other hand, drives the evolution of small-scale velocity perturbations along the lines of the root-mean-square velocity law of conventional Statistical Physics. As a consequence, in this model "peculiar velocities" slightly increase, instead of being redshifted away by cosmic expansion. What is more important is that, upon consideration of scale-invariant metric perturbations, the spectrum of their rest-mass density counterparts exhibits an effective power-law dependence on the (physical) wavenumber, with the associated scalar spectral index being equal to $n_s = 0.970$; a theoretical value that actually reproduces the corresponding observational (Planck) result (Ade et al. 2016).

[39]  arXiv:1707.08537 [pdf, other]
Title: Radio QPO in the $γ$-ray-loud X-ray binary LS I +61${^\circ}$303
Comments: 5 pages, 4 figures, accepted for publication in MNRAS
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

LS I +61${^\circ}$303 is a $\gamma$-ray emitting X-ray binary with periodic radio outbursts with time scales of one month. Previous observations have revealed microflares superimposed on these large outbursts with periods ranging from a few minutes to hours. This makes LS I +61${^\circ}$303, along with Cyg X-1, the only TeV emitting X-ray binary exhibiting radio microflares. To further investigate these microflaring activity in LS I +61${^\circ}$303 we observed the source with the 100-m Effelsberg radio telescope at 4.85, 8.35, and 10.45 GHz and performed timing analysis on the obtained data. Radio oscillations of 15 hours time scales are detected at all three frequencies. We also compare the spectral index evolution of radio data to that of the photon index of GeV data observed by Fermi-LAT. We conclude that the observed QPO could result from multiple shocks in a jet.

[40]  arXiv:1707.08563 [pdf, other]
Title: HEK VI: On the Dearth of Galilean Analogs in Kepler and the Exomoon Candidate Kepler-1625b I
Comments: Submitted to AAS journals. TTV posteriors available at this https URL
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

Exomoons represent an outstanding challenge in modern astronomy, with the potential to provide rich insights into planet formation theory and habitability. In this work, we stack the phase-folded transits of 284 viable moon hosting Kepler planetary candidates, in order to search for satellites. These planets range from Earth-to-Jupiter sized and from ~0.1 to 1.0 AU in separation - so-called "warm" planets. Our data processing includes two-pass harmonic detrending, transit timing variations, model selection and careful data quality vetting to produce a grand light curve with a r.m.s. of 5.1 ppm. We find that the occurrence rate of Galilean-analog moon systems can be constrained to be $\eta<0.38$ to 95% confidence for the 284 KOIs considered, with a 68.3% confidence interval of $\eta=0.16_{-0.10}^{+0.13}$. A single-moon model of variable size and separation locates a slight preference for a population of Super-Ios, ~0.5 R_Earth moons orbiting at 5-10 planetary radii. However, we stress that the low Bayes factor of just 2 in this region means it should be treated as no more than a hint at this time. Splitting our data into various physically-motivated subsets reveals no strong signal. The dearth of Galilean-analogs around warm planets places the first strong constraint on exomoon formation models to date. Finally, we report evidence for an exomoon candidate Kepler-1625b I, which we briefly describe ahead of scheduled observations of the target with the Hubble Space Telescope.