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J.P. Magué & B. Ménard

[1]
Title: The Very Early Light Curve of SN 2015F in NGC 2442: A Possible Detection of Shock-Heated Cooling Emission and Constraints on SN Ia Progenitor System
Comments: 26 pages, 5 figures, 1 table, accepted for publication in ApJS
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Cosmology and Nongalactic Astrophysics (astro-ph.CO); Astrophysics of Galaxies (astro-ph.GA); Solar and Stellar Astrophysics (astro-ph.SR)

The main progenitor candidate of Type Ia supernovae (SNe Ia) is white dwarfs in binary systems where the companion star is another white dwarf (double degenerate system) or a less evolved non-degenerate star with R* >~ 0.1 Rsun (single degenerate system), but no direct observational evidence exists that tells which progenitor system is more common. Recent studies suggest that the light curve of a supernova shortly after its explosion can be used to set a limit on the progenitor size, R*. Here, we report a high cadence monitoring observation of SN 2015F, a normal SN Ia, in the galaxy NGC 2442 starting about 84 days before the first light time. With our daily cadence data, we catch the emergence of the radioactively powered light curve, but more importantly detect with a > 97.4% confidence a possible dim precursor emission that appears at roughly 1.5 days before the rise of the radioactively powered emission. The signal is consistent with theoretical expectations for a progenitor system involving a companion star with R* = ~0.1 -- 1 Rsun or a prompt explosion of a double degenerate system, but inconsistent with a typically invoked size of white dwarf progenitor of R* ~ 0.01 Rsun. Upper limits on the precursor emission also constrain the progenitor size to be R* < 0.1 Rsun, and a companion star size of R* < ~1.0 Rsun, excluding a very large companion star in the progenitor system. Additionally, we find that the distance to SN 2015F is 23.9 +-0.4 Mpc.

[2]
Title: What is the redshift of the gamma- ray BL Lac source S4 0954+65?
Comments: Minor comment and accepted for publication in Astronomical Journal
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Astrophysical Phenomena (astro-ph.HE)

High signal-to-noise ratio spectroscopic observations of the BL Lac object S4 0954+65 at the alleged redshift z = 0.367 are presented. This source was detected at gamma frequencies by MAGIC (TeV) and FERMI (GeV) telescopes during a remarkable outburst that occurred in February 2015, making the determination of its distance particularly relevant for our understanding of the properties of the Extragalactic Background Light. Contrary to previous reports on the redshift, we found that the optical spectrum is featureless at an equivalent width limit of \sim 0.1 Ang. A critical analysis of the existing observations indicates that the redshift is still unknown. Based on the new data we estimate a lower limit to the redshift at z \geq 0.45.

[3]
Title: Stealing the Gas: Giant Impacts and the Large Diversity in Exoplanet Densities
Comments: 12 pages, 4 figures. Submitted to ApJL
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

Although current sensitivity limits are such that true Solar System analogs remain challenging to detect, numerous planetary systems have been discovered that are very different from our own Solar System. The majority of systems harbor a new class of planets, bodies that are typically several times more massive than the Earth but that orbit their host stars well inside the orbit of Mercury. These planets frequently show evidence for large Hydrogen and Helium envelopes containing several percent of the planet's mass and display a large diversity in mean densities. Here we show that this wide range can be achieved by one or two late giant impacts, which are frequently needed to achieve long-term orbital stability in multiple planet systems once the gas disk has disappeared. We demonstrate using hydrodynamical simulations that a single collision between similarly sized exoplanets can easily reduce the envelope-to-core-mass ratio by a factor of two and show that this leads to a corresponding increase in the observed mean density by factors of 2-3. In addition we investigate how envelope-mass-loss depends on envelope mass, planet radius, semi-major axis, and the mass distribution inside the envelope. We propose that a small number of giant impacts may be responsible for the large observed spread in mean densities, especially for multiple-planet systems containing planets with very different densities and which have not been significantly sculpted by photo evaporation.

[4]
Title: Quark Nugget Dark Matter: Comparison with radio observations of nearby galaxies
Subjects: Astrophysics of Galaxies (astro-ph.GA); High Energy Astrophysical Phenomena (astro-ph.HE)

It has been recently claimed that radio observations of nearby spiral galaxies essentially rule out a dark matter source for the galactic haze. Here we consider the low energy thermal emission from a quark nugget dark matter model in the context of microwave emission from the galactic centre and radio observations of nearby Milky Way like galaxies. We demonstrate that observed emission levels do not strongly constrain this specific dark matter candidate across a broad range of the allowed parameter space in drastic contrast with conventional dark matter models based on the WIMP paradigm.

[5]
Title: Formation of Black Hole Low-Mass X-ray Binaries in Hierarchical Triple Systems
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR)

The formation of Black Hole (BH) Low-Mass X-ray Binaries (LMXB) poses a theoretical challenge, as low-mass companions are not expected to survive the common-envelope scenario with the BH progenitor. Here we propose a formation mechanism that skips the common-envelope scenario and relies on triple-body dynamics. We study the evolution of hierarchical triples, following the secular dynamical evolution up to the octupole-level of approximation, including general relativity, tidal effects and post-main-sequence evolution, such as mass loss, changes to stellar radii and supernovae. During the dynamical evolution of the triple system, the "eccentric Kozai-Lidov" mechanism can cause large eccentricity excitations in the LMXB progenitor, resulting in three main BH-LMXB formation channels. Here we define BH-LMXB candidates as systems where the inner BH companion star crosses its Roche limit. In the "eccentric" channel (~ 81% of the LMXBs in our simulations), the donor star crosses its Roche limit during an extreme eccentricity excitation, while still on a wide orbit. Second, we find a "giant" LMXB channel (~ 11%), where a system undergoes only moderate eccentricity excitations, but the donor star fills its Roche lobe after evolving toward the giant branch. Third, we identify a "classical" channel (~8%), where tidal forces and magnetic braking shrink and circularize the orbit to short periods, triggering mass transfer. Finally, for the giant channel, we predict an eccentric ($\sim 0.3-0.6$), preferably inclined (~40, ~140 degreed) tertiary, typically on a wide enough orbit (~10^4AU), to potentially become unbound later in the triple evolution.

[6]
Title: Growing the gas-giant planets by the gradual accumulation of pebbles
Journal-ref: Nature, Volume 524, Issue 7565, pp. 322-324 (2015)
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

It is widely held that the first step in forming the gas giant planets, such as Jupiter and Saturn, is to form solid cores' of roughly 10 M$_\oplus$. Getting the cores to form before the solar nebula dissipates ($\sim\!1-10\,$Myr) has been a major challenge for planet formation models. Recently models have emerged in which pebbles' (centimeter- to meter-size objects) are first concentrated by aerodynamic drag and then gravitationally collapse to form 100 --- 1000 km objects. These planetesimals' can then efficiently accrete leftover pebbles and directly form the cores of giant planets. This model known as pebble accretion', theoretically, can produce 10 M$_\oplus$ cores in only a few thousand years. Unfortunately, full simulations of this process show that, rather than creating a few 10 M$_\oplus$ cores, it produces a population of hundreds of Earth-mass objects that are inconsistent with the structure of the Solar System. Here we report that this difficulty can be overcome if pebbles form slowly enough to allow the planetesimals to gravitationally interact with one another. In this situation the largest planetesimals have time to scatter their smaller siblings out of the disk of pebbles, thereby stifling their growth. Our models show that, for a large, and physically reasonable region of parameter space, this typically leads to the formation of one to four gas giants between 5 and 15 AU in agreement with the observed structure of the Solar System.

[7]
Title: Growing the terrestrial planets from the gradual accumulation of sub-meter sized objects
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

Building the terrestrial planets has been a challenge for planet formation models. In particular, classical theories have been unable to reproduce the small mass of Mars and instead predict that a planet near 1.5 AU should roughly be the same mass as the Earth. Recently, a new model called Viscous Stirred Pebble Accretion (VSPA) has been developed that can explain the formation of the gas giants. This model envisions that the cores of the giant planets formed from 100 to 1000 km bodies that directly accreted a population of pebbles --- sub-meter sized objects that slowly grew in the protoplanetary disk. Here we apply this model to the terrestrial planet region and find that it can reproduce the basic structure of the inner Solar System, including a small Mars and a low-mass asteroid belt. Our models show that for an initial population of planetesimals with sizes similar to those of the main belt asteroids, VSPA becomes inefficient beyond $\sim\!$1.5 AU. As a result, Mars's growth is stunted and nothing large in the asteroid belt can accumulate.

[8]
Title: Mass Measurements of Isolated Objects from Space-based Microlensing
Comments: 9 papers, 4 figures, 2 tables; to be submitted to ApJ
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Earth and Planetary Astrophysics (astro-ph.EP)

We report on the mass and distance measurements of two single-lens events from the 2015 \emph{Spitzer} microlensing campaign. With both finite-source effect and microlens parallax measurements, we find that the lens of OGLE-2015-BLG-1268 is a $47\pm7$ $M_{\rm J}$ brown dwarf at $5.4\pm1.0$ kpc, and that the lens of OGLE-2015-BLG-0763 is a $0.50\pm0.04$ $M_\odot$ star at $6.9\pm1.0$ kpc. We show that the probability to definitively measure the mass of isolated microlenses, including isolated stellar mass black holes and free floating planets, is dramatically increased once simultaneous ground- and space-based observations are conducted.

[9]
Title: Detectability of Local Group Dwarf Galaxy Analogues at High Redshifts
Subjects: Astrophysics of Galaxies (astro-ph.GA); Cosmology and Nongalactic Astrophysics (astro-ph.CO)

The dwarf galaxies of the Local Group are believed to be similar to the most abundant galaxies during the epoch of reionization (z>6). As a result of their proximity, there is a wealth of information that can be obtained about these galaxies; however, due to their low surface brightnesses, detecting their progenitors at high redshifts is challenging. We compare the physical properties of these dwarf galaxies to those of galaxies detected at high redshifts using Hubble Space Telescope and Spitzer observations and consider the promise of the upcoming James Webb Space Telescope on the prospects for detecting high redshift analogues of these galaxies.

[10]
Title: Observations of supernova remnants and molecular clouds from the mm to the gamma-ray domain: bridging low and high energy cosmic rays
Comments: Highlight talk at ICRC 2015. 19 pages, 8 figures
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

New evidence that cosmic rays (hadronic component) are accelerated by supernova remnant shocks all the way from low energies to high energies, has come from recent works combining gamma-ray observations in the sub-GeV to TeV domain on the one hand, and in the submm-mm domain on the other hand. These observations concern the specific cases of supernova remnants interacting with molecular cloud complexes, that have long been suspected to be ideal laboratories to study in situ cosmic ray acceleration and diffusion. Indeed, enhanced gamma-ray emission from neutral pion decay, as well as enhanced ionization (both by at least one order of magnitude with respect to average galactic values) have been observed in several regions of massive star formation housing supernova remnants interacting with molecular cloud complexes. This paper summarizes the main physical and chemical processes at work, as well as recent observations, that further support the paradigm of cosmic ray acceleration by supernova remnants all the way from the MeV domain up to several tens of TeV, although much work remains to be done to understand cosmic ray penetration and diffusion inside and around molecular clouds, and reveal the actual spectrum of the accelerated cosmic rays.

[11]
Title: The 3D-HST Survey: Hubble Space Telescope WFC3/G141 grism spectra, redshifts, and emission line measurements for $\sim 100,000$ galaxies
Comments: Submitted to ApJS. All 2D and 1D spectra, as well as redshifts, line fluxes, and other derived parameters, are publicly available at available at this http URL
Subjects: Astrophysics of Galaxies (astro-ph.GA); Cosmology and Nongalactic Astrophysics (astro-ph.CO)

We present reduced data and data products from the 3D-HST survey, a 248-orbit HST Treasury program. The survey obtained WFC3 G141 grism spectroscopy in four of the five CANDELS fields: AEGIS, COSMOS, GOODS-S, and UDS, along with WFC3 $H_{140}$ imaging, parallel ACS G800L spectroscopy, and parallel $I_{814}$ imaging. In a previous paper (Skelton et al. 2014) we presented photometric catalogs in these four fields and in GOODS-N, the fifth CANDELS field. Here we describe and present the WFC3 G141 spectroscopic data, again augmented with data from GO-1600 in GOODS-N. The data analysis is complicated by the fact that no slits are used: all objects in the WFC3 field are dispersed, and many spectra overlap. We developed software to automatically and optimally extract interlaced 2D and 1D spectra for all objects in the Skelton et al. (2014) photometric catalogs. The 2D spectra and the multi-band photometry were fit simultaneously to determine redshifts and emission line strengths, taking the morphology of the galaxies explicitly into account. The resulting catalog has 98,663 measured redshifts and line strengths down to $JH_{IR}\leq 26$ and 22,548 with $JH_{IR}\leq 24$, where we comfortably detect continuum emission. Of this sample 5,459 galaxies are at $z>1.5$ and 9,621 are at $0.7<z<1.5$, where H$\alpha$ falls in the G141 wavelength coverage. Based on comparisons with ground-based spectroscopic redshifts, and on analyses of paired galaxies and repeat observations, the typical redshift error for $JH_{IR}\leq 24$ galaxies in our catalog is $\sigma_z \approx 0.003 \times (1+z)$, i.e., one native WFC3 pixel. The $3\sigma$ limit for emission line fluxes of point sources is $1.5\times10^{-17}$ ergs s$^{-1}$ cm$^{-2}$. We show various representations of the full dataset, as well as individual examples that highlight the range of spectra that we find in the survey.

[12]
Title: Warm molecular Hydrogen at high redshift with the James Webb Space Telescope
Comments: 5 pages, 3 figures. To appear in the Proceedings of the annual meeting of the French society of astronomy and astrophysics (SF2A 2015)
Subjects: Astrophysics of Galaxies (astro-ph.GA)

The build-up of galaxies is regulated by a complex interplay between gravitational collapse, galaxy merging and feedback related to AGN and star formation. The energy released by these processes has to dissipate for gas to cool, condense, and form stars. How gas cools is thus a key to understand galaxy formation. \textit{Spitzer Space Telescope} infrared spectroscopy revealed a population of galaxies with weak star formation and unusually powerful H$_2$ line emission. This is a signature of turbulent dissipation, sustained by large-scale mechanical energy injection. The cooling of the multiphase interstellar medium is associated with emission in the H$_2$ lines. These results have profound consequences on our understanding of regulation of star formation, feedback and energetics of galaxy formation in general. The fact that H$_2$ lines can be strongly enhanced in high-redshift turbulent galaxies will be of great importance for the \textit{James Webb Space Telescope} observations which will unveil the role that H$_2$ plays as a cooling agent in the era of galaxy assembly.

[13]
Title: An Exo-Jupiter Candidate in the Eclipsing Binary FL Lyr
Comments: 37 pages, 8 figures, 4 tables
Journal-ref: Astronomy Reports, 2015, Vol. 59, No. 11, pp. 1035-1051
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Earth and Planetary Astrophysics (astro-ph.EP)

Light curves of the eclipsing binary FL Lyr acquired by the Kepler space telescope are analyzed. Eclipse timing measurements for FL Lyr testify to the presence of a third body in the system. Preliminary estimates of its mass and orbital period are > 2M_Jupiter and > 7 yrs. The times of primary minimum in the light curve of FL Lyr during the operation of the Kepler mission are presented.

[14]
Title: Theoretical Model of Non-Conservative Mass Transfer with Uniform Mass Accretion Rate in Contact Binary Stars
Comments: 6 pages, four figures. Accepted for publication in Bulgarian Astronomical Journal
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

In contact binaries mass transfer is usually non-conservative which ends into loss of mass as well as angular momentum in the system. In the present work we have presented a new mathematical model of the non-conservative mass transfer with a uniform mass accretion rate in a contact binary system with lower angular momentum. The model has been developed under the consideration of reverse mass transfer which may occur simultaneously with the original mass transfer as a result of the large scale circulations encircling the entire donor and a significant portion of the gainer. These circulations in contact binaries with lower angular momentum are caused by the overflow of the critical equipotential surface by both the components of the binary system making the governing system more intricate and uncertain.

[15]
Title: The magnetic field of the hot spectroscopic binary HD5550
Comments: 3 pages, 1 figure, proceedings of the SF2A conference
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

HD5550 is a spectroscopic binary composed of two A stars observed with Narval at TBL in the frame of the BinaMIcS (Binarity and Magnetic Interactions in various classes of Stars) Large Program. One component of the system is found to be an Ap star with a surprisingly weak dipolar field of ~65 G. The companion is an Am star for which no magnetic field is detected, with a detection threshold on the dipolar field of ~40 G. The system is tidally locked, the primary component is synchronised with the orbit, but the system is probably not completely circularised yet. This work is only the second detailed study of magnetic fields in a hot short-period spectroscopic binary. More systems are currently being observed with both Narval at TBL and ESPaDOnS at CFHT within the BinaMIcS project, with the goal of understanding how magnetism can impact binary evolution and vice versa.

[16]
Title: The "Binarity and Magnetic Interactions in various classes of Stars" (BinaMIcS) project
Comments: 4 pages, 2 figures, proceedings of the SF2A conference
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

The "Binarity and Magnetic Interactions in various classes of stars" (BinaMIcS) project is based on two large programs of spectropolarimetric observations with ESPaDOnS at CFHT and Narval at TBL. Three samples of spectroscopic binaries with two spectra (SB2) are observed: known cool magnetic binaries, the few known hot magnetic binaries, and a survey sample of hot binaries to search for additional hot magnetic binaries. The goal of BinaMIcS is to understand the complex interplay between stellar magnetism and binarity. To this aim, we will characterise and model the magnetic fields, magnetospheric structure and coupling of both components of hot and cool close binary systems over a significant range of evolutionary stages, to confront current theories and trigger new ones. First results already provided interesting clues, e.g. about the origin of magnetism in hot stars.

[17]
Title: A spectro-polarimetric study of the planet-hosting G dwarf, HD 147513
Comments: 7 pages, 5 figures, accepted by A&A
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

The results from a spectro-polarimetric study of the planet-hosting Sun-like star, HD 147513 (G5V), are presented here. Robust detections of Zeeman signatures at all observed epochs indicate a surface magnetic field, with longitudinal magnetic field strengths varying between 1.0-3.2 G. Radial velocity variations from night to night modulate on a similar timescale to the longitudinal magnetic field measurements. These variations are therefore likely due to the rotational modulation of stellar active regions rather than the much longer timescale of the planetary orbit (Porb=528 d). Both the longitudinal magnetic field measurements and radial velocity variations are consistent with a rotation period of 10 +/- 2 days, which are also consistent with the measured chromospheric activity level of the star (log R'(HK)=-4.64). Together, these quantities indicate a low inclination angle, i~18 degrees. We present preliminary magnetic field maps of the star based on the above period and find a simple poloidal large-scale field. Chemical analyses of the star have revealed that it is likely to have undergone a barium-enrichment phase in its evolution because of a higher mass companion. Despite this, our study reveals that the star has a fairly typical activity level for its rotation period and spectral type. Future studies will enable us to explore the long-term evolution of the field, as well as to measure the stellar rotation period, with greater accuracy.

[18]
Title: Silicates on Iapetus from Cassini's Composite Infrared Spectrometer
Journal-ref: The Astrophysical Journal Letters, 2015, 811(2)
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

We present the first spectral features obtained from Cassini's Composite Infrared Spectrometer (CIRS) for any icy moon. The spectral region covered by CIRS focal planes (FP) 3 and 4 is rich in emissivity features, but previous studies at these wavelengths have been limited by low signal to noise ratios (S/Rs) for individual spectra. Our approach is to average CIRS FP3 spectra to increase the S/R and use emissivity spectra to constrain the composition of the dark material on Iapetus. We find an emissivity feature at ~855 cm-1 and a possible doublet at 660 and 690 cm-1 that do not correspond to any known instrument artifacts. We attribute the 855 cm-1 feature to fine-grained silicates, similar to those found in dust on Mars and in meteorites, which are nearly featureless at shorter wavelengths. Silicates on the dark terrains of Saturn's icy moons have been suspected for decades, but there have been no definitive detections until now. Serpentines reported in the literature at ambient temperature and pressure have features near 855 and 660 cm-1. However, peaks can shift depending on temperature and pressure, so measurements at Iapetus-like conditions are necessary for more positive feature identifications. As a first investigation, we measured muscovite at 125K in a vacuum and found that this spectrum does match the emissivity feature near 855 cm-1 and the location of the doublet. Further measurements are needed to robustly identify a specific silicate, which would provide clues regarding the origin and implications of the dark material.

[19]
Title: Kinematics of the Envelope and Two Bipolar Jets in the Class 0 Protostellar System L1157
Authors: Woojin Kwon (1,2,3), Manuel Fernandez-Lopez (2,4), Ian W. Stephens (2,5), Leslie W. Looney (2) ((1) SRON, (2) University of Illinois, (3) KASI, (4) IAR, (5) Boston University)
Comments: 43 pages, 13 figures, 3 tables, to be published in ApJ
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

A massive envelope and a strong bipolar outflow are the two main structures characterizing the youngest protostellar systems. In order to understand the physical properties of a bipolar outflow and the relationship with those of the envelope, we obtained a mosaic map covering the whole bipolar outflow of the youngest protostellar system L1157 with about $5"$ angular resolution in CO J=2-1 using the Combined Array for Research in Millimeter-wave Astronomy. By utilizing these observations of the whole bipolar outflow, we estimate its physical properties and show that they are consistent with multiple jets. We also constrain a preferred precession direction. In addition, we observed the central envelope structure with $2"$ resolution in the $\lambda=1.3$ and 3 mm continua and various molecular lines: C$^{17}$O, C$^{18}$O, $^{13}$CO, CS, CN, N$_2$H$^+$, CH$_3$OH, H$_2$O, SO, and SO$_2$. All the CO isotopes and CS, CN, and N$_2$H$^+$ have been detected and imaged. We marginally detected the features that can be interpreted as a rotating inner envelope in C$^{17}$O and C$^{18}$O and as an infalling outer envelope in N$_2$H$^+$. We also estimated the envelope and central protostellar masses and found that the dust opacity spectral index changes with radius.

[20]
Title: Line shape variability in a sample of AGN with broad lines
Comments: Accepted in Journal of Astrophysics and Astronomy, Springer
Subjects: Astrophysics of Galaxies (astro-ph.GA)

The spectral variability of active galactic nuclei (AGN) is one of their key features that enables us to study in more details the structure of AGN emitting regions. Especially, the broad line profiles, that vary both in flux and shape, give us invaluable information about the kinematics and geometry of the broad line region (BLR) where these lines are originating from. We give here a comparative review of the line shape variability in a sample of five type 1 AGN, those with broad emission lines in their spectra, of the data obtained from the international long-term optical monitoring campaign coordinated by the Special Astrophysical Observatory of the Russian Academy of Science. The main aim of this campaign is to study the physics and kinematics of the BLR on a uniform data set, focusing on the problems of the photoionization heating of the BLR and its geometry, where in this paper we give for a first time a comparative analysis of the variabilty of five type 1 AGN, discussing their complex BLR physics and geometry in the framework of the estimates of the supermassive black hole mass in AGN.

[21]
Title: The CO2 Abundance in Comets C/2012 K1 (PanSTARRS), C/2012 K5 (LINEAR), and 290P/Jager as Measured with Spitzer
Comments: 29 pages, 6 tables, 7 figures, submitted to Icarus
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

We present analysis of observations of CO2 and OI emission in three comets to measure the CO2 abundance and evaluate the possibility of employing observations of OI emission in comets as a proxy for CO2. We obtained NIR imaging sensitive to CO2 of comets C/2012 K1 (PanSTARRS), C/2012 K5 (LINEAR), and 290P/Jager with the IRAC instrument on Spitzer. We acquired observations of OI emission in these comets with the ARCES echelle spectrometer mounted on the 3.5-meter telescope at Apache Point Observatory and observations of OH with the Swift observatory (PanSTARRS) and with Keck HIRES (Jager). The CO2/H2O ratios derived from the Spitzer images are 12.6 +/- 1.3% (PanSTARRS), 28.9 +/- 3.6% (LINEAR), and 31.3 +/- 4.2% (Jager). These abundances are derived under the assumption that contamination from CO emission is negligible. The CO2 abundance for PanSTARRS is close to the average abundance measured in comets at similar heliocentric distance to date, while the abundances measured for LINEAR and Jager are significantly larger than the average abundance. From the coma morphology observed in PanSTARRS and the assumed gas expansion velocity, we derive a rotation period for the nucleus of about 9.2 hours. Comparison of H2O production rates derived from ARCES and Swift data, as well as other observations, suggest the possibility of sublimation from icy grains in the inner coma. We evaluate the possibility that the OI emission can be employed as a proxy for CO2 by comparing CO2/H2O ratios inferred from the OI lines to those measured directly by Spitzer. We find that for PanSTARRS we can reproduce the observed CO2 abundance to an accuracy of ~20%. For LINEAR and Jager, we were only able to obtain upper limits on the CO2 abundance inferred from the OI lines. These upper limits are consistent with the CO2 abundances measured by Spitzer.

[22]
Title: H$_α$ line as an indicator of envelope presence around the Cepheid Polaris Aa ($α~ UMi$)
Comments: 5 pages, 6 figures, 1 table
Journal-ref: Odessa Astronomical Publications, vol. 28, p.80, 2015
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

We present the results of the radial velocity ($RV$) measurements of metallic lines as well as H$_{\alpha}$ (H$_{\beta}$) obtained in 55 high-resolution spectra of the Cepheid $\alpha$ UMi (Polaris Aa) in 1994-2010. While the $RV$ amplitudes of these lines are roughly equal, their mean $RV$ begin to differ essentially with growth of the Polaris Aa pulsational activity. This difference is accompanied by the H$_{\alpha}$ line core asymmetries on the red side mainly (so-called knife-like profiles) and reaches 8-12 km/s in 2003 with a subsequent decrease to 1.5-2 km/s. We interpret a so unusual behaviour of the H$_{\alpha}$ line core as dynamical changes in the envelope around Polaris Aa.

[23]
Title: Insights into the evolution of symbiotic recurrent novae from radio synchrotron emission: V745 Scorpii and RS Ophiuchi
Comments: Accepted for publication in MNRAS Letters
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

We present observations at 610 MHz and 235 MHz using the Giant Metrewave Radio Telescope (GMRT) of the recurrent nova V745 Scorpii which recorded its last outburst on 6 February 2014. This is the second symbiotic recurrent nova whose light curve at GMRT frequencies has been followed in detail, the first being RS Ophiuchi in 2006. We fitted the 610 MHz light curve by a model of synchrotron emission from an expanding shell being modified by radiative transfer effects due to local absorbing gas consisting of a uniformly distributed and a clumpy component. Using our model parameters, we find that the emission at 235 MHz peaked around day 35 which is consistent with our GMRT observations. The two main results of our study are: (1) The radio emission at a given frequency is visible sooner after the outburst in successive outbursts of both V745 Scorpii and RS Ophiuchi. The earlier detection of radio emission is interpreted to be caused by decreasing foreground densities. (2) The clumpy material is located close to the white dwarf which we interpret as being due to the material from the hot accretion disk. The uniform density gas is widespread and attributed to the winds blown by the white dwarf. We present implications of these results on the evolution of both novae. Such studies alongwith theoretical understanding have the potential of resolving several outstanding issues such as why all recurrent novae are not detectable in synchrotron radio and whether recurrent novae are progenitor systems of type 1a supernova.

[24]
Title: Validation of LAMOST Stellar Parameters with the PASTEL Catalog
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

Recently the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) published its first data release (DR1), which is ranked as the largest stellar spectra dataset in the world so far. We combine the PASTEL catalog and SIMBAD radial velocities as a testing standard to validate the DR1 stellar parameters (effective temperature $T_{\mathrm{eff}}$, surface gravity $\log g$, metallicity $\mathrm{[Fe/H]}$ and radial velocity $V_{\mathrm{r}}$). Through cross-identification of the DR1 catalogs and the PASTEL catalog, we obtain a preliminary sample of 422 stars. After removal of stellar parameter measurements from problematic spectra and applying effective temperature constraints to the sample, we compare the stellar parameters from DR1 with those from PASTEL and SIMBAD to prove that the DR1 results are reliable in restricted $T_{\mathrm{eff}}$ ranges. We derive standard deviations of 110 K, 0.19 dex, 0.11 dex and 4.91 $\mathrm{km\,s^{-1}}$ , for $T_{\mathrm{eff}}$, $\log g$, $[\mathrm{Fe/H}]$ when $T_{\mathrm{eff}}<8000\,\mathrm{K}$, and for $V_{\mathrm{r}}$ when $T_{\mathrm{eff}}<10000\,\mathrm{K}$, respectively. Systematic errors are negligible except for that of $V_{\mathrm{r}}$. Besides, metallicities in DR1 are systematically higher than those in PASTEL, in the range of PASTEL $[\mathrm{Fe/H}]<-1.5$.

[25]
Title: Discovery of an Edge-on Debris Disk with a Dust Ring and an Outer Disk Wing-tilt Asymmetry
Comments: 13 pages, 3 figures, accepted for publication in ApJL
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

Using VLT/SPHERE near-infrared dual-band imaging and integral field spectroscopy we discovered an edge-on debris disk around the 17\,Myr old A-type member of the Scorpius-Centaurus OB association HD 110058. The edge-on disk can be traced to about 0.6" or 65 AU projected separation. In its northern and southern wings, the disk shows at all wavelengths two prominent, bright and symmetrically placed knots at 0.3" or 32 AU from the star. We interpret these knots as a ring of planetesimals whose collisions may produce most of the dust observed in the disk. We find no evidence for a bow in the disk, but we identify a pair of symmetric, hook-like features in both wings. Based on similar features in the Beta Pictoris disk we propose that this wing-tilt asymmetry traces either an outer planetesimal belt that is inclined with respect to the disk midplane or radiation-pressure-driven dust blown out from a yet unseen, inner belt which is inclined with respect to the disk midplane. The misaligned inner or outer disk may be a result of interaction with a yet unseen planet. Overall, the disk geometry resembles the nearby disk around Beta Pictoris, albeit seen at smaller radial scales.

[26]
Title: Discovery of a Two-Armed Spiral Structure in the Gapped Disk in HD 100453
Comments: 12 pages, 5 figures, accepted for publication in ApJL
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)

We present VLT/SPHERE adaptive optics imaging in Y$-$, J$-$, H$-$, and K-bands of the HD 100453 system and the discovery of a two-armed spiral structure in a disk extending to 0.37" ($\sim$42 AU) from the star, with highly symmetric arms to the Northeast and Southwest. Inside of the spiral arms, we resolve a ring of emission from 0.18"-0.25" ($\sim$21-29 AU). By assuming that the ring is intrinsically circular we estimate an inclination of $\sim$34$^{o}$ from face-on. We detect dark crescents on opposite sides (NW and SE) which begin at 0.18" and continue to radii smaller than our inner working angle of 0.15", which we interpret as the signature of a gap at $\lesssim$21 AU that has likely been cleared by forming planets. We also detect the $\sim$120 AU companion HD 100453 B, and by comparing our data to 2003 HST/ACS and VLT/NACO images we estimate an orbital period of $\sim$850 yr. We discuss what implications the discovery of the spiral arms and finer structures of the disk may have on our understanding of the possible planetary system in HD 100453, and how the morphology of this disk compares to other related objects.

[27]
Title: Determining the evolutionary stage of HD163899 on the basis of its oscillation spectrum
Comments: 6 pages, 4 figures, conference
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

We present the new interpretation of the oscillation spectrum of HD 163899 based on the new determinations of the effective temperature, mass-luminosity ratio and rotational velocity. These new parameters strongly prefer the more massive models than previously considered. Now it is also possible that the star could be in the main sequence stage. Using the oscillation spectrum as a gauge, we intend to establish which stage of evolution corresponds better to HD 163899.

[28]
Title: Physical conditions in the central molecular zone inferred by H3+
Subjects: Astrophysics of Galaxies (astro-ph.GA)

The H3+ molecule has been detected in many lines of sight within the central molecular zone (CMZ) with exceptionally large column densities and unusual excitation properties compared to diffuse local clouds. The detection of the (3,3) metastable level has been suggested to be the signature of warm and diffuse gas in the CMZ. We use the Meudon PDR code to re-examine the relationship between the column density of H3+ and the cosmic-ray ionization rate, $\zeta$, up to large values of $\zeta$. We study the impact of the various mechanisms that can excite H3+ in its metastable state. We produce grids of PDR models exploring different parameters ($\zeta$, size of clouds, metallicity) and infer the physical conditions that best match the observations toward ten lines of sight in the CMZ. For one of them, Herschel observations of HF, OH+, H2O+, and H3O+ can be used as additional constraints. We check that the results found for H3+ also account for the observations of these molecules. We find that the linear relationship between N(H3+) and $\zeta$ only holds up to a certain value of the cosmic-ray ionization rate, which depends on the proton density. A value $\zeta \sim 1 - 11 \times 10^{-14}$ s$^{-1}$ explains both the large observed H3+ column density and its excitation in the metastable level (3,3) in the CMZ. It also reproduces N(OH+), N(H2O+) and N(H3O+) detected toward Sgr B2(N). We confirm that the CMZ probed by H3+ is diffuse, nH $\lesssim$ 100 cm-3 and warm, T $\sim$ 212-505 K. This warm medium is due to cosmic-ray heating. We also find that the diffuse component probed by H3+ must fill a large fraction of the CMZ. Finally, we suggest the warm gas in the CMZ enables efficient H2 formation via chemisorption sites as in PDRs. This contributes to enhance the abundance of H3+ in this high cosmic-ray flux environment.

[29]
Title: As above, so below: exploiting mass scaling in black hole accretion to break degeneracies in spectral interpretation
Authors: Sera Markoff (U Amsterdam), Michael Nowak (MIT), Elena Gallo (U Michigan), Robert Hynes (LSU), Jörn Wilms (U Erlangen-Nürnberg), Richard M. Plotkin (U Michigan), Dipankar Maitra (Wheaton College), Catia V. Silva (U Amsterdam/SRON), Samia Drappeau (IRAP)
Comments: 6 pages, 5 Figures, 1 Table, accepted for publication in ApJL
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Astrophysics of Galaxies (astro-ph.GA)

Over the last decade, the evidence is mounting that several aspects of black hole accretion physics proceed in a mass-invariant way. One of the best examples of this scaling is the empirical "Fundamental Plane of Black Hole Accretion" relation linking mass, radio and X-ray luminosity over eight orders of magnitude in black hole mass. The currently favored theoretical interpretation of this relation is that the physics governing power output in weakly accreting black holes depends more on relative accretion rate than on mass. In order to test this theory, we explore whether a mass-invariant approach can simultaneously explain the broadband spectral energy distributions from two black holes at opposite ends of the mass scale but at similar Eddington accretion fractions. We find that the same model, with the same value of several fitted physical parameters expressed in mass-scaling units to enforce self-similarity, can provide a good description of two datasets from V404 Cyg and M81*, a stellar and supermassive black hole, respectively. Furthermore, only one of several potential emission scenarios for the X-ray band is successful, suggesting it is the dominant process driving the Fundamental Plane relation at this accretion rate. This approach thus holds promise for breaking current degeneracies in the interpretation of black hole high-energy spectra, and for constructing better prescriptions of black hole accretion for use in various local and cosmological feedback applications.

[30]
Subjects: Astrophysics of Galaxies (astro-ph.GA); High Energy Astrophysical Phenomena (astro-ph.HE)

The dependence of the cosmic ray intensity on Galactocentric distance is known to be much less rapid than that to be thought-to-be sources: supernova remnants. This is an old problem ('the radial gradient problem') which has led to a number of possible 'scenarios'. Here, we use recent data on the supernova's radial distribution and correlate it with the measured HII electron temperature ({\em T}). We examined two models of cosmic ray injection and acceleration and in both of them the injection efficiency increases with increasing ambient temperature {\em T}. The increase is expected to vary as a high power of {\em T} in view of the strong temperature dependence of the tail of the Maxwell-Boltzmann distribution of particle energies. Writing the efficiency as proportional to $T^n$ we find $n\approx 8.4$. There is thus, yet another possible explanation of the radial gradient problem.

[31]
Title: Ongoing star formation in the proto-cluster IRAS 22134+5834
Comments: 22 pages, 17 figures, Accepted by A&A in Oct. 2015
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Astrophysics of Galaxies (astro-ph.GA)

IRAS 22134+5834 was observed in the centimeter with (E)VLA, 3~mm with CARMA, 2~mm with PdBI, and 1.3~mm with SMA, to study the continuum emission as well as the molecular lines, that trace different physical conditions of the gas to study the influence of massive YSOs on nearby starless cores, and the possible implications in the clustered star formation process. The multi-wavelength centimeter continuum observations revealed two radio sources within the cluster, VLA1 and VLA2. VLA1 is considered to be an optically thin UCHII region with a size of 0.01~pc and sits at the edge of the near-infrared (NIR) cluster. The flux of ionizing photons of the VLA1 corresponds to a B1 ZAMS star. VLA2 is associated with an infrared point source and has a negative spectral index. We resolved six millimeter continuum cores at 2~mm, MM2 is associated with the UCHII region VLA1, and other dense cores are distributed around the UCH{\sc ii} region. Two high-mass starless clumps (HMSC), HMSC-E (east) and HMSC-W (west), are detected around the NIR cluster with N$_2$H$^+$(1--0) and NH$_3$ emission, and show different physical and chemical properties. Two N$_2$D$^+$ cores are detected on an NH$_3$ filament close to the UCHII region, with a projected separation of $\sim$8000~AU at the assumed distance of 2.6~kpc. The kinematic properties of the molecular line emission confirm the expansion of the UCHII region and that the molecular cloud around the near infrared (NIR) cluster is also expanding. Our multi-wavelength study has revealed different generations of star formation in IRAS 22134+5834. The formed intermediate- to massive stars show strong impact on nearby starless clumps. We propose that while the stellar wind from the UCHII region and the NIR cluster drives the large scale bubble, the starless clumps and HMPOs formed at the edge of the cluster.

[32]
Title: Spectral analysis of Uranus' 2014 bright storm with VLT/SINFONI
Journal-ref: Icarus 264 (2016) 72 - 89
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

An extremely bright storm system observed in Uranus' atmosphere by amateur observers in September 2014 triggered an international campaign to observe this feature with many telescopes across the world. Observations of the storm system in the near infrared were acquired in October and November 2014 with SINFONI on ESO's Very Large Telescope (VLT) in Chile. SINFONI is an Integral Field Unit spectrometer returning 64x64 pixel images with 2048 wavelengths. Image cubes in the H-band (1.43 - 1.87 microns) were obtained at spatial resolutions of ~0.1". The observations show that the centre of the storm feature shifts markedly with increasing altitude, moving in the retrograde direction and slightly poleward with increasing altitude. We also see a faint 'tail' of more reflective material to the immediate south of the storm, which again trails in the retrograde direction. The observed spectra were analysed with the radiative transfer and retrieval code, NEMESIS. We find that the storm is well-modelled using either two main cloud layers of a 5-layer aerosol model based on Sromovsky et al. (2011) or by the simpler two-cloud-layer model of Tice et al. (2013). The deep component appears to be due to an increase in reflectivity and altitude of the main tropospheric cloud deck at 2 - 3 bars for both models, while the upper component of the feature was modelled as being due to either a thickening of the tropospheric haze of the 2-layer model or a vertical extension of the upper tropospheric cloud of the 5-layer model, assumed to be composed of methane ice and based at the methane condensation level at 1.23 bar. During the twelve days between our sets of observations the higher-altitude component of the feature was observed to have brightened significantly and extended to even higher altitudes, while the deeper component faded.

[33]
Title: IVOA Recommendation: Registry Relational Schema Version 1.0
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM)

Registries provide a mechanism with which VO applications can discover and select resources - first and foremost data and services - that are relevant for a particular scientific problem. This specification defines an interface for searching this resource metadata based on the IVOA's TAP protocol. It specifies a set of tables that comprise a useful subset of the information contained in the registry records, as well as the table's data content in terms of the XML VOResource data model. The general design of the system is geared towards allowing easy authoring of queries.

[34]
Title: An Intermediate-Mass Black Hole Candidate in M51?
Authors: H.M. Earnshaw
Comments: 6 pages, 4 figures, conference proceedings from the 2015 XMM-Newton Science Workshop, to be published in Astronomical Notes (Astronomische Nachrichten)
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

We present the current results of an investigation into M51 ULX-7, using archival data from XMM-Newton, Chandra and NuSTAR, and optical and radio data from HST and VLA. The source has a consistently hard power-law X-ray spectrum and high short-term variability. This is unusual variability behaviour for a ULX, as we would expect highly variable ULXs to have soft energy spectra. The power spectrum features a break at ~1e-3 Hz, from low frequency spectral index alpha=0.1 to high frequency spectral index alpha=0.8, analogous to the low frequency break found in power spectra of black holes accreting in the low/hard state. We do not observe a corresponding high frequency break, however taking the white noise level as a frequency lower limit of the break, we can calculate a black hole mass upper limit of 9.12e4 solar masses, assuming that the ULX is in the low/hard state. While there is no radio detection, we find a flux density upper limit of 87 micro-Jy/beam. Using the X-ray/radio fundamental plane, we calculate a black hole mass upper limit of 1.95e5 solar masses. Therefore, this ULX is consistent with being an IMBH accreting in the low/hard state.

[35]
Title: Size and albedo distributions of asteroids in cometary orbits using WISE data
Comments: 10 pages, 10 figures, A&A in press
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

We study the distributions of effective diameter ($D$), beaming parameter ($\eta$), and visible geometric albedo ($p_V$) of asteroids in cometry orbits (ACOs) populations, derived from NASA's Wide-field Infrared Explorer (WISE) observations, and compare these with the same, independently determined properties of the comets. The near-Earth asteroid thermal model (NEATM) is used to compute the $D$, $p_V$ and $\eta$. We obtained $D$ and $p_V$ for 49 ACOs in Jupiter family cometary orbits (JF-ACOs) and 16 ACOs in Halley-type orbits (Damocloids). We also obtained $\eta$ for 45 of them. All but three JF-ACOs (95% of the sample) present a low albedo compatible with a cometary origin. The $p_V$ and $\eta$ distributions of both ACO populations are very similar. For the entire sample of ACOs, the mean geometric albedo is $\bar{p_V} = 0.05 \pm 0.02$, ($\bar{p_V} = 0.05 \pm 0.01$ and $\bar{p_V} =0.05 \pm 0.02$ for JF-ACOs and Damocloids, respectively) compatible with a narrow albedo distribution similar to that of the Jupiter family comets (JFCs), with a $\bar{p_V} \sim 0.04$. The $\bar{\eta} =1.0 \pm 0.2$. We find no correlations between $D$, $p_V$ , or $\eta$. We compare the cumulative size distribution (CSD) of ACOs, Centaurs, and JFCs. Although the Centaur sample contains larger objects, the linear parts in their log-log plot of the CSDs presents a similar cumulative exponent ($\beta = 1.85 \pm 0.30$ and $1.76 \pm 0.35$, respectively). The CSD for Damocloids presents a much shallower exponent $\beta = 0.89 \pm 0.17$. The CSD for JF-ACOs is shallower and shifted towards larger diameters with respect to the CSD of active JFCs, which suggests that the mantling process has a size dependency whereby large comets tend to reach an inactive stage faster than small ones. Finally, the population of JF-ACOs is comparable in number that of JFCs, although there are more tens-km JF-ACOs than JFCs.

[36]
Title: The Effect of Interplanetary Scintillation on Epoch of Reionisation Power Spectra
Comments: Accepted to the Astrophysical Journal; 21 pages, 6 figures
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); Solar and Stellar Astrophysics (astro-ph.SR)

Interplanetary Scintillation (IPS) induces intensity fluctuations in small angular size astronomical radio sources via the distortive effects of spatially and temporally varying electron density associated with outflows from the Sun. These radio sources are a potential foreground contaminant signal for redshifted HI emission from the Epoch of Reionisation (EoR) because they yield time-dependent flux density variations in bright extragalactic point sources. Contamination from foreground continuum sources complicates efforts to discriminate the cosmological signal from other sources in the sky. In IPS, at large angles from the Sun applicable to EoR observations, weak scattering induces spatially and temporally correlated fluctuations in the measured flux density of sources in the field, potentially affecting the detectability of the EoR signal by inducing non-static variations in the signal strength. In this work, we explore the impact of interplanetary weak scintillation on EoR power spectrum measurements, accounting for the instrumental spatial and temporal sampling. We use published power spectra of electron density fluctuations and parameters of EoR experiments to derive the IPS power spectrum in the wavenumber phase space of EoR power spectrum measurements. The contrast of IPS power to expected cosmological power is used as a metric to assess the impact of IPS. We show that IPS has a different spectral structure to power from foregrounds alone, but the additional leakage into the EoR observation parameter space is negligible under typical IPS conditions, unless data are used from deep within the foreground contamination region.

[37]
Title: Effect of an isotropic outflow from the Galactic centre on the bow-shock evolution along the orbit
Comments: 20 pages, 36 figures; accepted by MNRAS Main Journal
Subjects: Astrophysics of Galaxies (astro-ph.GA)

Motivated by the observations of several infrared-excess bow-shock sources and proplyd-like objects near the Galactic centre, we analyse the effect of a potential outflow from the centre on bow shock properties. We show that due to the non-negligible isotropic central outflow the bow-shock evolution along the orbit becomes asymmetric between the pre-peribothron and post-peribothron phases. This is demonstrated by the calculation of the bow-shock size evolution, the velocity along the shocked layer, the surface density of the bow-shock, and by emission-measure maps close to the peribothron passage. Within the ambient velocity range of $\lesssim 2000\,{\rm km\, s^{-1}}$ the asymmetry is profound and the changes are considerable for different outflow velocities. As a case study we perform model calculations for the Dusty S-cluster Object (DSO/G2) as a potential young stellar object that is currently being monitored and has passed the pericentre at $\sim 2000$ Schwarzschild radii from the supermassive black hole (Sgr A*) in 2014. We show that the velocity field of the shocked layer can contribute to the observed increasing line width of the DSO source up to the peribothron. Subsequently, supposing that the line emission originates in the bow shock, a decrease of the line width is expected. Furthermore, the decline of the bow-shock emission measure in the post-peribothron phase could help to reveal the emission of the putative star. The dominant contribution of circumstellar matter (either inflow or outflow) is consistent with the observed stable luminosity and compactness of the DSO/G2 source during its pericentre passage.

[38]
Title: Non-LTE Equivalent Widths for NII with Error Estimates
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

Non-LTE calculations are performed for NII in stellar atmospheric models appropriate to main sequence B-stars to produce new grids of equivalent widths for the strongest NII lines commonly used for abundance analysis. There is reasonable agreement between our calculations and previous results, although we find weaker non-LTE effects in the strongest optical NII transition. We also present a detailed estimation of the uncertainties in the equivalent widths due to inaccuracies in the atomic data via Monte Carlo simulation and investigate the completeness of our model atom in terms of included energy levels. Uncertainties in the basic NII atomic data limit the accuracy of abundance determinations to ~+/-0.10 dex at the peak of the NII optical spectrum near Teff~ 24,000 K.

[39]
Title: Detailed modelling of the 21-cm Forest
Authors: Benoit Semelin
Comments: 13 pages, accepted for publication in MNRAS
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)

The 21-cm forest is a promising probe of the Epoch of Reionization. The local state of the intergalactic medium (IGM) is encoded in the spectrum of a background source (radio-loud quasars or gamma ray burst afterglow) by absorption at the local 21-cm wavelength, resulting in a continuous and fluctuating absorption level. Small-scale structures (filaments and minihaloes) in the IGM are responsible for the strongest absorption features. The absorption can also be modulated on large scales by inhomogeneous heating and Wouthuysen-Field coupling.
We present the results from a simulation that attempts to preserve the cosmological environment while resolving some of the small-scale structures (a few kpc resolution in a 50 Mpc/h box). The simulation couples the dynamics and the ionizing radiative transfer and includes X-ray and Lyman lines radiative transfer for a detailed physical modelling. As a result we find that soft X-ray self-shielding, Lyman-alpha self-shielding and shock heating all have an impact on the predicted values of the 21-cm optical depth of moderately overdense structures like filaments. An correct treatment of the peculiar velocities is also critical. Modelling these processes seems necessary for accurate predictions and can be done only at high enough resolution. As a result, based on our fiducial model, we estimate that LOFAR should be able to detect a few (strong) absorptions features in a frequency range of a few tens of MHz for a 20 mJy source located at z=10, while the SKA would extract a large fraction of the absorption information for the same source.

[40]
Title: Kinematic properties of the dual AGN system J0038+4128 based on long-slit spectroscopy
Authors: Yang-Wei Zhang (YNAO), Yang Huang (PKU), Jin-Ming Bai (YNAO), Xiao-Wei Liu (PKU, KIAA), Jian-Guo Wang (YNAO)
Comments: 12 pages, 5 figures, 3 tables, Research in Astronomy and Astrophysics accepted
Subjects: Astrophysics of Galaxies (astro-ph.GA)

The study of kiloparsec-scale dual active galactic nuclei (AGN) will provide important clues to understand the co-evolution between the host galaxies and their central supermassive black holes undergoing a merging process. We present long-slit spectroscopy of the J0038$+$4128, a kiloparsec-scale dual AGN candidate discovered by Huang et al. recently, using the Yunnan Faint Object Spectrograph and Camera (YFOSC) mounted on Li-Jiang 2.4-m telescope at Yunnan observatories. From the long-slit spectra, we find that the average relative line-of-sight (LOS) velocity between the two nuclei (J0038$+$4128N and J0038$+$4128S) is about 150 km s$^{-1}$. The LOS velocities of the emission lines from the gas ionized by the nuclei activities and of the absorption lines from stars governed by the host galaxies for different regions of the J0038$+$4128 exhibit the same trend. The same velocities trend indicates that the gaseous disks are co-rotating with the stellar disks in this ongoing merge system. We also find several knots/giant HII regions scattered around the two nuclei with strong star formation revealed by the observed line ratios from the spectra. Those regions are also detected clearly in HST $F336W/U$-band and HST $F555W/V$-band images.

[41]
Title: Optical and X-ray Variability of Blazars
Authors: A. C. Gupta
Comments: 2 pages, Accepted for publication to ASI Conference Series for RETCO II held at ARIES in May 6-8, 2015
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Cosmology and Nongalactic Astrophysics (astro-ph.CO)

Here we report our recent results of variability studies in optical and X-ray bands of three blazars namely 3C 273, PKS 2155 - 304 and BL Lacertae with XMM-Newton. We found large amplitude optical to X-rays variability in 3C 273, and PKS 2155 - 304 on year time scale. In 3C 273, we noticed that synchrotron cooling and particle acceleration are at work at different epoch of observations. In PKS 2155 - 304, spectral energy distribution from optical to X-ray is fitted with LPPL (log parabolic + power law) model. In BL Lacertae, optical flux and degree of polarization were anti-correlated.

[42]
Title: Wave-like Formation of Hot Loop Arcades
Comments: Published in Solar Physics, 2015. Online first
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

We present observations of hot arcades made with the Mg XII spectroheliograph onboard the CORONAS-F mission, which provides monochromatic images of hot plasma in the Mg XII 8.42 A resonance line. The arcades were observed to form above the polarity inversion line between Active Regions NOAA 09847 and 09848 at four successive episodes: at 09:18, 14:13, and 22:28 UT on 28 February 2002, and at 00:40 UT on 1 March 2002. The arcades all evolved in the same way: a) a small flare (precursor) appeared near the edge of the still invisible arcade, b) the arcade brightened in a wave-like manner - closer loops brightened earlier, and c) the arcade intensity gradually decreased in $\approx$ 1 h. The estimated wave speed was $\approx$ 700 km s$^{-1}$, and the distance between the hot loops was $\approx$ 50 Mm. The arcades formed without visible changes in their magnetic structure. The arcades were probably heated up by the instabilities of the current sheet above the arcade, which were caused by an MHD wave excited by the precursor.

[43]
Title: V2653 Ophiuchii with a pulsating component and Ppuls-Porb, Ppuls-g correlations for gamma-Dor type pulsators
Comments: 40 pages, 10 figures, accepted by New Astronomy
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

We present new spectroscopic observations of the double-lined eclipsing binary V2653\,Oph. The photometric observations obtained by $ASAS$ were analysed and combined with the analysis of radial velocities for deriving the absolute parameters of the components. Masses and radii were determined for the first time as M$_p$=1.537$\pm$0.021 M$_{\odot}$ and R$_p$=2.215$\pm$0.055 R$_{\odot}$, M$_s$=1.273$\pm$0.019 M$_{\odot}$ and R$_s$=2.000$\pm$0.056 R$_{\odot}$ for the components of V2653\,Oph. We estimate an interstellar reddening of 0.15$\pm$0.08\,mag and a distance of 300$\pm$50\,pc for the system, both supporting the membership of the open cluster Collinder\,359. Using the out-of-eclipse photometric data we have made frequency analysis and detected a periodic signal at 1.0029$\pm$0.0019\,c/d. This frequency and the location of the more massive star on the HR diagram lead to classification of a $\gamma$ Dor type variable. Up to date only eleven $\gamma$ Dor type pulsators in the eclipsing binaries have been discovered. For six out of 11 systems, the physical parameters were determined. Although a small sample, we find empirical relations that $P_{puls}$ $\propto$ $P_{orb}^{0.43}$ and $P_{puls}$ $\propto$ $g^{-0.83}$. While the pulsation periods increase with longer orbital periods, they decrease with increasing surface gravities of pulsating components and gravitational pull exerted by the companions. We present, briefly, the underlying physics behind

[44]
Title: A study of spatial correlations in pulsar timing array data
Comments: 13 pages, 7 figures. Accepted for publication in MNRAS
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Solar and Stellar Astrophysics (astro-ph.SR)

Pulsar timing array experiments search for phenomena that produce angular correlations in the arrival times of signals from millisecond pulsars. The primary goal is to detect an isotropic and stochastic gravitational wave background. We use simulated data to show that this search can be affected by the presence of other spatially correlated noise, such as errors in the reference time standard, errors in the planetary ephemeris, the solar wind and instrumentation issues. All these effects can induce significant false detections of gravitational waves. We test mitigation routines to account for clock errors, ephemeris errors and the solar wind. We demonstrate that it is non-trivial to find an effective mitigation routine for the planetary ephemeris and emphasise that other spatially correlated signals may be present in the data.

[45]
Title: ALMA unveils a triple merger and gas exchange in a hyper-luminous radio galaxy at z=2: the Dragonfly Galaxy (II)
Authors: B.H.C. Emonts (1), C. De Breuck (2), M.D. Lehnert (3), J. Vernet (2), B. Gullberg (2), M. Villar-Martín (1), N. Nesvadba (4), G. Drouart (5), R. Ivison (2,6), N. Seymour (7), D. Wylezalek (8), P. Barthel (9) ((1) Centro de Astrobiología (CSIC/INTA), (2) ESO, (3) IAP, (4) IAS, (5) Onsala, (6), Univ. of Edinburgh, (7) ICRAR, (8) Johns Hopkins Univ., (9) Kapteyn Astronomical Institute)
Comments: Accepted for publication in A&A (6 pages, 5 figures)
Subjects: Astrophysics of Galaxies (astro-ph.GA)

The Dragonfly Galaxy (MRC0152-209), at redshift z~2, is one of the most vigorously star-forming radio galaxies in the Universe. What triggered its activity? We present ALMA Cycle 2 observations of cold molecular CO(6-5) gas and dust, which reveal that this is likely a gas-rich triple merger. It consists of a close double nucleus (separation ~4 kpc) and a weak CO-emitter at ~10 kpc distance, all of which have counterparts in HST/NICMOS imagery. The hyper-luminous starburst and powerful radio-AGN were triggered at this precoalescent stage of the merger. The CO(6-5) traces dense molecular gas in the central region, and complements existing CO(1-0) data, which revealed more widespread tidal debris of cold gas. We also find ~10$^{10}$ M(sun) of molecular gas with enhanced excitation at the highest velocities. At least 20-50% of this high-excitation, high-velocity gas shows kinematics that suggests it is being displaced and redistributed within the merger, although with line-of-sight velocities of |v| < 500 km/s, this gas will probably not escape the system. The processes that drive the redistribution of cold gas are likely related to either the gravitational interaction between two kpc-scale discs, or starburst/AGN-driven outflows. We estimate that the rate at which the molecular gas is redistributed is at least ~1200 +- 500 M(sun)/yr, and could perhaps even approach the star formation rate of ~3000 +- 800 M(sun)/yr. The fact that the gas depletion and gas redistribution timescales are similar implies that dynamical processes can be important in the evolution of massive high-z galaxies.

[46]
Title: Hierarchical Bayesian approach for estimating physical properties in spiral galaxies: Age Maps for M74
Comments: 12 pages, 6 figures, conference
Journal-ref: 4th International Conference on Mathematical Modeling in Physical Sciencies (IC-MSquare2015) IOP Publishing. Journal of Physics: Conference Series 633 (2015) 012140
Subjects: Astrophysics of Galaxies (astro-ph.GA)

One of the fundamental goals of modern Astronomy is to estimate the physical parameters of galaxies from images in different spectral bands. We present a hierarchical Bayesian model for obtaining age maps from images in the \Ha\ line (taken with Taurus Tunable Filter (TTF)), ultraviolet band (far UV or FUV, from GALEX) and infrared bands (24, 70 and 160 microns ($\mu$m), from Spitzer). As shown in S\'anchez-Gil et al. (2011), we present the burst ages for young stellar populations in the nearby and nearly face on galaxy M74.
As it is shown in the previous work, the \Ha\ to FUV flux ratio gives a good relative indicator of very recent star formation history (SFH). As a nascent star-forming region evolves, the \Ha\ line emission declines earlier than the UV continuum, leading to a decrease in the \Ha\/FUV ratio. Through a specific star-forming galaxy model (Starburst 99, SB99), we can obtain the corresponding theoretical ratio \Ha\ / FUV to compare with our observed flux ratios, and thus to estimate the ages of the observed regions.
Due to the nature of the problem, it is necessary to propose a model of high complexity to take into account the mean uncertainties, and the interrelationship between parameters when the \Ha\ / FUV flux ratio mentioned above is obtained. To address the complexity of the model, we propose a Bayesian hierarchical model, where a joint probability distribution is defined to determine the parameters (age, metallicity, IMF), from the observed data, in this case the observed flux ratios \Ha\ / FUV. The joint distribution of the parameters is described through an i.i.d. (independent and identically distributed random variables), generated through MCMC (Markov Chain Monte Carlo) techniques.

[47]
Title: Reconstruction of Chirp Mass in the Search of Compact Binaries
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); High Energy Astrophysical Phenomena (astro-ph.HE)

Excess energy method is used in searches of gravitational waves (GWs) produced from sources with poorly modeled characteristics. It identifies GW events by searching for coincidence appearance of excess energy in a GW detector network. While it is sensitive to a wide range of signal morphologies, the energy outliers in signal amplitude can be populated by background noise induced events (background), thereby reducing the statistical confidence of a true signal. However, if the spectral characteristics of the source is partially understood, weak model dependent constraints can be imposed to suppress the background. This letter presents a novel idea of using the reconstructed chirp mass along with two goodness of fit parameters for suppressing background when search is focused on GW produced from the compact binary coalescence.

[48]
Title: Resolving Ionisation and Metallicity on Parsec Scales Across Mrk 71 (NGC2363) with HST-WFC3
Comments: 20 pages, 14 figures, submitted to ApJ
Subjects: Astrophysics of Galaxies (astro-ph.GA)

Blue Compact Dwarf (BCD) Galaxies in the nearby Universe provide a means for studying feedback mechanisms and star-formation processes in low-metallicity environments in great detail. Due to their vicinity, these local analogues to young galaxies are well suited for high-resolution studies that would be unfeasible for primordial galaxies in the high-redshift universe. Here we present HST-WFC3 observations of one such BCD, Mrk 71 (NGC 2363), one of the most powerful local starbursts known, in the light of [O II], He II, Hb, [O III], Ha, and [S II]. At D=3.44 Mpc, this extensive suite of emission line images enables us to explore the chemical and physical conditions of Mrk 71 on ~2 pc scales. Using these high spatial-resolution observations, we use emission line diagnostics to distinguish ionisation mechanisms on a pixel-by-pixel basis and show that despite the previously reported hypersonic gas and super-bubble blow out, the gas in Mrk 71 is photoionised, with no sign of shock-excited emission. Using strong-line metallicity diagnostics, we present the first 'metallicity image' of a galaxy, revealing chemically inhomogeneity on scales of <50 pc. We additionally demonstrate that while chemical structure can be lost at large spatial scales, metallicity-diagnostics can break down on spatial scales smaller than a HII region. HeII emission line images are used to identify up to six Wolf-Rayet stars in Mrk 71, three of which lie on the edge of blow-out region. This study not only demonstrates the benefits of high-resolution spatially-resolved observations in assessing the effects of feedback mechanisms, but also the limitations of fine spatial scales when employing emission-line diagnostics. Both aspects are especially relevant as we enter the era of extremely large telescopes, when observing structure on ~10 pc scales will no longer be limited to the local universe.

[49]
Title: Recovering hidden signals of statistical anisotropy from a masked or partial CMB sky
Comments: Submitted to Proceeding of 11th Rencontres du Vietnam on Cosmology - 50 years after CMB discovery, Quy Nhon, Vietnam (August 16-22, 2015)
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); Instrumentation and Methods for Astrophysics (astro-ph.IM)

Any isotropy violating phenomena on cosmic microwave background (CMB) induces off-diagonal correlations in the two-point function. These correlations themselves can be used to estimate the underlying anisotropic signals. Masking due to residual foregrounds, or availability of partial sky due to survey limitation, are unavoidable circumstances in CMB studies. But, masking induces additional correlations, and thus complicates the recovery of such signals. In this work, we discuss a procedure based on bipolar spherical harmonic (BipoSH) formalism to comprehensively addresses any spurious correlations induced by masking and successfully recover hidden signals of anisotropy in observed CMB maps. This method is generic, and can be applied to recover a variety of isotropy violating phenomena. Here, we illustrate the procedure by recovering the subtle Doppler boost signal from simulated boosted CMB skies, which has become possible with the unprecedented full-sky sensitivity of PLANCK probe.