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Papers for Thursday, Jul 08 2021

Papers with local authors

ShiChuan Zhang, XiangCong Kong, YueYing Zhou, LingYao Chen, XiaoYing Zheng, Chun-Ling Xu, Bao-Qiang Lao, Tao An
0 votes
Paper 26 — arXiv:2107.03071
0 votes
Paper 26 — arXiv:2107.03071

The discovery of pulsars is of great significance in the field of physics and astronomy. As the astronomical equipment produces a large amount of pulsar data, an algorithm for automatically identifying pulsars becomes urgent. We propose a deep learning framework for pulsar recognition. In response to the extreme imbalance between positive and negative examples and the hard negative sample issue presented in the HTRU Medlat Training Data,there are two coping strategies in our framework: the smart under-sampling and the improved loss function. We also apply the early-fusion strategy to integrate features obtained from different attributes before classification to improve the performance. To our best knowledge,this is the first study that integrates these strategies and techniques together in pulsar recognition. The experiment results show that our framework outperforms previous works with the respect to either the training time or F1 score. We can not only speed up the training time by 10X compared with the state-of-the-art work, but also get a competitive result in terms of F1 score.

X. Chen, W. Wang, Y. M. Tang, Y. Z. Ding, Y. L. Tuo, A. A. Mushtukov, O. Nishimura, S. N. Zhang, M. Y. Ge, L. M. Song, F. J. Lu, S. Zhang, J. L. Qu

9 pages. 5 figures, 2 tables, accept for publication in ApJ

0 votes
Paper 34 — arXiv:2107.03267
0 votes
Paper 34 — arXiv:2107.03267

Cyclotron line scattering features are detected in a few tens of X-ray pulsars (XRPs) and used as direct indicators of a strong magnetic field at the surface of accreting neutron stars (NSs). In a few cases, cyclotron lines are known to be variable with accretion luminosity of XRPs. It is accepted that the observed variations of cyclotron line scattering features are related to variations of geometry and dynamics of accretion flow above the magnetic poles of a NS. A positive correlation between the line centroid energy and luminosity is typical for sub-critical XRPs, where the accretion results in hot spots at the magnetic poles. The negative correlation was proposed to be a specific feature of bright super-critical XRPs, where radiation pressure supports accretion columns above the stellar surface. Cyclotron line in spectra of Be-transient X-ray pulsar GRO J1008-57 is detected at energies from 7590 keV, the highest observed energy of cyclotron line feature in XRPs. We report the peculiar relation of cyclotron line centroid energies with luminosity in GRO J1008-57 during the Type II outburst in August 2017 observed by Insight-HXMT. The cyclotron line energy was detected to be negatively correlated with the luminosity at 3.2×1037\ergs<L<4.2×1037\ergs, and positively correlated at L. We speculate that the observed peculiar behavior of a cyclotron line would be due to variations of accretion channel geometry.

Papers with votes

Fred C Adams

29 pages, 4 figures, accepted to ApJ

1 vote
Paper 39 — arXiv:2107.03329
1 vote
Paper 39 — arXiv:2107.03329

Young stellar objects are observed to have large X-ray fluxes and are thought to produce commensurate luminosities in energetic particles (cosmic rays). This particle radiation, in turn, can synthesize short-lived radioactive nuclei through spallation. With a focus on ^{26}Al, this paper estimates the expected abundances of radioactive nulcei produced by spallation during the epoch of planet formation. In this model, cosmic rays are accelerated near the inner truncation radii of circumstellar disks, r_{\scriptstyle X}\approx0.1 AU, where intense magnetic activity takes place. For planets forming in this region, radioactive abundances can be enhanced over the values inferred for the early solar system (from meteoritic measurements) by factors of \sim10-20. These short-lived radioactive nuclei influence the process of planet formation and the properties of planets in several ways. The minimum size required for planetesimals to become fully molten decreases with increasing levels of radioactive enrichment, and such melting leads to loss of volatile components including water. Planets produced with an enhanced radioactive inventory have significant internal luminosity which can be comparable to that provided by the host star; this additional heating affects both atmospheric mass loss and chemical composition. Finally, the habitable zone of red dwarf stars is coincident with the magnetic reconnection region, so that planets forming at those locations will experience maximum exposure to particle radiation, and subsequent depletion of volatiles.

Papers reserved for later discussion

These are papers reserved by people for discussion at a later date. All reservations are kept for 2 days after the date of the reservation.

Christina D. Kreisch, Alice Pisani, Francisco Villaescusa-Navarro, David N. Spergel, Benjamin D. Wandelt, Nico Hamaus, Adrian E. Bayer

14 pages + appendix, to be submitted to ApJ

0 votes
07/07/2021: arXiv:2107.02304
0 votes
07/07/2021: arXiv:2107.02304

We present GIGANTES, the most extensive and realistic void catalog suite ever released -- containing over 1 billion cosmic voids covering a volume larger than the observable Universe, more than 20 TB of data, and created by running the void finder VIDE on QUIJOTE's halo simulations. The expansive and detailed GIGANTES suite, spanning thousands of cosmological models, opens up the study of voids, answering compelling questions: Do voids carry unique cosmological information? How is this information correlated with galaxy information? Leveraging the large number of voids in the GIGANTES suite, our Fisher constraints demonstrate voids contain additional information, critically tightening constraints on cosmological parameters. We use traditional void summary statistics (void size function, void density profile) and the void auto-correlation function, which independently yields an error of 0.13\,\mathrm{eV} on \sum\,m_{\nu} for a 1 h^{-3}\mathrm{Gpc}^3 simulation, without CMB priors. Combining halos and voids we forecast an error of 0.09\,\mathrm{eV} from the same volume. Extrapolating to next generation multi-Gpc^3 surveys such as DESI, Euclid, SPHEREx, and the Roman Space Telescope, we expect voids should yield an independent determination of neutrino mass. Crucially, GIGANTES is the first void catalog suite expressly built for intensive machine learning exploration. We illustrate this by training a neural network to perform likelihood-free inference on the void size function. Cosmology problems provide an impetus to develop novel deep learning techniques, leveraging the symmetries embedded throughout the universe from physical laws, interpreting models, and accurately predicting errors. With GIGANTES, machine learning gains an impressive dataset, offering unique problems that will stimulate new techniques.

All other papers

A. Bodaghee (1), V. Antoniou (2 and 3), A. Zezas (4), J.A. Tomsick (5), Z. Jordan (1), E. Frechette (1), B. Jackson (1), R. Agnew (1), A.E. Hornschemeier (6 and 7), J. Rodriguez (8) ((1) GCSU, (2) TTU, (3) CfA - Harvard, (4) U. Crete, (5) SSL - UC Berkeley, (6) NASA - GSFC, (7) JHU, (8) CEA/CNRS - Saclay)

10 pages, 7 figures, accepted for publication in the Astrophysical Journal

We present the two-point cross-correlation function between high-mass X-ray binaries (HMXBs) in the Small Magellanic Cloud (SMC) and their likely birthplaces (OB Associations: OBAs). This function compares the spatial correlation between the observed HMXB and OBA populations against mock catalogs in which the members are distributed randomly across the sky. A significant correlation (15 sigma) is found for the HMXB and OBA populations when compared with a randomized catalog in which the OBAs are distributed uniformly over the SMC. A less significant correlation (4 sigma) is found for a randomized catalog of OBAs built with a bootstrap method. However, no significant correlation is detected when the randomized catalogs assume the form of a Gaussian ellipsoid or a distribution that reflects the star-formation history from 40 Myr ago. Based on their observed distributions and assuming a range of migration timescales, we infer that the average value of the kick velocity inherited by an HMXB during the formation of its compact object is 2-34 km/s. This is considerably less than the value obtained for their counterparts in the Milky Way hinting that the galactic environment affecting stellar evolution plays a role in setting the average kick velocity of HMXBs.

Zhoujian Zhang (1), Michael C. Liu (1), Zachary R. Claytor (1), William M. J. Best (2), Trent J. Dupuy (3), Robert J. Siverd (4) ((1) Institute for Astronomy, University of Hawaii, (2) The University of Texas at Austin, Department of Astronomy, (3) Institute for Astronomy, University of Edinburgh, (4) Gemini Observatory/NSF's NOIRLab)

Accepted for publication in ApJ Letters

We present the identification of the COCONUTS-2 system, composed of the M3 dwarf L 34-26 and the T9 dwarf WISEPA J075108.79-763449.6. Given their common proper motions and parallaxes, these two field objects constitute a physically bound pair with a projected separation of 594" (6471 au). The primary star COCONUTS-2A has strong stellar activity (H\alpha, X-ray, and UV emission) and is rapidly rotating (P_{\rm rot} = 2.83 days), from which we estimate an age of 150-800 Myr. Comparing equatorial rotational velocity derived from the TESS light curve to spectroscopic v\sin{i}, we find COCONUTS-2A has a nearly edge-on inclination. The wide exoplanet COCONUTS-2b has an effective temperature of T_{\rm eff}=434 \pm 9 K, a surface gravity of \log{g} = 4.11^{+0.11}_{-0.18} dex, and a mass of M=6.3^{+1.5}_{-1.9} M_{\rm Jup} based on hot-start evolutionary models, leading to a 0.016^{+0.004}_{-0.005} mass ratio for the COCONUTS-2 system. COCONUTS-2b is the second coldest (after WD 0806-661B) and the second widest (after TYC 9486-927-1 b) exoplanet imaged to date. Comparison of COCONUTS-2b's infrared photometry with ultracool model atmospheres suggests the presence of both condensate clouds and non-equilibrium chemistry in its photosphere. Similar to 51 Eri b, COCONUTS-2b has a sufficiently low luminosity (\log{(L_{\rm bol}/L_{\odot})} = -6.384 \pm 0.028 dex) to be consistent with the cold-start process that may form gas-giant (exo)planets, though its large separation means such formation would not have occurred in situ. Finally, at a distance of 10.9 pc, COCONUTS-2b is the nearest imaged exoplanet to Earth known to date.

Elisabeta Lusso, Emanuele Nardini, Susanna Bisogni, Guido Risaliti, Roberto Gilli, Gordon T. Richards, Francesco Salvestrini, Cristian Vignali, Giada Bargiacchi, Francesca Civano, Martin Elvis, Giuseppina Fabbiano, Alessandro Marconi, Andrea Sacchi, Matilde Signorini

22 pages, 15 figures (with 3 more figures in the Appendix), abstract abridged. Accepted for publication in A&A

We analyse the properties of the CIV broad emission line in connection with the X-ray emission of 30 bright SDSS quasars at z~3.0-3.3 with pointed XMM-Newton observations, which were selected to test the suitability of AGN as cosmological tools. In our previous work, we found that a large fraction (~25%) of the quasars in this sample are X-ray underluminous by factors of >3-10. As absorbing columns of >10^{23} cm^{-2} can be safely ruled out, their weakness is most likely intrinsic. Here we explore possible correlations between the UV and X-ray features of these sources to investigate the origin of X-ray weakness. We fit their UV SDSS spectra and analyse their CIV properties (e.g., equivalent width, EW; line peak velocity, \upsilon_{\rm peak}) as a function of the X-ray photon index and 2-10 keV flux. We confirm the trends of CIV \upsilon_{\rm peak} and EW with UV luminosity at 2500 angstrom for both X-ray weak and X-ray normal quasars, as well as the correlation between X-ray weakness and CIV EW. In contrast to some recent work, we do not observe any clear relation between the 2-10 keV luminosity and \upsilon_{\rm peak}. We find a correlation between the hard X-ray flux and the integrated CIV flux for X-ray normal quasars, whilst X-ray weak quasars deviate from the main trend by more than 0.5 dex. We argue that X-ray weakness might be interpreted in a starved X-ray corona picture associated with an ongoing disc-wind phase. If the wind is ejected in the vicinity of the black hole, the extreme-UV radiation that reaches the corona will be depleted, depriving the corona of seeds photons and generating an X-ray weak quasar. Yet, at the largest UV luminosities (>10^{47} erg s^{-1}), there will still be an ample reservoir of ionising photons that can explain the excess CIV emission observed in the X-ray weak quasars with respect to normal sources of similar X-ray luminosities.

Pavel E. Mancera Piña, Lorenzo Posti, Gabriele Pezzulli, Filippo Fraternali, S. Michael Fall, Tom Oosterloo, Elizabeth A. K. Adams

Accepted for publication in A&A Letters. Data catalogue will be available via CDS and at this link this https URL

The relations between specific angular momenta (j) and masses (M) of galaxies are often used as a benchmark in analytic models and hydrodynamical simulations, as they are considered among the most fundamental scaling relations. Using accurate measurements of the stellar (j_\ast), gas (j_{\rm gas}) and baryonic (j_{\rm bar}) specific angular momenta for a large sample of disc galaxies, we report the discovery of tight correlations between j, M, and the cold gas fraction of the interstellar medium (f_{\rm gas}). At fixed f_{\rm gas}, galaxies follow parallel power-laws in the 2D (j,M) spaces, with gas-rich galaxies having a larger j_\ast and j_{\rm bar} (but lower j_{\rm gas}) than gas-poor ones. The slopes of the relations have a value around 0.7. These new relations are amongst the tightest known scaling laws for galaxies. In particular, the baryonic relation (j_{\rm bar}-M_{\rm bar}-f_{\rm gas}), arguably the most fundamental of the three, is followed not only by typical discs but also by galaxies with extreme properties such as size and gas content, and by galaxies previously claimed to be outliers of the standard 2D j-M relations. The stellar relation (j_{\ast}-M_{\ast}-f_{\rm gas}) may be connected to the known j_\ast-M_\ast-bulge fraction relation, while we argue that the j_{\rm bar}-M_{\rm bar}-f_{\rm gas} relation can originate from the radial variation of the star formation efficiency in galaxies, although it is not explained by current disc instability models.

Paul A. Draghis, Jon M. Miller, Abderahmen Zoghbi, Elias S. Kammoun, Mark T. Reynolds, John A. Tomsick

16 pages, 7 figures, 3 tables. Accepted for publication in ApJ

NuSTAR observed the black hole candidate XTE J1908+094 during its 2013 and 2019 outbursts. We use relativistic reflection to measure the spin of the black hole through 19 different assumptions of relxill flavors and parameter combinations. The most favored model in terms of Deviance Information Criterion (DIC) measures the spin of the black hole to be a = 0.55^{+0.29}_{-0.45}, and an inclination of \theta=27^{+2}_{-3} degrees (1\sigma statistical errors). We look at the effects of coronal geometry assumptions and density of the accretion disk on the spin prediction. All 19 tested models provide consistent spin estimates. We discuss the evolution of spin measurement techniques using relativistic reflection in X-ray binaries and discuss the implications of this spin measurement in reconciling the distributions of stellar mass black hole spin measurements made through X-ray and gravitational wave observations.

Sebastian Baum, William DeRocco, Thomas D. P. Edwards, Saarik Kalia

25 pages, 16 figures, 2 tables, code available at this https URL and this https URL

Paleo-detectors are a proposed experimental technique to search for dark matter by reading out the damage tracks caused by nuclear recoils in small samples of natural minerals. Unlike a conventional real-time direct detection experiment, paleo-detectors have been accumulating these tracks for up to a billion years. These long integration times offer a unique possibility: by reading out paleo-detectors of different ages, one can explore the time-variation of signals on megayear to gigayear timescales. We investigate two examples of dark matter substructure that could give rise to such time-varying signals. First, a dark disk through which the Earth would pass every \sim45 Myr, and second, a dark matter subhalo that the Earth encountered during the past gigayear. We demonstrate that paleo-detectors are sensitive to these examples under a wide variety of experimental scenarios, even in the presence of substantial background uncertainties. This paper shows that paleo-detectors may hold the key to unraveling our Galactic history.

R. Scott Barrows, Julia M. Comerford, Daniel Stern, Roberto J. Assef

21 pages, 17 figures. Accepted for publication in the Astrophysical Journal. The full catalog is available from the publisher or from the corresponding author upon request

We present a catalog of physical properties for galaxies hosting active galactic nuclei (AGN) detected by the Wide-field Infrared Survey Explorer (WISE). By fitting broadband spectral energy distributions of sources in the WISE AGN Catalog (Assef et al. 2018) with empirical galaxy and AGN templates, we derive photometric redshifts, AGN bolometric luminosities, measures of AGN obscuration, host galaxy stellar masses, and host galaxy star formation rates (SFRs) for 695,273 WISE AGN. The wide-area nature of this catalog significantly augments the known number of obscured AGN out to redshifts of z~3 and will be useful for studies focused on AGN or their host galaxy physical properties. We first show that the most likely non-AGN contaminants are galaxies at redshifts of z=0.2-0.3, with relatively blue W1-W2 colors, and with high specific SFRs for which the dust continuum emission is elevated in the W2 filter. Toward increasingly lower redshifts, WISE AGN host galaxies have systematically lower specific SFRs, relative to those of normal star forming galaxies, likely due to decreased cold gas fractions and the time delay between global star formation and AGN triggering. Finally, WISE AGN obscuration is not strongly correlated with AGN bolometric luminosity but shows a significant negative correlation with Eddington ratio. This result is consistent with a version of the `receding torus' model in which the obscuring material is located within the supermassive black hole gravitational sphere of influence and the dust inner radius increases due to radiation pressure.

Miho Kawabata, Keiichi Maeda, Masayuki Yamanaka, Tatsuya Nakaoka, Koji S. Kawabata, Kentaro Aoki, G. C. Anupama, Umut Burgaz, Anirban Dutta, Keisuke Isogai, Masaru Kino, Naoto Kojiguchi, Iida Kota, Brajesh Kumar, Daisuke Kuroda, Hiroyuki Maehara, Kazuya Matsubayashi, Kumiko Morihana, Katsuhiro L. Murata, Tomohito Ohshima, Masaaki Otsuka, Devendra K. Sahu, Avinash Singh, Koji Sugitani, Jun Takahashi, Kengo Takagi

37 pages, 22 figures, 6 tables, accepted for publication in PASJ

We present comprehensive spectroscopic and photometric analyses of the intermediate luminosity Type Iax supernova (SN Iax) 2019muj based on multi-band datasets observed through the framework of the OISTER target-of-opportunity program. SN 2019muj exhibits almost identical characteristics with the subluminous SNe Iax 2008ha and 2010ae in terms of the observed spectral features and the light curve evolution at the early phase, except for the peak luminosity. The long-term observations unveil the flattening light curves at the late time as seen in a luminous SN Iax 2014dt. This can be explained by the existence of an inner dense and optically-thick component possibly associated with a bound white dwarf remnant left behind the explosion. We demonstrate that the weak deflagration model with a wide range of the explosion parameters can reproduce the late-phase light curves of other SNe Iax. Therefore, we conclude that a common explosion mechanism operates for different subclass SNe Iax.

Aaron M. Geller, Ava Polzin, Andrew Bowen, Adam A. Miller

15 pages, 8 figures, accepted for publication in ApJ

We present a study of the detection and recovery efficiency of the Rubin Observatory for detached eclipsing binaries (EBs) in the galactic field, globular clusters (GCs) and open clusters (OCs), with a focus on comparing two proposed observing strategies: a standard cadence ("baseline"), and a cadence which samples the galactic plane more evenly ("colossus"). We generate realistic input binary populations in all observing fields of the Rubin Observatory, simulate the expected observations in each filter, and attempt to characterize the EBs using these simulated observations. In our models, we predict the baseline cadence will enable the Rubin Observatory to observe about three million EBs; our technique could recover and characterize nearly one million of these in the field and thousands within star clusters. If the colossus cadence is used, the number of recovered EBs would increase by an overall factor of about 1.7 in the field and in globular clusters, and a factor of about three in open clusters. Including semi-detached and contact systems could increase the number of recovered EBs by an additional factor of about 2.5 to 3. Regardless of the cadence, observations from the Rubin Observatory could reveal statistically significant physical distinctions between the distributions of EB orbital elements between the field, GCs and OCs. Simulations such as these can be used to bias correct the sample of Rubin Observatory EBs to study the intrinsic properties of the full binary populations in the field and star clusters.

Arindam Mazumdar, Subhendra Mohanty, Priyank Parashari

A mini review to apear in EPJST (18 pages, 4 figures)

The idea of a negative-pressure dark energy component in the Universe which causes an accelerated expansion in the late Universe has deep implications in models of field theory and general relativity. In this article, we survey the evidence for dark energy from cosmological observations which started from the compilation of distance-luminosity plots of Type Ia supernovae. This turned out to be consistent with the dark energy inferred from the CMB observations and large scale surveys and gave rise to the concordance \LambdaCDM model of cosmology. In this article, we discuss the observational evidence for dark energy from Type Ia supernovae, CMB, galaxy surveys, observations of the Sunyaev-Zeldovich effect from clusters, and lensing by clusters. We also discuss the observational discrepancy in the values of H_0 and \sigma_8 between CMB and large scale structures and discuss if varying dark energy models are able to resolve these tensions between different observations.

Tyler Gardner (1), John D. Monnier (1), Francis C. Fekel (2), Michael Williamson (2), Fabien Baron (3), Sasha Hinkley (4), Michael Ireland (5), Adam L. Kraus (6), Stefan Kraus (4), Rachael M. Roettenbacher (7), Gail Schaefer (3), Judit Sturmann (3), Laszlo Sturmann (3), Theo Ten Brummelaar (3) ((1) University of Michigan, Ann Arbor, (2) Tennessee State University, (3) The CHARA Array of Georgia State University, (4) University of Exeter, (5) Australian National University, (6) University of Texas at Austin, (7) Yale University)

17 pages, 7 figures, accepted for publication in ApJ

Alpha Ophiuchi (Rasalhague) is a nearby rapidly rotating A5IV star which has been imaged by infrared interferometry. \alpha Oph is also part of a known binary system, with a companion semi-major axis of \sim430 milli-arcseconds and high eccentricity of 0.92. The binary companion provides the unique opportunity to measure the dynamical mass to compare with the results of rapid rotator evolution models. The lack of data near periastron passage limited the precision of mass measurements in previous work. We add new interferometric data from the MIRC combiner at the CHARA Array as well as new Keck adaptive optics imaging data with NIRC2, including epochs taken near periastron passage. We also obtained new radial velocities of both components at Fairborn Observatory. Our updated combined orbit for the system drastically reduces the errors of the orbital elements, and allows for precise measurement of the primary star mass at the few percent level. Our resulting primary star mass of 2.20\pm0.06 M_{\odot} agrees well with predictions from imaging results, and matches evolution models with rotation when plotting on an HR diagram. However, to truly distinguish between non-rotating and rotating evolution models for this system we need \sim1\% errors on mass, which might be achieved once the distance is known to higher precision in future Gaia releases. We find that the secondary mass of 0.824\pm0.023 M_{\odot} is slightly under-luminous when compared to stellar evolution models. We show that \alpha Oph is a useful reference source for programs that need \pm1 milli-arcsecond astrometry.

Solar power is being used to satisfy a higher and higher percentage of our energy needs. We must be able to evaluate the performance of the hardware. Here we present an analysis of the performance of a fixed grid of 13 solar panels installed in the spring of 2021. We confirm that the power output is linearly proportional to the cosine of the angle of the incidence of sunlight with respect to the vector perpendicular to the panels. However, in order to confirm this, we need to consider the dimming effect of the Earth's atmosphere on the intensity of the Sun's light, which is to say we need to rely on astronomical photometric methods. We find a weighted mean value of 0.168 +/- 0.007 mag/airmass for the extinction term, which corresponds to the sea level value at a wavelength of about 0.76 microns. As the efficiency of the solar panels is expected to degrade slowly over time, the data presented here provide a baseline for comparison to the future performance of the system.

Nigel J. Mason, Perry A. Hailey, Duncan V. Mifsud, James S. Urquhart

32 pages including 11 figures and 2 tables. To be submitted in Frontiers in Astronomy and Space Science

Laboratory experiments play a key role in deciphering the chemistry of the interstellar medium (ISM) and the role that product complex organic molecules (COMs) may play in the origins of life. However, to date, most studies in experimental astrochemistry have made use of reductionist approaches to experimental design in which chemical responses to variations in a single parameter are investigated while all other parameters are held constant. Although such work does afford insight into the chemistry of the ISM, it is likely that several important points, such as the relative importance of an experimental parameter in determining the chemical outcome of a reaction and the interaction between parameters, remain ambiguous. In light of this, we propose adopting a new systems astrochemistry framework for experimental studies which draws on current work performed in the field of prebiotic chemistry, and present the basic tenants of such an approach in this article. This systems approach would focus on the emergent properties of the chemical system by performing the simultaneous variation of multiple experimental parameters and would allow for the effect of each parameter, as well as their interactions, to be quantified. We anticipate that the application of systems science to laboratory astrochemistry, coupled with developments in hyphenated analytical techniques and data analytics, will uncover significant new data hitherto unknown, and will aid in better linking laboratory experiments to observations and modelling work.

M. Khademi, Y. Yang, F. Hammer, S. Nasiri

12 pages, 6 figures, accepted for publication in Astronomy and Astrophysics (A & A)

WLM is a dwarf irregular that is seen almost edge-on, which has prompted many kinematical studies to investigate its rotation curve and its dark matter content. In this paper, we investigate the origin of the strong asymmetry of the rotation curve, which shows a significant discrepancy between the approaching and the receding side. We first examine whether an m = 1 perturbation (lopsidedness) in the halo potential could be a mechanism creating such kinematical asymmetry. To do so, we fit a theoretical rotational velocity associated with an m = 1 perturbation in the halo potential model to the observed data via a \chi-squared minimization method. We show that a lopsided halo potential model can explain the asymmetry in the kinematic data reasonably well. We then verify that the kinematical classification of WLM shows that its velocity field is significantly perturbed, because of both its asymmetrical rotation curve and also because of its peculiar velocity dispersion map. Also based on kinemetry analysis, it is possible that WLM lies in the transition region, in which disk and merger coexist. In conclusion, it appears that the rotation curve of WLM diverges significantly from that of an ideal rotating disk, which may significantly affect investigations of its dark matter content.

We present a detailed analysis to clarify what determines the growth of the \ltw instability in the context of rapidly rotating core-collapse of massive stars. To this end, we perform three-dimensional core-collapse supernova (CCSN) simulations of a 27 M_{\odot} star including several updates in the general relativistic correction to gravity, the multi-energy treatment of heavy-lepton neutrinos, and the nuclear equation of state. Non-axisymmetric deformations are analyzed from the point of view of the time evolution of the pattern frequency and the corotation radius. The corotation radius is found to coincide with the convective layer in the proto neutron star (PNS). We propose a new mechanism to account for the growth of the \ltw instability in the CCSN environment. Near the convective boundary where a small \BV frequency is expected, Rossby waves propagating in the azimuthal direction at mid latitude induce non-axisymmetric unstable modes, in both hemispheres. They merge with each other and finally become the spiral arm in the equatorial plane. We also investigate how the growth of the \ltw instability impacts the neutrino and gravitational-wave signatures.

Magnetic field may distort neutron stars (NSs), but the effect has not been robustly tested through gravitational-wave observation yet due to the absence of a fast rotating Galactic magnetar. The central objects of Gamma-ray bursts (GRBs) could be millisecond magnetars. Under the magnetar scenario on the X-ray plateaus of GRB afterglows,the spindown evolution modulated by the gravitational-wave radiation may be inferred from some special samples,so that the magnetically-induced distorting can be further estimated. According to two samples, GRB 060807 and GRB 070521, we found that the correlation between the effective ellipticity, \varepsilon_{\rm B,eff}, and effective magnetic field, B_{\rm eff}, is \varepsilon_{\rm B,eff}\sim 10^{-4} (\frac{B_{\rm eff}}{10^{14}\;\rm G})^{2}. This result demands that B_{\rm eff}\sim 0.01 B_{\rm t} with B_{\rm t} being the internal toroidal magnetic field strength of NSs. We suggested that the nonzero moment of force generated during few massive-star collapses may induce differential rotation between the interior and exterior of the proto-NS to amplify the internal toroidal field.

Toshihiro Fujii, Justin Albury, Jose Bellido, Ladislav Chytka, John Farmer, Petr Hamal, Pavel Horvath, Miroslav Hrabovsky, Hidetoshi Kubo, Jiri Kvita, Max Malacari, Dusan Mandat, Massimo Mastrodicasa, John Matthews, Stanislav Michal, Xiaochen Ni, Seiya Nozaki, Libor Nozka, Tomohiko Oka, Miroslav Palatka, Miroslav Pech, Paolo Privitera, Petr Schovanek, Francesco Salamida, Radomir Smida, Stan Thomas, Akimichi Taketa, Kenta Terauchi, Petr Travnicek, Martin Vacula, Seokhyun Yoo (The FAST Collaboration)

8 pages, 6 figures, Proceedings of the 37th International Cosmic Ray Conference (ICRC 2021)

The origin and nature of ultra-high-energy cosmic rays (UHECRs) remains an open question in astroparticle physics. Motivated by the need for an unprecedented aperture for further advancements, the Fluorescence detector Array of Single-pixel Telescopes (FAST) is a prospective next-generation, ground-based UHECR observatory that aims to cover a huge area by deploying a large array of low-cost fluorescence detectors. The full-scale FAST prototype consists of four 20 cm photomultiplier tubes at the focus of a segmented mirror 1.6 m in diameter. Over the last five years, three prototypes have been installed at the Telescope Array Experiment in Utah, USA, and one prototype at the Pierre Auger Observatory in Mendoza, Argentina, commencing remote observation of UHECRs in both hemispheres. We report on the latest results of these FAST prototypes, including telescope calibrations, atmospheric monitoring, ongoing electronics upgrades, development of sophisticated reconstruction methods, and UHECR detections.

Daniel Forero-Sánchez, Cheng Zhao, Charling Tao, Chia-Hsun Chuang, Francisco-Shu Kitaura, Andrei Variu, Amélie Tamone, Jean-Paul Kneib

13 pages, 11 figures. Submitted to MNRAS

In the context of the study of large-scale structure of the Universe, we analyze the response of cosmic void clustering to selection effects, such as angular incompleteness due to observational systematics and radial selection functions. We find for the case of moderate (<20%) incompleteness: that void sample selection based on a constant radius cut yields robust measurements. This is particularly true for BAO-reconstructed galaxy samples, where large-scale void exclusion effects are mitigated. We also find for the case of severe (up to 90%) incompleteness, a stronger void exclusion effect that can affect the clustering on large scales even for post-reconstructed data, when using the constant cut. For these cases, we introduce void radius selection criteria depending on the (local) observed tracer density that maximizes the BAO peak signal to noise ratio. This selection prevents large exclusion features from contaminating the BAO signal. An accurate estimation of the void distribution is necessary to obtain unbiased clustering measurements with either criterion when dealing with severe incompleteness, such as can be found at the edges of the radial selection function. Moreover we finally verify, with large simulated data sets including lightcone evolution, that both void sample definitions (local and constant) yield unbiased BAO scale measurements. In conclusion, cosmic voids can be used as robust tracers for clustering measurements, even in the case of (moderately) unknown systematics.

In this work, we study detecting free-floating planets (FFPs) by microlensing observations towards the Magellanic Clouds (MCs). In comparison to similar events toward the Galactic bulge, an FFP in the Galactic halo produces on average longer microlensing events with smaller projected source radii toward these clouds. For these microlensing events, the relative lens-source velocities are on average smaller. The MC self-lensing events due to FFPs suffer from severe finite-source effects. We first simulate microlensing events due to FFPs towards MCs and assume a log-uniform step function for their mass. The efficiencies for capturing their lensing signatures (with signal-to-noise greater than 50) are found to be 0.1-0.6\% and 3-6\% through ground-based optical surveys and space-based near-infrared surveys, respectively. We then promote these simulations and assume the \wfirst~telescope continuously observes each MC during one 72-day season with the 15min observing cadence. From simulated microlensing events with the resolvable source stars at the baseline due to FFPs with the masses \sim 0.01-10^{4}M_{\oplus}, \wfirst~discovers their lensing effects with the efficiencies \sim 10-80\%, respectively. By adopting 5\% as halos fraction from FFPs we estimate the expected number of events. The highest number of detectable FFPs which is \sim1700-2200 per season per square degree happens for ones with masses \sim 0.01 M_{\oplus}. Our simulations show that \wfirst~potentially extends the mass range of detectable FFPs in halos down to 5.9\times 10^{-7} M_{\oplus} with continuous observations during one observing season from the Large Magellanic Cloud.

Meng-Hua Chen (GXU), Li-Xin Li (PKU), Da-Bin Lin (GXU), En-Wei Liang (GXU)

24 pages, 7 figures, 2 tables, accepted for publication in ApJ

The observation of a radioactively powered kilonova AT~2017gfo associated with the gravitational wave-event GW170817 from binary neutron star merger proves that these events are ideal sites for the production of heavy r-process elements. The gamma-ray photons produced by the radioactive decay of heavy elements are unique probes for the detailed nuclide compositions. Basing on the detailed r-process nucleosynthesis calculations and considering radiative transport calculations for the gamma-rays in different shells, we study the gamma-ray emission in a merger ejecta on a timescale of a few days. It is found that the total gamma-ray energy generation rate evolution is roughly depicted as \dot{E}\propto t^{-1.3}. For the dynamical ejecta with a low electron fraction (Y_{\rm e}\lesssim0.20), the dominant contributors of gamma-ray energy are the nuclides around the second r-process peak (A\sim130), and the decay chain of ^{132}Te (t_{1/2}=3.21~days) \rightarrow ^{132}I (t_{1/2}=0.10~days) \rightarrow ^{132}Xe produces gamma-ray lines at 228 keV, 668 keV, and 773 keV. For the case of a wind ejecta with Y_{\rm e}\gtrsim0.30, the dominant contributors of gamma-ray energy are the nuclides around the first r-process peak (A\sim80), and the decay chain of ^{72}Zn (t_{1/2}=1.93~days) \rightarrow ^{72}Ga (t_{1/2}=0.59~days) \rightarrow ^{72}Ge produces gamma-ray lines at 145 keV, 834 keV, 2202 keV, and 2508 keV. The peak fluxes of these lines are 10^{-9}\sim 10^{-7}~ph~cm^{-2} s^{-1}, which are marginally detectable with the next-generation MeV gamma-ray detector \emph{ETCC} if the source is at a distance of 40~Mpc.

D. Yong, C. Kobayashi, G. S. Da Costa, M. S. Bessell, A. Chiti, A. Frebel, K. Lind, A. D. Mackey, T. Nordlander, M. Asplund, A. R. Casey, A. F. Marino, S. J. Murphy, B. P. Schmidt

Author's version of a Letter published in Nature on July 8th, 2021

Neutron-star mergers were recently confirmed as sites of rapid-neutron-capture (r-process) nucleosynthesis. However, in Galactic chemical evolution models, neutron-star mergers alone cannot reproduce the observed element abundance patterns of extremely metal-poor stars, which indicates the existence of other sites of r-process nucleosynthesis. These sites may be investigated by studying the element abundance patterns of chemically primitive stars in the halo of the Milky Way, because these objects retain the nucleosynthetic signatures of the earliest generation of stars. Here we report the element abundance pattern of the extremely metal-poor star SMSS J200322.54-114203.3. We observe a large enhancement in r-process elements, with very low overall metallicity. The element abundance pattern is well matched by the yields of a single 25-solar-mass magnetorotational hypernova. Such a hypernova could produce not only the r-process elements, but also light elements during stellar evolution, and iron-peak elements during explosive nuclear burning. Hypernovae are often associated with long-duration gamma-ray bursts in the nearby Universe. This connection indicates that similar explosions of fast-spinning strongly magnetized stars occurred during the earliest epochs of star formation in our Galaxy.

R. Darma, M. I. Arifyanto, M. B. N. Kouwenhoven

accepted 2021 July 5, to be published in MNRAS, 19 pages

Recent observations of young embedded clumpy clusters and statistical identifications of binary star clusters have provided new insights into the formation process and subsequent dynamical evolution of star clusters. The early dynamical evolution of clumpy stellar structures provides the conditions for the origin of binary star clusters. Here, we carry out N-body simulations in order to investigate the formation of binary star clusters in the Milky Way and in the Large Magellanic Cloud (LMC). We find that binary star clusters can form from stellar aggregates with a variety of initial conditions. For a given initial virial ratio, a higher degree of initial substructure results in a higher fraction of binary star clusters. The number of binary star clusters decreases over time due to merging or dissolution of the binary system. Typically, \sim 45\% of the aggregates evolve into binary/multiple clusters within t=20~Myr in the Milky Way environment, while merely \sim30\% survives beyond t=50~Myr, with separations \lesssim 50~pc. On the other hand, in the LMC, \sim 90\% of the binary/multiple clusters survive beyond t=20~Myr and the fraction decreases to \sim 80\% at t=50~Myr, with separations \lesssim 35~pc. Multiple clusters are also rapidly formed for highly-substructured and expanding clusters. The additional components tend to detach and the remaining binary star cluster merges. The merging process can produce fast rotating star clusters with mostly flat rotation curves that speed up in the outskirts.

Wen-Chao Su, Jian-Ning Fu, Jian-Xing Chen, Lester Fox-Machado, Shi-Jie Zhao, Carmen Ayala-Loera, Jiang-Tao Wang, Yang Pan

Hydrogen atmosphere pulsating white dwarfs, also known as DAV stars, are the most abundant type of pulsating white dwarfs. High-temperature DAV stars exhibit in general a small number of pulsation modes and stable frequencies. G132-12 is one of the pulsating hydrogen atmosphere white dwarf stars which lies close to the blue edge of the instability strip. Previous researches reported that G132-12 might have only one pulsation mode with the period of 212.69 s. To study the pulsation properties of G132-12 in detail, we carried out a bi-site observation campaign in October 2019. Time series photometric data were collected during around 154 hours in total. A Fourier Analysis reveals 3 frequencies which are identified as the triplet of a l = 1 g-mode pulsation with the period of 212.499 s. The rotational period is derived as P_{rot} = 35.0\pm6.7 hours and the inclination of the rotational axis to the line of sight is 70^{\circ}. G132-12 could be an ideal target for measuring the cooling scale of this white dwarf star with only one excited pulsation mode detected.

A. F. Lanza (INAF-Catania, Italy)

18 pages, 1 appendix, 9 figures, 3 tables; accepted by Astronomy & Astrophysics

A new mechanism for the internal heating of ultra-short-period planets is proposed based on the gravitational perturbation by a non-axisymmetric quadrupole moment of their host stars. Such a quadrupole is due to the magnetic flux tubes in the stellar convection zone, unevenly distributed in longitude and persisting for many stellar rotations as observed in young late-type stars. The rotation period of the host star evolves from its shortest value on the zero-age main sequence to longer periods due to the loss of angular momentum through a magnetized wind. If the stellar rotation period comes close to twice the orbital period of the planet, the quadrupole leads to a spin-orbit resonance that excites oscillations of the star-planet separation. As a consequence, a strong tidal dissipation is produced inside the planet. We illustrate the operation of the mechanism by modeling the evolution of the stellar rotation and of the innermost planetary orbit in the cases of CoRoT-7, Kepler-78, and K2-141 whose present orbital periods range between 0.28 and 0.85 days. If the spin-orbit resonance occurs, the maximum power dissipated inside the planets ranges between 10^{18} and 10^{19} W, while the total dissipated energy is of the order of 10^{30}-10^{32} J over a time interval as short as (1-4.5) \times 10^{4} yr. Such a huge heating over a so short time interval produces a complete melting of the planetary interiors and may shut off their hydromagnetic dynamos. These may initiate a successive phase of intense internal heating owing to unipolar magnetic star-planet interactions and affect the composition and the escape of their atmospheres, producing effects that could be observable during the entire lifetime of the planets [abridged abstract].

Patrick M. Meyers, Nicholas J. O'Neill, Andrew Melatos, Robin J. Evans

15 pages, 7 figures, accepted to MNRAS

The classic, two-component, crust-superfluid model of a neutron star can be formulated as a noise-driven, linear dynamical system, in which the angular velocities of the crust and superfluid are tracked using a Kalman filter applied to electromagnetic pulse timing data and gravitational wave data, when available. Here it is shown how to combine the marginal likelihood of the Kalman filter and nested sampling to estimate full posterior distributions of the six model parameters, extending previous analyses based on a maximum-likelihood approach. The method is tested across an astrophysically plausible parameter domain using Monte Carlo simulations. It recovers the injected parameters to \lesssim 10 per cent for time series containing \sim 10^3 samples, typical of long-term pulsar timing campaigns. It runs efficiently in \mathcal O(1) CPU-hr for data sets of the above size. In a present-day observational scenario, when electromagnetic data are available only, the method accurately estimates three parameters: the relaxation time, the ensemble-averaged spin-down of the system, and the amplitude of the stochastic torques applied to the crust. In a future observational scenario, where gravitational wave data are also available, the method also estimates the ratio between the moments of inertia of the crust and the superfluid, the amplitude of the stochastic torque applied to the superfluid, and the crust-superfluid lag. These empirical results are consistent with a formal identifiability analysis of the linear dynamical system.

Baoqiang Lao, Tao An, Ailing Wang, Zhijun Xu, Shaoguang Guo, Weijia Lv, Xiaocong Wu, Yingkang Zhang

Accepted by Science Bulletin. Note that the final version of the paper in the journal is formatted slightly differently from the one in astro-ph because of the journal's layout

Large surveys using modern telescopes are producing images that are increasing exponentially in size and quality. Identifying objects in the generated images by visual recognition is time-consuming and labor-intensive, while classifying the extracted radio sources is even more challenging. To address these challenges, we develop a deep learning-based radio source detector, named \textsc{HeTu}, which is capable of rapidly identifying and classifying radio sources in an automated manner for both compact and extended radio sources. \textsc{HeTu} is based on a combination of a residual network (ResNet) and feature pyramid network (FPN). We classify radio sources into four classes based on their morphology. The training images are manually labeled and data augmentation methods are applied to solve the data imbalance between the different classes. \textsc{HeTu} automatically locates the radio sources in the images and assigns them to one of the four classes. The experiment on the testing dataset shows an average operation time of 5.4 millisecond per image and a precision of 99.4\% for compact point-like sources and 98.1\% for double-lobe sources. We applied \textsc{HeTu} to the images obtained from the GaLactic and the Galactic Extragalactic All-Object Murchison Wide-field Array (GLEAM) survey project. More than 96.9\% of the \textsc{HeTu}-detected compact sources are matched compared to the source finding software used in the GLEAM. We also detected and classified 2,298 extended sources (including Fanaroff-Riley type I and II sources, and core-jet sources) above 5\sigma. The cross-matching rates of extended sources are higher than 97\%, showing excellent performance of \textsc{HeTu} in identifying extended radio sources. \textsc{HeTu} provides an efficient tool for radio source finding and classification and can be applied to other scientific fields.

Oliver Jennrich, Nora Lutzgendorf, James Ira Thorpe, Jacob Slutsky, Curt Cutler

Space-based interferometric gravitational wave instruments such as the ESA/NASA Laser Interferometer Space Antenna (LISA) observe gravitational waves by measuring changes in the light travel time between widely-separated spacecraft. One potential noise source for these instruments is interaction with the solar wind, in particular the free electrons in the interplanetary plasma. Variations in the integrated column density of free electrons along the laser links will lead to time-of-flight delays which directly compete with signals produced by gravitational waves. In this paper we present a simplified model of the solar plasma relevant for this problem, anchor key parameters of our model using data from the NASA \emph{Wind}/SWE instrument, and derive estimates for the effect in the LISA measurement. We find that under normal solar conditions, the gravitational-wave sensitivity limit from the free-electron effect is smaller than other noise sources that are expected to limit LISA's sensitivity.

R. Abbasi, M. Ackermann, J. Adams, J. A. Aguilar, M. Ahlers, M. Ahrens, C. Alispach, A. A. Alves Jr., N. M. Amin, R. An, K. Andeen, T. Anderson, G. Anton, C. Argüelles, Y. Ashida, S. Axani, X. Bai, A. Balagopal V., A. Barbano, S. W. Barwick, B. Bastian, V. Basu, S. Baur, R. Bay, J. J. Beatty, K.-H. Becker, J. Becker Tjus, C. Bellenghi, S. BenZvi, D. Berley, E. Bernardini, D. Z. Besson, G. Binder, D. Bindig, E. Blaufuss, S. Blot, M. Boddenberg, F. Bontempo, J. Borowka, S. Böser, O. Botner, J. Böttcher, E. Bourbeau, F. Bradascio, J. Braun, S. Bron, J. Brostean-Kaiser, S. Browne, A. Burgman, R. T. Burley, R. S. Busse, M. A. Campana, E. G. Carnie-Bronca, C. Chen, D. Chirkin, K. Choi, B. A. Clark, K. Clark, L. Classen, A. Coleman, G. H. Collin, J. M. Conrad, P. Coppin, P. Correa, et al. (317 additional authors not shown)

Submitted to ApJ. 18 pages, 5 figures, 3 tables

Ultra-luminous infrared galaxies (ULIRGs) have infrared luminosities L_{\mathrm{IR}} \geq 10^{12} L_{\odot}, making them the most luminous objects in the infrared sky. These dusty objects are generally powered by starbursts with star-formation rates that exceed 100~ M_{\odot}~ \mathrm{yr}^{-1}, possibly combined with a contribution from an active galactic nucleus. Such environments make ULIRGs plausible sources of astrophysical high-energy neutrinos, which can be observed by the IceCube Neutrino Observatory at the South Pole. We present a stacking search for high-energy neutrinos from a representative sample of 75 ULIRGs with redshift z \leq 0.13 using 7.5 years of IceCube data. The results are consistent with a background-only observation, yielding upper limits on the neutrino flux from these 75 ULIRGs. For an unbroken E^{-2.5} power-law spectrum, we report an upper limit on the stacked flux \Phi_{\nu_\mu + \bar{\nu}_\mu}^{90\%} = 3.24 \times 10^{-14}~ \mathrm{TeV^{-1}~ cm^{-2}~ s^{-1}}~ (E/10~ \mathrm{TeV})^{-2.5} at 90% confidence level. In addition, we constrain the contribution of the ULIRG source population to the observed diffuse astrophysical neutrino flux as well as model predictions.

During the first stages of planet formation, the collision growth of dust aggregates in protoplanetary discs (PPDs) is interrupted at the bouncing barrier. Dust aggregates coated by different species of ice turn out to be helpful to shift the bouncing barrier towards larger sizes due to their enhanced sticking properties in some cases. A rarely noticed fact is that H_2O- and H_2O-CH_3OH-NH_3-ice behave liquid-like when UV-irradiated within a PPD-similar environment. Dust aggregates coated by these ice species might be damped in collisions due to the liquid-like ice-shell which would effectively results in an increase of the sticking velocity. In this work, collisions of dust aggregates covered by the liquid-like H_2O-CH_3OH-NH_3-ice-shell are considered numerically. The coefficient of restitution and the sticking velocity are calculated for different thicknesses of the ice-shell. The simulation predicts that an ice-shell-thickness of few microns would be sufficient to allow the growth of cm-sized clusters in the PPD.

Valentin Decoene, Olivier Martineau-Huynh, Matìas Tueros, Simon Chiche

8 pages, ICRC2021 proceeding

Very inclined extensive air showers (EAS), with both down-going and up-going trajectories, are particularly targeted by the next generation of extended radio arrays, such as GRAND. Methods to reconstruct the incoming direction, core position, primary energy and composition of showers with these specific geometries, remain to be developed. Towards that goal, we present a new reconstruction procedure based on the arrival times and the amplitudes of the radio signal, measured at each antenna station. This hybrid reconstruction method, harnesses the fact that the emission is observed, at the antenna level, far away from the emission region, thus allowing for a point-like emission description. Thanks to this assumption, the arrival times are modelled following a spherical wavefront emission, which offers the possibility to reconstruct the radio emission zone as a fixed point along the shower axis. From that point the amplitude distribution at the antenna level is described through an Angular Distribution Function (ADF) taking into account at once all geo-magnetic asymmetries and early late effects as well as additional signal asymmetries featured by very inclined EAS. This method shows promising results in terms of arrival direction reconstruction, within the 0.1{\deg} range, even when taking into account experimental uncertainties, and interesting potential for the energy reconstruction and primary composition identification.

Mark S. Linton, Robert Crittenden, Alkistis Pourtsidou

22 pages, 10 figures, 3 tables

We consider two models of interacting dark energy, both of which interact only through momentum exchange. One is a phenomenological one-parameter extension to wCDM, and the other is a coupled quintessence model described by a Lagrangian formalism. Using a variety of high and low redshift data sets, we perform a global fitting of cosmological parameters and compare to \LambdaCDM, uncoupled quintessence, and wCDM. We find that the models are competitive with \LambdaCDM, even obtaining a better fit when certain data sets are included.

Vittoria Vecchiotti, Giulia Pagliaroli, Francesco Lorenzo Villante

The large-scale diffuse \gamma-ray flux observed by Fermi-LAT in the 1-100 GeV energy range, parameterized as \propto E^{-\Gamma}, has a spectral index \Gamma that depends on the distance from the Galactic center. This feature, if attributed to the diffuse emission produced by cosmic rays (CR) interactions with the interstellar gas, can be interpreted as the evidence of a progressive CR spectral hardening towards the Galactic center. This interpretation challenges the standard cosmic rays diffusion paradigm. We report on the implications of TeV Pulsar Wind Nebulae observed by the HESS Galactic Plane Survey in the 1-100 TeV energy range for the interpretation of Fermi-LAT data. We argue that a relevant fraction of this population cannot be resolved by Fermi-LAT in the GeV domain providing a relevant contribution to the large-scale diffuse emission, viz. the 30\% of the total diffuse \gamma-ray emission in the inner Galaxy. This additional component naturally accounts for a large part of the spectral index variation observed by Fermi-LAT, weakening the evidence of CR spectral hardening in the inner Galaxy.

Péter Németh, Joris Vos, Francisco Molina, Alexander Bastian

Accepted for publication in Astronomy and Astrophysics

A radial velocity follow-up of the long-period sdOB+G1V type spectroscopic binary SB 744 revealed strong lines of fluorine and lead in the optical spectrum of the sdOB star and subsolar metallicity in the G1V companion. With high-quality observations and Gaia astrometric data, we aim at measuring the chemical composition and Galactic kinematics of the system to put it in context with known populations of hot subdwarfs. Such binary systems have high potential, as they give insights into the late stages of binary evolution as well as into the mysterious formation of stripped core helium-burning stars. We have analyzed the optical spectra with homogeneous atmospheric models to derive surface parameters of the binary members from a direct wavelength space decomposition and independently measured the atmospheric properties of the cool companion. The two independent methods reached consistent results, which, amended with constraints from spectral energy distributions provided a subdwarf mass. The Gaia astrometry allowed us to derive the Galactic kinematics of the system. SB 744 turned out to be an old, Population II system, that has gone through dramatic events. The hot subdwarf star belongs to the heavy-metal subclass of sdOB stars and we report super-solar abundances of lead, based on Pb III/IV lines. The He abundance of the hot subdwarf is the lowest among the known heavy-metal sdOB stars. The presence of fluorine implies that SB 744 was once a hierarchical triple system and the inner binary has merged in the near past. As an alternative scenario, single-star evolution through late core helium flash and atmospheric mixing can also produce the observed fluorine abundances. The atmospheric metal over-abundances currently observed are perhaps the results of a combination of mixing processes during formation and radiative support.

Satadru Bag, Varun Sahni, Arman Shafieloo, Yuri Shtanov

16 pages, 6 figures

Braneworld models with induced gravity exhibit phantom-like behaviour of the effective equation of state of dark energy. They can, therefore, naturally accommodate higher values of H_0, preferred by recent local measurements, while satisfying the CMB constraints. We test the background evolution in such phantom braneworld scenarios with the current observational datasets. We find that the phantom braneworld prefers a higher value of H_0 even without the R19 prior, thereby providing a much better fit to the local measurements. Although this braneworld model cannot fully satisfy all combinations of cosmological observables, among existing dark energy candidates the phantom brane provides one of the most compelling explanations of cosmic evolution.

Alex Ho, Margrethe Wold, John T. Conway, Mohammad Poursina

24 pages, 9 figures, accepted for publication in Celestial Mechanics and Dynamical Astronomy

A new technique that utilizes surface integrals to find the force, torque and potential energy between two non-spherical, rigid bodies is presented. The method is relatively fast, and allows us to solve the full rigid two-body problem for pairs of spheroids and ellipsoids with 12 degrees of freedom. We demonstrate the method with two dimensionless test scenarios, one where tumbling motion develops, and one where the motion of the bodies resemble spinning tops. We also test the method on the asteroid binary (66391) 1999 KW4, where both components are modelled either as spheroids or ellipsoids. The two different shape models have negligible effects on the eccentricity and semi-major axis, but have a larger impact on the angular velocity along the z-direction. In all cases, energy and total angular momentum is conserved, and the simulation accuracy is kept at the machine accuracy level.

Eric Masington, Thomas J. Maccarone (Texas Tech University), Liliana Rivera Sandoval, Craig Heinke (University of Alberta), Arash Bahramian (Curtin University), Aarran Shaw (University of Nevada-Reno)

3 pages, 1 figure, accepted to the Journal of the American Association of Variable Star Observers

The subclass of magnetic Cataclysmic Variables (CV), known as asynchronous polars, are still relatively poorly understood. An asynchronous polar is a polar in which the spin period of the white dwarf is either shorter or longer than the binary orbital period (typically within a few percent). The asynchronous polars have been disproportionately detected in soft gamma-ray observations, leading us to consider the possibility that they have intrinsically harder X-ray spectra. We compared standard and asynchronous polars in order to examine the relationship between a CV's synchronization status and its spectral shape. Using the entire sample of asynchronous polars, we find that the asynchronous polars may, indeed, have harder spectra, but that the result is not statistically significant.

Erin M. May, Thaddeus D. Komacek, Kevin B. Stevenson, Eliza M.-R. Kempton, Jacob L. Bean, Matej Malik, Jegug Ih, Megan Mansfield, Arjun B. Savel, Drake Deming, Jean-Michel Desert, Y. Katherina Feng, Jonathan J. Fortney, Tiffany Kataria, Nikole Lewis, Caroline Morley, Emily Rauscher, Adam Showman

24 pages, 10 Figures, 5 Tables. Accepted to AJ. Co-First Authors

The large radii of many hot Jupiters can only be matched by models that have hot interior adiabats, and recent theoretical work has shown that the interior evolution of hot Jupiters has a significant impact on their atmospheric structure. Due to its inflated radius, low gravity, and ultra-hot equilibrium temperature, WASP-76b is an ideal case study for the impact of internal evolution on observable properties. Hot interiors should most strongly affect the non-irradiated side of the planet, and thus full phase curve observations are critical to ascertain the effect of the interior on the atmospheres of hot Jupiters. In this work, we present the first Spitzer phase curve observations of WASP-76b. We find that WASP-76b has an ultra-hot day side and relatively cold nightside with brightness temperatures of 2471 \pm 27~\mathrm{K}/1518 \pm 61~\mathrm{K} at 3.6~\micron and 2699 \pm 32~\mathrm{K}/1259 \pm 44~\mathrm{K} at 4.5~\micron, respectively. These results provide evidence for a dayside thermal inversion. Both channels exhibit small phase offsets of 0.68 \pm 0.48^{\circ} at 3.6~\micron and 0.67 \pm 0.2^{\circ} at 4.5~\mu\mathrm{m}. We compare our observations to a suite of general circulation models that consider two end-members of interior temperature along with a broad range of frictional drag strengths. Strong frictional drag is necessary to match the small phase offsets and cold nightside temperatures observed. From our suite of cloud-free GCMs, we find that only cases with a cold interior can reproduce the cold nightsides and large phase curve amplitude at 4.5~\micron, hinting that the hot interior adiabat of WASP-76b does not significantly impact its atmospheric dynamics or that clouds blanket its nightside.

Jennifer Bergner, Fred Ciesla

Accepted to ApJ

The compositions of planet-forming disks are set by a combination of material inherited from the interstellar medium and material reprocessed during disk formation and evolution. Indeed, comets and primitive meteorites exhibit interstellar-like isotopic ratios and/or volatile compositions, supporting that some pristine material was incorporated intact into icy planetesimals in the Solar Nebula. To date, the survival of volatile interstellar material in the disk stage has not been modeled using realistic disk physics. Here, we present a modeling framework to track the destruction of interstellar ices on dust grains undergoing transport processes within a disk, with a particular focus on explaining the incorporation of pristine material into icy planetesimals. We find it is difficult to explain inheritance through the local assembly of comets, as ice destruction is rapid for small (<10um) grains in the inner few tens of au. Instead, a plausible pathway to inheritance is to form pebbles at larger disk radii, which then drift inwards to the comet-forming zone with their ices mostly preserved. Small grains beyond ~100 au can experience ice photodissociation at the tens of percent level, however little of the ice is actually lost from the grain, likely making this a robust site for in situ ice chemistry. Our models also indicate that many complex organic species should survive passage through the disk intact. This raises the possibility that organics synthesized in the interstellar medium can be delivered to terrestrial planets by icy body impact and thus potentially participate in origins of life chemistry.

Matija Ćuk, Simon J. Lock, Sarah T. Stewart, Douglas P. Hamilton

Accepted for the Planetary Science Journal

A giant impact origin for the Moon is generally accepted, but many aspects of lunar formation remain poorly understood and debated. \'Cuk et al. (2016) proposed that an impact that left the Earth-Moon system with high obliquity and angular momentum could explain the Moon's orbital inclination and isotopic similarity to Earth. In this scenario, instability during the Laplace Plane transition, when the Moon's orbit transitions from the gravitational influence of Earth's figure to that of the Sun, would both lower the system's angular momentum to its present-day value and generate the Moon's orbital inclination. Recently, Tian and Wisdom (2020) discovered new dynamical constraints on the Laplace Plane transition and concluded that the Earth-Moon system could not have evolved from an initial state with high obliquity. Here we demonstrate that the Earth-Moon system with an initially high obliquity can evolve into the present state, and we identify a spin-orbit secular resonance as a key dynamical mechanism in the later stages of the Laplace Plane transition. Some of the simulations by Tian and Wisdom (2020) did not encounter this late secular resonance, as their model suppressed obliquity tides and the resulting inclination damping. Our results demonstrate that a giant impact that left Earth with high angular momentum and high obliquity (\theta > 61^{\circ}) is a promising scenario for explaining many properties of the Earth-Moon system, including its angular momentum and obliquity, the geochemistry of Earth and the Moon, and the lunar inclination.

Oriol Pujolas, Ville Vaskonen, Hardi Veermäe

8 pages, 3 figures

We study the prospects of future gravitational wave (GW) detectors in probing primordial black hole (PBH) binaries. We show that across a broad mass range from 10^{-5}M_\odot to 10^7M_\odot, future GW interferometers provide a potential probe of the PBH abundance that is more sensitive than any currently existing experiment. In particular, we find that galactic PBH binaries with masses as low as 10^{-5}M_\odot may be probed with ET, AEDGE and LISA by searching for nearly monochromatic continuous GW signals. Such searches could independently test the PBH interpretation of the ultrashort microlensing events observed by OGLE. We also consider the possibility of observing GWs from asteroid mass PBH binaries through graviton-photon conversion.

P. De Vis, S. J. Maddox, H. L. Gomez, A. P. Jones, L. Dunne

21 pages, 11 Figures. Published in MNRAS on 07 June 2021

We build a rigorous statistical framework to provide constraints on the chemical and dust evolution parameters for nearby late-type galaxies with a wide range of gas fractions (3\%<f_g<94\%). A Bayesian Monte Carlo Markov Chain framework provides statistical constraints on the parameters used in chemical evolution models. Nearly a million one-zone chemical and dust evolution models were compared to 340 galaxies. Relative probabilities were calculated from the \chi^2 between data and models, marginalised over the different time steps, galaxy masses and star formation histories. We applied this method to find `best fitting' model parameters related to metallicity, and subsequently fix these metal parameters to study the dust parameters. For the metal parameters, a degeneracy was found between the choice of initial mass function, supernova metal yield tables and outflow prescription. For the dust parameters, the uncertainties on the best fit values are often large except for the fraction of metals available for grain growth, which is well constrained. We find a number of degeneracies between the dust parameters, limiting our ability to discriminate between chemical models using observations only. For example, we show that the low dust content of low-metallicity galaxies can be resolved by either reducing the supernova dust yields and/or including photo-fragmentation. We also show that supernova dust dominates the dust mass for low metallicity galaxies and grain growth dominates for high metallicity galaxies. The transition occurs around 12+\log({\rm O/H})=7.75, which is lower than found in most studies in the literature.

A heavy hadron traversing Quark-Gluon Plasma and dragged along in rotational motion is subject to the Lorentz and centrifugal forces. The Lorentz force, sourced by the valence quarks of heavy-ions, possesses the electric and magnetic components in the hadron comoving frame. The electric component renders the hadron unstable by empowering one of its quarks to tunnel through the potential barrier. Assuming that the magnetic field is parallel to the plasma vorticity, the hadron dissociation probability is computed using the Imaginary Time Method and is found to strongly depend on the sign of the quark electric charge. The dissociation probability monotonically increases as a function of vorticity for negative electric charges, whereas for positive charges it exhibits a minimum at a finite value of vorticity. The dissociation probability for the negative charges is larger than for the positive ones at the same magnetic field and vorticity. In relativistic heavy-ion collisions this implies lower abundance of the negatively charged hadrons as compared to the positively charges ones. This effect is significant at moderate collision energies where the plasma vorticity is comparable or larger than the synchrotron frequency.

Stochastic gravitational wave background (SGWB) is a promising tool to probe the very early universe where the standard model of particle physics and cosmology are connected closely. As a possible component of SGWB, gravitational waves (GW) from bubble collisions during the first order cosmological phase transitions deserve comprehensive analyses. In 2017, Ryusuke Jinno and Masahiro Takimoto proposed an elegant analysis approach to derive the analytical expressions of energy spectra of GW from bubble collisions in Minkowski spacetime avoiding large-scale numerical simulations for the first time[1]. However, they neglect the expansion of the universe and regard the duration of phase transitions as infinity in their derivation which could deviate their estimations from true values. For these two reasons, we give a new expression of GW spectra by adopting their method, switching spacetime background to FLRW spacetime and considering a finite duration of phase transitions. By denoting \sigma as the fraction of the speed of phase transitions to the expansion speed of the universe, we find for different \sigma, the maxima of GW energy spectra drop by around 1-3 orders of magnitude than the results given by their previous work. Such a significant decrease may bring about new challenges for detectability of GW from bubble collisions. Luckily, by comparing new spectra with PLI (power-law integrated) sensitivity curves of GW detectors, we find GW from bubble collisions still could be detectable for BBO and LISA in future detection.

If the strange quark were lighter, QCD phase transition could have been first order. Is this near-criticality just a coincidence? We show that this can explain the weak scale criticality through cosmological selection. We first explore quantum critical points of N_f=3 QCD, parameterized by the Higgs vev v_h at T=0, and show that they can be attractors for the quantum-dominated evolution of v_h during eternal inflation -- Hubble selection. This results in the sharply localized weak scale which is critical, not to the cross-over at zero, but to the quantum transition at {\sim}\Lambda_{\rm QCD}. It presents a wishful account of scale hierarchies, using quantum cosmology and near-criticality of SM.

Julia LaFond, Jason T. Wright, Macy J. Huston

7 pages, 3 figures, accepted to JBIS

In 2019, Reyes & Wright used the NASA Astrophysics Data System (ADS) to initiate a comprehensive bibliography for SETI accessible to the public. Since then, updates to the library have been incomplete, partly due to the difficulty in managing the large number of false positive publications generated by searching ADS using simple search terms. In preparation for a recent update, the scope of the library was revised and reexamined. The scope now includes social sciences and commensal SETI. Results were curated based on five SETI keyword searches: "SETI", "technosignature", "Fermi Paradox," "Drake Equation", and "extraterrestrial intelligence." These keywords returned 553 publications that merited inclusion in the bibliography that were not previously present. A curated library of false positive results is now concurrently maintained to facilitate their exclusion from future searches. A search query and workflow was developed to capture nearly all SETI-related papers indexed by ADS while minimizing false positives. These tools will enable efficient, consistent updates of the SETI library by future curators, and could be adopted for other bibliography projects as well.

A. A. Saharian, A. V. Timoshkin

13 pages, 2 figures, to appear in International Journal of Geometric Methods in Modern Physics

In present article we consider an axion F(R) gravity model and described with the help of holographic principle the cosmological models of viscous dark fluid coupled with axion matter in a spatially flat Friedmann-Robertson-Walker (FRW) universe. This description based on generalized infrared-cutoff holographic dark energy, proposed by Nojiri and Odintsov. We explored the Little Rip, the Pseudo Rip, and the power-law bounce cosmological models in terms of the parameters of the inhomogeneous equation of the state of viscous dark fluid and calculated the infrared cutoffs analytically. We represented the energy conservation equation for the dark fluid from a holographic point of view and showed a correspondence between the cosmology of a viscous fluid and holographic cosmology. We analyzed the autonomous dynamic system. In the absence of interaction between fluids, solutions are obtained corresponding to two cases. In the first case, dark energy is missing and the extension describes the component of dark matter. The second case corresponds to cosmological models with an extension due to dark energy. The solutions obtained are investigated for stability. For a cosmological model with the interaction of a special type, the stability of solutions of the dynamic system is also investigated.

Rahul Ramesh, Ashish Kumar Meena, J. S. Bagla (IISER Mohali)

13 pages, 11 figures. Comments welcome

We discuss the prospects of gravitational lensing of gravitational waves (GWs) coming from core-collapse supernovae (CCSN). As the CCSN GW signal can only be detected from within our own Galaxy and the local group by current and upcoming ground-based GW detectors, we focus on microlensing. We introduce a new technique based on analysis of the power spectrum and association of peaks of the power spectrum with the peaks of the amplification factor to identify lensed signals. We validate our method by applying it on the CCSN-like mock signals lensed by a point mass lens. We find that the lensed and unlensed signal can be differentiated using the association of peaks by more than one sigma for lens masses larger than 150 solar masses. We also study the correlation integral between the power spectra and corresponding amplification factor. This statistical approach is able to differentiate between unlensed and lensed signals for lenses as small as 15 solar masses. Further, we demonstrate that this method can be used to estimate the mass of a lens in case the signal is lensed. The power spectrum based analysis is general and can be applied to any broad band signal and is especially useful for incoherent signals.

M. Shokri, J. Sadeghi, M. R. Setare

7 pages, 2 figures

We study the inflationary period driven by a fermionic field which is non-minimally coupled to gravity in the context of the constant-roll approach. We consider the model for a specific form of coupling and perform the corresponding inflationary analysis. By comparing the result with the Planck observations coming from CMB anisotropies, we find the observational constraints on the parameters space of the model and also the predictions the model. We find that the values of r and n_{s} for -1.5<\beta\leq-0.9 are in good agreement with the observations when |\xi|=0.1 and N=60.

F. Acernese, M. Agathos, A. Ain, S. Albanesi, A. Allocca, A. Amato, T. Andrade, N. Andres, T. Andrić, S. Ansoldi, S. Antier, M. Arène, N. Arnaud, M. Assiduo, P. Astone, F. Aubin, S. Babak, F. Badaracco, M. K. M. Bader, S. Bagnasco, J. Baird, G. Ballardin, G. Baltus, C. Barbieri, P. Barneo, F. Barone, M. Barsuglia, D. Barta, A. Basti, M. Bawaj, M. Bazzan, M. Bejger, I. Belahcene, V. Benedetto, S. Bernuzzi, D. Bersanetti, A. Bertolini, U. Bhardwaj, S. Bini, M. Bischi, M. Bitossi, M.-A. Bizouard, F. Bobba, M. Boer, G. Bogaert, M. Boldrini, L. D. Bonavena, F. Bondu, R. Bonnand, B. A. Boom, V. Boschi, V. Boudart, Y. Bouffanais, A. Bozzi, C. Bradaschia, M. Branchesi, M. Breschi, T. Briant, A. Brillet, J. Brooks, G. Bruno, T. Bulik, H. J. Bulten, D. Buskulic, C. Buy, et al. (382 additional authors not shown)

50 pages, 30 figures. Submitted to Class. and Quantum Grav. (July 2021)

The three Advanced Virgo and LIGO gravitational wave detectors participated to the third observing run (O3) between 1 April 2019 15:00 UTC and 27 March 2020 17:00 UTC,leading to weekly detections of gravitational waves. This paper describes the Advanced Virgo detector calibration and the reconstruction of the detector strain h(t) during O3, as well as the estimation of the associated uncertainties. For the first time, the photon calibration technique as been used as reference for Virgo calibration, which allowed to cross-calibrate the strain amplitude of the Virgo and LIGO detectors. The previous reference, so-called free swinging Michelson technique, has still been used but as an independent cross-check. h(t) reconstruction and noise subtraction were processed online, with good enough quality to prevent the need for offline reprocessing, except for the two last weeks of September 2019. The uncertainties for the reconstructed h(t) strain, estimated in this paper, are frequency independent: 5% in amplitude, 35 mrad in phase and 10 \mus in timing, with the exception of larger uncertainties around 50 Hz.