adsabs/SciX_UAT_keywords huggingface dataset:
Detection of the Extended γ-Ray Emission from the High Galactic Latitude Calvera's SNR Candidate

We report the extended GeV γ-ray emission that is spatially associated with the high Galactic latitude supernova remnant (SNR) candidate-Calvera's SNR with the Pass 8 data recorded by the Fermi Large Area Telescope. The γ-ray spectrum of Calvera's SNR between 100 MeV and 1 TeV shows an evident (~3.4σ) spectral curvature at several tens of GeV. The multiwavelength data can be fitted with either a leptonic model or a hadronic one. However, the leptonic model exhibits inconsistency between the flat radio spectrum and the hard GeV γ-ray spectrum of Calvera's SNR. For the hadronic model, the spectral index of protons should be harder than 1.6 and the total energy of protons is fitted to be more than one order of magnitude higher than the explosion energy of a typical supernova, which also challenges the hadronic model. The evident spectral curvature and the absence of nonthermal X-ray emission from Calvera's SNR makes it to be an interesting source bridging young-aged SNRs with bright nonthermal X-ray emission and old-aged SNRs interacting with molecular clouds.

Keywords: supernova remnants; gamma-ray astronomy; gamma-ray sources
The Evolutionary Status of 17 Com, The Hottest Member of Coma Berenices

The integrated flux, linear radius and effective temperature of 17 Com A (A0p CrEu), the hottest member of the Coma Berenices open cluster, are determined using the Infrared Flux Method. The surface gravity is derived by fitting the Hβ profile. The effective temperature and surface gravity are found to be smaller than most previous determinations. The evolutionary status of 17 Com A is discussed in light of these new parameters using stellar evolution modeling. 17 Com A appears to be finishing its lifetime on the Main Sequence.

Keywords: stellar evolution; ap stars; open star clusters
Subkiloparsec Scaling Relations between Hot Gas, Dense Gas, and Star Formation Rate in Five Nearby Star-forming Galaxies

Based on the newly acquired dense gas observations from the JCMT MALATANG survey and X-ray data from Chandra, we explore the correlation between hot gas and HCN J = 4 → 3 and HCO+ J = 4 → 3 emission for the first time at subkiloparsec scale of five nearby star-forming galaxies, namely M82, M83, IC 342, NGC 253, and NGC 6946. We find that both HCN J = 4 → 3 and HCO+ J = 4 → 3 line luminosity show a statistically significant correlation with the 0.5‑2 keV X-ray emission of the diffuse hot gas ( ${L}_{0.5-2\,\mathrm{keV}}^{\mathrm{gas}}$ ). The Bayesian regression analysis gives the best fit of $\mathrm{log}({L}_{0.5-2\,\mathrm{keV}}^{\mathrm{gas}}$ / $\mathrm{erg}\,{{\rm{s}}}^{-1})=2.39\,\mathrm{log}({L}_{\mathrm{HCN}(4-3)}^{{\prime} }$ /K km s‑1 pc2) + 24.83 and $\mathrm{log}({L}_{0.5-2\,\mathrm{keV}}^{\mathrm{gas}}$ / $\mathrm{erg}\,{{\rm{s}}}^{-1})=2.48\,\mathrm{log}({L}_{{\mathrm{HCO}}^{+}(4-3)}^{{\prime} }$ /K km s‑1 pc2) + 23.84, with dispersion of ∼0.69 dex and 0.54 dex, respectively. At the subkiloparsec scale, we find that the power-law index of the ${L}_{0.5-2\,\mathrm{keV}}^{\mathrm{gas}}$ ‑star formation rate (SFR) relation is $\mathrm{log}({L}_{0.5-2\,\mathrm{keV}}^{\mathrm{gas}}/\mathrm{erg}\,{{\rm{s}}}^{-1})=1.80\,\mathrm{log}(\mathrm{SFR}/{M}_{\odot }\,{\mathrm{yr}}^{-1})+39.16$ , deviated from previous linear relations at the global scale. This implies that the global property of hot gas significantly differs from individual resolved regions, which is influenced by the local physical conditions close to the sites of star formation.

Keywords: star formation; interstellar medium
Voyager 1 Electron Densities in the Very Local Interstellar Medium to beyond 160 au

The two Voyager spacecraft have been exploring the interstellar medium beyond the heliopause since 2012 (Voyager 1) and 2018 (Voyager 2). Electron plasma oscillations and a quasi-thermal noise line at the electron plasma frequency have enabled the determination of the electron density in this region, revealing a radial density gradient convolved with shocks and pressure fronts. Voyager 1 has a functioning wideband receiver that provides high-spectral-resolution observations allowing the detection of the quasi-thermal noise line and has now provided electron densities to 161.4 au. Since a pressure pulse observed in 2020 around day 146 at about 149 au, the density has remained relatively constant at 0.147 cm‑3 based on the most recent observations from 2023, suggesting that Voyager 1 has reached a broad density peak and possibly a new regime.

Keywords: interstellar medium; interstellar plasma; space plasmas; astrosphere interstellar medium interactions
The Giant Accreting Protoplanet Survey (GAPlanetS)-Results from a 6 yr Campaign to Image Accreting Protoplanets

Accreting protoplanets are windows into planet formation processes, and high-contrast differential imaging is an effective way to identify them. We report results from the Giant Accreting Protoplanet Survey (GAPlanetS), which collected Hα differential imagery of 14 transitional disk host stars with the Magellan Adaptive Optics System. To address the twin challenges of morphological complexity and point-spread function instability, GAPlanetS required novel approaches for frame selection and optimization of the Karhounen-Loéve Image Processing algorithm pyKLIP. We detect one new candidate, CS Cha "c," at a separation of 68 mas and a modest Δmag of 2.3. We recover the HD 142527 B and HD 100453 B accreting stellar companions in several epochs, and the protoplanet PDS 70 c in 2017 imagery, extending its astrometric record by nine months. Though we cannot rule out scattered light structure, we also recover LkCa 15 "b," at Hα; its presence inside the disk cavity, absence in Continuum imagery, and consistency with a forward-modeled point source suggest that it remains a viable protoplanet candidate. Through targeted optimization, we tentatively recover PDS 70 c at two additional epochs and PDS 70 b in one epoch. Despite numerous previously reported companion candidates around GAplanetS targets, we recover no additional point sources. Our moderate Hα contrasts do not preclude most protoplanets, and we report limiting Hα contrasts at unrecovered candidate locations. We find an overall detection rate of ~36 ${}_{-22}^{+26} \% $ , considerably higher than most direct imaging surveys, speaking to both GAPlanetS's highly targeted nature and the promise of Hα differential imaging for protoplanet identification.

Keywords: direct imaging; exoplanet astronomy; exoplanet detection methods; exoplanet formation; exoplanets; planet formation; protoplanetary disks; stellar accretion; high contrast techniques; adaptive optics; astronomy image processing
Simple Yet Powerful: Hot Galactic Outflows Driven by Supernovae

Supernovae (SNe) drive multiphase galactic outflows, impacting galaxy formation; however, cosmological simulations mostly use ad hoc feedback models for outflows, making outflow-related predictions from first principles problematic. Recent small-box simulations resolve individual SNe remnants in the interstellar medium (ISM), naturally driving outflows and permitting a determination of the wind loading factors of energy ηE, mass ${\eta }_{m}$ , and metals ${\eta }_{Z}$ . In this Letter, we compile small-box results, and find consensus that the hot outflows are much more powerful than the cool outflows: (I) hot outflows generally dominate the energy flux, and (II) their specific energy es,h is 10-1000 times higher than cool outflows. Moreover, the properties of hot outflows are remarkably simple: ${e}_{s,h}\propto {\eta }_{E,h}/{\eta }_{m,h}$ is almost invariant over four orders of magnitude of star formation surface density. Also, we find tentatively that ${\eta }_{E,h}/{\eta }_{Z,h}\sim $ 0.5. If corroborated by more simulation data, these correlations reduce the three hot phase loading factors into one. Finally, this one parameter is closely related to whether the ISM has a "breakout" condition. The narrow range of ${e}_{s,h}$ indicates that hot outflows cannot escape dark matter halos with log ${M}_{\mathrm{halo}}\ [{M}_{\odot }]\gtrsim 12$ . This mass is also where the galaxy mass-metallicity relation reaches its plateau, implying a deep connection between hot outflows and galaxy formation. We argue that hot outflows should be included explicitly in cosmological simulations and (semi-)analytic modeling of galaxy formation.

Keywords: stellar feedback; galaxy formation; galaxy evolution; galactic winds; interstellar medium; chemical enrichment; galaxy chemical evolution; metallicity; hydrodynamical simulations
A New Census of the 0.2 < z < 3.0 Universe. I. The Stellar Mass Function

There has been a long-standing factor-of-two tension between the observed star formation rate density and the observed stellar mass buildup after z ∼ 2. Recently, we have proposed that sophisticated panchromatic SED models can resolve this tension, as these methods infer systematically higher masses and lower star formation rates than standard approaches. In a series of papers, we now extend this analysis and present a complete, self-consistent census of galaxy formation over 0.2 < z < 3 inferred with the Prospector galaxy SED-fitting code. In this work, Paper I, we present the evolution of the galaxy stellar mass function using new mass measurements of ∼105 galaxies in the 3D-HST and COSMOS-2015 surveys. We employ a new methodology to infer the mass function from the observed stellar masses: instead of fitting independent mass functions in a series of fixed redshift intervals, we construct a continuity model that directly fits for the redshift evolution of the mass function. This approach ensures a smooth picture of galaxy assembly and makes use of the full, non-Gaussian uncertainty contours in our stellar mass inferences. The resulting mass function has higher number densities at a fixed stellar mass than almost any other measurement in the literature, largely owing to the older stellar ages inferred by Prospector. The stellar mass density is ∼50% higher than previous measurements, with the offset peaking at z ∼ 1. The next two papers in this series will present the new measurements of the star-forming main sequence and the cosmic star formation rate density, respectively.

Keywords: galaxy properties; galaxy formation; galaxy abundances; high-redshift galaxies
Constructing Mixture Models for Sensitivity Estimates from Subsets of Separate Injections

I investigate the general question of how to construct a set of samples (found injections) from a mixture of samples from separate subpopulations in order to estimate search sensitivity via Monte Carlo sums. This is of general interest for catalog science, in which one must estimate a survey's sensitivity to different types of sources. Sensitivity estimates targeting different subpopulations or different observing periods may be combined to provide overarching estimates of the sensitivity through larger regions of parameter space. Specifically, I consider 2 cases: (i) when injections from subpopulations were conducted over the same span of time and (ii) when injections from subpopulations were conducted in non-overlapping periods. Any general collection of subpopulations can be decomposed into these cases.

Keywords: gravitational wave astronomy; astronomical methods; gravitational waves; catalogs; surveys
pygwb: A Python-based Library for Gravitational-wave Background Searches

The collection of gravitational waves (GWs) that are either too weak or too numerous to be individually resolved is commonly referred to as the gravitational-wave background (GWB). A confident detection and model-driven characterization of such a signal will provide invaluable information about the evolution of the universe and the population of GW sources within it. We present a new, user-friendly, Python-based package for GW data analysis to search for an isotropic GWB in ground-based interferometer data. We employ cross-correlation spectra of GW detector pairs to construct an optimal estimator of the Gaussian and isotropic GWB, and Bayesian parameter estimation to constrain GWB models. The modularity and clarity of the code allow for both a shallow learning curve and flexibility in adjusting the analysis to one's own needs. We describe the individual modules that make up pygwb, following the traditional steps of stochastic analyses carried out within the LIGO, Virgo, and KAGRA Collaboration. We then describe the built-in pipeline that combines the different modules and validate it with both mock data and real GW data from the O3 Advanced LIGO and Virgo observing run. We successfully recover all mock data injections and reproduce published results.

Keywords: gravitational wave astronomy; gravitational waves; gravitational wave detectors
HST PanCET Program: A Complete Near-UV to Infrared Transmission Spectrum for the Hot Jupiter WASP-79b

We present a new optical transmission spectrum of the hot Jupiter WASP-79b. We observed three transits with the STIS instrument mounted on the Hubble Space Telescope (HST), spanning 0.3-1.0 μm. Combining these transits with previous observations, we construct a complete 0.3-5.0 μm transmission spectrum of WASP-79b. Both HST and ground-based observations show decreasing transit depths toward blue wavelengths, contrary to expectations from Rayleigh scattering or hazes. We infer atmospheric and stellar properties from the full near-UV to infrared transmission spectrum of WASP-79b using three independent retrieval codes, all of which yield consistent results. Our retrievals confirm previous detections of H2O (at 4.0σ confidence) while providing moderate evidence of H- bound-free opacity (3.3σ) and strong evidence of stellar contamination from unocculted faculae (4.7σ). The retrieved H2O abundance (~1%) suggests a superstellar atmospheric metallicity, though stellar or substellar abundances remain consistent with present observations (O/H = 0.3-34× stellar). All three retrieval codes obtain a precise H- abundance constraint: log( ${X}_{{{\rm{H}}}^{-}}$ ) ≈ -8.0 ± 0.7. The potential presence of H- suggests that James Webb Space Telescope observations may be sensitive to ionic chemistry in the atmosphere of WASP-79b. The inferred faculae are ~500 K hotter than the stellar photosphere, covering ~15% of the stellar surface. Our analysis underscores the importance of observing UV-optical transmission spectra in order to disentangle the influence of unocculted stellar heterogeneities from planetary transmission spectra.

Keywords: exoplanet atmospheres; exoplanet atmospheric composition; observational astronomy; hot jupiters; transmission spectroscopy
Narrowband Large Amplitude Whistler-mode Waves in the Solar Wind and Their Association with Electrons: STEREO Waveform Capture Observations

Large amplitude (up to 70 mV m-1) whistler-mode waves at frequencies of ∼0.2-0.4 fce (electron cyclotron frequency) are frequently observed in the solar wind. The waves are obliquely propagating at angles close to the resonance cone, resulting in significant electric fields parallel to the background magnetic field, enabling strong interactions with solar wind electrons. Very narrowband (sinusoidal waveforms) and less coherent waves (more irregular waveforms) occur, but do not have a bimodal distribution. Frequencies and/or propagation angles are distinctly different from whistler-mode waves usually observed in the solar wind, and amplitudes are 1-3 orders of magnitude larger. Waves occur most often in association with stream interaction regions, and are often "close-packed." Wave occurrence as a function of normalized electron heat flux and beta is consistent with the whistler heat flux fan instability for both the narrowband coherent and the incoherent waves. The incoherent waves are associated with zero or near zero heat flux. This suggests that the less coherent waves may be more effective in regulating the electron heat flux, or that the scattering and energization of solar wind electrons by the narrowband waves results in broadening of the waves. The oblique propagation and large amplitudes of both the narrowband and less coherent whistlers enable resonant interactions with electrons over a broad energy range, and, unlike parallel whistlers, do not require that the electrons and waves counter-propagate. Therefore, they are much more effective in modifying solar wind electron distributions than parallel propagating waves.

Keywords: interplanetary turbulence; space plasmas; solar wind; plasma physics; corotating streams; interplanetary physics; plasma astrophysics
Triggering Mechanism for Eruption of Two Filaments Observed by the Solar Dynamics Observatory, Nobeyama Radioheliograph, and RHESSI

We investigate the eruptive process of two filaments, which is associated with an M-class flare that occurred in 2011 August 4. The filaments are partly overlapped, one in the active region and the other just beside it, and erupt together as a halo coronal mass ejection. For this study, we used the Atmospheric Imaging Assembly and the Heliospheric Magnetic Imager on board the Solar Dynamics Observatory, the Nobeyama Radioheliograph 17 GHz, and the RHESSI Hard X-ray satellite. We found three distinct phases in the microwave flux profile and in the rising pattern of the filaments during the event. In the first phase, there was weak nonthermal emission at 17 GHz and hard X-rays. Those nonthermal sources appeared on one edge of the western filament (F2) in the active region. The F2 began to be bright and rose upward rapidly, while the eastern filament (F1), which was extended to the quiet region, started to brighten from the peak time of the 17 GHz flux. In the second phase, the nonthermal emission weakened and the F2 rose up slowly, while the F1 began to rise up. In the third phase, two filaments erupted together. Since the F1 was stable for a long time in the quiet region, breaking the equilibrium state of the F1 would be decisive for the successful eruption of two filaments and it seems clear that the evolution of the F2 provoked the unstable F1. We suggest that tether-cutting reconnection between two overlapped filaments triggers the eruption of the two filaments as a tangled identity.

Keywords: solar flares; solar filaments; solar corona; solar filament eruptions
Angular Momenta, Magnetization, and Accretion of Protostellar Cores

Building on our previous hydrodynamic study of the angular momenta of cloud cores formed during gravitational collapse of star-forming molecular gas in Kuznetsova et al., we now examine core properties assuming ideal magnetohydrodynamics (MHD). Using the same sink-patch implementation for the Athena MHD code, we characterize the statistical properties of cores, including the mass accretion rates, specific angular momenta, and alignments between the magnetic field and the spin axis of the core on the 0.1 pc scale. Our simulations, which reproduce the observed relation between magnetic field strength and gas density, show that magnetic fields can help collimate low-density flows and help seed the locations of filamentary structures. Consistent with our previous purely hydrodynamic simulations, stars (sinks) form within the heterogeneous environments of filaments, such that accretion onto cores is highly episodic leading to short-term variability but no long-term monotonic growth of the specific angular momenta. With statistical characterization of protostellar cores properties and behaviors, we aim to provide a starting point for building more realistic and self-consistent disk formation models, helping to address whether magnetic fields can prevent the development of (large) circumstellar disks in the ideal MHD limit.

Keywords: star formation; magnetic fields; protostars; protoplanetary disks
An Adaptive Optics Census of Companions to Northern Stars Within 25 pc with Robo-AO

In order to assess the multiplicity statistics of stars across spectral types and populations in a volume-limited sample, we censused nearby stars for companions with Robo-AO. We report on observations of 1157 stars of all spectral types within 25 pc with decl. >-13° searching for tight companions. We detected 154 companion candidates with separations ranging from ~0.″15 to 4.″0 and magnitude differences up to Δm ${}_{i^{\prime} }\leqslant 7$ using the robotic adaptive optics instrument Robo-AO. We confirmed physical association from Gaia EDR3 astrometry for 53 of the companion candidates, 99 remain to be confirmed, and two were ruled out as background objects. We complemented the high-resolution imaging companion search with a search for comoving objects with separations out to 10,000 au in Gaia EDR3, which resulted in an additional 147 companions registered. Of the 301 total companions reported in this study, 49 of them are new discoveries. Out of the 191 stars with significant acceleration measurements in the Hipparcos-Gaia catalog of accelerations, we detect companions around 115 of them, with the significance of the acceleration increasing as the companion separation decreases. From this survey, we report the following multiplicity fractions (compared to literature values): 40.9% ± 3.0% (44%) for FGK stars and 28.2% ± 2.3% (27%) for M stars, as well as higher-order fractions of 5.5% ± 1.1% (11%) and 3.9% ± 0.9% (5%) for FGK stars and M-type stars, respectively.

Keywords: binary stars; multiple stars; close binary stars; high angular resolution; direct imaging; astronomical methods; observational astronomy; astronomy data analysis; solar neighborhood
A Parametric Galactic Model toward the Galactic Bulge Based on Gaia and Microlensing Data

We developed a parametric Galactic model toward the Galactic bulge by fitting to spatial distributions of the Gaia DR2 disk velocity, VVV proper motion, BRAVA radial velocity, OGLE-III red clump star count, and OGLE-IV star count and microlens rate, optimized for use in microlensing studies. We include the asymmetric drift of Galactic disk stars and the dependence of velocity dispersion on Galactic location in the kinematic model, which has been ignored in most previous models used for microlensing studies. We show that our model predicts a microlensing parameter distribution significantly different from those typically used in previous studies. We estimate various fundamental model parameters for our Galaxy through our modeling, including the initial mass function (IMF) in the inner Galaxy. Combined constraints from star counts and the microlensing event timescale distribution from the OGLE-IV survey, in addition to a prior on the bulge stellar mass, enable us to successfully measure IMF slopes using a broken power-law form over a broad mass range, ${\alpha }_{\mathrm{bd}}={0.22}_{-0.55}^{+0.20}$ for M < 0.08 M⊙, ${\alpha }_{\mathrm{ms}}={1.16}_{-0.15}^{+0.08}$ for 0.08 M⊙ ≤ M < Mbr, and ${\alpha }_{\mathrm{hm}}={2.32}_{-0.10}^{+0.14}$ for M ≥ Mbr, as well as a break mass at ${M}_{\mathrm{br}}={0.90}_{-0.14}^{+0.05}\,{M}_{\odot }$ . This is significantly different from the Kroupa IMF for local stars, but similar to the Zoccali IMF measured from a bulge luminosity function. We also estimate the dark matter mass fraction in the bulge region of 28% ± 7% which could be larger than a previous estimate. Because our model is purely parametric, it can be universally applied using the parameters provided in this paper. (A tool for microlensing simulation using our Galactic model has been published, Koshimoto & Ranc 2021, and can be downloaded at https://github.com/nkoshimoto/genulens.)

Keywords: initial mass function; gravitational microlensing; galactic bulge; milky way disk; milky way galaxy