adsabs/SciX_UAT_keywords huggingface dataset:
The California-Kepler Survey. XI. A Survey of Chromospheric Activity through the Lens of Precise Stellar Properties

Surveys of exoplanet host stars are valuable tools for assessing population level trends in exoplanets, and their outputs can include stellar ages, activity, and rotation periods. We extracted chromospheric activity measurements from the California-Kepler Survey Gaia survey spectra in order to probe connections between stellar activity and fundamental stellar properties. Building on the California Kepler Survey's legacy of 1189 planet host star stellar properties including temperature, surface gravity metallicity, and isochronal age, we add measurements of the Ca II H and K lines as a proxy for chromospheric activity for 879 planet hosting stars. We used these chromospheric activity measurements to derive stellar rotation periods. We find a discrepancy between photometrically derived and activity-derived rotation periods for stars on the Rossby Ridge. These results support the theory of weakened magnetic braking. We find no evidence for metallicity-dependent activity relations, within the metallicity range of -0.2 to +0.3 dex. With our single epoch spectra we identify stars that are potentially in Maunder minimum-like state using a combination of log( ${R}_{\mathrm{HK}}^{{\prime} }$ ) and position below the main sequence. We do not yet have the multiyear time series needed to verify stars in Maunder minimum-like states. These results can help inform future theoretical studies that explore the relationship between stellar activity, stellar rotation, and magnetic dynamos.

Keywords: stellar activity; exoplanet astronomy; stellar chromospheres
Very High-energy Afterglow Emission of GRB 190829A: Evidence for Its Hadronic Origin?

The detection of multi-TeV gamma rays from the afterglow phase of GRB 190829A by the High Energy Stereoscopic System telescope is an addition to the already existing list of two GRBs observed in very high-energy (VHE) gamma rays in recent years. Jets of blazars and GRBs have many similarities and the photohadronic model is very successful in explaining the VHE gamma-ray spectra from the high-energy blazars. Recently, the photohadronic model has been successfully applied to study the sub-TeV gamma rays from the afterglow phases of GRB 180720B and GRB 190114C. We employed this model again to explain the VHE spectra observed for the two consecutive nights from GRB 190829A. We show that the spectra of GRB 190829A can be due to the interactions of high-energy protons with the synchrotron self-Compton photons in the forward shock region of the GRB jet, similar to the low emission state of the VHE flaring events of high-energy blazars. We speculate that, if in the future, it is possible to observe the VHE gamma-ray spectra from nearby GRBs in their afterglow phases, then some of them could only be explained by employing two different spectral indices. If confirmed, such VHE spectra could be interpreted as a result of the interactions of the high-energy protons with the photons, both from the synchrotron background and the synchrotron self-Compton background in the forward shock region.

Keywords: particle astrophysics; blazars; gamma-ray bursts; relativistic jets
Recurring Planetary Debris Transits and Circumstellar Gas around White Dwarf ZTF J0328-1219

We present follow-up photometry and spectroscopy of ZTF J0328-1219, strengthening its status as a white dwarf exhibiting transiting planetary debris. Using TESS and Zwicky Transient Facility photometry, along with follow-up high-speed photometry from various observatories, we find evidence for two significant periods of variability at 9.937 and 11.2 hr. We interpret these as most likely the orbital periods of different debris clumps. Changes in the detailed dip structures within the light curves are observed on nightly, weekly, and monthly timescales, reminiscent of the dynamic behavior observed in the first white dwarf discovered to harbor a disintegrating asteroid, WD 1145+017. We fit previously published spectroscopy along with broadband photometry to obtain new atmospheric parameters for the white dwarf, with M⋆ = 0.731 ± 0.023 M⊙, Teff = 7630 ± 140 K, and [Ca/He] = - 9.55 ± 0.12. With new high-resolution spectroscopy, we detect prominent and narrow Na D absorption features likely of circumstellar origin, with velocities 21.4 ± 1.0 km s-1 blueshifted relative to atmospheric lines. We attribute the periodically modulated photometric signal to dusty effluents from small orbiting bodies such as asteroids or comets, but we are unable to identify the most likely material that is being sublimated, or otherwise ejected, as the environmental temperatures range from roughly 400 to 700 K.

Keywords: white dwarf stars; transits; circumstellar dust; roche limit; tidal disruption; planetesimals
Col-OSSOS: The Distribution of Surface Classes in Neptune's Resonances

The distribution of surface classes of resonant trans-Neptunian objects (TNOs) provides constraints on the protoplanetesimal disk and giant planet migration. To better understand the surfaces of TNOs, the Colours of the Outer Solar System Origins Survey acquired multiband photometry of 102 TNOs and found that the surfaces of TNOs can be well described by two surface classifications: BrightIR and FaintIR. These classifications both include optically red members and are differentiated predominantly based on whether their near-infrared spectral slope is similar to their optical spectral slope. The vast majority of cold classical TNOs, with dynamically quiescent orbits, have the FaintIR surface classification, and we infer that TNOs in other dynamical classifications with FaintIR surfaces share a common origin with the cold classical TNOs. Comparison between the resonant populations and the possible parent populations of cold classical and dynamically excited TNOs reveal that the 3:2 has minimal contributions from the FaintIR class, which could be explained by the ν 8 secular resonance clearing the region near the 3:2 before any sweeping capture occurred. Conversely, the fraction of FaintIR objects in the 4:3 resonance, 2:1 resonance, and the resonances within the cold classical belt suggest that the FaintIR surface formed in the protoplanetary disk between ≳34.6 and ≲47 au, though the outer bound depends on the degree of resonance sweeping during migration. The presence and absence of the FaintIR surfaces in Neptune's resonances provides critical constraints for the history of Neptune's migration, the evolution of the ν 8, and the surface class distribution in the initial planetesimal disk.

Keywords: trans-neptunian objects; resonant kuiper belt objects
On the Walén Relation for Alfvénic Fluctuations in Interplanetary Space

In interplanetary space, the majority of the Alfvénic fluctuations cannot satisfy the Walén relation even though plasma and magnetic field fluctuations are correlated very well. Finding a proper de Hoffman-Teller (HT) wave frame velocity is thus important for characterizing the Alfvénic fluctuations. Recognizing that the Alfvénic fluctuations emanating from different sizes of solar wind streams have their own HT frames, we propose a new scheme called the wave frame with varying velocity (WFVV) method by considering the local averaged HT frame to find a time-varying profile of HT frame velocity. We apply this WFVV method to two Alfvénic events on 2002 October 14 and 17. Unlike the three other schemes discussed in this study, the WFVV method is preferable because it can provide the HT frame variation in more detail, particularly for the large solar wind changes associated with directional discontinuities observed in the October 14 event. For such Alfvénic structures, a time-dependent HT frame derived from the WFVV method, rather than a constant HT frame, produces a better result of the Walén test together with a smaller convection electric field. The difference of estimated HT frame velocities among different schemes was as large as 30 km s-1 for these two events. In addition, we noted that the degree of Alfvénicity tends to decrease with an increasing variance of HT frame velocity, suggesting that a constant HT frame will also give good results for cases of a small variance of HT frame velocity.

Keywords: alfven waves; solar wind; space plasmas; interplanetary magnetic fields; magnetohydrodynamics
AspGap: Augmented Stellar Parameters and Abundances for 37 Million Red Giant Branch Stars from Gaia XP Low-resolution Spectra

We present AspGap, a new approach to inferring stellar labels from the low-resolution Gaia XP spectra, including precise [α/M] estimates—the first time these are obtained by such an approach. AspGap is a neural-network-based regression model trained on APOGEE spectra. In the training step, AspGap learns to use not only XP spectra to predict stellar labels but also the high-resolution APOGEE spectra that lead to the same stellar labels. The inclusion of this last model component—dubbed the hallucinator—creates a more physically motivated mapping and significantly improves the prediction of stellar labels in the validation, particularly that of [α/M]. For giant stars, we find cross-validated rms accuracies for T eff, log g, [M/H], and [α/M] of ∼1%, 0.12 dex, 0.07 dex, and 0.03 dex, respectively. We also validate our labels through comparison with external data sets and through a range of astrophysical tests that demonstrate that we are indeed determining [α/M] from the XP spectra, rather than just inferring it indirectly from correlations with other labels. We publicly release the AspGap codebase, along with our stellar parameter catalog for all giants observed by Gaia XP. AspGap enables the discovery of new insights into the formation and chemodynamics of our Galaxy by providing precise [α/M] estimates for 37 million giant stars, including 14 million with radial velocities from Gaia.

Keywords: stellar abundances; catalogs; milky way galaxy; red giant stars; chemical abundances; metallicity; effective temperature; spectrophotometry; spectroscopy
Spectral Fit Residuals as an Indicator to Increase Model Complexity

Spectral fitting of X-ray data usually involves minimizing statistics like the chi-square and the Cash statistic. Here we discuss their limitations and introduce two measures based on the cumulative sum (CuSum) of model residuals to evaluate whether model complexity could be increased: the percentage of bins exceeding a nominal threshold in a CuSum array (pctCuSum), and the excess area under the CuSum compared to the nominal (p area). We demonstrate their use with an application to a Chandra ACIS spectral fit.

Keywords: astrostatistics tools; x-ray astronomy; astronomy software
Intermediate and Power-law Inflation in the Tachyon Model with Constant Sound Speed

By adopting the intermediate and power-law scale factors, we study the tachyon inflation with constant sound speed. We perform some numerical analysis on the perturbation and non-Gaussianity parameters in this model and compare the results with observational data. By using the constraints on the scalar spectral index and tensor-to-scalar ratio obtained from Planck2018 TT, TE, and EE+lowE+lensing+BAO+BK14 data; the constraints on the running of the scalar spectral index obtained from Planck2018 TT, TE, and EE+lowEB+lensing data; and the constraints on tensor spectral index obtained from Planck2018 TT, TE, and EE+lowE+lensing+BK14+BAO+LIGO and Virgo2016 data, we find the observationally viable ranges of the model's parameters at both 68% CL and 95% CL. We also analyze the non-Gaussian features of the model in the equilateral and orthogonal configurations. Based on Planck2018 TTT, EEE, TTE, and EET data, we find constraints on the sound speed of 0.276 ≤ c s ≤ 1 at 68% CL, 0.213 ≤ c s ≤ 1 at 95% CL, and 0.186 ≤ c s ≤ 1 at 97% CL.

Keywords: inflationary universe; observational cosmology; early universe
Early Results from GLASS-JWST. VII. Evidence for Lensed, Gravitationally Bound Protoglobular Clusters at z = 4 in the Hubble Frontier Field A2744

We investigate the blue and optical rest-frame sizes (λ ≃ 2300-4000 Å) of three compact star-forming regions in a galaxy at z = 4 strongly lensed (×30, ×45, and ×100) by the Hubble Frontier Field galaxy cluster A2744 using GLASS-ERS James Webb Space Telescope (JWST)/NIRISS imaging at 1.15 μm, 1.50 μm, and 2.0 μm with a point-spread function ≲0.″1. In particular, the Balmer break is probed in detail for all multiply imaged sources of the system. With ages of a few tens of Myr, stellar masses in the range (0.7-4.0) ×106 M ⊙ and optical/ultraviolet effective radii spanning the interval 3 < R eff < 20 pc, such objects are currently the highest-redshift (spectroscopically confirmed) gravitationally bound young massive star clusters (YMCs), with stellar mass surface densities resembling those of local globular clusters. Optical (4000 Å, JWST-based) and ultraviolet (1600 Å, Hubble Space Telescope-based) sizes are fully compatible. The contribution to the ultraviolet underlying continuum emission (1600 Å) is ~30%, which decreases by a factor of 2 in the optical for two of the YMCs (~4000 Å rest-frame), reflecting the young ages (<30 Myr) inferred from the spectral energy distribution fitting and supported by the presence of high-ionization lines secured with the Very Large Telescope/MUSE. Such bursty forming regions enhance the specific star formation rate of the galaxy, which is ≃10 Gyr-1. This galaxy would be among the extreme analogs observed in the local universe having a high star formation rate surface density and a high occurrence of massive stellar clusters in formation. *Based on observations collected with JWST under the ERS program 1324 (PI T. Treu).

Keywords: high-redshift galaxies; young star clusters
An Excited-state OH Maser Survey toward WISE Point Sources

We report a survey of excited-state hydroxyl (ex-OH) masers at the 4.7 and 6.0 GHz transitions toward a sample consisting of 3348 massive star-forming region candidates selected from the all-sky Wide-field Infrared Survey Explorer point-source catalog. The survey was conducted with the Shanghai Tianma Radio Telescope. In total, 6, 9, and 30 sources were detected with the ex-OH masers at the 4766, 6031, and 6035 MHz transitions, respectively. Among them, one 4766 MHz, one 6031 MHz, and five 6035 MHz ex-OH maser sources are newly identified. A series of statistical analyses derived that the ex-OH masers were detected efficiently toward the subsamples associated with both the 6.7 GHz CH3OH maser and radio recombination lines (RRLs), whereas compared to the CH3OH masers, the ex-OH masers are more likely to be produced toward the sources with stronger 22 μm band emission. A significant luminosity correlation is found between the ex-OH masers and RRLs. In addition, we found that the magnetic field strength of most sources with the 6.7 GHz CH3OH maser was stronger relative to that of sources without the CH3OH maser. Combined with these, it demonstrates that the ex-OH maser is associated with more evolved star-forming regions, likely associated with thicker dust envelopes. Meanwhile, the ex-OH masers might be a potential tracer for measuring the Galactic magnetic field information on the large-scale views using their Zeeman pairs.

Keywords: surveys; interstellar masers; star formation; interstellar molecules
Horizonless Spacetimes As Seen by Present and Next-generation Event Horizon Telescope Arrays

We study the capabilities of present and future radio very long baseline interferometry arrays to distinguish black holes from horizonless spacetimes. We consider an example of a horizonless spacetime, obtained by overspinning a regular black hole. Its image is distinct from the image of a Kerr spacetime due to a second set of photon rings interior to the shadow. These photon rings cannot be directly resolved by present and even next-generation Event Horizon Telescope arrays, but instead imprint themselves in horizon-scale images as excess central brightness relative to that of a black hole. We demonstrate that future arrays can decrease the upper bound on the central brightness depression by a factor of 10 and thereby detect such indirect imprints from non-Kerr spacetimes in reconstructed images.

Keywords: event horizons; black hole physics; very long baseline interferometry
Reconstruction of Cosmic Black Hole Growth and Mass Distribution from Quasar Luminosity Functions at z > 4: Implications for Faint and Low-mass Populations in JWST

The evolution of the quasar luminosity function (QLF) is fundamental to understanding the cosmic evolution of black holes (BHs) through their accretion phases. In the era of the James Webb Space Telescope (JWST), Euclid, and Nancy Grace Roman Space Telescope, their unprecedented detection sensitivity and wide survey area can unveil the low-luminosity quasar and low-mass BH population, and provide new insights into quasar host galaxies. We present a theoretical model describing BH growth from initial seeding at z ≳ 20 to ∼ 4, incorporating the duration of accretion episodes, the distribution of Eddington ratios, and the mass dependency of BH accretion rates. By constraining the model parameters with the observed QLFs at 4 ≤ z ≤ 6 across a wide UV luminosity range, we find that the high-redshift BH population grows rapidly at z ≳ 6, and decelerates the pace in subsequent epochs. Toward lower redshifts (z < 6), mass-dependent accretion inhibits the growth of high-mass BHs with M • > 108 M ⊙, leading to mass saturation at M • ≳ 1010 M ⊙. We predict the BH mass function down to M • ∼ 106 M ⊙ for both unobscured and obscured quasar populations at 4 ≤ z ≤ 11, offering a benchmark for future observational tests. Our model accounts for the presence of both bright and faint quasars at z > 4, including those discovered by JWST. Furthermore, our findings suggest two distinct pathways for the early assembly of the BH–galaxy mass correlation: the population with a BH-to-stellar-mass ratio near the local value of M •/M ⋆ ≃ 5 × 10‑3 maintains proximity to the relation via moderate growth, while the population that begins to grow above the local relation becomes as overmassive as M •/M ⋆ ∼ 0.01–0.1 by z ∼ 6 via rapid mass accretion.

Keywords: high-redshift galaxies; quasars; supermassive black holes
A Rotating Satellite Plane around Milky Way-like Galaxy from the TNG50 Simulation

We study the satellite plane problem of the Milky Way (MW) by using the recently published simulation data of TNG50-1. Here, we only consider the satellite plane consisting of the brightest 14 MW satellites (11 classical satellites plus Canes Venatici I, Crater II, and Antlia II). One halo (haloID = 395, at z = 0, hereafter halo395) of 231 MW-like candidates possesses a satellite plane as spatially thin and kinematically coherent as the observed one has been found. Halo395 resembles the MW in a number of intriguing ways: it hosts a spiral central galaxy, and its satellite plane is almost (~87°) perpendicular to the central stellar disk. In addition, halo395 is embedded in a sheet plane, with a void on the top and bottom, similar to the local environment of MW. More interestingly, we found that 11 of the 14 of the satellites on the plane of halo395 arise precisely from the peculiar geometry of its large-scale environment (e.g., sheet and voids). The remaining three members appeared at the right place with the right velocity by chance at z = 0. Our results support previous studies wherein the satellite plane problem is not seen as a serious challenge to the ΛCDM model and its formation is ascribed to the peculiarities of our environment.

Keywords: galaxies; dwarf galaxies
Quasar Properties from the Sloan Digital Sky Survey. III. The Quasars Obtained by the SDSS-IV

This paper provides the compilations of properties of the quasars newly obtained by the Sloan Digital Sky Survey (SDSS) during the fourth stage (SDSS-IV). The catalog is available on the journal's website. We have measured the main properties of emission lines around C IV, Mg II, Hβ, and Hα spectral regions. We estimate the quasar redshifts from our fits of narrow [O III], broad Mg II, and broad C IV emission lines and find that the best redshifts included in DR16Q are robust with respect to our measurements. Based on the broad C IV, Mg II, Hβ, and/or Hα emission lines, we calculate the virial black hole mass with empirical relationships provided by previous works. Systematic biases are found among the different line-based mass estimators.

Keywords: astronomy data reduction; active galaxies; quasars; supermassive black holes; catalogs
The Gravitational Wave AfterglowPy Analysis (GWAPA) webtool

We present the first release of the Gravitational Wave AfterglowPy Analysis (GWAPA) webtool (Available at https://gwapa.web.roma2.infn.it/). GWAPA is designed to provide the community with an interactive tool for rapid analysis of gravitational wave afterglow counterparts and can be extended to the general case of gamma-ray burst afterglows seen at different angles. It is based on the afterglowpy package and allows users to upload observational data and vary afterglow parameters to infer the properties of the explosion. Multiple jet structures, including top hat, Gaussian and power laws, in addition to a spherical outflow model are implemented. A Python script for MCMC fitting is also available to download, with initial guesses taken from GWAPA.

Keywords: gamma-ray bursts; astronomy data analysis; astronomy data modeling
Limitations and Biases in the Retrieval of the Polar Magnetic Field. I. The Role of the Magnetic Filling Factor in Milne-Eddington Inversions of Simulated Hinode/SP Data

We study the extent to which Milne-Eddington inversions are able to retrieve and characterize the magnetic landscape of the solar poles from observations by the spectropolarimeter on board Hinode. In particular, we evaluate whether a variable magnetic filling factor is an adequate modeling technique for retrieving the intrinsic magnetic properties from every pixel in the polar field of view. We first generate synthetic spectra emerging from a numerical simulation of a "plage" region at an inclined line of sight of 65°, and degrade the data to emulate real observations. Then, we invert the synthetic spectra with two Milne-Eddington inversion codes that feature different treatments of the magnetic filling factor, and relate the retrieved magnetic quantities back to their original values in the simulation cube. We find that, while the apparent retrieved magnetic properties map the spatially degraded simulation well, the intrinsic magnetic quantities bear little relation to the magnetic field at the native resolution of the simulation. We discuss the systematic biases caused by line-of-sight foreshortening, spatial degradation, photon noise, and modeling assumptions embedded in the inversion algorithm.

Keywords: spectropolarimetry; solar magnetic fields; solar photosphere