adsabs/SciX_UAT_keywords huggingface dataset:
Precision Photometric and Astrometric Calibration Using Alternating Satellite Speckles

Photometric and astrometric calibration of high-contrast images is essential for the characterization of companions at small angular separation from their stellar host. The main challenge to performing accurate relative photometry and astrometry of high-contrast companions with respect to the host star is that the central starlight cannot be directly used as a reference, as it is either blocked by a coronagraphic mask or saturating the detector. Our approach is to add fiducial incoherent faint copies of the host star in the image plane and alternate the pattern of these copies between exposures. Subtracting two frames with different calibration patterns removes measurement bias due to static and slowly varying incoherent speckle halo components, while ensuring that calibration references are inserted on each frame. Each calibration pattern is achieved by high-speed modulation of a pupil-plane deformable mirror to ensure incoherence. We implemented the technique on-sky on the Subaru Coronagraphic Extreme Adaptive Optics instrument with speckles which were of the order of 103 times fainter than the central host. The achieved relative photometric and astrometric measurement precisions for 10 s exposure were respectively 5% and 20 milliarcsecond. We also demonstrate, over a 540 s measurement span, that residual photometric and astrometric errors are uncorrelated in time, indicating that residual noise averages as the inverse square root of the number of exposures in longer time-series data sets.

Keywords: astronomical instrumentation; astrometry; photometry; coronagraphic imaging; astronomical techniques; direct imaging; artificial satellites
Minding the Gap: GW190521 as a Straddling Binary

Models for black hole (BH) formation from stellar evolution robustly predict the existence of a pair-instability supernova (PISN) mass gap in the range ∼50 to ∼120 solar masses. This theoretical prediction is supported by the binary black holes (BBHs) of LIGO/Virgo's first two observing runs, whose component masses are well fit by a power law with a maximum mass cutoff at ${m}_{\max }={40.8}_{-4.4}^{+11.8}\,{\text{}}{M}_{\odot }$ . Meanwhile, the BBH event GW190521 has a reported primary mass of ${m}_{1}={85}_{-14}^{+21}\,{\text{}}{M}_{\odot }$ , firmly above the inferred ${m}_{\max }$ , and secondary mass ${m}_{2}={66}_{-18}^{+17}\ {\text{}}{M}_{\odot }$ . Rather than concluding that both components of GW190521 belong to a new population of mass-gap BHs, we explore the conservative scenario in which GW190521's secondary mass belongs to the previously observed population of BHs. We replace the default priors on m1 and m2, which assume that BH detector-frame masses are uniformly distributed, with this population-informed prior on m2, finding ${m}_{2}\lt 48\,{\text{}}{M}_{\odot }$ at 90% credibility. Moreover, because the total mass of the system is better constrained than the individual masses, the population prior on m2 automatically increases the inferred m1 to sit above the gap (39% for m1 > 120 ${\text{}}{M}_{\odot }$ , or 25% probability for m1 > 130 ${\text{}}{M}_{\odot }$ ). As long as the prior odds for a double-mass-gap BBH are smaller than $\sim 1\,:\,15$ , it is more likely that GW190521 straddles the pair-instability gap. We argue that GW190521 may be the first example of a straddling binary black hole, composed of a conventional stellar mass BH and a BH from the "far side" of the PISN mass gap.

Keywords: astrophysical black holes; gravitational waves; gravitational wave astronomy; bayesian statistics; intermediate-mass black holes
A Massive Hot Jupiter Orbiting a Metal-rich Early M Star Discovered in the TESS Full-frame Images

Observations and statistical studies have shown that giant planets are rare around M dwarfs compared with Sun-like stars. The formation mechanism of these extreme systems has remained under debate for decades. With the help of the TESS mission and ground-based follow-up observations, we report the discovery of TOI-4201b, the most massive and densest hot Jupiter around an M dwarf known so far with a radius of 1.22 ± 0.04 R J and a mass of 2.48 ± 0.09 M J, about 5 times heavier than most other giant planets around M dwarfs. It also has the highest planet-to-star mass ratio (q ~ 4 × 10-3) among such systems. The host star is an early M dwarf with a mass of 0.61 ± 0.02 M ⊙ and a radius of 0.63 ± 0.02 R ⊙. It has significant supersolar iron abundance ([Fe/H] = 0.52 ± 0.08 dex). However, interior structure modeling suggests that its planet TOI-4201b is metal-poor, which challenges the classical core-accretion correlation of stellar-planet metallicity, unless the planet is inflated by additional energy sources. Building on the detection of this planet, we compare the stellar metallicity distribution of four planetary groups: hot/warm Jupiters around G/M dwarfs. We find that hot/warm Jupiters show a similar metallicity dependence around G-type stars. For M-dwarf host stars, the occurrence of hot Jupiters shows a much stronger correlation with iron abundance, while warm Jupiters display a weaker preference, indicating possible different formation histories.

Keywords: m dwarf stars; radial velocity; photometry; m stars; extrasolar gaseous planets
Evolution of Galaxy Star Formation and Metallicity: Impact on Double Compact Object Mergers

In this paper, we study the impact of different galaxy statistics and empirical metallicity scaling relations on the merging rates and properties of compact object binaries. Firstly, we analyze the similarities and differences of using the star formation rate functions versus stellar mass functions as galaxy statistics for the computation of cosmic star formation rate density. We then investigate the effects of adopting the Fundamental Metallicity Relation versus a classic Mass Metallicity Relation to assign metallicity to galaxies with given properties. We find that when the Fundamental Metallicity Relation is exploited, the bulk of the star formation occurs at relatively high metallicities, even at high redshift; the opposite holds when the Mass Metallicity Relation is employed, since in this case the metallicity at which most of the star formation takes place strongly decreases with redshift. We discuss the various reasons and possible biases giving rise to this discrepancy. Finally, we show the impact of these different astrophysical prescriptions on the merging rates and properties of compact object binaries; specifically, we present results for the redshift-dependent merging rates and for the chirp mass and time delay distributions of the merging binaries.

Keywords: galaxy evolution; early-type galaxies; luminosity function; stellar mass functions; metallicity; stellar mergers; compact objects; star formation; gravitational wave sources; gravitational waves; astrophysical black holes; neutron stars
Radial Velocity Monitoring of the Young Star Hubble 4: Disentangling Star-spot Lifetimes from Orbital Motion

We studied the weak-lined T Tauri star Hubble 4, a known long-period binary, and its star-spot phenomena. We used optical radial velocity (RV) data taken over a span of 14 yr (2004-2010, 2017-2019) at the McDonald Observatory 2.7 m Harlan J. Smith Telescope and single epoch imaging from the Hubble Space Telescope (HST)/Wide Field Camera 3 instrument. The observed and apparent RV variations show contributions, respectively, from the binary motion as well as from a large spot group on one of the stars, presumed to be the primary. Fitting and removing the orbital signal from the RVs, we found the lower bound on the lifetime of a previously identified large spot group on the surface of the star to be at least 5.1 yr. An ∼5 yr lower limit is a long, but not unprecedented, duration for a single spot group. The later epoch data indicate significant spot evolution has occurred, placing an upper bound on the spot group lifetime at 12 yr. We find that pre-main-sequence evolutionary models for the age of Taurus (∼2 Myr), combined with component mass estimates from the literature, permit us to reproduce the HST relative photometry and the binary-induced contribution to the apparent RV variations. The long-lived star spot we find on Hubble 4 has significant implications for dynamo models in young stars, as it adds evidence for long lifetimes of magnetic field topologies. There are also significant implications for young star exoplanet searches, as long-lived coherent RV signals may be spot induced and not the result of planetary motion. * This paper includes data taken at The McDonald Observatory of The University of Texas at Austin.

Keywords: radial velocity; t tauri stars; starspots; binary stars; pre-main sequence stars; stellar activity; stellar flares; optical flares
Ground- and Space-based Dust Observations of VV 191 Overlapping Galaxy Pair

The Balmer decrement (Hα/Hβ) provides a constraint on attenuation, the cumulative effects of dust grains in the ISM. The ratio is a reliable spectroscopic tool for deriving the dust properties of galaxies that determine many different quantities such as star formation rate, metallicity, and SED models. Here, we measure independently both the attenuation and Hα/Hβ of an occulting galaxy pair: VV 191. Attenuation measurements in the visible spectrum (A V,stars) from dust maps derived from the F606W filter of HST and the F090W filter of JWST are matched with spaxel-by-spaxel Hα/Hβ observations from the George and Cynthia Mitchell Spectrograph of the McDonald Observatory. The 0.5–0.7 μm bandpass covers the Balmer lines for VV 191. The dust maps of JWST and HST provide the high sensitivity necessary for comparisons and tracking trends of the geometrically favorable galaxy. We present maps and plots of the Balmer lines for the VV 191 galaxy pair and for a specific region highlighting dust lanes for VV 191b in the overlap region. We compute A V,H II from Hα/Hβ and plot both quantities against A V,stars. Our results show that regions with higher dust content, residing closer to the spiral center, dominate ionized gas attenuation, leading to an overestimation of A V,H II by a factor of 2. Further out in the spiral arms, the lower dust content leads to more agreement between the attenuations, indicating a lower star formation rate and larger contribution from older stars to the stellar continuum outside the Petrosian radius.

Keywords: disk galaxies; galaxy spectroscopy; emission line galaxies; interstellar medium; interstellar dust extinction; interstellar dust
Hydroxylated Mg-rich Amorphous Silicates: A New Component of the 3.2 μm Absorption Band of Comet 67P/Churyumov-Gerasimenko

The VIRTIS imaging spectrometer on board Rosetta has shown that the nucleus surface of comet 67P/Churyumov-Gerasimenko (67P/CG) is characterized by a broad absorption band at around 3.2 μm. The feature is ubiquitous across the surface and its attribution to (a) specific material(s) has been challenging. In the present Letter, we report an experimental investigation showing that the interaction of hydrogen atoms with Mg-rich amorphous silicates determines the formation of hydroxyl groups. The resulting IR spectrum exhibits a broad feature around 3.2 μm similar to that of comet 67P/CG. Hapke's radiative transfer model was employed to estimate an upper limit contribution of 65% of hydroxylated silicates to the observed cometary band intensity. The presence of a hydroxylated fraction in silicates on the cometary surface would represent an evolutionary link between primitive objects of the solar system and dust in the interstellar medium (ISM), where silicate grains can be hydroxylated after having interacted with hydrogen atoms. This link is consistent with the detection of the aliphatic organics in 67P/CG that also originate in the ISM.

Keywords: comets; astrochemistry; laboratory astrophysics
Selecting z 8 Galaxies with JWST Photometry in CEERS

We present a method for selecting high-redshift galaxies from imaging and use this method to select a sample of z ~ 8 candidates from the Cosmic Evolution Early Release Science survey. In our selection process, we make use of the photometric redshift-fitting code EAZY to identify high-redshift galaxies based on their colors. Following previous works, we put constraints on the detection significance and quantities derived from the full photometric redshift probability distribution functions P(z). To further eliminate spurious sources, the spectral energy distribution (SED) and the images from both the James Webb Space Telescope and Hubble Space Telescope of candidate z ~ 8 galaxies are also examined. From the visual inspection of the SEDs and images, we identify a sample of 117 galaxy candidates at z ~ 8.

Keywords: high-redshift galaxies
Implications of a Temperature-dependent Initial Mass Function. I. Photometric Template Fitting

A universal stellar initial mass function (IMF) should not be expected from theoretical models of star formation, but little conclusive observational evidence for a variable IMF has been uncovered. In this paper, a parameterization of the IMF is introduced into photometric template fitting of the COSMOS2015 catalog. The resulting best-fit templates suggest systematic variations in the IMF, with most galaxies exhibiting top-heavier stellar populations than in the Milky Way. At fixed redshift, only a small range of IMFs are found, with the typical IMF becoming progressively top-heavier with increasing redshift. Additionally, subpopulations of ULIRGs, quiescent and star-forming galaxies are compared with predictions of stellar population feedback and show clear qualitative similarities to the evolution of dust temperatures.

Keywords: galaxy evolution; initial mass function; stellar mass functions
Dynamical Modeling of Galaxies and Supermassive Black Holes: Axisymmetry in Triaxial Schwarzschild Orbit Superposition Models

We present a detailed analysis of the behavior of the triaxial Schwarzschild orbit superposition method near the axisymmetric limit. Orbit superposition modeling is the primary method used to determine dynamical masses of supermassive black holes (MBH) in nearby galaxies; however, prior studies have reported conflicting results when comparing the outcome from axisymmetric orbit codes with that from a triaxial orbit code in the axisymmetric limit. We show that in order to achieve (oblate) axisymmetry in a triaxial code, care needs to be taken to axisymmetrize the short-axis tube orbits and to exclude both the long-axis tube and box orbits from the orbit library. Using up to 12 Gauss-Hermite moments of the line-of-sight velocity distributions as constraints, we demonstrate the effects of orbit types on the best-fit MBH in orbit modeling of the massive elliptical galaxy NGC 1453 reported in Liepold et al. In addition, we verify the efficacy of our updated code on a mock galaxy data set. We identify a subset of slowly precessing quasi-planar orbits for which the typical integration times can be insufficient to fully capture the equilibrium orbital behavior in both axisymmetric and triaxial systems with central black holes. Further investigation is needed for a more reliable treatment of these orbits.

Keywords: elliptical galaxies; galaxies; galaxy dynamics; galaxy evolution; galaxy kinematics; galaxy structure; black holes; supermassive black holes
A Catalog of Broad Morphology of Pan-STARRS Galaxies Based on Deep Learning

Autonomous digital sky surveys such as Pan-STARRS have the ability to image a very large number of galactic and extragalactic objects, and the large and complex nature of the image data reinforces the use of automation. Here we describe the design and implementation of a data analysis process for automatic broad morphology annotation of galaxies, and applied it to the data of Pan-STARRS DR1. The process is based on filters followed by a two-step convolutional neural network (CNN) classification. Training samples are generated by using an augmented and balanced set of manually classified galaxies. Results are evaluated for accuracy by comparison to the annotation of Pan-STARRS included in a previous broad morphology catalog of Sloan Digital Sky Survey galaxies. Our analysis shows that a CNN combined with several filters is an effective approach for annotating the galaxies and removing unclean images. The catalog contains morphology labels for 1,662,190 galaxies with ∼95% accuracy. The accuracy can be further improved by selecting labels above certain confidence thresholds. The catalog is publicly available.

Keywords: catalogs; galaxies; spiral galaxies; astronomy data analysis
Gamma-Ray Burst Prompt Emission Spectrum and E p Evolution Patterns in the ICMART Model

In this paper, we simulate the prompt emission light curve, spectrum, and E p evolution patterns of gamma-ray bursts (GRBs) within the framework of the Internal-collision-induced Magnetic Reconnection and Turbulence (ICMART) model. We show that this model can produce a Band-shaped spectrum, whose parameters (E p, α, β) could follow the typical distribution of GRB observations, as long as the magnetic field and the electron acceleration process in the emission region are under appropriate conditions. On the other hand, we show that for one ICMART event, E p evolution is always a hard-to-soft pattern. However, a GRB light curve is usually composed of multiple ICMART events that are fundamentally driven by the erratic activity of the GRB central engine. In this case, we find that if one individual broad pulse in the GRB light curve is composed of multiple ICMART events, the overall E p evolution could be disguised as an intensity-tracking pattern. Therefore, mixed E p evolution patterns can coexist in the same burst, with a variety of combined patterns. Our results support the ICMART model as a competitive model to explain the main properties of GRB prompt emission. The possible challenges faced by the ICMART model are also discussed in detail.

Keywords: gamma-ray bursts
The Final Season Reimagined: 30 Tidal Disruption Events from the ZTF-I Survey

Tidal disruption events (TDEs) offer a unique way to study dormant black holes. While the number of observed TDEs has grown thanks to the emergence of wide-field surveys in the past few decades, questions regarding the nature of the observed optical, UV, and X-ray emission remain. We present a uniformly selected sample of 30 spectroscopically classified TDEs from the Zwicky Transient Facility Phase I survey operations with follow-up Swift UV and X-ray observations. Through our investigation into correlations between light-curve properties, we recover a shallow positive correlation between the peak bolometric luminosity and decay timescales. We introduce a new spectroscopic class of TDE, TDE-featureless, which are characterized by featureless optical spectra. The new TDE-featureless class shows larger peak bolometric luminosities, peak blackbody temperatures, and peak blackbody radii. We examine the differences between the X-ray bright and X-ray faint populations of TDEs in this sample, finding that X-ray bright TDEs show higher peak blackbody luminosities than the X-ray faint subsample. This sample of optically selected TDEs is the largest sample of TDEs from a single survey yet, and the systematic discovery, classification, and follow-up of this sample allows for robust characterization of TDE properties, an important stepping stone looking forward toward the Rubin era.

Keywords: astrophysical black holes; tidal disruption; galaxy nuclei; high energy astrophysics; supermassive black holes
Short-term Spectroscopic Variability of the Early Post-AGB Stage Star IRAS 22272+5435

High-resolution spectra gathered during an extensive monitoring of IRAS 22272+5435 are inspected to search for spectroscopic variability in the time span of less than 2 weeks. Significant variation are found both in the intensity and position of CN(1, 0) red system lines near the light maximum, when the star is the hottest. The intensity of variable CN lines correlates with their Doppler redshift-an increase in the radial velocity leads to a decrease of its equivalent width. The inward flow of increasing velocity from ≃14.4-21.6 km s-1 was confirmed in the atmosphere, propagating ~25 R⊙ toward the mass center of the star in 11 days. The variability of CN(1, 0) lines are accompanied by changes in the red wings of strong low-excitation lines. The observed short-term variations are attributed to large-scale convective flows and shock waves in the extended atmosphere of a cool pulsating post-AGB star.

Keywords: post-asymptotic giant branch stars; stellar atmospheres; stellar oscillations; shocks; circumstellar matter; high resolution spectroscopy
Laboratory Study of Magnetic Reconnection in Lunar-relevant Mini-magnetospheres

Mini-magnetospheres are small ion-scale structures that are well suited to studying kinetic-scale physics of collisionless space plasmas. Such ion-scale magnetospheres can be found on local regions of the Moon, associated with the lunar crustal magnetic field. In this paper, we report on the laboratory experimental study of magnetic reconnection in laser-driven, lunar-like ion-scale magnetospheres on the Large Plasma Device at the University of California, Los Angeles. In the experiment, a high-repetition rate (1 Hz), nanosecond laser is used to drive a fast-moving, collisionless plasma that expands into the field generated by a pulsed magnetic dipole embedded into a background plasma and magnetic field. The high-repetition rate enables the acquisition of time-resolved volumetric data of the magnetic and electric fields to characterize magnetic reconnection and calculate the reconnection rate. We notably observe the formation of Hall fields associated with reconnection. Particle-in-cell simulations reproducing the experimental results were performed to study the microphysics of the interaction. By analyzing the generalized Ohm's law terms, we find that the electron-only reconnection is driven by kinetic effects through the electron pressure anisotropy. These results are compared to recent satellite measurements that found evidence of magnetic reconnection near the lunar surface.

Keywords: laboratory astrophysics; the moon; space plasmas
A Fast and High-precision Alignment Method for IFU Based on Optical Interferometry and Fresnel Diffraction

High-precision alignment between the microlens array and the fiber-positioning microplate is of great significance in developing fiber-based integrated field units (IFU). In this paper, we propose a method combining optical interference and a Fresnel diffraction model to realize fast and accurate alignment. The minimum resolution angles of the tip and tilt in the optical interference-assisted alignment experiment are 2.6 × 10-4° and 1.3 × 10-4°, respectively. The errors in the remaining four degrees of freedom, x, y, z, and roll, are simulated by the Fresnel diffraction model. Finally, the output energy of 96.7% of the number of fibers is within a tolerance error of 10% and the relative energy reaches its highest level, which meets the IFU requirement.

Keywords: astronomical instrumentation; astronomical techniques; solar instruments; optical interferometry