adsabs/SciX_UAT_keywords huggingface dataset:
You Can't Always Get What You Want: The Impact of Prior Assumptions on Interpreting GW190412

GW190412 is the first observation of a black hole binary with definitively unequal masses. GW190412's mass asymmetry, along with the measured positive effective inspiral spin, allowed for inference of a component black hole spin: the primary black hole in the system was found to have a dimensionless spin magnitude between $0.17$ and $0.59$ (90% credible range). We investigate how the choice of priors for the spin magnitudes and tilts of the component black holes affect the robustness of parameter estimates for GW190412, and report Bayes factors across a suite of prior assumptions. Depending on the waveform family used to describe the signal, we find either marginal to moderate ( $2$ :1- $6$ :1) or strong (≳ $20$ :1) support for the primary black hole being spinning compared to cases where only the secondary is allowed to have spin. We show how these choices influence parameter estimates, and find the asymmetric masses and positive effective inspiral spin of GW190412 to be qualitatively, but not quantitatively, robust to prior assumptions. Our results highlight the importance of both considering astrophysically motivated or population-based priors in interpreting observations and considering their relative support from the data.

Keywords: gravitational waves; ligo; gravitational wave sources; binary stars; bayesian statistics; black holes; stellar evolution
Open Cluster Chemical Homogeneity throughout the Milky Way

The chemical homogeneity of surviving stellar clusters contains important clues about interstellar medium (ISM) mixing efficiency, star formation, and the enrichment history of the Galaxy. Existing measurements in a handful of open clusters suggest homogeneity in several elements at the 0.03 dex level. Here we present (i) a new cluster member catalog based only on APOGEE radial velocities and Gaia-DR2 proper motions, (ii) improved abundance uncertainties for APOGEE cluster members, and (iii) the dependence of cluster homogeneity on Galactic and cluster properties, using abundances of eight elements from the APOGEE survey for 10 high-quality clusters. We find that cluster homogeneity is uncorrelated with Galactocentric distance, $| Z| $ , age, and metallicity. However, velocity dispersion, which is a proxy for cluster mass, is positively correlated with intrinsic scatter at relatively high levels of significance for [Ca/Fe] and [Mg/Fe]. We also see a possible positive correlation at a low level of significance for [Ni/Fe], [Si/Fe], [Al/Fe], and [Fe/H], while [Cr/Fe] and [Mn/Fe] are uncorrelated. The elements that show a correlation with velocity dispersion are those that are predominantly produced by core-collapse supernovae (CCSNe). However, the small sample size and relatively low correlation significance highlight the need for follow-up studies. If borne out by future studies, these findings would suggest a quantitative difference between the correlation lengths of elements produced predominantly by Type Ia SNe versus CCSNe, which would have implications for Galactic chemical evolution models and the feasibility of chemical tagging.

Keywords: chemical enrichment; chemical abundances; star clusters; milky way evolution
Scintillation Arcs in Pulsar B0450-18

We report on Green Bank Telescope observations of interstellar scintillation from the pulsar B0450-18 at 340 and 825 MHz, revealing prominent arcs in the secondary spectra at both frequencies. The arcs are successfully modeled by one-dimensional angular brightness distributions, estimated by two independent techniques. The distributions do not follow the expected shape for a Kolmogorov plasma density spectrum, and their overall angular widths follow a scaling law, versus frequency, that is slightly slower than the inverse square law expected from plasma dispersion. They also exhibit discrete peaks that are the cause of the occasional reverse sub-arcs. Over a narrow (5%) frequency range these peaks do not participate in the overall spreading, having angular positions that are fixed on the sky. However, the peaks do evolve over a wider range of frequencies and cannot be traced from 825 to 340 MHz. Our conclusions add further evidence for a widespread distribution of highly localized regions of interstellar plasma with small-scale structure that is either elongated or flattened.

Keywords: interstellar medium; interstellar plasma; interstellar scintillation; radio pulsars
A Search for Technosignatures Around 11,680 Stars with the Green Bank Telescope at 1.15-1.73 GHz

We conducted a search for narrowband radio signals over four observing sessions in 2020-2023 with the L-band receiver (1.15-1.73 GHz) of the 100 m diameter Green Bank Telescope. We pointed the telescope in the directions of 62 TESS Objects of Interest, capturing radio emissions from a total of ~11,680 stars and planetary systems in the ~9' beam of the telescope. All detections were either automatically rejected or visually inspected and confirmed to be of anthropogenic nature. We also quantified the end-to-end efficiency of radio SETI pipelines with a signal injection and recovery analysis. The UCLA SETI pipeline recovers 94.0% of the injected signals over the usable frequency range of the receiver and 98.7% of the injections when regions of dense radio frequency interference are excluded. In another pipeline that uses incoherent sums of 51 consecutive spectra, the recovery rate is ~15 times smaller at ~6%. The pipeline efficiency affects calculations of transmitter prevalence and SETI search volume. Accordingly, we developed an improved Drake figure of merit and a formalism to place upper limits on transmitter prevalence that take the pipeline efficiency and transmitter duty cycle into account. Based on our observations, we can state at the 95% confidence level that fewer than 6.6% of stars within 100 pc host a transmitter that is continuously transmitting a narrowband signal with an equivalent isotropic radiated power (EIRP) > 1013 W. For stars within 20,000 ly, the fraction of stars with detectable transmitters (EIRP > 5 × 1016 W) is at most 3 × 10-4. Finally, we showed that the UCLA SETI pipeline natively detects the signals detected with AI techniques by Ma et al.

Keywords: search for extraterrestrial intelligence; technosignatures; astrobiology; exoplanets; radio astronomy; milky way galaxy
Galaxy And Mass Assembly (GAMA): The Merging Potential of Brightest Group Galaxies

Using a volume-limited sample of 550 groups from the Galaxy And Mass Assembly Galaxy Group Catalogue spanning the halo mass range $12.8\lt \mathrm{log}[{M}_{h}/{M}_{\odot }]\lt 14.2$ , we investigate the merging potential of central Brightest Group Galaxies (BGGs). We use spectroscopically confirmed close-companion galaxies as an indication of the potential stellar mass buildup of low-redshift BGGs, z ≤ 0.2. We identify 17 close-companion galaxies with projected separations rp < 30 kpc, relative velocities Δv ≤ 300 km s-1, and stellar mass ratios MBGG/MCC ≤ 4 relative to the BGG. These close-companion galaxies yield a total pair fraction of 0.03 ± 0.01. Overall, we find that BGGs in our sample have the potential to grow in stellar mass due to mergers by 2.2 ± 1.5% Gyr-1. This is lower than the stellar mass growth predicted by current galaxy evolution models.

Keywords: galaxy evolution; galaxy groups; early-type galaxies
Census of Variable Stars toward Serpens Main

We monitored a 3 deg2 area toward Serpens Main in the Pan-STARRS1 r, i, and z bands from 2016 April to September. Light curves of more than 11,000 stars in each band were obtained, and 143 variables have been identified. Among those, 119 variables are new discoveries, while 24 variables were previously known. We present variability classes and periods of 99 stars. Of these, 81 are located in the upper giant branch, displaying long periods, while the remaining 18 variables are pre-main-sequence objects with short periods. We also identify eight eclipsing binary systems, including the known binary V0623 Ser, and derive their physical parameters. According to a clustering analysis of Gaia DR2 stars in the observed field, there are 10 variable members in Serpens Main, where six members have been classified as young stellar objects in previous studies. Here we provide color-magnitude and color-color diagrams for these variables. The color variability of most variables in the color-magnitude diagrams produces the expected displacements, while the movements of cluster members point in different directions; this behavior may be associated with accretion spots or circumstellar disks.

Keywords: variable stars; catalogs; eclipsing binary stars
Great Refractor Domes: Pantheons of Astronomy

Height-to-diameter ratios of the enclosures of large refracting telescopes are contrasted with the classical domed structure of the Roman Pantheon. Enclosures whose domes do not sit upon a multi-storied drum, or atop an extended building complex, tend to evince a Pantheon-like ratio.

Keywords: optical observatories; domes; history of astronomy
Dating and Tracing the Origin of Enstatite Chondrite Chondrules with Cr Isotopes

Chondrules are major components of chondrites and are believed to drive the accretion of planetary embryos. As such, constraining the timing and origin of chondrules is central for understanding the early evolution of the solar system and the formation of planets. Enstatite chondrites (ECs) have isotope compositions for multiple elements that match that of the Earth and, thus, are considered to be good analogs of the precursor material from which the Earth formed. Here, we report the first high-precision mass-independent Cr isotope data of nine chondrules in one of the least-altered EH chondrites, Sahara 97096. Seven primitive chondrules show typical 54Cr/52Cr ratios of bulk ECs, whereas two chondrules have ratios similar to carbonaceous chondrites. The presence of two chondrules with a carbonaceous chondrite signature suggests early inward transport of material to the EC accretion region. The Mn/Cr ratios of the EC-like chondrules (except one with high Fe content) correlate with their 53Cr/52Cr isotope ratios, which we interpret as a fossil isochron, with a slope corresponding to a 53Mn/55Mn initial ratio of (5.01 ± 0.59) × 10-6 (2σ). When anchored to the D'Orbigny angrite, this 53Mn/55Mn ratio returns an absolute age of 4565.7 ± 0.7 Ma for EC chondrule formation (precursor age), 1.6 ± 0.7 Ma after solar system formation. This protracted formation of EC chondrules may suggest that the mass transfer of outer solar system material started prior to the end of planetary embryo accretion, as chondrules could represent the main building blocks of terrestrial planets.

Keywords: astrochemistry; cosmochemistry; cosmochronology; solar system; isotopic abundances; meteoroids; chondrules; nucleosynthesis; chondrites
AB Dor: Coronal Imaging and Activity Cycles

Using long-term X-ray observations, we present short-term and long-term X-ray variability analysis of the ultrafast rotating active star AB Dor. Flaring events are common in X-ray observations of AB Dor and occupy a substantial portion of the total observation time, averaging at around 57% ± 23%. The flare-free X-ray light curves show rotational modulation, indicating the presence of highly active regions in the star's corona. We have developed a light-curve inversion code to image the corona of active fast rotating stars. The results of coronal imaging reveal the presence of two active regions of different brightness that are separated by ∼180° in longitude. These active regions are also found to migrate along the longitude and also show variation in their brightness. Our analysis of long-term X-ray data spanning from 1979 to 2022 shows multiple periodicities. The existence of a ∼19.2 yr cycle and its first harmonic indicates the presence of a solar-like, long-term pattern. In comparison, the periodicities of ∼3.6 and ∼5.4 yr are possibly due to the presence of a flip-flop cycle in the X-rays, which is also supported by findings for similar periods from the optical data in earlier studies. Further confirmation of the existence of the X-ray flip-flop cycle requires long-term observations at regular intervals in the quiescent state.

Keywords: stellar coronae; observational astronomy; stellar activity; x-ray astronomy; x-ray stars
Search for Correlations of High-energy Neutrinos Detected in IceCube with Radio-bright AGN and Gamma-Ray Emission from Blazars

The IceCube Neutrino Observatory sends realtime neutrino alerts with a high probability of being astrophysical in origin. We present a new method to correlate these events and possible candidate sources using 2089 blazars from the Fermi-LAT 4LAC-DR2 catalog and with 3413 active galactic nuclei (AGNs) from the Radio Fundamental Catalog. No statistically significant neutrino emission was found in any of the catalog searches. The result suggests that a small fraction, <1%, of the studied AGNs emit neutrinos that pass the alert criteria, and is compatible with prior evidence for neutrino emission presented by IceCube and other authors from sources such as TXS 0506 + 056 and PKS 1502 + 106. We also present cross-checks to other analyses that claim a significant correlation using similar data samples.

Keywords: neutrino astronomy; gamma-ray sources; radio active galactic nuclei
Detection of Carbon Monoxide in the Atmosphere of WASP-39b Applying Standard Cross-correlation Techniques to JWST NIRSpec G395H Data

Carbon monoxide was recently reported in the atmosphere of the hot Jupiter WASP-39b using the NIRSpec PRISM transit observation of this planet, collected as part of the JWST Transiting Exoplanet Community Early Release Science Program. This detection, however, could not be confidently confirmed in the initial analysis of the higher-resolution observations with NIRSpec G395H disperser. Here we confirm the detection of CO in the atmosphere of WASP-39b using the NIRSpec G395H data and cross-correlation techniques. We do this by searching for the CO signal in the unbinned transmission spectrum of the planet between 4.6 and 5.0 μm, where the contribution of CO is expected to be higher than that of other anticipated molecules in the planet's atmosphere. Our search results in a detection of CO with a cross-correlation function (CCF) significance of 6.6σ when using a template with only 12C16O lines. The CCF significance of the CO signal increases to 7.5σ when including in the template lines from additional CO isotopologues, with the largest contribution being from 13C16O. Our results highlight how cross-correlation techniques can be a powerful tool for unveiling the chemical composition of exoplanetary atmospheres from medium-resolution transmission spectra, including the detection of isotopologues.

Keywords: exoplanet atmospheres; exoplanet atmospheric composition; hot jupiters; astronomical methods
The γ-Ray Emission of Star-forming Galaxies

A majority of the γ-ray emission from star-forming galaxies is generated by the interaction of high-energy cosmic rays with the interstellar gas and radiation fields. Star-forming galaxies are expected to contribute to both the extragalactic γ-ray background and the IceCube astrophysical neutrino flux. Using roughly 10 yr of γ-ray data taken by the Fermi Large Area Telescope, in this study we constrain the γ-ray properties of star-forming galaxies. We report the detection of 11 bona fide γ-ray-emitting galaxies and 2 candidates. Moreover, we show that the cumulative γ-ray emission of below-threshold galaxies is also significantly detected at ∼5σ confidence. The γ-ray luminosity of resolved and unresolved galaxies is found to correlate with the total (8-1000 μm) infrared luminosity as previously determined. Above 1 GeV, the spectral energy distribution of resolved and unresolved galaxies is found to be compatible with a power law with a photon index of ≈2.2-2.3. Finally, we find that star-forming galaxies account for roughly 5% and 3% of the extragalactic γ-ray background and the IceCube neutrino flux, respectively.

Keywords: starburst galaxies; gamma-rays; neutrino astronomy
The Life Cycle of Magnetars: A Novel Approach to Estimate Their Ages

Anomalous X-ray pulsars and soft gamma repeaters are slowly rotating, young, and isolated neutron stars exhibiting sporadic outbursts and high X-ray quiescent luminosities. They are believed to be powered by ultrastrong magnetic fields, B ∼ 1014-1015 G, associated with "magnetars." In the peculiar case of SGR 0418+5729, timing parameters imply a dipolar B-field of 6.1 × 1012 G. This discovery has challenged the traditional picture of magnetars in terms of B-field strengths, evolutionary stages, and ages. Here we provide a novel approach to estimate a magnetar's age by considering the self-consistent time evolution of a plasma-filled oblique pulsar with the state-of-the-art magnetospheric particle acceleration gaps. The rotational period of magnetars increases over time due to angular momentum extraction by gravitational-wave radiations, magnetic dipole radiations, and particle winds. These torques also change the obliquity angle between the magnetic and rotation axes. For SGR 0418+5729, we obtain a dipolar B-field of 1.0 × 1014 G, and a realistic age of ∼18 kyr, consistent within the magnetar paradigm.

Keywords: magnetars; pulsars; neutron stars
The Absence of Far UV Variability in the IUE Spectra of ξ Oct (HD 215573)

The analysis of high resolution SWP spectra obtained through the large aperture with the International Ultraviolet Explorer reveals that the far-ultraviolet flux of ξ Oct did not vary. In particular, the flux remained stable in a series of seven spectra taken consecutively over 3 hr and 24 minutes. This time interval is much shorter than the 1.78 days rotational period proposed for this star from its TESS lightcurve, which could explain for the absence of variability in the FUV. The comparison of the STIS spectrum of ξ Oct in the range 1300-1340 Å with synthetic spectra computed for the fundamental parameters of ξ Oct and a solar composition allows the identification of the strongest absorption features in the far-ultraviolet as due to resonance lines of O I, Si II and C II.

Keywords: pulsating variable stars
GRB 170817A as a Refreshed Shock Afterglow Viewed Off-axis

Energy injection into the external shock system that generates the afterglow to a gamma-ray burst (GRB) can result in a rebrightening of the emission. Here we investigate the off-axis view of a rebrightened refreshed shock afterglow. We find that the afterglow light curve, when viewed from outside of the jet opening angle, could be characterized by a slow rise, or long plateau, with a maximum flux determined by the total system energy. Using the broadband afterglow data for GRB 170817A, associated with the gravitational-wave-detected binary neutron star merger GW170817, we show that a refreshed shock model with a simple top-hat jet can reproduce the observed afterglow features. We consider two refreshed shock models: a single episode of energy injection, and an episode of continuous energy injection. The best-fit model parameters give a jet opening angle for our first and second models, respectively, of θj = 5° ${2}_{-0.6}^{+1.1}\,$ and 6° ${3}_{-1.1}^{+1.7}$ , an inclination to the line of sight ι = 16° ${0}_{-1.1}^{+3.4}\,$ and 17° ${8}_{-2.9}^{+4.5}$ , an initial on-axis isotropic equivalent kinetic energy ${E}_{1}=({0.3}_{-0.3}^{+3.5}\,$ and $\,{0.5}_{-0.2}^{+6.7})\times {10}^{52}$ erg, and a total/final, on-axis isotropic equivalent refreshed shock energy ${E}_{\mathrm{total}}=({0.42}_{-0.4}^{+5.6}\,$ and $\,{1.26}_{-0.7}^{+18.2})\times {10}^{53}$ erg. The first model fitting prefers an initial bulk Lorentz factor Γ0,1 < 60, with a comparatively low central value of Γ0,1 = 19.5, indicating that, in this case, the on-axis jet could have been a "failed GRB." Alternatively, our second model is consistent with a bright GRB for an on-axis observer, with ${{\rm{\Gamma }}}_{\mathrm{0,1}}={162.2}_{-122.1}^{+219.7}$ . Due to the low Lorentz factor and/or the jet opening angles at θj ∼ ι/3, both models are unable to reproduce the γ-ray emission observed in GRB 170817A, which would therefore require an alternative explanation such as cocoon shock breakout.

Keywords: gamma-ray bursts; transient sources
On the Tidal Capture of White Dwarfs by Intermediate-mass Black Holes in Dense Stellar Environments

Intermediate-mass black holes (IMBHs) are the missing link between stellar-mass and supermassive black holes, widely believed to reside in at least some dense star clusters, but not yet observed directly. Tidal disruptions of white dwarfs (WDs) are luminous only for black holes less massive than ~105 M ⊙, therefore providing a unique smoking gun that could finally prove the existence of IMBHs beyond any reasonable doubt. Here, we investigate the tidal captures of WDs by IMBHs in dense star clusters, and estimate upper limits to the capture rates of ~1 Myr-1 for galactic nuclei and ~0.01 Myr-1 for globular clusters. Following the capture, the WD inspirals onto the IMBH, producing gravitational waves detectable out to ~100 Mpc by LISA for ~104 M ⊙ IMBHs. The subsequent tidal stripping/disruption of the WD can also release bright X-ray and gamma-ray emission with luminosities of at least ≳1040 erg s-1, detectable by Chandra, Swift, and upcoming telescopes, such as the Einstein Probe.

Keywords: intermediate-mass black holes; star clusters; tidal interaction; white dwarf stars
Cosmology from One Galaxy in a Void?

Understanding galaxy properties may be the key to unlocking some of the most intriguing mysteries of modern cosmology. Recent work relied on machine learning to extract cosmological constraints on Ωm using only one galaxy. But if this is true, how should we select the galaxy to use for cosmology inference? In this Letter, we consider selecting a galaxy that lies in cosmic voids, the underdense regions of the cosmic web, and compare the constraints obtained with the ones obtained when randomly selecting a galaxy in the whole sample. We use the IllustrisTNG galaxy catalog from the Cosmology and Astrophysics with MachinE Learning Simulations (CAMELS) project and the VIDE void finder to identify galaxies inside voids. We show that void galaxies provide stronger constraints on Ωm compared to randomly selected galaxies. This result suggests that the distinctive characteristics of void galaxies may provide a cleaner and more effective environment for extracting cosmological information.

Keywords: galaxy properties; voids; cosmology; astrostatistics