adsabs/SciX_UAT_keywords huggingface dataset:
Discerning Parallax Amplitude in Astrometric Microlensing

Gravitational microlensing is a powerful method for discovering isolated stellar-mass black holes (ISMBHs). These objects make long-duration microlensing events. To characterize these lensing objects by fully resolving the microlensing degeneracy, measurements of parallax and astrometric deflections are necessary. Microlensing events due to ISMBHs have considerable astrometric deflections but small parallax amplitudes, ${\pi }_{{\rm{E}}}\propto 1/\sqrt{{M}_{{\rm{l}}}}$ , where M l is the lens mass. We numerically investigate the possibility of inferring parallax amplitude from astrometric deflection in microlensing events due to ISMBHs. The parallax amplitude in astrometric deflections is proportional to the relative parallax π rel, which means that it (i) does not strongly depend on M l and (ii) increases in microlensing observations toward the Magellanic Clouds. We assume that these events will be potentially detected in upcoming microlensing surveys such as (1) the Roman observations of the Galactic bulge (GB) and (2) the LSST observations of the Large Magellanic Cloud (LMC) and that the Extremely Large Telescope (ELT) will follow up on them with one data point every 10 days. We evaluate the probability of inferring parallax amplitude from these observations by calculating the Fisher and covariance matrices. For the GB, the efficiencies for discerning parallax amplitudes with a relative error of <4% through astrometric and photometric observations are 3.8% and 29.1%, respectively. For observations toward the LMC, these efficiencies are 41.1% and 23.0%, respectively. Measuring parallax amplitude through astrometric deflections is plausible in GB events with a lens distance of ≲2.7 kpc and in LMC halo lensing. By monitoring long-duration microlensing events, the ELT can detect astrometric deflections and their parallax-induced deviations.

Keywords: gravitational microlensing; astrometric microlensing effect; annual microlensing parallax; monte carlo methods; computational methods
Comprehensive Multimessenger Modeling of the Extreme Blazar 3HSP J095507.9+355101 and Predictions for IceCube

3HSP J095507.9+355101 is an extreme blazar that has been possibly associated with a high-energy neutrino (IceCube-200107A) detected 1 day before the blazar was found to undergo a hard X-ray flare. We perform a comprehensive study of the predicted multimessenger emission from 3HSP J095507.9+355101 during its recent X-ray flare, but also in the long term. We focus on one-zone leptohadronic models, but we also explore alternative scenarios: (i) a blazar-core model, which considers neutrino production in the inner jet, close to the supermassive black hole; (ii) a hidden external-photon model, which considers neutrino production in the jet through interactions with photons from a weak broad line region; (iii) a proton-synchrotron model, where high-energy protons in the jet produce γ-rays via synchrotron; and (iv) an intergalactic cascade scenario, where neutrinos are produced in the intergalactic medium by interactions of a high-energy cosmic-ray beam escaping the jet. The Poisson probability to detect a single muon neutrino in 10 years from 3HSP J095507.9+355101 with the real-time IceCube alert analysis is ∼1% (3%) for the most optimistic one-zone leptohadronic model (the multi-zone blazar-core model). Meanwhile, detection of a single neutrino during the 44-day-long high X-ray flux-state period following the neutrino detection is 0.06%, according to our most optimistic leptohadronic model. The most promising scenarios for neutrino production also predict strong intrasource γ-ray attenuation above ∼100 GeV. If the association is real, then IceCube-Gen2 and other future detectors should be able to provide additional evidence for neutrino production in 3HSP J095507.9+355101 and other extreme blazars.

Keywords: bl lacertae objects; blazars; gamma-rays; neutrino astronomy; high energy astrophysics
On the Possibility of Generalized Wormhole Formation in the Galactic Halo Due to Dark Matter Using the Observational Data within the Matter Coupling Gravity Formalism

In this article, we find the possibility of generalized wormhole formation in the galactic halo due to dark matter using observational data within the matter coupling gravity formalism. Keeping this as a target, we specifically employ f(R, T) gravity with (i) a variational approach concerning the metric, and (ii) the anisotropic source of matter. To understand the features of the wormholes, we thoroughly calculated and analyzed the energy conditions under f(R, T) gravity. We discuss the second embedded wormhole solution, known as the generalized Ellis-Bronnikov spacetime (ultrastatic wormhole model), in terms of the tortoise coordinate. Thereafter we generate and compare different wormhole solutions depending on the parametric values. In the second part of our investigation, we presented dark matter halos and provided interesting features by considering a couple of profiles. For the dark matter halos models, we particularly use the observational data of the M87 galaxy and the Milky Way galaxy.

Keywords: dark matter
Radio Activity of Supermassive Black Holes with Extremely High Accretion Rates

Radio emission from the high- and super-Eddington accreting active galactic nuclei (AGNs) has various origins: a persistent jet, the magnetized corona, and the wind-like outflows. It is still unclear which is the leading mechanism responsible for the observed radio emission and how the radio emission is related to other characteristic parameters such as the Eddington ratio and black hole mass. In this paper, we present the 5 GHz Very Large Array (VLA) observational results of a sample of 25 extremely high Eddington accreting supermassive black holes (EESBHs, the Eddington ratio λEdd close to or above 1) in narrow-line Seyfert 1 galaxies, among which 22 sources are detected. Most of the EESBHs show a compact radio structure from a few hundred parsecs to 1 kpc scale. We estimated the lowest star formation rate surface density required for producing the observed radio emission and found that it is higher than the largest value previously detected in circumnuclear starburst galaxies, implying that the radio emission is from the AGN activity. Along with a comparison sample, we find an overall inverse ${ \mathcal R }$ -λEdd correlation ranging from sub- to super-Eddington ratios. The high-Eddington and mildly super-Eddington AGNs (-0.5 < log ${\lambda }_{\mathrm{Edd}}\lt 0.6$ ) have a radio-to-X-ray luminosity ratio LR/LX ∼ 10-5-10-4 and a steep radio spectrum, supporting that the radio emission is from transient ejecta (outflows) of corona; however, the jet contribution cannot be entirely ruled out. Our highly super-Eddington sources (log ${\lambda }_{\mathrm{Edd}}\gtrsim 0.6$ ) have a flatter radio spectrum, along with its low radio luminosity: ${L}_{{\rm{R}}}/{L}_{{\rm{X}}}\sim {10}^{-5}$ ; their radio emission is likely dominated by a magnetized corona, and a radiation-pressure-caused jet is also proposed in this paper.

Keywords: supermassive black holes; active galaxies; jets; active galactic nuclei
The Dark Side of Pluto

During its departure from Pluto, New Horizons used its LORRI camera to image a portion of Pluto's southern hemisphere that was in a decades-long seasonal winter darkness, but still very faintly illuminated by sunlight reflected by Charon. Recovery of this faint signal was technically challenging. The bright ring of sunlight forward-scattered by haze in the Plutonian atmosphere encircling the nightside hemisphere was severely overexposed, defeating the standard smeared-charge removal required for LORRI images. Reconstruction of the overexposed portions of the raw images, however, allowed adequate corrections to be accomplished. The small solar elongation of Pluto during the departure phase also generated a complex scattered-sunlight background in the images that was three orders of magnitude stronger than the estimated Charon-light flux (the Charon-light flux is similar to the flux of moonlight on Earth a few days before first quarter). A model background image was constructed for each Pluto image based on principal component analysis applied to an ensemble of scattered-sunlight images taken at identical Sun-spacecraft geometry to the Pluto images. The recovered Charon-light image revealed a high-albedo region in the southern hemisphere. We argue that this may be a regional deposit of N2 or CH4 ice. The Charon-light image also shows that the south polar region currently has markedly lower albedo than the north polar region of Pluto, which may reflect the sublimation of N2 ice or the deposition of haze particulates during the recent southern summer.

Keywords: pluto; planetary surfaces
The Splashback Radius of Halos from Particle Dynamics. III. Halo Catalogs, Merger Trees, and Host-Subhalo Relations

Virtually any investigation involving dark matter halos relies on a definition of their radius, of their mass, and of whether they are a subhalo. The halo boundary is most commonly defined to include a spherical overdensity contrast (such as ${R}_{200{\rm{c}}}$ , ${R}_{\mathrm{vir}}$ , and ${R}_{200{\rm{m}}}$ ), but different thresholds lead to significant differences in radius and mass. The splashback radius has recently been suggested as a more physically motivated (and generally larger) halo boundary, adding to the range of definitions. It is often difficult to assess the impact of a particular choice because most halo catalogs contain only one or a few definitions and generally only one set of host-subhalo relations. To alleviate this issue, we present halo catalogs and merger trees for 14 N-body simulations of ΛCDM and self-similar universes. Based on ROCKSTAR catalogs, we compute additional halo properties using the SPARTA code and recombine them with the original catalogs. The new catalogs contain numerous variants of spherical overdensity and splashback radii and masses and, most critically, host-subhalo relations for each definition. We also present a new merger tree format where the data are stored as a compressed, two-dimensional matrix. We perform basic tests of the relation between different definitions and present an updated model for the splashback-spherical overdensity connection. The SPARTA code, as well as our catalogs and merger trees, are publicly available.

Keywords: large-scale structure of the universe; dark matter
Timescales for Detection of Super-Chandrasekhar White Dwarfs by Gravitational-wave Astronomy

Over the past two decades, the inference of the violation of the Chandrasekhar mass limit of white dwarfs (WDs) from indirect observation has been a revolutionary discovery in astronomy. Various researchers have already proposed different theories to explain this interesting phenomenon. However, such massive WDs usually possess very little luminosity, hence they so far cannot be detected directly by any observations. We have already proposed that the continuous gravitational wave may be one of the probes to detect them directly, and in the future various space-based detectors, such as LISA, DECIGO, and BBO, should be able to detect many of those WDs (provided they behave like pulsars). In this paper, we address various timescales related to the emission of gravitational as well as dipole radiations. This exploration sets a timescale for the detectors to observe the massive WDs.

Keywords: white dwarf stars; rotation powered pulsars; gravitational waves; astronomical radiation sources; stellar magnetic fields; chandrasekhar limit; gravitational wave astronomy; gravitational wave sources; pulsars; stellar luminosities
Identification of a Local Sample of Gamma-Ray Bursts Consistent with a Magnetar Giant Flare Origin

Cosmological gamma-ray bursts (GRBs) are known to arise from distinct progenitor channels: short GRBs mostly from neutron star mergers and long GRBs from a rare type of core-collapse supernova (CCSN) called collapsars. Highly magnetized neutron stars called magnetars also generate energetic, short-duration gamma-ray transients called magnetar giant flares (MGFs). Three have been observed from the Milky Way and its satellite galaxies, and they have long been suspected to constitute a third class of extragalactic GRBs. We report the unambiguous identification of a distinct population of four local (<5 Mpc) short GRBs, adding GRB 070222 to previously discussed events. While identified solely based on alignment with nearby star-forming galaxies, their rise time and isotropic energy release are independently inconsistent with the larger short GRB population at >99.9% confidence. These properties, the host galaxies, and nondetection in gravitational waves all point to an extragalactic MGF origin. Despite the small sample, the inferred volumetric rates for events above 4 × 1044 erg of ${R}_{\mathrm{MGF}}={3.8}_{-3.1}^{+4.0}\times {10}^{5}$ Gpc-3 yr-1 make MGFs the dominant gamma-ray transient detected from extragalactic sources. As previously suggested, these rates imply that some magnetars produce multiple MGFs, providing a source of repeating GRBs. The rates and host galaxies favor common CCSN as key progenitors of magnetars.

Keywords: gamma-ray bursts; magnetars; soft gamma-ray repeaters
Variability of Jupiter's Synchrotron Radiation: Goldstone Apple Valley Radio Telescope (GAVRT) Observations -II

Jupiter's decimeter-wavelength flux density is dominated by synchrotron emission from magnetically trapped ~5-50 MeV electrons in the radiation belts. Synchrotron radio emission remains the most useful diagnostic of the radiation belts, and a global picture is provided by ground-based observations. Monitoring of the long-term variations of Jupiter's Synchrotron Radiation (JSR) flux density is crucial to understanding its relationship with the solar wind. The GAVRT (Goldstone-Apple Valley Radio Telescope) program operates two retired Deep Space Network (DSN) antennas, and as part of their K-12 program and Juno support, GAVRT has been collecting data to monitor JSR radio emission at 2280 MHz (13 cm wavelength). We present new results from 2019 August to 2021 December GAVRT monitoring observations. As viewed from Earth the JSR varies systematically (by about 10%) with Jupiter's 9.9 hr rotation period, and our observations were typically much shorter than 9.9 hr. To estimate the daily flux density of JSR, we took advantage of recent progress in modeling the radiation belt, scaling individual observations by the predicted relative variation due to Jupiter's rotation as viewed from Earth. We discuss the JSR variability from 2015 to 2021, combining our results with previous GAVRT data. Our new results show a marked decrease (~1 Jy) in JSR flux density between 2018 and 2021, while earlier observations showed an increase from 2015 to 2018. These results are remarkably consistent with long-term variability shown by the simulations of Han et al. based on models driven by the solar wind ram pressure.

Keywords: radio astronomy; radio observatories; jupiter
Updated Orbital Ephemeris and Detection of Superhump Modulation in X-Ray Band for the Ultra-compact Low Mass X-Ray Binary 4U 1820-30

The 4U 1820-30 is an ultra-compact low-mass X-ray binary (LMXB) near the center of the globular cluster NGC 6624. Its negative orbital period derivative, observed from the phase evolution of its sinusoidal-like orbital variation, contradicts the positive value that was obtained from the theoretical prediction. In this paper, we present the analysis of the 4U 1820-30 orbital modulation from light curves obtained from the Neutron star Interior Composition ExploreR (NICER) observations from 2017 to mid-2022. Combined with historical records, the orbital derivative is measured from the orbital phase evolution between 1976 and 2002 is $\dot{P}/P=(-5.21\pm 0.13)\times {10}^{-8}$ yr-1. No significant second order orbital period derivative is detected with a 2σ upper limit of $| \ddot{P}| \lt 5.48\times {10}^{-22}$ s s-2. We discuss the possible intrinsic orbital period derivative of 4U 1820-30 and suggest that this binary system may have a significant mass outflow similar to some other LMXBs. In addition, a periodic modulation with a period of 691.6 ± 0.7 s, which is consistent with the superhump period discovered in the far-ultraviolet band of the Hubble Space Telescope, was also detected in the X-ray light curves that were collected by NICER. We conclude that this modulation is probably caused by a period of 0.8 ± 0.1 day apsidal precession of the accretion disk, similar to the SU UMa type dwarf novae and some LMXBs. However we cannot exclude the possibility that it is induced by a hierarchical third star that orbits around the binary system.

Keywords: low-mass x-ray binary stars; close binary stars; stellar accretion disks
Multimessenger Pulsar Timing Array Constraints on Supermassive Black Hole Binaries Traced by Periodic Light Curves

Supermassive black hole binary systems (SMBHBs) emitting gravitational waves may be traced by periodic light curves. We assembled a catalog of 149 such periodic light curves, and using their masses, distances, and periods, predicted the gravitational-wave strain and detectability of each binary candidate using all-sky detection maps. We found that the International Pulsar Timing Array (IPTA) provides almost uniform sky coverage-a unique ability of the IPTA-and by 2025 will improve NANOGrav's current minimum detectable strain by a factor of 6 and its volume by a factor of 216. Moreover, IPTA will reach detection sensitivities for three candidates by 2025, and 13 by the end of the decade, enabling us to constrain the underlying empirical relations used to estimate supermassive black hole masses. We find that we can in fact already constrain the mass of a binary in Mrk 504 to M < 3.3 × 109 M⊙. We also identify 24 high-mass, high-redshift galaxies that, according to our models, should not be able to host SMBHBs. Importantly, the GW detection of even one of these candidates would be an essentially eternal multimessenger system, and identifying common false-positive signals from nondetections will be useful to filter the data from future large-scale surveys such as LSST.

Keywords: gravitational waves; astrophysical black holes; millisecond pulsars; supermassive black holes; agn host galaxies; active galactic nuclei; gravitational wave astronomy; gravitational wave sources; general relativity
Quantitative and Qualitative Results from Orbital Plane Precession of Medium-high Near-circular Orbits

The theoretical analysis of Allan & Cook on the mechanisms of orbital plane precession for medium-high circular orbits is briefly reviewed, and the fact that there are two types of possible precession mechanisms (not only the classical Laplace precession) for the long-term evolution of the orbital plane of medium-high near-circular orbits is especially emphasized. Based on two types of possible precession mechanisms, the analytical formulae of the quantitative variation ranges of orbital inclination derived by Zhao et al. are revised, and the complete analytical formulae for medium-high near-circular orbits are obtained. The qualitative characteristic formula for the variation of orbital inclination-longitude of the ascending node of geostationary orbits in Zhao et al. is generalized to medium-high near-circular orbits, and the more general analytical formulae are obtained. Taking the near-circular orbits with the altitudes as the geosynchronous and medium orbits of the BeiDou navigation satellites as examples, the theoretically quantitative and qualitative results from orbital plane precession are verified by the first-order semianalytical calculations with simplified models and numerical calculations with precise models to a certain extent. Moreover, the specific quantitative and qualitative results for medium-high near-circular orbits with the given initial inclinations and different initial longitudes of the ascending node are particularly presented, from which some conclusions are summarized. Due to the high similarity of orbital plane precession for natural satellites to that of artificial satellites, the results and methodology in this paper can be directly extended to the long-term evolution of the orbital plane for natural satellites and help to understand and explain some orbit dynamic phenomena of natural satellites.

Keywords: celestial mechanics; orbits; orbital motion
Implementation of the Polarimetry Focusing Telescope Array Observation Simulator on board the X-Ray Timing and Polarimetry Observatory

An observation simulator is established, on an event-by-event basis, for the Polarimetry Focusing telescope Array (PFA) on board the planned enhanced X-ray Timing and Polarimetry observatory (eXTP). An event generator, based on XIMPOL, is used to sample the parameters of the X-rays reaching the aperture of the telescope. The trajectories and interactions of X-rays through the telescope and the corresponding secondaries are calculated using the optics and detector simulation model built in GEANT4, before being translated into signals in the pixelated readout electronics. It is shown that mirror deformation is required for the optics simulation model, and transportation of ionization electrons is required for the detector simulation model to reproduce the overall performance of the telescope. The developed tool is useful in different mission phases, such as payload optimization in the design phase, discrimination of new phenomena against known physics models in the calibration phases, and sensitivity studies of potential polarized X-ray sources in observation planning. The sensitivity of PFA to the Crab Nebula and Crab pulsar is investigated to demonstrate the application of the tool. Even with the dilution effect, space-resolved and phase-resolved polarimetry can reveal important aspects of the Crab Nebula and Crab pulsar and help break the degeneracy between different models.

Keywords: x-ray detectors; polarimeters; astronomical methods
The Spin of a Newborn Black Hole: Swift J1728.9-3613

The origin and distribution of stellar-mass black hole spins are a rare window into the progenitor stars and supernova events that create them. Swift J1728.9-3613 is an X-ray binary, likely associated with the supernova remnant (SNR) G351.9-0.9. An NuSTAR X-ray spectrum of this source during its 2019 outburst reveals reflection from an accretion disk extending to the innermost stable circular orbit. Modeling of the relativistic Doppler shifts and gravitational redshifts imprinted on the spectrum measures a dimensionless spin parameter of a = 0.86 ± 0.02 (1σ confidence), a small inclination angle of the inner accretion disk θ < 10°, and a subsolar iron abundance in the disk A Fe < 0.84. This high spin value rules out a neutron star primary at the 5σ level of confidence. If the black hole is located in a still visible SNR, it must be young. Therefore, we place a lower limit on the natal black hole spin of a > 0.82, concluding that the black hole must have formed with a high spin. This demonstrates that black hole formation channels that leave an SNR, and those that do not (e.g., Cyg X-1), can both lead to high natal spin with no requirement for subsequent accretion within the binary system. Emerging disparities between the population of high-spin black holes in X-ray binaries and the low-spin black holes that merge in gravitational wave events may therefore be explained in terms of different stellar conditions prior to collapse, rather than different environmental factors after formation.

Keywords: black hole physics; high energy astrophysics; x-ray binary stars; compact binary stars; accretion