adsabs/SciX_UAT_keywords huggingface dataset:
Lorentz Invariance Violation Test from Time Delays Measured with Gravitationally Lensed GRB Candidates 950830 and 200716C

The spectral lag features in gamma-ray bursts (GRBs) have been widely used to investigate possible Lorentz invariance violation (LIV). However, these constraints could depend on the unknown source-intrinsic time delays in different energy bands. Biesiada & Piórkowska theoretically proposed that gravitational lensing time delays in a strongly lensed GRB can become a tool for testing LIV free from the intrinsic time lag problem. Recently GRB 950830 and GRB 200716C have been proposed to be lensed by an intermediate-mass black hole. They should still be considered as candidates of strongly lensed bursts, since no angular offset (i.e., the evidence for multiple images) was detected, but only a double peak structure in the light curve. The redshift of the burst z s and of the lens z l have not been measured in either case; hence we assumed a reasonable guess of z l = 1.0, z s = 2.0 for GRB 950830 and z l = 0.174, z s = 0.348 for GRB 200716C. Bearing all this in mind, we attempted to constrain LIV theories in a prospective way based on the two GRBs by considering time delays between two pulses in different energy channels. By directly fitting the time delay data of GRBs 950830 and 200716C we obtained the following limits on LIV energy scale: E QG,1 ≥ 3.2 × 109 GeV and E QG,1 ≥ 6.3 × 109 GeV, respectively. Sensitivity analysis regarding the (unknown) redshifts leads to the most conservative estimate, E QG,1 ≥ 1.5 × 108 GeV for GRB 950830 and E QG,1 ≥ 4.8 × 108 GeV for GRB 200716C, when they would be located at z s ~ 5.

Keywords: gamma-ray bursts
Asymmetry Revisited: The Effect of Dust Attenuation and Galaxy Inclination

Dust attenuation of an inclined galaxy can cause additional asymmetries in observations, even if the galaxy has a perfectly symmetric structure. Taking advantage of the integral field spectroscopic data observed by the Sloan Digital Sky Survey-IV Mapping Nearby Galaxies at the Apache Point Observatory survey, we investigate the asymmetries of the emission-line and continuum maps of star-forming disk galaxies. We define new parameters, Aa and Ab, to estimate the asymmetries of a galaxy about its major and minor axes, respectively. Comparing Aa and Ab in different inclination bins, we attempt to detect the asymmetries caused by dust. For the continuum images, we find that Aa increases with the inclination, while Ab is a constant as inclination changes. Similar trends are found for g - r, g - i, and r - i color images. The dependence of the asymmetry on inclination suggests a thin dust layer with a scale height smaller than the stellar populations. For the Hα and Hβ images, neither Aa nor Ab shows a significant correlation with inclination. Also, we do not find any significant dependence of the asymmetry of E(B - V)g on inclination, implying that the dust in the thick disk component is not significant. Compared to the SKIRT simulation, the results suggest that the thin dust disk has an optical depth of τV ∼ 0.2. This is the first time that the asymmetries caused by the dust attenuation and the inclination are probed statistically with a large sample. Our results indicate that the combination of the dust attenuation and the inclination effects is a potential indicator of the 3D disk orientation.

Keywords: galaxy structure
Atmospheric Circulation of Tidally Locked Gas Giants with Increasing Rotation and Implications for White Dwarf-Brown Dwarf Systems

Tidally locked gas giants, which exhibit a novel regime of day-night thermal forcing and extreme stellar irradiation, are typically in several-day orbits, implying a modest role for rotation in the atmospheric circulation. Nevertheless, there exist a class of gas-giant, highly irradiated objects—brown dwarfs orbiting white dwarfs in extremely tight orbits—whose orbital and hence rotation periods are as short as 1-2 hr. Phase curves and other observations have already been obtained for this class of objects, raising fundamental questions about the role of an increasing planetary rotation rate in controlling the circulation. So far, most modeling studies have investigated rotation periods exceeding a day, as appropriate for typical hot Jupiters. In this work, we investigate atmospheric circulation of tidally locked atmospheres with decreasing rotation periods (increasing rotation rate) down to 2.5 hr. With a decreasing rotation period, we show that the width of the equatorial eastward jet decreases, consistent with the narrowing of the equatorial waveguide due to a decrease of the equatorial deformation radius. The eastward-shifted equatorial hot-spot offset decreases accordingly, and the off-equatorial westward-shifted hot areas become increasingly distinctive. At high latitudes, winds become weaker and more rotationally dominated. The day-night temperature contrast becomes larger due to the stronger influence of rotation. Our simulated atmospheres exhibit variability, presumably caused by instabilities and wave interactions. Unlike typical hot Jupiter models, the thermal phase curves of rapidly rotating models show a near alignment of peak flux to secondary eclipse. This result helps to explain why, unlike hot Jupiters, brown dwarfs closely orbiting white dwarfs tend to exhibit IR flux peaks nearly aligned with secondary eclipse. Our results have important implications for understanding fast-rotating, tidally locked atmospheres.

Keywords: brown dwarfs; exoplanet atmospheres; white dwarf stars; hydrodynamics; hot jupiters
The Metallicity Distribution Function in Outer Halo Fields of Simulated Elliptical Galaxies Compared to Observations of NGC 5128

Stellar metallicity distribution functions (MDFs) have been measured for resolved stellar populations in the outer halos of many galaxies in nearby groups. Among them, the MDF of NGC 5128, the central giant elliptical in the Centaurus group, provides essential constraints for theories of massive galaxy formation and hierarchical assembly. To investigate the formation and chemical evolution history of the outer halo of giant elliptical galaxies, we examine the chemical properties of three zoom-in high-resolution cosmological hydrodynamical simulations of an NGC 5128-like giant elliptical galaxy and compare their outer halo MDFs to the observed one of NGC 5128. Even though the simulated galaxies have different merging histories and age distributions, all predicted MDFs are in good qualitative agreement with the observed one. The median metallicity of the simulated galaxies is, on average, [M/H] = -0.41 ± 0.06 compared to the observed value of [M/H] = -0.38 ± 0.02 for NGC 5128, and the dispersion in metallicity is ~0.77 dex for both observed and simulated galaxies. We investigate the origin of the stars ending up in the outer halo field of simulated galaxies and show that most have an "accreted" origin, formed in other small galaxies and later accreted in mergers. Only ~15% of the stars are formed in situ within the main progenitor of the galaxy and radially migrate outward. We show that the contribution of metal-rich in situ stars is subdominant in the outer halos of our simulated galaxies but can be prominent in the inner regions.

Keywords: elliptical galaxies; galaxy formation; galaxy chemical evolution; chemical enrichment
The Baryonic Tully–Fisher Relation. I. WISE/Spitzer Photometry

We present Wide-field Infrared Survey Explorer (WISE) W1 photometry of the Spitzer Photometry and Accurate Rotation Curves sample. The baseline of near-IR fluxes is established for use by stellar mass models, a key component to the baryonic Tully–Fisher relation and other kinematic galaxies scaling relations. We focus this paper on determination of the characteristics of the W1 fluxes compared to IRAC 3.6 μm fluxes, internal accuracy limitations from photometric techniques, external accuracy by comparison to other work in the literature and the range of W1 to IRAC 3.6 μm colors. We outline the behavior of SDSS g, W1 and IRAC 3.6 colors with respect to underlying spectral energy distribution features. We also note a previously unknown correlation between WISE colors and the central surface brightness, probably related to the low metallicity of low-surface-brightness dwarfs.

Keywords: galaxy structure; galaxy photometry; disk galaxies
No Evolution in the Half-mass Radius of Milky Way-type Galaxies over the Last 10 Gyr

The Milky Way (MW) galaxy is in focus, thanks to new observational data. Here we shed new light on the MW's past by studying the structural evolution of MW progenitors, which we identify from extragalactic surveys. Specifically, we constrain the stellar-mass growth history (SMGH) of the MW with two methods: (i) direct measurement of the MW's star formation history, and (ii) assuming the MW is a typical star-forming galaxy that remains on the star-forming main sequence. We select MW progenitors based on these two SMGHs at z = 0.2-2.0 from the CANDELS/3D-HST data. We estimate the structural parameters (including half-mass radius r 50 and Sérsic index) from the stellar-mass profiles. Our key finding is that the progenitors of the MW galaxy grow self-similarly on spatially resolved scales with roughly a constant half-mass radius (~2-3 kpc) over the past 10 Gyr, while their stellar masses increase by about 1 dex, implying little-to-no inside-out growth. We discover that the radius containing 20% of the stellar mass (r 20) decreases by 60% between redshifts of z = 2.0 and z = 0.7, while the central stellar-mass density (Σ1) increases by a factor of 1.3 dex over the same time and the Sérsic index changes as $n\propto {\left(1+z\right)}^{-1.41\pm 0.19}$ . This is consistent with an early (z > 1) formation of a thick disk, followed by the formation of a bar that led to an increase in the mass in the core. The formation and evolution of the thin disk had only little impact on the overall half-mass size. We also show that the constant-size evolution of the MW progenitors challenges semiempirical approaches and numerical simulations.

Keywords: galaxy evolution; galaxy formation; milky way formation; milky way evolution; galaxy structure; milky way galaxy
Neutrino Mass Constraint from an Implicit Likelihood Analysis of BOSS Voids

Cosmic voids identified in the spatial distribution of galaxies provide complementary information to two-point statistics. In particular, constraints on the neutrino mass sum, ∑m ν , promise to benefit from the inclusion of void statistics. We perform inference on the CMASS Northern Galactic Cap sample of the third-generation Sloan Digital Sky Survey/Baryon Oscillation Spectroscopic Survey (BOSS) with the aim of constraining ∑m ν . We utilize the void size function, the void–galaxy cross power spectrum, and the galaxy auto power spectrum. To extract constraints from these summary statistics we use a simulation-based approach, specifically implicit likelihood inference. We populate approximate gravity-only, particle-neutrino cosmological simulations with an expressive halo occupation distribution model. With a conservative scale cut of and a Planck-inspired Lambda cold dark matter prior, we find upper bounds on ∑m ν of 0.43 and 0.35 eV from the galaxy auto power spectrum and the full data vector, respectively (95% credible interval). Relaxing the scale cut to , we find 0.28 and 0.32 eV. Generally, void statistics appear to add modest but nonzero information beyond the auto power spectrum. We also substantiate the usual assumption that the void size function is Poisson distributed.

Keywords: redshift surveys; voids; cosmological neutrinos; neutrino masses; n-body simulations; neural networks
A Data-constrained Scheme for the Reconstruction of Solar Wind Parameters in the Inner Heliosphere

With the development of our industrial society, the reconstruction of solar wind parameters in the inner heliosphere becomes very important to understanding the interplanetary propagation of various types of space weather disturbance. However, the situ observations of solar wind parameters are only applicable to several points where spacecraft are located. Therefore, we have to rely on the numerical technologies to reconstruct the solar wind parameters. The scheme for the reconstruction of solar wind parameters can be classified into two categories: one is based on the remote-sensing data at the Sun, and the other is based on the in situ data at 1 au. In this paper, the solar wind parameters in the inner heliosphere are reconstructed with magnetohydrodynamic simulations from 20 R s to 1 au. The inner boundary conditions are constrained by Wind observations at 1 au. The modeled results are compared with data from multispacecraft observations, such as those by Parker Solar Probe, Solar Orbiter, and the Solar Terrestrial Relations Observatory A and B. The results show that the solar wind parameters obtained with this new scheme agree with the in situ observations much better, which will provide a more realistic configuration for the study of various types of space weather disturbance in future.

Keywords: solar wind
The 3D Galactocentric Velocities of Kepler Stars: Marginalizing Over Missing Radial Velocities

Precise Gaia measurements of positions, parallaxes, and proper motions provide an opportunity to calculate 3D positions and 2D velocities (i.e., 5D phase-space) of Milky Way stars. Where available, spectroscopic radial velocity (RV) measurements provide full 6D phase-space information, however there are now and will remain many stars without RV measurements. Without an RV it is not possible to directly calculate 3D stellar velocities; however, one can infer 3D stellar velocities by marginalizing over the missing RV dimension. In this paper, we infer the 3D velocities of stars in the Kepler field in Cartesian Galactocentric coordinates (v x , v y , v z ). We directly calculate velocities for around a quarter of all Kepler targets, using RV measurements available from the Gaia, LAMOST, and APOGEE spectroscopic surveys. Using the velocity distributions of these stars as our prior, we infer velocities for the remaining three quarters of the sample by marginalizing over the RV dimension. The median uncertainties on our inferred v x , v y , and v z velocities are around 4, 18, and 4 km s-1, respectively. We provide 3D velocities for a total of 148,590 stars in the Kepler field. These 3D velocities could enable kinematic age-dating, Milky Way stellar population studies, and other scientific studies using the benchmark sample of well-studied Kepler stars. Although the methodology used here is broadly applicable to targets across the sky, our prior is specifically constructed from and for the Kepler field. Care should be taken to use a suitable prior when extending this method to other parts of the Galaxy.

Keywords: milky way dynamics; late-type stars; solar neighborhood; stellar properties; stellar ages
Is the Compact Object Associated with HESS J1731-347 a Strange Quark Star? A Possible Astrophysical Scenario for Its Formation

The analysis of the central compact object within the supernova (SN) remnant HESS J1731-347 suggests that it has a small radius and, even more interestingly, a mass of the order or smaller than 1 M ⊙. This raises the question of which astrophysical process could lead to such a small mass, since the analysis of various types of SN explosions indicate that is it not possible to produce a neutron star with a mass smaller than about 1.17 M ⊙. Here we show that masses of the order or smaller than 1 M ⊙ can be obtained in the case of strange quark stars and that it is possible to build a coherent model explaining not only the mass and the radius of that object, but also its slow cooling suggested in various analyses. We also show that an astrophysical path exists, which leads to the formation of such an object, and we discuss the role played in that scenario by strangelets assumed to constitute the dark matter.

Keywords: compact objects; neutron stars; dark matter; baryonic dark matter
X-Ray and Radio Bursts from the Magnetar 1E 1547.0-5408

We report on simultaneous radio and X-ray observations of the radio-emitting magnetar 1E 1547.0-5408 on 2009 January 25 and February 3, with the 64 m Parkes radio telescope and the Chandra and XMM-Newton X-ray observatories. The magnetar was observed in a period of intense X-ray bursting activity and enhanced X-ray emission. We report here on the detection of two radio bursts from 1E 1547.0-5408 reminiscent of fast radio bursts (FRBs). One of the radio bursts was anticipated by ∼1 s (about half a rotation period of the pulsar) by a bright SGR-like X-ray burst, resulting in a Fradio/FX ∼ 10-9. Radio pulsations were not detected during the observation showing the FRB-like radio bursts, while they were detected in the previous radio observation. We also found that the two radio bursts are neither aligned with the latter radio pulsations nor with the peak of the X-ray pulse profile (phase shift of ∼0.2). Comparing the luminosity of these FRB-like bursts and those reported from SGR 1935+2154, we find that the wide range in radio efficiency and/or luminosity of magnetar bursts in the Galaxy may bridge the gap between "ordinary" pulsar radio bursts and the extragalactic FRB phenomenon.

Keywords: x-ray bursts; magnetars; radio transient sources; radio bursts; pulsars; neutron stars
Disconnecting the Dots: Re-examining the Nature of Stellar "Strings" in the Milky Way

Recent analyses of Gaia data have resulted in the identification of new stellar structures, including a new class of extended stellar filaments called stellar "strings," first proposed by Kounkel & Covey. We explore the spatial, kinematic, and chemical composition of strings to demonstrate that these newfound structures are largely inconsistent with being physical objects whose members share a common origin. Examining the 3D spatial distribution of string members, we find that the spatial dispersion around the claimed string spine does not improve in the latest Gaia DR3 data release-despite tangible gains in the signal-to-noise ratio of the parallax measurements-counter to expectations of a bona fide structure. Using the radial velocity dispersion of the strings (averaging ${\sigma }_{{V}_{r}}=16\,\mathrm{km}\,{{\rm{s}}}^{-1}$ ) to estimate their virial masses, we find that all strings are gravitationally unbound. Given the finding that the strings are dispersing, the reported stellar ages of the strings are typically 120× larger than their measured dispersal times. Finally, we validate prior work that stellar strings are more chemically homogeneous than their local field stars but show it is possible to obtain the same signatures of chemical homogeneity by drawing random samples of stars from spatially, temporally, and kinematically unrelated open clusters. Our results show that while some strings may be composed of real substructures, there is no consistent evidence for larger string-like connections over the sample. These results underscore the need for caution in over-interpreting the significance of these strings and their role in understanding the star formation history of the Milky Way.

Keywords: star clusters; stellar dynamics; interstellar filaments; milky way galaxy
Possible Evidence for Lorentz Invariance Violation in Gamma-Ray Burst 221009A

The preliminary detections of the gamma-ray burst 221009A up to 18 TeV by LHAASO and up to 251 TeV by Carpet 2 have been reported through Astronomer's Telegrams and Gamma-ray Coordination Network circulars. Since this burst is at redshift z = 0.1505, these photons may at first seem to have a low probability to avoid pair production off of background radiation fields and survive to reach detectors on Earth. By extrapolating the reported 0.1-1.0 GeV Fermi Large Area Telescope spectrum from this burst to higher energies and using this to limit the intrinsic spectrum of the burst, we show that the survival of the 18 TeV photon detected by LHAASO is not unlikely with many recent extragalactic background light models, although the detection of a 251 TeV event is still very unlikely. This can be resolved if Lorentz invariance is violated at an energy scale E QG ≲ 49E Planck in the linear (n = 1) case, and E QG ≲ 10-6 E Planck in the quadratic (n = 2) case (95% confidence limits), where E Planck is the Planck energy. This could potentially be the first evidence for subluminal Lorentz invariance violation.

Keywords: gamma-ray bursts; gamma-ray astronomy; quantum gravity
Outflows from Super Star Clusters in the Central Starburst of NGC 253

Young massive clusters play an important role in the evolution of their host galaxies, and feedback from the high-mass stars in these clusters can have profound effects on the surrounding interstellar medium. The nuclear starburst in the nearby galaxy NGC 253 at a distance of 3.5 Mpc is a key laboratory in which to study star formation in an extreme environment. Previous high-resolution (1.9 pc) dust continuum observations from the Atacama Large Millimeter/submillimeter Array (ALMA) discovered 14 compact, massive super star clusters (SSCs) still in formation. We present here ALMA data at 350 GHz with 28 mas (0.5 pc) resolution. We detect blueshifted absorption and redshifted emission (P-Cygni profiles) toward three of these SSCs in multiple lines, including CS 7-6 and H13CN 4-3, which represent direct evidence for previously unobserved outflows. The mass contained in these outflows is a significant fraction of the cluster gas masses, which suggests we are witnessing a short but important phase. Further evidence of this is the finding of a molecular shell around the only SSC visible at near-IR wavelengths. We model the P-Cygni line profiles to constrain the outflow geometry, finding that the outflows must be nearly spherical. Through a comparison of the outflow properties with predictions from simulations, we find that none of the available mechanisms completely explains the observations, although dust-reprocessed radiation pressure and O star stellar winds are the most likely candidates. The observed outflows will have a very substantial effect on the clusters' evolution and star formation efficiency.

Keywords: starburst galaxies; interstellar medium; star clusters; young massive clusters; stellar feedback; galaxies; interstellar molecules; star formation
Toward Complete Characterization: Prospects for Directly Imaging Transiting Exoplanets

High-contrast direct imaging of exoplanets can provide many important observables, including measurements of the orbit, spectra that probe the lower layers of the atmosphere, and phase variations of the planet, but cannot directly measure planet radius or mass. Our future understanding of directly imaged exoplanets will therefore rely on extrapolated models of planetary atmospheres and bulk composition, which need robust calibration. We estimate the population of extrasolar planets that could serve as calibrators for these models. Critically, this population of "standard planets" must be accessible to both direct imaging and the transit method, allowing for radius measurement. We show that the search volume of a direct imaging mission eventually overcomes the transit probability falloff with semimajor axis, so that as long as cold planets are not exceedingly rare, the population of transiting planets and directly imageable planets overlaps. Using current extrapolations of Kepler occurrence rates, we estimate that ∼8 standard planets could be characterized shortward of 800 nm with an ambitious future direct imaging mission like LUVOIR-A and several dozen could be detected at the V band. We show the design space that would expand the sample size and discuss the extent to which ground- and space-based surveys could detect this small but crucial population of planets.

Keywords: exoplanet detection methods; exoplanets; transits; direct imaging; coronagraphic imaging; radial velocity; astrometric exoplanet detection; space telescopes