Sazuna/UAT_keywords huggingface dataset:
The PIPER Survey. I. An Initial Look at the Intergalactic Globular Cluster Population in the Perseus Cluster. We describe the goals and first results of the Program for Imaging of the PERseus cluster of galaxies (PIPER). The first phase of the program builds on imaging of fields obtained with the Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS)/WFC and WFC3/UVIS cameras. Our PIPER target fields with HST include major early-type galaxies including the active central giant NGC 1275, known ultra-diffuse galaxies, and the intracluster medium. The resulting two-color photometry in F475W and F814W reaches deep enough to resolve and measure the globular cluster (GC) populations in the Perseus member galaxies. Here we present initial results for eight pairs of outer fields that confirm the presence of intergalactic GCs (IGCs) in fields as distant as 740 kpc from the Perseus center (40% of the virial radius of the cluster). Roughly 90% of these IGCs are identifiably blue (metal-poor) but there is a clear trace of a red (metal-rich) component as well, even at these very remote distances.

Keywords: Globular star clusters, Rich galaxy clusters, Intracluster medium, Perseus Cluster
Peter Pan Disks: Long-lived Accretion Disks Around Young M Stars. WISEA J080822.18-644357.3, an M star in the Carina association, exhibits extreme infrared excess and accretion activity at an age greater than the expected accretion disk lifetime. We consider J0808 as the prototypical example of a class of M star accretion disks at ages ≳20 Myr, which we call "Peter Pan" disks, because they apparently refuse to grow up. We present four new Peter Pan disk candidates identified via the Disk Detective citizen science project, coupled with Gaia astrometry. We find that WISEA J044634.16-262756.1 and WISEA J094900.65-713803.1 both exhibit significant infrared excess after accounting for nearby stars within the Two Micron All Sky Survey (2MASS) beams. The J0446 system has &gt;95% likelihood of Columba membership. The J0949 system shows &gt;95% likelihood of Carina membership. We present new Gemini Multi-Object Spectrograph optical spectra of all four objects, showing possible accretion signatures on all four stars. We present ground-based and TESS light curves of J0808 and 2MASS J0501-4337, including a large flare and aperiodic dipping activity on J0808, and strong periodicity on J0501. We find Paβ and Brγ emission indicating ongoing accretion in near-IR spectroscopy of J0808. Using observed characteristics of these systems, we discuss mechanisms that lead to accretion disks at ages ≳20 Myr, and find that these objects most plausibly represent long-lived CO-poor primordial disks, or "hybrid" disks, exhibiting both debris and primordial-disk features. The question remains: why have gas-rich disks persisted so long around these particular stars?

Keywords: M dwarf stars, Stellar activity, Protoplanetary disks, Circumstellar disks, Stellar accretion disks, Exoplanet formation
Internal Structure and CO<SUB>2</SUB> Reservoirs of Habitable Water Worlds. Water worlds are water-rich (&gt;1 wt% H2O) exoplanets. The classical models of water worlds considered layered structures determined by the phase boundaries of pure water. However, water worlds are likely to possess comet-like compositions, with between ∼3 and 30 mol% CO2 relative to water. In this study, we build an interior structure model of habitable (I.e., surface liquid ocean-bearing) water worlds using the latest results from experimental data on the CO2-H2O system to explore the CO2 budget and localize the main CO2 reservoirs inside of these planets. We show that CO2 dissolved in the ocean and trapped inside of a clathrate layer cannot accommodate a cometary amount of CO2 if the planet accretes more than 11 wt% of volatiles (CO2 + H2O) during its formation. If the atmosphere holds more than a negligible amount of the CO2 (&gt;0.01% of the planet mass), the planet will not have a habitable surface temperature. We propose a new, potentially dominant, CO2 reservoir for water worlds: CO2 buried inside of the high-pressure water ice mantle as CO2 ices or (H2CO3 × H2O), the monohydrate of carbonic acid. If insufficient amounts of CO2 are sequestered in either this reservoir or the planet's iron core, habitable-zone water worlds could generically be stalled in their cooling before liquid oceans have a chance to condense.

Keywords: Ocean planets, Hydrosphere, Exoplanets, Ocean-atmosphere interactions, Carbon dioxide, Planetary interior, Habitable planets
The NANOGrav 11 yr Data Set: Evolution of Gravitational-wave Background Statistics. An ensemble of inspiraling supermassive black hole binaries should produce a stochastic background of very low frequency gravitational waves. This stochastic background is predicted to be a power law, with a gravitational-wave strain spectral index of -2/3, and it should be detectable by a network of precisely timed millisecond pulsars, widely distributed on the sky. This paper reports a new "time slicing" analysis of the 11 yr data release from the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) using 34 millisecond pulsars. Methods to flag potential "false-positive" signatures are developed, including techniques to identify responsible pulsars. Mitigation strategies are then presented. We demonstrate how an incorrect noise model can lead to spurious signals, and we show how independently modeling noise across 30 Fourier components, spanning NANOGrav's frequency range, effectively diagnoses and absorbs the excess power in gravitational-wave searches. This results in a nominal, and expected, progression of our gravitational-wave statistics. Additionally, we show that the first interstellar medium event in PSR J1713+0747 pollutes the common red-noise process with low spectral index noise, and we use a tailored noise model to remove these effects.

Keywords: Gravitational wave detectors, Pulsar timing method, Millisecond pulsars, Gravitational waves, Red noise, Radio pulsars
Standing MHD Waves in a Magnetic Slab Embedded in an Asymmetric Plasma Environment: Slow Surface Waves. The field of solar magnetoseismology (SMS) is heavily reliant upon our understanding of magnetohydrodynamic (MHD) waves that occur in many solar features. Building on previous studies of propagating MHD waves in a magnetic slab embedded in a nonmagnetic asymmetric environment, in this study we assume a line-tying boundary condition and use analytical techniques to derive the dispersion relation for linear standing MHD oscillations. The slab is first assumed thin, with arbitrary asymmetry, in order to derive the frequencies of the standing harmonic modes for both slow quasi-sausage and slow quasi-kink waves. Besides this, the asymmetry is assumed to be weak in order to determine the frequency dependence on the width of the slab and the asymmetry of the system, to leading order. For both the quasi-sausage and quasi-kink modes, the derived eigenfrequencies show that the dependence on the asymmetry in the system is much weaker than the dependence on the width of the slab. Using the eigenfrequencies, other observable quantities are derived (such as, e.g., the frequency ratio) providing an opportunity to use SMS to infer background diagnostics of the system.

Keywords: Solar atmosphere, Magnetohydrodynamics, Solar prominences, The Sun, Solar physics, Solar magnetic fields, Solar oscillations, Magnetic fields
Applying Noether's Theorem to Matter in the Milky Way: Evidence for External Perturbations and Non-steady-state Effects from Gaia Data Release 2. We apply Noether's theorem to observations of main-sequence stars from the Gaia Data Release 2 archive to probe the matter distribution function of the Galaxy. That is, we examine the axial symmetry of stars at vertical heights z, $0.2\leqslant | z| \leqslant 3\,\mathrm{kpc}$ , to probe the quality of the angular momentum Lz as an integral of motion. The failure of this symmetry test would speak to a Milky Way, in both its visible and dark matter, that is not isolated and/or not in steady state. The left-right symmetry-breaking pattern we have observed, north and south, reveals both effects, with a measured deviation from symmetry of typically 0.5%. We show that a prolate form of the gravitational distortion of the Milky Way by the Large Magellanic Cloud, determined from fits to the Orphan stream by Erkal et al., is compatible with the size and sign of the axial-symmetry-breaking effects we have discovered in our sample of up to 14.4 million main-sequence stars, speaking to a distortion of an emergent, rather than static, nature.

Keywords: Milky Way dark matter halo, Milky Way evolution, Milky Way dynamics
A Search for MeV to TeV Neutrinos from Fast Radio Bursts with IceCube. We present two searches for IceCube neutrino events coincident with 28 fast radio bursts (FRBs) and 1 repeating FRB. The first improves on a previous IceCube analysis—searching for spatial and temporal correlation of events with FRBs at energies greater than roughly 50 GeV—by increasing the effective area by an order of magnitude. The second is a search for temporal correlation of MeV neutrino events with FRBs. No significant correlation is found in either search; therefore, we set upper limits on the time-integrated neutrino flux emitted by FRBs for a range of emission timescales less than one day. These are the first limits on FRB neutrino emission at the MeV scale, and the limits set at higher energies are an order-of-magnitude improvement over those set by any neutrino telescope.

Keywords: Neutrino astronomy, High energy astrophysics, Astronomical radiation sources
A Strategy to Search for an Inner Binary Black Hole from the Motion of the Tertiary Star. There are several ongoing projects to search for stars orbiting around an invisible companion. A fraction of such candidates may be a triple, instead of a binary, consisting of an inner binary black hole (BBH) and an outer orbiting star. In this paper, we propose a methodology to search for a signature of such an inner BBH, possibly a progenitor of gravitational-wave sources discovered by LIGO, from the precise radial velocity (RV) follow-up of the outer star. We first describe a methodology using an existing approximate RV formula for coplanar circular triples. We apply this method and constrain the parameters of a possible inner binary object in 2M05215658+4359220, which consists of a red giant and an unseen companion. Next we consider coplanar but non-circular triples. We compute numerically the RV variation of a tertiary star orbiting around an inner BBH, generate mock RV curves, and examine the feasibility of detection of the BBH for our fiducial models. We conclude that short-cadence RV monitoring of a star-BH binary provides an interesting and realistic method to constrain and/or search for possible inner BBHs. Indeed a recent discovery of the star-BH binary system LB-1 may imply that there are a large number of such unknown objects in our Galaxy, which are ideal targets for the methodology proposed here.

Keywords: Multiple stars, Black holes, Compact binary stars, Celestial mechanics, Three-body problem, Radial velocity
The Formation of a 70 M<SUB>⊙</SUB> Black Hole at High Metallicity. A 70 ${M}_{\odot }$ black hole (BH) was discovered in the Milky Way disk in a long-period detached binary system (LB-1) with a high-metallicity 8 ${M}_{\odot }$ B star companion. Current consensus on the formation of BHs from high-metallicity stars limits the BH mass to be below 20 ${M}_{\odot }$ due to strong mass loss in stellar winds. Using analytic evolutionary formulae, we show that the formation of a 70 ${M}_{\odot }$ BH in a high-metallicity environment is possible if wind mass-loss rates are reduced by factor of five. As observations indicate, a fraction of massive stars have surface magnetic fields that may quench the wind mass-loss, independently of stellar mass and metallicity. We confirm such a scenario with detailed stellar evolution models. A nonrotating 85 ${M}_{\odot }$ star model at Z = 0.014 with decreased winds ends up as a 71 ${M}_{\odot }$ star prior to core collapse with a 32 ${M}_{\odot }$ He core and a 28 ${M}_{\odot }$ CO core. Such a star avoids the pair-instability pulsation supernova mass loss that severely limits BH mass and may form a ∼70 ${M}_{\odot }$ BH in the direct collapse. Stars that can form 70 ${M}_{\odot }$ BHs at high Z expand to significant sizes, with radii of R ≳ 600 ${R}_{\odot }$ , however, exceeding the size of the LB-1 orbit. Therefore, we can explain the formation of BHs up to 70 ${M}_{\odot }$ at high metallicity and this result is valid whether or not LB-1 hosts a massive BH. However, if LB-1 hosts a massive BH we are unable to explain how such a binary star system could have formed without invoking some exotic scenarios.

Keywords: Black hole physics, Classical black holes, Binary stars
Thermodynamics of Dipolarization Fronts of Magnetic Reconnection in Anisotropic Plasma: MMS Observations and Resistive Double-polytropic MHD Simulations. Dipolarization fronts (DFs) of magnetic reconnection are a transient field structure accompanied with a sharp increase of magnetic field component normal to plasma sheet and a high-speed plasma flow. The thermodynamics of DFs in the anisotropic plasma, which have not been studied so far, are investigated in this paper using two-dimensional, resistive magnetohydrodynamic simulations with double-polytropic energy laws in which two polytropic exponents, γ∥ and ${\gamma }_{\perp }$ , are used as parameters to describe various thermodynamic conditions. The subscripts ∥ and $\perp $ denote, respectively, directions parallel and perpendicular to the local magnetic field. Four different types of DFs observed by the Magnetospheric Multiscale Mission (MMS) in the plasma sheet of the Earth's magnetotail are presented—namely, (1) both temperatures T∥ and ${T}_{\perp }$ decrease; (2) both T∥ and ${T}_{\perp }$ increase; (3) T∥ decreases while ${T}_{\perp }$ increases; (4) T∥ increases while ${T}_{\perp }$ decreases. By using four different pairs of γ∥ and ${\gamma }_{\perp }$ , these four types of DFs can be reproduced, where the thermodynamics of Type-4 DF may correspond to the double-adiabatic Chew-Goldberger-Low conditions. It is concluded that the thermodynamic condition is seen to resemble most closely an adiabatic process for Type-1, -2, and -4 DFs, but to an isothermal process for Type-3 DF.

Keywords: Magnetohydrodynamics, Magnetohydrodynamical simulations
Modeling the IRIS Lines During a Flare. I. The Blue-wing Enhancement in the Mg II k Line. The Interface Region Imaging Spectrograph (IRIS) Mg II k line serves as a very good tool to diagnose the heating processes in solar flares. Recent studies have shown that apart from the usual red asymmetries that are interpreted as the result of condensation downflows, this line could also show a blue-wing enhancement. To investigate how such a blue asymmetry is formed, we perform a grid of radiative hydrodynamic simulations and calculate the corresponding line profiles. We find that such a spectral feature is likely to originate from the upward plasma motion in the upper chromosphere. However, the formation region that is responsible for the blue-wing enhancement could be located in an evaporation region, in an upward-moving blob, and even an upward-moving condensation region. We discuss how the electron beam parameters affect these different dynamics of the atmosphere.

Keywords: Radiative transfer simulations, Solar chromosphere, Solar flare spectra
Two-temperature Radiative Hot Accretion Flow around Neutron Stars. Numerical simulations of radiative two-temperature hot accretion flows (HAFs) around Neutron stars (NSs) are performed. We assume that all of the energy carried by the HAF around a NS will be thermalized and radiated out at the surface of the NS. The thermal photons will propagate outwards radially and cool the HAF via Comptonization. We define $\dot{m}$ as the mass accretion rate at the surface of the central object in unit of Eddington accretion rate ( ${\dot{M}}_{\mathrm{Edd}}=10{L}_{\mathrm{Edd}}/{c}^{2}$ , with LEdd and c being Eddington luminosity and speed of light, respectively). When $\dot{m}$ is lower than ∼10-4, the cooling of the HAF is not important and outflows are very strong. When $\dot{m}\gt \sim {10}^{-3}$ , cooling becomes important and outflows are significantly weak. In the range ${10}^{-4}\lt \dot{m}\lt {10}^{-3}$ , the HAFs transients from a strong outflow phase to a very weak outflow phase with increase of $\dot{m}$ . The properties of the HAF around a NS are also compared with those of the HAF around a BH. We find that with a similar $\dot{m}$ , the dynamical properties of the HAF around a NS are quite similar as those of the HAF around a BH. However, the emitted spectrum of a HAF around a NS can be quite different from that of a HAF around a BH due to the presence of a thermal soft X-ray component coming from the surface of the NS.

Keywords: Neutron stars, Black hole physics, Accretion, Compact objects, Low-mass x-ray binary stars
Trojans in the Solar Neighborhood. About 20% of stars in the solar vicinity are in the Hercules stream, a bundle of stars that move together with a velocity distinct from the Sun. Its origin is still uncertain. Here, we explore the possibility that Hercules is made of trojans, stars captured at L4, one of the Lagrangian points of the stellar bar. Using GALAKOS-a high-resolution N-body simulation of the Galactic disk-we follow the motions of stars in the corotating frame of the bar and confirm previous studies on Hercules being formed by stars in corotation resonance with the bar. Unlike previous work, we demonstrate that the retrograde nature of trojan orbits causes the asymmetry in the radial velocity distribution, typical of Hercules in the solar vicinity. We show that trojans remain at capture for only a finite amount of time, before escaping L4 without being captured again. We anticipate that in the kinematic plane the Hercules stream will depopulate along the bar's major axis and be visible at azimuthal angles behind the solar vicinity with a peak toward L4. This test can exclude the outer Lindblad resonance origin of the Hercules stream and be validated by Gaia DR3 and DR4.

Keywords: Galaxy dynamics, Galaxy kinematics
The Megamaser Cosmology Project. XI. A Geometric Distance to CGCG 074-064. As part of the survey component of the Megamaser Cosmology Project, we have discovered a disk megamaser system in the galaxy CGCG 074-064. Using the Green Bank Telescope and the Very Large Array, we have obtained spectral monitoring observations of this maser system at a monthly cadence over the course of two years. We find that the systemic maser features display line-of-sight accelerations of ∼4.4 km s-1 yr-1 that are nearly constant with velocity, while the high-velocity maser features show accelerations that are consistent with zero. We have also used the High-Sensitivity Array to make a high-sensitivity very long baseline interferometric map of the maser system in CGCG 074-064, which reveals that the masers reside in a thin, edge-on disk with a diameter of ∼1.5 mas (0.6 pc). Fitting a three-dimensional warped disk model to the data, we measure a black hole mass of ${2.42}_{-0.20}^{+0.22}\times {10}^{7}\,{M}_{\odot }$ and a geometric distance to the system of ${87.6}_{-7.2}^{+7.9}$ Mpc. Assuming a cosmic microwave background-frame recession velocity of 7308 ± 150 km s-1, we constrain the Hubble constant to ${H}_{0}={81.0}_{-6.9}^{+7.4}$ (stat.) ± 1.4 (sys.) km s-1 Mpc-1.

Keywords: Supermassive black holes, Very long baseline interferometry, Megamasers, Water masers, Active galactic nuclei
Detailed Iron-peak Element Abundances in Three Very Metal-poor Stars. We have obtained new detailed abundances of the Fe-group elements Sc through Zn (Z = 21-30) in three very metal-poor ([Fe/H] ≈ -3) stars: BD+03o740, BD-13o3442, and CD-33o1173. High-resolution ultraviolet Hubble Space Telescope/Space Telescope Imaging Spectrograph spectra in the wavelength range 2300-3050 Å were gathered, and complemented by an assortment of optical echelle spectra. The analysis featured recent laboratory atomic data for a number of neutral and ionized species for all Fe-group elements except Cu and Zn. A detailed examination of scandium, titanium, and vanadium abundances in large-sample spectroscopic surveys indicates that they are positively correlated in stars with [Fe/H] ≤ -2. The abundances of these elements in BD+03o740, BD-13o3442, CD-33o1173, and HD 84937 (studied in a previous paper of this series) are in accord with these trends and lie at the high end of the correlations. Six elements have detectable neutral and ionized features, and generally their abundances are in reasonable agreement. For Cr we find only minimal abundance disagreement between the neutral (mean of [Cr I/Fe] = +0.01) and ionized species (mean of [Cr II/Fe] = +0.08), unlike most studies in the past. The prominent exception is Co, for which the neutral species indicates a significant overabundance (mean of [Co I/H] = -2.53), while no such enhancement is seen for the ionized species (mean of [Co II/H] = -2.93). These new stellar abundances, especially the correlations among Sc, Ti, and V, suggest that models of element production in early high-mass metal-poor stars should be revisited.

Keywords: Galaxy chemical evolution, Abundance ratios, Atomic physics, Stellar abundances, Stellar nucleosynthesis
Study of the Cosmic Rays and Interstellar Medium in Local H I Clouds Using Fermi-LAT Gamma-Ray Observations. An accurate estimate of the interstellar gas density distribution is crucial to understanding the interstellar medium (ISM) and Galactic cosmic rays (CRs). To comprehend the ISM and CRs in a local environment, a study of the diffuse γ-ray emission in a midlatitude region of the third quadrant was performed. The γ-ray data in the 0.1-25.6 GeV energy range of the Fermi Large Area Telescope (LAT) and other interstellar gas tracers such as the HI4PI survey data and the Planck dust thermal emission model were used, and the northern and southern regions were analyzed separately. The variation of the dust emission ${D}_{\mathrm{em}}$ with the total neutral gas column density ${N}_{{\rm{H}}}$ was studied in high dust temperature areas, and the ${N}_{{\rm{H}}}$ / ${D}_{\mathrm{em}}$ ratio was calibrated using γ-ray data under the assumption of a uniform CR intensity in the studied regions. The measured integrated γ-ray emissivities above 100 MeV are $(1.58\pm 0.04)\times {10}^{-26}\,\mathrm{photons}\,{{\rm{s}}}^{-1}\,{\mathrm{sr}}^{-1}\,{\rm{H}} \mbox{-} {\mathrm{atom}}^{-1}$ and $(1.59\pm 0.02)\times {10}^{-26}\,\mathrm{photons}\,{{\rm{s}}}^{-1}\,{\mathrm{sr}}^{-1}\,{\rm{H}} \mbox{-} {\mathrm{atom}}^{-1}$ in the northern and southern regions, respectively, supporting the existence of a uniform CR intensity in the vicinity of the solar system. While most of the gas can be interpreted to be ${\rm{H}}\,{\rm{I}}$ with a spin temperature of ${T}_{{\rm{S}}}=125\,{\rm{K}}$ or higher, an area dominated by optically thick ${\rm{H}}\,{\rm{I}}$ with ${T}_{{\rm{S}}}\sim 40\,{\rm{K}}$ was identified.

Keywords: Galactic cosmic rays, Gamma-rays, Interstellar medium