adsabs/SciX_UAT_keywords huggingface dataset:
A Deep Chandra X-Ray Observatory Study of the Millisecond Pulsar Population in the Globular Cluster Terzan 5

We present an analysis of 745.8 ks of archival Chandra X-Ray Observatory Advanced CCD Imaging Spectrometer data accumulated between 2000 and 2016 of the millisecond pulsar (MSP) population in the rich Galactic globular cluster Terzan 5. Eight of the 38 MSPs with precise positions are found to have plausible X-ray source matches. Despite the deep exposure, the remaining MSPs are either marginally detected or have no obvious X-ray counterparts, which can be attributed to the typically soft thermal spectra of rotation-powered MSPs, which are strongly attenuated by the high intervening absorbing column (∼1022 cm-2) toward the cluster, and in some instances to severe source crowding/blending. For the "redback" MSP binaries PSR J1748-2446P and PSR J1748-2446ad and the "black widow" binary system PSR J1748-2446O, we find clear evidence for large-amplitude X-ray variability at the orbital period consistent with an intrabinary shock origin. The third redback MSP in the cluster, PSR J1748-2446A, shows order-of-magnitude variations in flux on timescales of years, possibly due to state transitions or intense flaring episodes from a magnetically active secondary star.

Keywords: pulsars; binary pulsars; millisecond pulsars; globular star clusters; x-ray astronomy; x-ray sources; x-ray identification; astronomical methods; x-ray binary stars
Finding Signs of Life in Transits: High-resolution Transmission Spectra of Earth-line Planets around FGKM Host Stars

Thousands of transiting exoplanets have already been detected orbiting a wide range of host stars, including the first planets that could potentially be similar to Earth. The upcoming Extremely Large Telescopes and the James Webb Space Telescope will enable the first searches for signatures of life in transiting exoplanet atmospheres. Here, we quantify the strength of spectral features in transit that could indicate a biosphere similar to the modern Earth on exoplanets orbiting a wide grid of host stars (F0 to M8) with effective temperatures between 2500 and 7000 K: transit depths vary between about 6000 ppm (M8 host) to 30 ppm (F0 host) due to the different sizes of the host stars. CO2 possess the strongest spectral features in transit between 0.4 and 20 μm. The atmospheric biosignature pairs O2+CH4 and O3+CH4—which identify Earth as a living planet—are most prominent for Sun-like and cooler host stars in transit spectra of modern Earth analogs. Assessing biosignatures and water on such planets orbiting hotter stars than the Sun will be extremely challenging even for high-resolution observations. All high-resolution transit spectra and model profiles are available online: they provide a tool for observers to prioritize exoplanets for transmission spectroscopy, test atmospheric retrieval algorithms, and optimize observing strategies to find life in the cosmos. In the search for life in the cosmos, transiting planets provide the first opportunity to discover whether or not we are alone, with this database as one of the keys to optimize the search strategies.

Keywords: astrobiology; exoplanet atmospheric composition; exoplanet atmospheres; high resolution spectroscopy; transmission spectroscopy; observational astronomy; exoplanets; habitable planets; biosignatures; extrasolar rocky planets; exoplanet catalogs; transits
Comparison of Exact and Approximate MHD Slow Body Mode Solutions in Photospheric Waveguides

In this study, we explore the possibility of simplifying the modeling of magnetohydrodynamic slow body modes observed in photospheric magnetic structures such as the umbrae of sunspots and pores. The simplifying approach assumes that the variation of the eigenvalues of slow body waves can be derived by imposing that the longitudinal component of velocity with respect to the tube axis is zero at the boundary of the magnetic flux tube, which is in good agreement with observations. To justify our approach, we compare the results of our simplified model for slow body modes in cylindrical flux tubes with the model prediction obtained by imposing the continuity of the radial component of the velocity and total pressure at the boundary of the flux tube. Our results show that, to a high accuracy (less than 1% for the considered model), the conditions of continuity of the component of transversal velocity and pressure at the boundary can be neglected when modeling slow body modes under photospheric conditions.

Keywords: solar photosphere; magnetohydrodynamics; sunspots
Destruction of Molecular Hydrogen Ice and Implications for 1I/2017 U1 ('Oumuamua)

The first interstellar object observed in our solar system, 1I/2017 U1 ('Oumuamua), exhibited a number of peculiar properties, including extreme elongation and acceleration excess. Recently, Seligman & Laughlin proposed that the object was made out of molecular hydrogen (H2) ice. The question is whether H2 objects could survive their travel from the birth sites to the solar system. Here we study destruction processes of icy H2 objects through their journey from giant molecular clouds (GMCs) to the interstellar medium (ISM) and the solar system, owing to interstellar radiation, gas and dust, and cosmic rays. We find that thermal sublimation due to heating by starlight can destroy 'Oumuamua-size objects in less than 10 Myr. Thermal sublimation by collisional heating in GMCs could destroy H2 objects of 'Oumuamua-size before their escape into the ISM. Most importantly, the formation of icy grains rich in H2 is unlikely to occur in dense environments because collisional heating raises the temperature of the icy grains, so that thermal sublimation rapidly destroys the H2 mantle before grain growth.

Keywords: a stars; amor group; interstellar dynamics; dense interstellar clouds; astrosphere interstellar medium interactions; comets; interstellar objects; asteroids
Evolution of the Hub-filament Structures in IC 5146 in the Context of the Energy Balance of Gravity, Turbulence, and Magnetic Field

We present the results of 850 μm polarization and C18O (3 - 2) line observations toward the western hub-filament structure (W-HFS) of the dark Streamer in IC 5146 using the James Clerk Maxwell Telescope SCUBA-2/POL-2 and HARP instruments. We aim to investigate how the relative importance of the magnetic field, gravity, and turbulence affects core formation in HFS by comparing the energy budget of this region. We identified four 850 μm cores and estimated the magnetic field strengths (B pos) of the cores and the hub and filament using the Davis-Chandrasekhar-Fermi method. The estimated B pos is ~80 to 1200 μG. From Wang et al., B pos of E-47, a core in the eastern hub (E-hub), and E-hub were reestimated to be 500 and 320 μG, respectively, with the same method. We measured the gravitational (E G), kinematic (E K), and magnetic energies (E B) in the filament and hubs and compared the relative importance among them. We found that an E B-dominant filament has aligned fragmentation type, while E G-dominant hubs show no and clustered fragmentation types. In the E G dominant hubs, it seems that the portion of E K determines whether the hub becomes to have clustered (the portion of E K ~ 20%) or no fragmentation type (~10%). We propose an evolutionary scenario for the E- and W-HFSs, where the HFS forms first by the collision of turbulent flows, and then the hubs and filaments can go into various types of fragmentation depending on their energy balance of gravity, turbulence, and magnetic field.

Keywords: interstellar magnetic fields; interstellar medium; polarimetry; submillimeter astronomy; star forming regions
In-situ Switchback Formation in the Expanding Solar Wind

Recent near-Sun solar-wind observations from Parker Solar Probe have found a highly dynamic magnetic environment, permeated by abrupt radial-field reversals, or "switchbacks." We show that many features of the observed turbulence are reproduced by a spectrum of Alfvénic fluctuations advected by a radially expanding flow. Starting from simple superpositions of low-amplitude outward-propagating waves, our expanding-box compressible magnetohydrodynamic simulations naturally develop switchbacks because (I) the normalized amplitude of waves grows due to expansion and (II) fluctuations evolve toward spherical polarization (I.e., nearly constant field strength). These results suggest that switchbacks form in situ in the expanding solar wind and are not indicative of impulsive processes in the chromosphere or corona.

Keywords: space plasmas; alfven waves; solar wind; solar magnetic fields; interplanetary turbulence
Detection Sensitivities from the Anglo-Australian Planet Search

Our understanding of the occurrence rates and demographics of long-period planets depends critically on data from legacy radial-velocity surveys with the long-term sensitivity to Jupiter-like planets in Jupiter-like orbits. A recent paper presented such an analysis for giant planets (m sin i > 0.3 M J) from the now-completed Anglo-Australian Planet Search. In this work, I deliver the detailed detection sensitivities for all 203 individual stars in that study, as a function of orbital periods from 100 to 6000 days. We present these data as a companion to Wittenmyer et al.

Keywords: exoplanets; extrasolar gaseous planets
Near-infrared Spectroscopy of Dense Ejecta Knots in the Outer Eastern Area of the Cassiopeia A Supernova Remnant

The Cassiopeia A supernova remnant has a complex structure, manifesting the multidimensional nature of core-collapse supernova explosions. To further understand this, we carried out near-infrared multiobject spectroscopy on the ejecta knots located in the northeastern (NE) jet and Fe K plume regions, which are two distinct features in the outer eastern area of the remnant. Our study reveals that the knots exhibit varying ratios of [S II] 1.03, [P II] 1.189, and [Fe II] 1.257 μm lines depending on their locations within the remnant, suggesting regional differences in elemental composition. Notably, the knots in the NE jet are mostly S-rich with weak or no [P II] lines, implying that they originated below the explosive Ne-burning layer, consistent with the results of previous studies. We detected no ejecta knots exhibiting only [Fe II] lines in the NE jet area that are expected in the jet-driven supernova explosion model. Instead, we discovered a dozen Fe-rich knots in the Fe K plume area. We propose that they are dense knots produced by a complete Si burning with α-rich freeze-out in the innermost region of the progenitor and ejected with the diffuse X-ray-emitting Fe ejecta but decoupled after crossing the reverse shock. In addition to these metal-rich ejecta knots, several knots emitting only He I 1.083 μm lines were detected, and their origin remains unclear. We also detected three extended H emission features of circumstellar or interstellar origin in this area and discuss their association with the supernova remnant.

Keywords: supernova remnants; supernovae; core-collapse supernovae
An IRTF-iSHELL Survey of 4.52-5.25 μm CO Spectra in Protoplanetary Disks of Intermediate-mass Stars: Preliminary Sample and Analysis

We are conducting a survey of high-resolution near-infrared CO rovibrational spectra in protoplanetary disks around young intermediate-mass stars. We use IRTF-iSHELL with the 0"375 and 0"75 slits, providing 4 km s-1 and 6 km s-1 resolution and covering 4.52-5.25 μm in one single exposure. This includes part of the rovibrational R branch and most of the P branch of the CO fundamental band (Δv = 1), one of the best tracers of warm/hot gas in disks. The high quality of the spectra and the large sample covered in this survey will support multiple investigations to study the structure, kinematics, composition, and evolution of the inner 10 au in disks for years to come. The survey currently includes ∼30 stars mostly within 200 pc, complementing extensive imaging campaigns that are observing their disks at optical, infrared, and millimeter wavelengths and revealing structures and planets.

Keywords: protoplanetary disks; planetary system formation; circumstellar disks; planet formation; molecular gas; molecular spectroscopy; infrared astronomy
Optical and Near-infrared Observations of the Distant but Bright "New Year's Burst" GRB 220101A

High-redshift gamma-ray bursts (GRBs) are useful to probe the early Universe, but only a few candidates have been detected so far. Here, we report the optical and near-infrared observations of the afterglow of a relatively high-redshift event GRB 220101A, which was triggered on New Year's Day of 2022, and therefore referred to as the "New Year's burst." With the optical spectra obtained by XL2.16/BFOSC and NOT/ALFOSC, we determine the redshift of the burst to be z = 4.615. We find that the optical afterglow of GRB 220101A is one of the most luminous ever detected. Based on our optical and near-infrared data, and combined with the X-ray observations, we perform a multiband fit with the Python package afterglowpy. The jet opening angle is constrained to ~3.°4, which is consistent with the jet-break time at ~0.7 day. We also determine the circumburst density of n 0 = 0.15 cm-3 and kinetic energy E K,iso = 3.5 × 1054 erg. In the prompt phase of the burst, we find a "mirror" feature in the lightcurve from 80 s to 120 s. The physical origin of such a mirror feature is unclear.

Keywords: gamma-ray bursts
CO, Water, and Tentative Methanol in η Carinae Approaching Periastron

The complex circumstellar environment around the massive binary and luminous blue variable η Carinae is known to harbor numerous light molecules, emitting most strongly in rotational states with upper level energies to ∼300 K. In circumstellar gas, the complex organic molecule methanol (CH3OH) has been found almost exclusively around young stellar objects, and thus regarded as a signpost of recent star formation. Here we report the first potential detection of methanol around a highly evolved high-mass star, while using the Atacama Large Millimeter Array to investigate molecular cloud conditions traced by CO (2-1) in an orbit phase preceding the 2020 periastron. The methanol emission originates from hot (Tgas ≃ 700 K) material, ∼2″ (0.02 pc) across, centered on the dust-obscured binary, and is accompanied by prominent absorption of continuum radiation in a cooler (Tgas ≃ 110 K) layer of gas. We also report a first detection of water in Herschel observations at 557 and 988 GHz. The methanol abundance is several to 50 times higher than observed toward several lower-mass stars, while water abundances are similar to those observed in cool, dense molecular clouds. The very high methanol:water abundance ratio in the core of η Car may suggest methanol formation processes similar to Fischer-Tropsch-type catalytic reactions on dust grains. These observations prove that complex molecule formation can occur in a chemically evolved massive stellar environment, given sufficient gas densities and shielding conditions as may occur in material around massive interacting companions and merger remnants.

Keywords: circumstellar matter; molecule formation; astrochemistry; reaction catalysts; massive stars; luminous blue variable stars
Dynamics of Companion Galaxies of Early-type Galaxies

We estimated the dynamical masses of 115 early-type galaxies (ETGs) by analyzing the dynamics of satellite and companion galaxies of these ETGs. We selected galaxies with absolute magnitudes between -22 and -25 in the Ks-band from the Extragalactic Distance Database. We also selected 216 spiral galaxies for comparison. We employed a simple model to simulate the observed dynamical mass from satellite galaxies at various distances. Our simulations showed that the dynamical masses derived from satellite galaxies with elliptical orbits would be smaller than those with circular orbits even though they contain the same dark mass halos. Therefore, relationships between the observed Mdyn/Mb distributions and distances would depend on orbital shapes. From the relationships between our observed Mdyn/Mb distributions and distances, we suggest that the satellite galaxies of the ETGs have relatively more elliptical orbits than those of the spiral galaxies and the Mdyn/Mb of the ETGs are greater than those of the spiral galaxies.

Keywords: galaxy evolution; early-type galaxies; galaxy dark matter halos
Interstellar Extinction and Elemental Abundances

Elements in the interstellar medium (ISM) exist in the form of gas or dust. The interstellar extinction and elemental abundances provide crucial constraints on the composition, size, and quantity of interstellar dust. Most of the extinction modeling efforts have assumed the total (gas and dust) abundances of the dust-forming elements—known as the "interstellar abundances," "interstellar reference abundances," or "cosmic abundances"—to be solar and the gas-phase abundances to be environmentally independent. However, it remains unclear whether the solar abundances are an appropriate representation of the interstellar abundances. Meanwhile, the gas-phase abundances are known to exhibit appreciable variations with local environments. Here we explore the viability of the abundances of B stars, the solar and protosolar abundances, and the protosolar abundances augmented by Galactic chemical enrichment (GCE) as an appropriate representation of the interstellar abundances by quantitatively examining the extinction and abundances of 10 interstellar sight lines for which both the extinction curves and the gas-phase abundances of all the major dust-forming elements (i.e., C, O, Mg, Si and Fe) have been observationally determined. Instead of assuming a specific dust model and then fitting the observed extinction curves, for each sight line we apply the model-independent Kramers-Kronig relation, which relates the wavelength-integrated extinction to the total dust volume, to place a lower limit on the dust depletion. This, together with the observationally derived gas-phase abundances, allows us to rule out the B-star, solar, and protosolar abundances as the interstellar reference standard and support the GCE-augmented protosolar abundances as a viable representation of the interstellar abundances.

Keywords: gas-to-dust ratio; interstellar dust extinction; interstellar dust; cosmic abundances; interstellar abundances; solar abundances
Physical Characterization of Early Galaxies in the Webb's First Deep Field SMACS J0723.3-7323

This paper highlights initial photometric analyses of JWST NIRCam imaging data in the sightline of SMACS0723, aiming to identify galaxies at redshift z > 7. By applying a conservative Lyman-break selection followed by photometric-redshift analysis and visual inspection, we identify four F090W-dropout and two F150W-dropout sources, three of which were recently confirmed in an independent spectroscopic analysis to z = 7.663, 7.665, and 8.499. We then supplement our sample with a photometric-redshift selection, and identify five additional candidates at 7 < z phot < 13. The NIRCam images clearly resolve all sources and reveal their subgalactic components that were not resolved/detected in the previous imaging by Hubble Space Telescope. Our spectral energy distribution analysis reveals that the selected galaxies are characterized by young stellar populations (median age of ~50 Myr) of subsolar metallicity (~0.2 Z ⊙) and little dust attenuation (A V ~ 0.5). In several cases, we observe extreme Hβ+[O III] lines being captured in the F444W band and seen as color excess, which is consistent with their observed high star formation rate surface density. Eight of the 11 sources identified in this study appear in at least one of the recent studies (Adams et al.; Atek et al.; Donnan et al.; Harikane et al.; Yan et al.) of the same fields, implying the high fidelity of our selection. We crossmatch all high-z galaxy candidates presented in the five studies with our catalog and discuss the possible causes of discrepancy in the final lists.

Keywords: galaxy evolution; lyman-break galaxies; starburst galaxies
Radio Sources Associated with Optical Galaxies and Having Unresolved or Extended Morphologies (ROGUE). I. A Catalog of SDSS Galaxies with FIRST Core Identifications

We present the catalog of Radio sources associated with Optical Galaxies and having Unresolved or Extended morphologies I (ROGUE I), consisting of 32,616 spectroscopically selected galaxies. It is the largest handmade catalog of this kind, obtained by cross-matching galaxies from the Sloan Digital Sky Survey (SDSS) Data Release 7 and radio sources from both the First Images of Radio Sky at Twenty Centimetre (FIRST) survey and the NRAO Very Large Array Sky Survey, without imposing a limit on the radio flux densities. The catalog provides a visual classification of radio and optical morphologies of galaxies presenting a FIRST core within 3″ of the optical position. The radio morphological classification is performed by examining the radio-optical overlays of linear sizes equal to 1 Mpc at the source distance, while the 120″ image snapshots from the SDSS database are used for optical classification. The results of our search are as follows: (I) single-component unresolved and elongated radio sources constitute the major group in the ROGUE I catalog (∼90%), and ∼8% exhibit extended morphologies; (II) samples of 269, 730, and 115 Fanaroff-Riley (FR) type I, II, and hybrid galaxies, respectively, are presented; (III) we report 55 newly discovered giant/possible giant, 16 double-double, 9 X-shaped, and 25 Z-shaped radio sources; (IV) on the optical front, most galaxies have elliptical morphologies (∼62%) while spirals form the second major category (∼17%) followed by distorted (∼12%) and lenticular (∼7%) morphologies; and (V) division between the FR I and the FR II sources in the radio-optical luminosity plane is blurred, in tune with recent studies.

Keywords: catalogs; radio galaxies; surveys; fanaroff-riley radio galaxies
Plasma Sheath around Chandrayaan-3 Landing Site: A Case Study

India's lander-rover mission Chandrayaan-3 is scheduled to be launched in mid-2023. We have simulated a realistic scenario and investigated the electric potential development over the Chandrayaan-3 landing site under the influence of observed solar ultraviolet/extreme-ultraviolet radiation and real plasma parameters measured by THEMIS as a case study. The electric potential structures have been derived by solving Poisson's equation, which is coupled with latitude-dependent fermionic photoelectrons, non-Maxwellian plasma electrons, and cold ions. A dynamic variation of the potential structure around the sunlit landing site has been observed through the analysis. This study predicts a photoelectron density range from 10 to 40 cm-3 and mean energy range from 2.6 to 3 eV near the surface of the Chandrayaan-3 landing site, which may be tested by the in situ measurement.

Keywords: space plasmas; solar wind; the moon
Flares from Space Debris in LSST Images

Owing to the exceptional sensitivity of the Vera C. Rubin Observatory, we predict that its upcoming LSST images will be contaminated by numerous flares from centimeter-scale space debris in Low Earth Orbits (LEO). Millisecond-duration flares from these LEO objects are expected to produce detectable image streaks of a few arcseconds with AB magnitudes brighter than 14.

Keywords: sky surveys