adsabs/SciX_UAT_keywords huggingface dataset:
4FGL J1318.2+6754: A Long Orbital-period Redback Candidate

By combining the Fermi catalog and the single-lined spectroscopic binaries of Gaia Data Release 3 (DR3), we report a new candidate redback millisecond pulsar binary, which is recommended as a target for radio telescopes to detect pulsed signals. Using TESS data in the T band spanning over 4 yr, we find a period of ~4.13 days, which is consistent with the radial velocity solution of the Gaia DR3 and optical spectroscopy from the LAMOST telescope. The light curve in the T band reveals periodic modulation of low amplitude that is a characteristic feature of the heating of the photosphere of a nondegenerate low-mass stellar companion by the pulsar wind. The nondegenerate companion is a bright (G = 11.96), slightly metal-poor ([Fe/H] = - 0.55), G-type main-sequence star (T eff = 5891 K; $\mathrm{log}g=4.07;$ R = 1.356R ⊙). This orbital period of 4.13 days would be the longest one for known redback candidates, which could hardly be understood for its formation in the standard recycling scenario due to its large Roche-lobe radius (≫the radius of the G-type main-sequence star). It is proposed here that this candidate redback millisecond pulsar binary could be created via accretion-induced collapse of an oxygen-neon-magnesium white dwarf.

Keywords: neutron stars
Spectroscopic Identification and Photochemistry of Astrochemically Relevant Phosphorus-bearing Molecules [O, C, N, P] and [2O, C, N, P]

Diatomic molecules phosphorus monoxide (PO) and phosphorus mononitride (PN) are the main reservoirs of gas-phase phosphorus in interstellar and circumstellar environments, indicating the possibility of forming new phosphorus-bearing molecules through reactions with other interstellar species. To explore the astrochemistry of PO and PN, new simple phosphorus-bearing molecules [O, C, N, P] and [2O, C, N, P] were generated in the gas phase and isolated in cryogenic matrices for characterization with matrix-isolation IR and UV/vis spectroscopy in combination with calculations at the CCSD(T)-F12a/VTZ-F12 level of theory. In an inert argon matrix, OPCN isomerizes to OPNC upon UV-light irradiation at 365 nm, followed by successive isomerizations to PNCO and POCN with concomitant dissociation to diatomic PN and CO under further irradiation at 193 nm. By analogy, the isomerization of O2PCN to O2PNC and OPNCO followed by fragmentation to OPN/CO and PN/CO2 occurs in the matrix upon irradiation at 193 nm. In a chemically active CO ice, the photolytic reaction of OPCN with CO yields CO2 and PCN, and O2PCN reacts with CO by forming OPCN and CO2, in which the photochemical networks for these P-bearing species linking the astrochemically important PN and PO have been proposed. The experimental identification of these phosphorus-bearing molecules is supported by quantum chemical calculations, and the spectroscopic data may aid in their detection in the interstellar and circumstellar medium.

Keywords: astrochemistry; interstellar medium; interstellar molecules; molecular spectroscopy
A Gap at 1 au in the Disk of DI Cha A Revealed by Infrared Interferometry

DI Cha A is K0-type pre-main-sequence star, the brightest component of a quadruple stellar system. Here we report on a detailed study of this star based on archival VLTI/MIDI and VLTI/PIONIER infrared interferometric observations, as well as optical-infrared photometric monitoring from ground-based and space-born instruments. We determined the structure of the circumstellar disk by fitting simultaneously the interferometric visibilities and the spectral energy distribution, using both analytical models and the radiative transfer code RADMC-3D. The modeling revealed that the radial density distribution of the disk appears to have a gap between 0.21 and 3.0 au. The inner ring, whose inner size coincides with the sublimation radius, is devoid of small, submicrometer-sized dust grains. The inner edge of the outer disk features a puffed-up rim, typically seen in intermediate-mass stars. Grain growth, although less progressed, was also detected in the outer disk. The inner ring is variable at mid-infrared wavelengths on both daily and annual timescales, while the star stays remarkably constant in the optical, pointing to geometrical or accretion changes in the disk as possible explanations for the flux variations. *Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere under ESO programs 077.C-0662, 079.C-0101, and 081.C-0020

Keywords: pre-main sequence stars; t tauri stars; protoplanetary disks; interferometry; astronomy data modeling
A Resolved Search for AGN in the Centers of Nearby Galaxies with WISE

We investigate the mid-infrared detection of active galactic nucleus (AGN) in nearby galaxies and the effects of contamination by starlight and dust emission from the host galaxy. We used a sample of ~14,000 nearby galaxies from the z = 0 Multiwavelength Galaxy Synthesis to study the effect of isolating the galaxy center on AGN detection. We identify 39 known AGN and 9 additional previously selected AGN candidates using color selection in WISE Bands 1 and 2. Most AGN identified using the smallest apertures around the nucleus are lost from the WISE color selection at larger aperture radii. This suggests that when low spatial resolution or integrated galaxy measurements are used to identify AGN in the mid-IR, lower luminosity AGN may go undetected due to contamination from the galaxy's dust emission and starlight.

Keywords: active galactic nuclei; galaxy nuclei; infrared astronomy
Gaia EDR3 Confirms a Red Dwarf Companion of the nearby F1 Star HD 105452 and Reveals a New Brown Dwarf Companion of the M4.5 Dwarf SCR J1214-2345

There are 88 stars which lack colors, but have measured parallaxes in Gaia EDR3 that place them within 20 pc from the Sun. Among them we found two new common parallax and proper motion (CPPM) companions separated from their primaries by about 3″. The CPPM companion of a nearby (d = 14.98 pc) F1 star, HD 105452 B, was already imaged with the Hubble Space Telescope and is now confirmed with Gaia data and photometrically classified by us as M4 dwarf. The other CPPM companion, SCR J1214-2345 B orbiting an M4.5 dwarf at d = 10.77 pc, represents the faintest brown dwarf discovery made by Gaia so far. It was also imaged by the VISTA Hemisphere Survey and partly detected in the near-infrared. Our photometric classification led to an uncertain spectral type of T1 ± 3 and needs to be confirmed by spectroscopic follow-up.

Keywords: parallax; proper motions; binary stars; brown dwarfs; stellar distance; solar neighborhood
Asteroid Orbit Determination Using Gaia FPR: Statistical Analysis

The Gaia mission has provided astrometric observations of unprecedented accuracy for more than 156,000 asteroids. The reported astrometric uncertainties are of the order of milliarcseconds, about 2 orders of magnitude smaller than that of traditional ground-based observations. The accuracy of Gaia data requires a high-fidelity orbit determination process, especially in the observation modeling. We present a statistical analysis of Gaia Focused Product Release to test the accuracy of the reported positions and associated uncertainties. We find that center-of-light offsets due to phase variations need to be modeled to properly fit the observational data. Prediction tests show that the uncertainty in the fitted orbits can be optimistic unless the observational uncertainty is inflated to account for errors in finding the center-of-mass of the body. Moreover, errors in the masses of small-body perturbers can cause differences in the orbital solution that exceed formal uncertainties of the best constrained orbits. As an example, we provide an update of the impact hazard analysis of 1950 DA, one of the asteroids observed by Gaia, and find that the impact probability in the year 2880 increases to 3.8 × 10‑4.

Keywords: asteroids; orbit determination; astrometry; gaia; phase angle
Distinguishing Oceans of Water from Magma on Mini-Neptune K2-18b

Mildly irradiated mini-Neptunes have densities potentially consistent with them hosting substantial liquid-water oceans ("Hycean" planets). The presence of CO2 and simultaneous absence of ammonia (NH3) in their atmospheres has been proposed as a fingerprint of such worlds. JWST observations of K2-18b, the archetypal Hycean, have found the presence of CO2 and the depletion of NH3 to <100 ppm; hence, it has been inferred that this planet may host liquid-water oceans. In contrast, climate modeling suggests that many of these mini-Neptunes, including K2-18b, may likely be too hot to host liquid water. We propose a solution to this discrepancy between observation and climate modeling by investigating the effect of a magma ocean on the atmospheric chemistry of mini-Neptunes. We demonstrate that atmospheric NH3 depletion is a natural consequence of the high solubility of nitrogen species in magma at reducing conditions; precisely the conditions prevailing where a thick hydrogen envelope is in communication with a molten planetary surface. The magma ocean model reproduces the present JWST spectrum of K2-18b to ≲3σ, suggesting this is as credible an explanation for current observations as the planet hosting a liquid-water ocean. Spectral areas that could be used to rule out the magma ocean model include the >4 μm region, where CO2 and CO features dominate: magma ocean models suggest a systematically lower CO2/CO ratio than estimated from free-chemistry retrieval, indicating that deeper observations of this spectral region may be able to distinguish between oceans of liquid water and magma on mini-Neptunes.

Keywords: exoplanet atmospheres; exoplanet structure; exoplanet atmospheric composition
An Open-source Bayesian Atmospheric Radiative Transfer (BART) Code. II. The TRANSIT Radiative Transfer Module and Retrieval of HAT-P-11b

This and companion papers by Harrington et al. and Blecic et al. present the Bayesian Atmospheric Radiative Transfer (BART) code, an open-source, open-development package to characterize extrasolar planet atmospheres. BART combines a thermochemical equilibrium abundance (TEA), a radiative transfer (TRANSIT), and a Bayesian statistical (MC3) module to constrain atmospheric temperatures and molecular abundances for given spectroscopic observations. Here we describe the TRANSIT radiative transfer package, an efficient line-by-line radiative transfer C code for one-dimensional atmospheres, developed by P. Rojo and further modified by the UCF exoplanet group. This code produces transmission and hemisphere-integrated emission spectra. TRANSIT handles line-by-line opacities from HITRAN, Partridge & Schwenke (H2O), Schwenke (TiO), and Plez (VO) and collision-induced absorption from Borysow, HITRAN, and ExoMol. TRANSIT emission spectra models agree with models from C. Morley (private communication) within a few percent. We applied BART to the Spitzer and Hubble transit observations of the Neptune-sized planet HAT-P-11b. Our analysis of the combined HST and Spitzer data generally agrees with those from previous studies, finding atmospheric models with enhanced metallicity (≳100× solar) and high-altitude clouds (≲1 mbar level). When analyzing only the HST data, our models favor high-metallicity atmospheres, in contrast with the previous analysis by Chachan et al. We suspect that this discrepancy arises from the different choice of chemistry modeling (free constant-with-altitude versus thermochemical equilibrium) and the enhanced parameter correlations found when neglecting the Spitzer observations. The BART source code and documentation are available at https://github.com/exosports/BART.

Keywords: exoplanet atmospheric composition; astrostatistics techniques; open source software; planetary atmospheres
Parametric Simulation Studies on the Wave Propagation of Solar Radio Emission: The Source Size, Duration, and Position

The observed features of the radio source indicate that the waves of solar radio bursts are convoluted with complex propagation effects. In this work, we perform ray-tracing simulations on radio wave transport in the corona and interplanetary region with anisotropic electron density fluctuations. For the first time, the variation of the apparent source size, burst duration, and source position for the fundamental emission and harmonic emission at the frequency of 35 MHz are simulated as a function of the anisotropic parameter α and the angular scattering rate coefficient η = ɛ2/h0, where ɛ2 = ⟨δn2⟩/n2 is the density fluctuation level and h0 is its correlation length near the wave excitation site. It is found that isotropic fluctuations produce a much larger decay time than a highly anisotropic fluctuation for fundamental emission. By comparing the observed duration and source size with the simulation results in the parameter space, we can estimate the scattering coefficient and the anisotropic parameter η = 8.9 × 10-5 km-1 and α = 0.719 with a point pulse source assumption. Position offsets due to wave scattering and refraction can produce the co-spatial of the fundamental and harmonic waves in the observation of some type III radio bursts. The visual speed due to the wave propagation effect can reach 1.5c for η = 2.4 × 10-4 km-1 and α = 0.2 for the fundamental emission in the sky plane, accompanied with large expansion rate of the source size. The direction of the visual speed is mostly identical to the direction of the offset, thus, for the observation aimed at obtaining the source position, the source centroid at the starting time is closer to the wave excitation site.

Keywords: solar radio emission; radiative transfer simulations; radio astronomy; solar coronal radio emission
An Assessment of the LEISA Spectrometer for Extragalactic Background Light Measurements

The extragalactic background light (EBL) is the summed emission from sources beyond the Milky Way. An accurate measurement of the EBL can be used as a benchmark to search for any diffuse components in excess of the integrated light from galaxies. We have studied archival data from the Linear Etalon Imaging Spectral Array (LEISA) aboard the New Horizons spacecraft to assess its capability to measure the near-IR EBL at wavelengths between 1.2 and 2.5 μm. We estimate LEISAs sensitivity to diffuse brightness to be ~105 nW m-2 sr-1 in 1.5 s exposures, which precludes the possibility of reaching EBL signals at the level of 10 nW m-2 sr-1.

Keywords: diffuse radiation; space vehicle instruments
Diversity of Dark Matter Density Profiles in the Galactic Dwarf Spheroidal Satellites

The core-cusp problem is one of the controversial issues in the standard paradigm of Λ cold dark matter (ΛCDM) theory. However, under the assumption of conventional spherical symmetry, the strong degeneracy among model parameters makes it unclear whether dwarf spheroidal (dSph) galaxies indeed have cored dark matter density profiles at their centers. In this work, we revisit this problem using nonspherical mass models, which have the advantage of being able to alleviate the degeneracy. Applying our mass models to the currently available kinematic data of the eight classical dSphs, we find that within finite uncertainties, most of these dSphs favor cusped central profiles rather than cored ones. In particular, Draco has a cusped dark matter halo with high probability even considering a prior bias. We also find the diversity of the inner slopes in their dark matter halos. To clarify the origin of this diversity, we investigate the relation between the inner dark matter density slope and stellar-to-halo mass ratio for the sample dSphs and find that this relation is generally in agreement with the predictions from recent ΛCDM and hydrodynamical simulations. We also find that the simulated subhalos have an anticorrelation between the dark matter density at 150 pc and pericenter distance, which is consistent with the observed one. We estimate their astrophysical factors for dark matter indirect searches and circular velocity profiles associated with huge uncertainties. To more precisely estimate their dark matter profiles, wide-field spectroscopic surveys for the dSphs are essential.

Keywords: dark matter; local group; dwarf spheroidal galaxies; galaxy dynamics; galaxy structure; galaxy kinematics
A Low-mass Stellar-debris Stream Associated with a Globular Cluster Pair in the Halo

There are expected to be physical relationships between the globular clusters (GCs) and stellar substructures in the Milky Way, not all of which have yet been found. We search for such substructures from a combined halo sample of SDSS blue horizontal-branch and SDSS+LAMOST RR Lyrae stars, cross-matched with astrometric information from Gaia DR2. This is a sample of old stars which are also excellent tracers of structures, ideal for searching for ancient relics in the outer stellar halo. By applying the neural-network-based method STARGO to the full 4D dynamical space of our sample, we rediscover the Sagittarius Stream, and find the debris of the Gaia-Enceladus-Sausage and the Sequoia events in the outer halo, as well as their linkages with several GCs. Most importantly, we find a new, low-mass, debris stream associated with a pair of GCs (NGC 5024 and NGC 5053), which we dub LMS-1. This stream has a very polar orbit, and occupies a region between 10 to 20 kpc from the Galactic center. NGC 5024 (M53), the more massive of the associated GC pair, is very likely the nuclear star cluster of a now-disrupted dwarf galaxy progenitor, based on the results from N-body simulations.

Keywords: milky way stellar halo; globular star clusters
Multiwavelength Absolute Magnitudes and Colors of Red Clump Stars in the Gaia Era

This study presents the multiwavelength investigation of the absolute magnitudes and colors of the red clump (RC) stars selected from APOGEE and GALAH DR2 combined catalog which is complemented with Gaia DR2 astrometric data and multiwavelength photometric data of GALEX GR6/7, SDSS DR7, Gaia DR2, 2MASS, and WISE sky surveys. The analyses are centered on the different distance estimation methods using Gaia trigonometric parallaxes, (1/ϖ) and Bayes statistics, and chemically defined Galactic disk populations on [α/Fe] × [Fe/H] plane. This investigation questions the long-studied problem of the population effects on RC luminosity. Using two different distance estimation approaches, (I) chemical thin and chemical thick disk RC stars are shown to have different absolute magnitudes, while colors remain the same in all photometric bands. Absolute magnitudes vary between -0.12 and +0.13 mag for the 1/ϖ with the change of the Galactic population. This variation in absolute magnitudes is found to be larger for the other method, (II) the Besançon population synthesis model of Galaxy for 2MASS photometry, in which the absolute magnitude difference between chemical populations were found between -0.35 and -0.40 mag from thin disk to thick disk. When results compared with each other, differences of absolute magnitudes are about three times larger in the model than in the observations. We confirm that the RC absolute magnitudes depend on α-element abundances of Galactic populations.

Keywords: red giant clump; absolute magnitude; stellar populations
Sensitive 3 mm Imaging of Discrete Sources in the Fields of Thermal Sunyaev–Zel'dovich Effect–Selected Galaxy Clusters

In this paper, we present the results of a blind survey for compact sources in 243 Galaxy clusters that were identified using the thermal Sunyaev–Zel'dovich effect (tSZ). The survey was carried out at 90 GHz using MUSTANG2 on the Green Bank Telescope and achieved a 5σ detection limit of 1 mJy in the center of each cluster. We detected 24 discrete sources. The majority (18) of these correspond to known radio sources, and of these, five show signs of significant variability, either with time or in spectral index. The remaining sources have no clear counterparts at other wavelengths. Searches for galaxy clusters via the tSZ strongly rely on observations at 90 GHz, and the sources found have the potential to bias mass estimates of clusters. We compare our results to the Websky simulation that can be used to estimate the source contamination in galaxy cluster catalogs. While the simulation shows a good match to our observations at the clusters' centers, it does not match our source distribution further out. Sources over 104″ from a cluster's center bias the tSZ signal high, for some of the sources found, by over 50%. When averaged over the whole cluster population, the effect is smaller but still at a level of 1%–2%. We also discovered that unlike previous measurements and simulations, we see an enhancement of source counts in the outer regions of the clusters and fewer sources than expected in the centers of this tSZ-selected sample.

Keywords: galaxy clusters; sunyaev-zeldovich effect; surveys
High-order Harmonics of a Kink Wave and a Narrow Quasiperiodic Fast-propagating Wave Train Excited Simultaneously in a Plasma Resonator

We present the observations of multimode kink waves and a narrow quasiperiodic fast-propagating (QFP) wave train in association with a jet on 2011 December 11. The jet impinged on a loop, which excited a propagating kink mode transitioning into a standing kink mode and also excited a QFP wave train away from the jet. Motion magnification is used to fit the higher harmonic standing wave oscillation profile with three periods at three different spatial locations. The periods have the ratio 6:3:2. The ratio of the fundamental mode to the second harmonic of the standing wave is about 1.95, suggesting that the magnetic field strength variation effect is strong enough to cancel out the density stratification. The differential emission measure is used to estimate the loop's plasma property at these three points, and it found the density and the temperature are roughly constant. The magnetic field strength, B = 51 ± 16 G, is derived by the coronal seismology using the fundamental kink mode. It is striking to find that the the ratio of the second harmonic to the third harmonic of the kink wave coincides with that of the periods of the QFP wave train, and the ratio of periods is about 1.5 in both cases. We propose that the excitation of the high-order harmonics and the QFP wave train could be the nonlinear response of the steep density-gradient plasma interacting with electromagnetic field in the southwest foot region. This region, like a resonator, might play an important role in energy reservoir capture and act as a frequency filter to generate propagating waves of particular frequencies.

Keywords: solar coronal loops; solar coronal waves
Universal Multistream Radial Structures of Cold Dark Matter Halos

Virialized halos of cold dark matter generically exhibit multistream structures of accreted dark matter within an outermost radial caustic known as the splashback radius. By tracking the particle trajectories that accrete onto the halos in cosmological N-body simulations, we count their number of apocenter passages (p) and use them to characterize the multistream structure of dark matter particles. We find that the radial density profile for each stream, classified by the number of apocenter passages, exhibits universal features and can be described by a double power-law function comprising shallow inner slopes and steep outer slopes of indices of -1 and -8, respectively. Surprisingly, these properties hold over a wide range of halo masses. The double power-law feature is persistent when dividing the sample by concentration or accretion rate. The dependence of the characteristic scale and amplitude of the profile on p cannot be replicated by known self-similar solutions, requiring consideration of complexities such as the distribution of angular momentum or mergers.

Keywords: galaxy dark matter halos; large-scale structure of the universe