adsabs/SciX_UAT_keywords huggingface dataset:
Revealing Short-period Exoplanets and Brown Dwarfs in the Galactic Bulge Using the Microlensing Xallarap Effect with the Nancy Grace Roman Space Telescope

The Nancy Grace Roman Space Telescope (Roman) will provide an enormous number of microlensing light curves with much better photometric precision than ongoing ground-based observations. Such light curves will enable us to observe high-order microlensing effects which have been previously difficult to detect. In this paper, we investigate Roman's potential to detect and characterize short-period planets and brown dwarfs (BDs) in source systems using the orbital motion of source stars, the so-called xallarap effect. We analytically estimate the measurement uncertainties of xallarap parameters using Fisher matrix analysis. We show that the Roman Galactic Exoplanet Survey can detect warm Jupiters with masses down to 0.5 MJup and orbital periods of 30 days via the xallarap effect. Assuming a planetary frequency function from Cumming et al., we find Roman will detect ∼10 hot and warm Jupiters and ∼30 close-in BDs around microlensed source stars during the microlensing survey. These detections are likely to be accompanied by the measurements of the companion's masses and orbital elements, which will aid in the study of the physical properties for close-in planet and BD populations in the Galactic bulge.

Keywords: gravitational microlensing; xallarap effect; exoplanets; brown dwarfs; galactic bulge; gravitational microlensing exoplanet detection; exoplanet detection methods; astronomical simulations; hot jupiters
Heliocentric Distance and Solar Activity Dependence of Sustained Quasi-radial Interplanetary Magnetic Field Occurrence

Planets close to their stars experience an interplanetary magnetic field (IMF) that is dominantly quasi-radial. Our solar system serves as a laboratory to study how the occurrence of quasi-radial IMF varies away from the star and under different stellar activities. Furthermore, on time and spatial scales relevant to magnetospheric physics, solar wind variability prevails in the form of structures generated both at the Sun and locally in the interplanetary space. The stationary Parker spiral model only approximates the large-scale structure of the IMF. Deviations from the Parker spiral often result in strongly radial magnetic fields that give rise to kinetic foreshock turbulence, which in turn can impact planetary magnetospheres. The relative significance of this type of interaction can be estimated statistically based on the occurrence rate of cases where the IMF is directed along the radial direction, leading to the entire day-side magnetosphere being downstream of the ion foreshock. We use observations covering radial distances from 0.1 to 10 au and more than 2 solar cycles to quantify the prevalence of radial IMFs throughout the heliosphere. Near Earth's orbit, it is found that the occurrence rates of quasi-radial and southward IMF orientations are similar, and that the Pearson correlation coefficient is ${{ \mathcal R }}_{{xy}}\sim -0.7$ calculated between quasi-radial IMF occurrence rate and solar activity. A negative correlation is demonstrated for radial distances extending to at least Mars but not to Saturn.

Keywords: interplanetary magnetic fields; planetary bow shocks; solar cycle
Photometry of the Four Anti-Galactocentric Old Open Clusters: Czernik 30, Berkeley 34, Berkeley 75, and Berkeley 76

We present a BVI photometric study of four old open clusters (OCs) in the the Milky Way, Czernik 30, Berkeley 34, Berkeley 75, and Berkeley 76 using the observation data obtained with the Small and Moderate Aperture Research Telescope System 1.0 m telescope at the Cerro Tololo Inter-American Observatory, Chile. These four OCs are located at the anti-Galactocentric direction and in the Galactic plane. We determine the fundamental physical parameters for the four OCs, such as age, metallicity, distance modulus, and color excess, using red clump and PARSEC isochrone fitting methods after finding center and size of the four OCs. These four old OCs are 2-3 Gyr old and 6-8 kpc away from the Sun. The metallicity ([Fe/H]) values of the four OCs are between -0.6 and 0.0 dex. We combine data for these four OCs with those for old OCs from five literatures resulting in 236 objects to investigate Galactic radial-metallicity distribution. The gradient of a single linear fit for this Galactocentric [Fe/H] distribution is -0.052 ± 0.004 dex kpc-1. If we assume the existence of a discontinuity in this radial-metallicity distribution, the gradient at Galactocentric radius <12 kpc is -0.070 ± 0.006 dex kpc-1, while that at the outer part is -0.016 ± 0.010 which is flatter than that of the inner part. Although there are not many sample clusters at the outer part, the broken linear fit seems to better follow the observation data.

Keywords: open star clusters; red giant clump; galaxy disks
The Decay of α-configuration Sunspots

To better understand the decay of different types of sunspots, we studied the decay of eight α-configuration sunspots by using the data that were acquired by the Helioseismic and Magnetic Imager on board the Solar Dynamic Observatory. We followed their decay for about four days and analyzed the evolution of their photospheric area and magnetic field parameters. We found that the area and total magnetic flux of α sunspots show a near-linear decrease during their decay. Meanwhile, the area decay rate of an individual sunspot is not constant. The area decay of a sunspot can be divided into two stages, a slow and a rapid decay process. Moreover, according to the difference of the area decay of the penumbra and umbra, the α sunspots decay can be classified in three ways: the penumbra and umbra decay synchronously, the penumbra decays first, and the umbra decays first. In addition, the flux decay of the penumbra is lagging behind the decay of the penumbral area. This finding suggests that the vertical magnetic field of the sunspot penumbra increases significantly in the early stage of sunspot decay.

Keywords: sunspots; solar magnetic fields; solar photosphere
Constrained Wave-telescope Technique

We revisit the mathematics behind the application of the physically informed constraint matrix used in the wave-telescope technique. The constraint matrix, used to enforce the divergence-free nature of the magnetic field when processing in situ multi-spacecraft data, is found in a few different forms in the literature. We give brief analytical and computational evidence to support a particular combination of constraint matrix and spectral energy density equation for the wave-telescope technique.

Keywords: magnetic fields; plasma physics; analytical mathematics; computational methods; space plasmas
Elemental Abundances in M31: The Kinematics and Chemical Evolution of Dwarf Spheroidal Satellite Galaxies

We present deep spectroscopy from Keck/DEIMOS of Andromeda I, III, V, VII, and X, all of which are dwarf spheroidal satellites of M31. The sample includes 256 spectroscopic members across all five dSphs. We confirm previous measurements of the velocity dispersions and dynamical masses, and we provide upper limits on bulk rotation. Our measurements confirm that M31 satellites obey the same relation between stellar mass and stellar metallicity as Milky Way (MW) satellites and other dwarf galaxies in the Local Group. The metallicity distributions show trends with stellar mass that are similar to those of MW satellites, including evidence in massive satellites for external influence, like pre-enrichment or gas accretion. We present the first measurements of individual element ratios, like [Si/Fe], in the M31 system, as well as measurements of the average [α/Fe] ratio. The trends of [α/Fe] with [Fe/H] also follow the same galaxy mass-dependent patterns as MW satellites. Less massive galaxies have more steeply declining slopes of [α/Fe] that begin at lower [Fe/H]. Finally, we compare the chemical evolution of M31 satellites to M31's Giant Stellar Stream and smooth halo. The properties of the M31 system support the theoretical prediction that the inner halo is composed primarily of massive galaxies that were accreted early. As a result, the inner halo exhibits higher [Fe/H] and [α/Fe] than surviving satellite galaxies.

The data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.

Keywords: andromeda galaxy; dwarf galaxies; stellar abundances; local group
On the Formation of Vinylamine (C2H3NH2) in Interstellar Ice Analogs

Amines-organic molecules carrying the -NH2 moiety-have been recognized as a vital intermediate in the formation of prebiotic molecules such as amino acids and nucleobases. Here we report the formation of vinylamine (C2H3NH2), which was recently detected toward G+0.693-0.027, in interstellar ice analogs composed of acetylene (C2H2) and ammonia (NH3) exposed to energetic electrons. Our experiments mimic cascades of secondary electrons in the tracks of galactic cosmic rays impinging on interstellar ice in molecular clouds. Tunable photoionization reflectron time-of-flight mass spectrometry (PI-Re-TOF-MS), along with isomer-specific assignments, reveals the production of vinylamine (C2H3NH2). Quantum chemical computations suggest that both a radical-radical recombination of the amino (NH2) with the vinyl (C2H3) radical and a one-step concerted route are feasible pathways to vinylamine (C2H3NH2). The results present the first documented route to form vinylamine in interstellar ice analogs. This unsaturated amine, which is isovalent to vinylalcohol (C2H3OH), could be a key precursor for the abiotic synthesis of prebiotic molecules such as amino acids and nucleobases, with implications for the origins-of-life theme.

Keywords: pre-biotic astrochemistry; astrochemistry; laboratory astrophysics; interstellar medium
The Possibility of Modeling the Very High Energy Afterglow of GRB 221009A in a Wind Environment

In this paper, we model the dynamics and radiation physics of the rarity event GRB 221009A afterglow in detail. By introducing a top-hat jet that propagates in an environment dominated by stellar winds, we explain the publicly available observations of afterglow associated with GRB 221009A over the first week. It is predicted that GRB 221009A emits a luminous very high energy afterglow based on the synchrotron self-Compton (SSC) process in our model. We show the broadband spectral energy distribution (SED) analysis results of GRB 221009A and find that the SSC radiation component of GRB 221009A is very bright in the 0.1-10 TeV band. The integrated SED shows that the SSC emission in the TeV band has detection sensitivity significantly higher than that of LHASSO, MAGIC, and CTA. However, since the release of further observations, deviations from the standard wind environment model have gradually shown up in data. For example, the late-time multiband afterglow cannot be consistently explained under the standard wind environment scenario. It may be necessary to consider modeling with a structured jet with complex geometry or a partial revision of the standard model. Furthermore, we find that the inclusion of GeV observations could break the degeneracy between model parameters, highlighting the significance of high-energy observations in determining accurate parameters for GRB afterglows.

Keywords: gamma-ray bursts; high energy astrophysics
First Detection of a Linear Structure in the Midplane of the Young HH 211 Protostellar Disk: A Spiral Arm?

Spiral structures have been detected in evolved protostellar disks, driving the disk accretion toward the central protostars to facilitate star formation. However, it is still unclear if these structures can form earlier in young protostellar disks. With the Atacama Large Millimeter/submillimeter Array, we have detected and spatially resolved a very young and nearly edge-on dusty disk with a radius of only ~20 au in the HH 211 protostellar system at submillimeter wavelength. It is geometrically thick, indicating that the submillimeter-light-emitting dust grains have yet to settle to the midplane for planet formation. Intriguingly, it shows three bright linear structures parallel to the equatorial plane, resembling a three-layer pancake that has not been seen before. The top and bottom ones arise from the warm disk surfaces, unveiling the flared structure of the disk. More importantly, the middle one is in the dense midplane of the disk and can be modeled as a trailing spiral arm excited by disk gravity, as seen in evolved protostellar disks, supporting the presence of spiral structures in the very early phase for disk accretion.

Keywords: star formation; jets; stellar accretion disks
Gaia17bpp: A Giant Star with the Deepest and Longest Known Dimming Event

We report the serendipitous discovery of Gaia17bpp/2MASS J19372316+1759029, a binary star with a deep single large-amplitude dimming event of ~4.5 mag that lasted over 6.5 yr. Using the optical-to-IR spectral energy distribution (SED), we constrain the primary star to be a cool giant M0III star with effective temperature T eff = 3850 K and radius R = 58 R ⊙. Based on the SED fitting, we obtained a bimodal posterior distribution of primary stellar masses with a stronger preference for a 1.5 M ⊙ mass star. Within the last 66 yr of photometric coverage, no other significant dimming events of this depth and duration were identified in the optical light curves. Using a Gaussian process, we fit a generalized Gaussian distribution to the optical and IR light curves and conclude that the dimming event exhibits moderate asymmetries from optical to IR. At the minimum of the dimming event, the Wide-field Infrared Survey Explorer color (W1-W2) differed by ~0.2 mag relative to the primary star color outside the dimming event. The ingress and egress colors show a shallow reddening profile. We suggest that the main culprit of the dimming event is likely due to the presence of a large, optically thick disk transiting the primary giant star. By fitting a monochromatic transit model of an oblate disk transiting a star, we found good agreement with a slow-moving (0.005 km s-1) disk with a ~1.4 au radius. We propose that Gaia17bpp belongs to a rare binary star population similar to the ϵ Aurigae system, which consists of a secondary star enshrouded by an optically thick debris disk.

Keywords: stellar occultation; binary stars; peculiar variable stars
Evidence of Magnetic Reconnection with Multiple X Lines and Flux Ropes in Thin Magnetotail Currents Observed by the MMS Spacecraft: Results of Grad-Shafranov Reconstruction

There is some observational evidence for the existence of multiple X line magnetic reconnection (MR) in various planetary magnetotails but the overall observationally based MR topology in two or three dimensions is still not available. This study reports the first 2D structures of MR with multiple X lines and magnetic islands observed by the Magnetospheric Multiscale (MMS) spacecraft in the Earth's magnetotail based on the Grad-Shafranov (GS) reconstruction model with temperature anisotropy. The tearing mode geometry is revealed within the spatial domain of 3800 km × 800 km with multiple X lines and magnetic islands on the spatial scale of the sub-ion inertial length or a few times the electron gyroradius. The MR event is seen by all four MMS spacecraft but the magnetic islands are caught only by the MMS3 spacecraft, and exhibit large firehose-type temperature anisotropy. The GS reconstructed maps based on the MMS1, 2, and 4 show a single X line and partial ion-scale magnetic islands with a smaller degree of temperature anisotropy. The reconstruction results remain the same for various energy closures, and the firehose-type anisotropy is found to yield smaller magnetic islands than the isotropic cases, which is opposite to the previous findings for MR events with mirror-type temperature anisotropy.

Keywords: space plasmas; plasma astrophysics; plasma physics; planetary magnetospheres
Effective Reaction Temperatures of Irreversible Dust Chemical Reactions in a Protoplanetary Disk

Dust particles in protoplanetary disks experience various chemical reactions under different physicochemical conditions through their accretion and diffusion, which results in the radial chemical gradient of dust. We performed three-dimensional Monte Carlo simulations to evaluate the dust trajectories and the progress of fictitious irreversible reactions, of which kinetics is expressed by the Johnson-Mehl-Avrami equation. The distribution of the highest temperature that each particle experiences before the degree of reaction exceeds a certain level shows the lognormal distribution, and its mode temperature was used as the effective reaction temperature. Semi-analytical prediction formulas of the effective reaction temperature and its dispersion were derived by comparing a reaction timescale with a diffusive transport timescale of dust as a function of the reaction parameters and the disk parameters. The formulas reproduce the numerical results of the effective reaction temperatures and their dispersions within 5.5% and 24%, respectively, in a wide temperature range (200-1400 K). We applied the formulas for the crystallization of amorphous silicate dust and its oxygen isotope exchange with the H2O vapor based on the experimentally determined kinetics. For submicron-sized amorphous forsterite dust, the predicted effective reaction temperature for the oxygen isotope exchange was lower than that of crystallization without overlap even considering their dispersions. This suggests that the amorphous silicate dust in the protosolar disk could exchange their oxygen isotopes efficiently with the 16O-poor H2O vapor, resulting in the distinct oxygen isotope compositions from the Sun.

Keywords: solar system; solar system evolution; cosmochemistry; astrochemistry; dust composition; protoplanetary disks
Retrieval Survey of Metals in Six Ultrahot Jupiters: Trends in Chemistry, Rain-out, Ionization, and Atmospheric Dynamics

Ground-based high-resolution spectroscopy (HRS) has detected numerous chemical species and atmospheric dynamics in exoplanets, most notably ultrahot Jupiters (UHJs). However, quantitative estimates on abundances have been challenging but are essential for accurate comparative characterization and to determine formation scenarios. In this work, we retrieve the atmospheres of six UHJs (WASP-76 b, MASCARA-4 b, MASCARA-2 b, WASP-121 b, HAT-P-70 b, and WASP-189 b) with ESPRESSO and HARPS-N/HARPS observations, exploring trends in eleven neutral species and dynamics. While Fe abundances agree well with stellar values, Mg, Ni, Cr, Mn, and V show more variation, highlighting the difficulty in using a single species as a proxy for metallicity. We find that Ca, Na, Ti, and TiO are underabundant, potentially due to ionization and/or nightside rain-out. Our retrievals also show that relative abundances between species are more robust, consistent with previous works. We perform spatially resolved and phase-resolved retrievals for WASP-76 b and WASP-121 b given their high signal-to-noise observations, and find the chemical abundances in each of the terminator regions are broadly consistent. We additionally constrain dynamics for our sample through Doppler shifts and broadening of the planetary signals during the primary eclipse, with median blueshifts between ~0.9 and 9.0 km s-1 due to day-night winds. Furthermore, we constrain spectroscopic masses for MASCARA-2 b and HAT-P-70 b consistent with their known upper limits, but we note that these may be biased due to degeneracies. This work highlights the importance of future HRS studies to further probe differences and trends between exoplanets.

Keywords: exoplanet atmospheric composition; atmospheric dynamics; extrasolar gaseous giant planets; high resolution spectroscopy
EMPRESS. VIII. A New Determination of Primordial He Abundance with Extremely Metal-poor Galaxies: A Suggestion of the Lepton Asymmetry and Implications for the Hubble Tension

The primordial He abundance Y P is a powerful probe of cosmology. Currently, Y P is best determined by observations of metal-poor galaxies, while there are only a few known local extremely metal-poor (<0.1Z ⊙) galaxies (EMPGs) having reliable He/H measurements with He I λ10830 near-infrared (NIR) emission. Here we present deep Subaru NIR spectroscopy for 10 EMPGs. Combining the existing optical data, He/H values of 5 out of the 10 EMPGs are reliably derived by the Markov chain Monte Carlo algorithm. Adding the existing 3 EMPGs and 51 moderately metal-poor (0.1-0.4Z ⊙) galaxies with reliable He/H estimates, we obtain ${Y}_{{\rm{P}}}={0.2370}_{-0.0034}^{+0.0033}$ by linear regression in the (He/H) - (O/H) plane, where we increase the number of EMPGs from three to eight anchoring He/H of the most metal-poor gas in galaxies. Although our Y P measurement and previous measurements are consistent, our result is slightly (~1σ) smaller due to our EMPGs. Including the existing primordial deuterium D P measurement, we constrain the effective number of neutrino species N eff and the baryon-to-photon ratio η showing ≳1-2σ tensions with the Standard Model and Planck Collaboration et al. (2020). Motivated by the tensions, we allow the degeneracy parameter of the electron neutrino ξ e , as well as N eff and η, to vary. We obtain ${\xi }_{e}={0.05}_{-0.02}^{+0.03}$ , ${N}_{\mathrm{eff}}={3.11}_{-0.31}^{+0.34}$ , and $\eta \times {10}^{10}={6.08}_{-0.06}^{+0.06}$ from the Y P and D P measurements with a prior of η taken from Planck Collaboration et al. Our constraints suggest a lepton asymmetry and allow for a high value of N eff within the 1σ level, which could mitigate the Hubble tension.

Keywords: galaxy abundances; galaxy chemical evolution; cosmological parameters; big bang nucleosynthesis
Change of Rankine-Hugoniot Relations during Postshock Relaxation of Anisotropic Distributions

Collisionless shocks channel the energy of the directed plasma flow into the heating of the plasma species and magnetic field enhancement. The kinetic processes at the shock transition cause the ion distributions just behind the shock to be nongyrotropic. Gyrotropization and subsequent isotropization occur at different spatial scales. Accordingly, for a given upstream plasma and magnetic field state, there would be different downstream states corresponding to the anisotropic and isotropic regions. Thus, at least two sets of Rankine-Hugoniot relations are needed, in general, to describe the connection of the downstream measurable parameters to the upstream ones. We establish the relation between the two sets.

Keywords: shocks; interplanetary shocks; planetary bow shocks