adsabs/SciX_UAT_keywords huggingface dataset:
Jupiter Co-Orbital Comet P/2023 V6 (PANSTARRS): Orbital History and Modern Activity State

The discovery of the transient Jupiter co-orbital comet P/2019 LD2 (ATLAS) drew significant interest. Not only will LD2 transition between being a Centaur and a Jupiter-family comet (JFC) in 2063, the first time this process can be observed as it happens, it is also very active for its large heliocentric distance. We present observations and orbital integrations of the newly discovered transient Jupiter co-orbital comet P/2023 V6 (PANSTARRS), the second such object known. Despite similar modern orbits, V6 is significantly (15×) less active than LD2 and most JFCs as determined via Af ρ measurements at the same R H . We find that V6 is co-orbital between 2020 and 2044, twice the duration of LD2, but it will not become a JFC soon. We interpret these differences in activity as evolutionary, with V6 having lost a significant fraction of its near-surface ice compared to LD2 by previously being warmer. While V6's pre-encounter orbit was somewhat warmer than LD2's, future thermal modeling will be needed to understand if this can explain their differences or if a more significant difference further into the past is required. This is more evidence that LD2 is a pristine and ice-rich object, and thus it may display very strong activity when it becomes a JFC. We use the differences between V6 and LD2 to discuss the interpretation of cometary activity at large heliocentric distances as well as the small end of the cratering record of the Galilean satellites. Continuing observations of both objects are highly encouraged.

Keywords: comets; comet dynamics; centaur group
Numerical Study on Excitation of Turbulence and Oscillation in Above-the-loop-top Region of a Solar Flare

Extreme-ultraviolet imaging spectroscopic observations often show an increase in line width around the loop-top or above-the-loop-top (ALT) region of solar flares, suggestive of turbulence. In addition, recent spectroscopic observations found the oscillation in the Doppler velocity around the ALT region. We performed 3D magnetohydrodynamic (MHD) simulations to investigate the dynamics in the ALT region, with a particular focus on the generation of turbulence and the excitation of the oscillatory motion. We found a rapid growth of MHD instabilities around the upper parts of the ALT region (arms of the magnetic tuning fork). The instabilities grow more rapidly than the magnetic Rayleigh-Taylor-type instabilities at the density interface beneath the reconnecting current sheet. Eventually, the ALT region is filled with turbulent flows. The arms of the magnetic tuning fork have bad-curvature and transonic flows. Therefore, we consider that the rapidly growing instabilities are combinations of pressure-driven and centrifugally driven Rayleigh-Taylor-type instabilities. Despite the presence of turbulent flows, the ALT region shows a coherent oscillation driven by the backflow of the reconnection jet. We examine the numerical results by reanalyzing the solar flare presented in Reeves et al. We find that the highest nonthermal velocity is always at the uppermost visible edge of the ALT region, where oscillations are present. This result is consistent with our models. We also argue that the turbulent magnetic field has a significant impact on the confinement of nonthermal electrons in the ALT region.

Keywords: solar flares; magnetohydrodynamics; magnetohydrodynamical simulations; plasma astrophysics; solar physics
JADES Initial Data Release for the Hubble Ultra Deep Field: Revealing the Faint Infrared Sky with Deep JWST NIRCam Imaging

JWST has revolutionized the field of extragalactic astronomy with its sensitive and high-resolution infrared view of the distant Universe. Adding to the new legacy of JWST observations, we present the first NIRCam imaging data release from the JWST Advanced Deep Extragalactic Survey (JADES), providing nine filters of infrared imaging of ~25 arcmin2 covering the Hubble Ultra Deep Field and portions of Great Observatories Origins Deep Survey South. Utilizing 87 on-sky dual-filter hours of exposure time, these images reveal the deepest ever near-infrared view of this iconic field. We supply carefully constructed nine-band mosaics of the JADES bands, as well as matching reductions of five additional bands from the JWST Extragalactic Medium-band Survey. Combining with existing Hubble Space Telescope imaging, we provide 23-band space-based photometric catalogs and photometric redshifts for ≈47,500 sources. To promote broad engagement with JADES, we have created an interactive FitsMap website to provide an interface for professional researchers and the public to experience these JWST data sets. Combined with the first JADES NIRSpec data release, these public JADES imaging and spectroscopic data sets provide a new foundation for discoveries of the infrared Universe by the worldwide scientific community.

Keywords: high-redshift galaxies
Identifying Exoplanets with Deep Learning. IV. Removing Stellar Activity Signals from Radial Velocity Measurements Using Neural Networks

Exoplanet detection with precise radial velocity (RV) observations is currently limited by spurious RV signals introduced by stellar activity. We show that machine-learning techniques such as linear regression and neural networks can effectively remove the activity signals (due to starspots/faculae) from RV observations. Previous efforts focused on carefully filtering out activity signals in time using modeling techniques like Gaussian process regression. Instead, we systematically remove activity signals using only changes to the average shape of spectral lines, and use no timing information. We trained our machine-learning models on both simulated data (generated with the SOAP 2.0 software) and observations of the Sun from the HARPS-N Solar Telescope. We find that these techniques can predict and remove stellar activity both from simulated data (improving RV scatter from 82 to 3 cm s-1) and from more than 600 real observations taken nearly daily over 3 yr with the HARPS-N Solar Telescope (improving the RV scatter from 1.753 to 1.039 m s-1, a factor of ~1.7 improvement). In the future, these or similar techniques could remove activity signals from observations of stars outside our solar system and eventually help detect habitable-zone Earth-mass exoplanets around Sun-like stars.

Keywords: exoplanet astronomy; radial velocity; convolutional neural networks
THOR: An Algorithm for Cadence-independent Asteroid Discovery

We present "Tracklet-less Heliocentric Orbit Recovery" (THOR), an algorithm for linking of observations of Solar System objects across multiple epochs that does not require intranight tracklets or a predefined cadence of observations within a search window. By sparsely covering regions of interest in the phase space with "test orbits," transforming nearby observations over a few nights into the corotating frame of the test orbit at each epoch, and then performing a generalized Hough transform on the transformed detections followed by orbit determination filtering, candidate clusters of observations belonging to the same objects can be recovered at moderate computational cost and with little to no constraint on cadence. We validate the effectiveness of this approach by running on simulations as well as on real data from the Zwicky Transient Facility (ZTF). Applied to a short, two-week slice of ZTF observations, we demonstrate THOR can recover 97.4% of all previously known and discoverable objects in the targeted (a > 1.7 au) population with five or more observations and with purity between 97.7% and 100%. This includes 10 likely new discoveries, and a recovery of an e ~ 1 comet C/2018 U1 (the comet would have been a ZTF discovery had THOR been running in 2018 when the data were taken). The THOR package and demo Jupyter notebooks are open source and available at https://github.com/moeyensj/thor.

Keywords: astronomy software; asteroids; trans-neptunian objects; sky surveys
Mitigating the Noise-source Coupling Effect in Shear Measurement

Subpercent level accuracy in shear measurement is required by the Stage-IV weak lensing surveys. One important challenge is suppressing the shear bias on source images of low signal-to-noise ratios (S/N ≲ 10). Previously, it has been demonstrated that the shear estimators defined in the Fourier_Quad (FQ) method can achieve subpercent accuracy at the very faint end (S/N ≲ 5) through ensemble averaging. Later, it was found that we can approach the minimum statistical error (the Cramer-Rao Bound) by symmetrizing the full probability distribution function (PDF) of the FQ shear estimators (the PDF_SYM approach), instead of taking ensemble averages. Recently, with a large amount of mock galaxy images, we were able to identify some small amount of shear biases in the PDF_SYM approach at the faint end. The multiplicative bias goes up to (1-2) × 10-2 at S/N ≲ 10, and the anisotropy of the point-spread function causes an additive bias that can reach a few times 10-4. We find that these biases originate from the noise-source coupling in the galaxy power spectrum. It turns out that this problem can be largely fixed by adding additional terms to the FQ shear estimators. The resulting multiplicative and additive biases can be significantly suppressed to the level of 10-3 and 10-5, respectively. These corrections substantially extend the available S/N range for accurate shear measurement with the PDF_SYM approach.

Keywords: weak gravitational lensing; astronomy data analysis
Parallelization of the Symplectic Massive Body Algorithm (SyMBA) N-body Code

Direct N-body simulations of a large number of particles, especially in the study of planetesimal dynamics and planet formation, have been computationally challenging even with modern machines. This work presents the combination of fully parallelized N 2/2 interactions and the incorporation of the GENGA code's close encounter pair grouping strategy to enable MIMD parallelization of the Symplectic Massive Body Algorithm (SyMBA) with OpenMP on multi-core CPUs in shared-memory environment. SyMBAp (SyMBA parallelized) preserves the symplectic nature of SyMBA and shows good scalability, with a speedup of 30.8 times with 56 cores in a simulation with 5000 fully interactive particles.

Keywords: celestial mechanics; n-body simulations; computational methods; planetary dynamics; dynamical evolution; planetary system formation
The Strongest Cluster Lenses: An Analysis of the Relation between Strong Gravitational Lensing Strength and the Physical Properties of Galaxy Clusters

Strong gravitational lensing provides unique opportunities to investigate the mass distribution at the cores of galaxy clusters and to study high-redshift galaxies. Using 110 strong-lensing models of 74 cluster fields from the Hubble Frontier Fields (HFF), Reionization Lensing Cluster Survey (RELICS), and Sloan Giant Arcs Survey (SGAS), we evaluate the lensing strength of each cluster (area with ∣μ∣ ≥ 3 for z s = 9, normalized to a lens redshift of z = 0.5). We assess how large-scale mass, projected inner-core mass, and the inner slope of the projected mass-density profile relate to lensing strength. While we do identify a possible trend between lensing strength and large-scale mass (Kendall τ = 0.26 and Spearman r = 0.36), we find that the inner slope (50 kpc ≤ r ≤ 200 kpc) of the projected mass-density profile has a higher probability of correlation with lensing strength and can set an upper bound on the possible lensing strength of a cluster (Kendall τ = 0.53 and Spearman r = 0.71). As anticipated, we find that the lensing strength correlates with the effective Einstein area and that a large ( ≳ 30.″0) radial extent of lensing evidence is a strong indicator of a powerful lens. We attribute the spread in the relation to the complexity of individual lensing clusters, which is well captured by the lensing-strength estimator. These results can help us to more efficiently design future observations to use clusters as cosmic telescopes.

Keywords: galaxy clusters; strong gravitational lensing
Formation of PSR J1012+5307 with an Extremely Low-mass White Dwarf: Testing Magnetic Braking Models

PSR J1012+5307 is a millisecond pulsar with an extremely low-mass white dwarf (WD) companion in an orbit of 14.5 hr. Magnetic braking (MB) plays an important role in influencing the orbital evolution of binary systems with a low-mass (≲1–2 M ⊙) donor star. At present, there exist several different MB descriptions. In this paper, we investigate the formation of PSR J1012+5307 as a probe to test plausible MB models. Employing a detailed stellar evolution model with the MESA code, we find that the convection- and rotation-boosted MB and "Intermediate" MB models can reproduce the WD mass, WD radius, WD surface gravity, neutron star mass, and orbital period observed in PSR J1012+5307. However, our simulated WD has a higher effective temperature than the observations. Three other MB mechanisms, including the standard MB model, are too weak to account for the observed orbital period in the Hubble time. A long cooling timescale caused by H-shell flashes of the WD may alleviate the discrepancy between the simulated effective temperature and the observed value.

Keywords: neutron stars; orbital evolution; x-ray binary stars; white dwarf stars; accretion
Primary Velocity and Orbital Phase Effects on Planetary Detectability from Small Epoch Number Data Sets

Cross-correlation analyses of high-resolution spectroscopic data have recently shown great success in directly detecting planetary signals and enabling the characterization of their atmospheres. One such technique aims to observe a system at multiple epochs and combine the measured planetary radial velocities from each epoch into a measurement of the planetary Keplerian orbital velocity Kp, constituting a direct detection of the planetary signal. Recent work has shown that in few-epoch (5) data sets, unintended structure can arise at a high level, obscuring the planetary detection. In this work, we look to simulations to examine whether there are ways to reduce this structured noise in few-epoch data sets by careful planning of observations. The choice of observation date allows observers to select the primary (stellar) velocity through a set systemic velocity and chosen barycentric velocity and the planetary orbital phase so we focus on the effects of these two parameters. We find that epochs taken when the primary velocity is near zero and the stellar lines remain relatively fixed to the telluric rest-frame greatly reduce the level of structured noise and allow for much stronger planetary detections, on average more than twice the significance of detections made with epochs using randomly selected primary velocities. Following these results, we recommend that observers looking to build up high-resolution multi-epoch data sets target nights when their system has a near-zero primary velocity.

Keywords: exoplanet atmospheres; radial velocity; high resolution spectroscopy
Abundances of Heavy Elements in the B8 Mn Star HD 110073

The synthesis of several spectral intervals in the optical range allows the determination of LTE abundances of strontium, yttrium, zirconium, barium, praseodymium, neodymium, platinum and mercury for this B8 Mn star. Compared to the solar abundances, strontium, yttrium, barium, praseodymium and mercury are found to be overabundant by factors of 2.5, 130, 10, 150 and 60,000. Only upper limits could be determined for zirconium and platinum. The lines of Nd III are blended with lines of more abundant elements which precludes the determination of the abundance of neodymium. The abundance of manganese, derived from the Mn II line at 3986.59 Å is about 100 times larger than in the Sun.

Keywords: chemically peculiar stars; mercury-manganese stars
Investigating the Ultracompact X-Ray Binary Candidate SLX 1735-269 with NICER and NuSTAR

We present two simultaneous NICER and NuSTAR observations of the ultracompact X-ray binary (UCXB) candidate SLX 1735‑269 while the source was in two different spectral states. Using various reflection modeling techniques, we find that XILLVERCO, a model used for fitting X-ray spectra of UCXBs with high carbon and oxygen abundances is an improvement over RELXILL or RELXILLNS, which instead contains solar-like chemical abundances. This provides indirect evidence in support of the source being ultracompact. We also use this reflection model to get a preliminary measurement of the inclination of the system, degrees. This is consistent with our timing analysis, where a lack of eclipses indicates an inclination of i < 80°. The timing analysis is otherwise inconclusive, and we cannot confidently measure the orbital period of the system.

Keywords: low-mass x-ray binary stars; x-ray binary stars; neutron stars
Measuring Dark Matter in Galaxies: The Mass Fraction within Five Effective Radii

Large galaxies may contain an "atmosphere" of hot interstellar X-ray gas, and the temperature and radial density profile of this gas can be used to measure the total mass of the galaxy contained within a given radius r. We use this technique for 102 early-type galaxies with stellar masses M⋆ > 1010M⊙, to evaluate the mass fraction of dark matter (DM) within the fiducial radius r = 5re, denoted f5 = fDM(5re). On average, these systems have a median $\overline{{f}_{5}}\simeq 0.8\mbox{--}0.9$ with a typical galaxy-to-galaxy scatter ±0.15. Comparisons with mass estimates made through the alternative techniques of satellite dynamics (e.g., velocity distributions of globular clusters, planetary nebulae, satellite dwarfs) as well as strong lensing show encouraging consistency over the same range of stellar mass. We find that many of the disk galaxies (S0/SA0/SB0) have a significantly higher mean f5 than do the pure ellipticals, by Δf5 ≃ 0.1. We suggest that this higher level may be a consequence of sparse stellar haloes and quieter histories with fewer major episodes of feedback or mergers. Comparisons are made with the Magneticum Pathfinder suite of simulations for both normal and centrally dominant "Brightest Cluster" galaxies. Though the observed data exhibit somewhat larger scatter at a given galaxy mass than do the simulations, the mean level of DM mass fraction for all classes of galaxies is in good first-order agreement with the simulations. Finally, we find that the group galaxies with stellar masses near M⋆ ∼ 1011M⊙ have relatively more outliers at low f5 than in other mass ranges, possibly the result of especially effective AGN feedback in that mass range leading to expansion of their DM halos.

Keywords: x-ray surveys; galaxy masses; baryonic dark matter; galaxy dark matter halos
Comparing Energetic Storm Particle Heavy-ion Properties in Solar Cycles 23 and 24

We examine variations in energetic storm particle (ESP) heavy-ion average intensities and energy spectra between ~0.1 and 75 MeV nucleon-1 at coronal mass ejection (CME)-driven interplanetary shocks for events observed at the ACE spacecraft. We compare ESP events observed during the weaker solar cycle (SC) 24 and the relatively stronger SC 23 to investigate any effects on the strength of an SC, including the associated transient events, on ESP properties at 1 au. We find that the number of clearly defined heavy-ion ESP events at ACE during SC 23 is about twice that observed during SC 24 (76 versus 41). The average transit speed of the driving interplanetary CMEs (ICMEs) at 1 au is 20% higher during SC 23 than during SC 24 (859.4 km s-1 versus 729.1 km s-1). The correlation of ESP average intensities with ICME speeds shows that lower-speed ICMEs in SC 24 can be as efficient as the higher-speed events in SC 23 at producing ESPs below 2 MeV nucleon-1. The distribution and magnitude of the average intensities for energies below ~1 MeV nucleon-1 are consistent between both SCs. However, events with intensity enhancements at higher energies (>~10 MeV nucleon-1) are more frequent and their intensity distributions are harder for SC 23, resulting in an increase in the rollover energy (E 0) for their spectra profiles. This suggests more efficient ESP acceleration at >10 MeV nucleon-1 during SC 23.

Keywords: interplanetary particle acceleration; solar energetic particles; solar coronal mass ejections; solar cycle; sunspot cycle
Molecular Hydrogen and its Proxies HCO+ and CO in the Diffuse Interstellar Medium

There is a robust polyatomic chemistry in diffuse, partially molecular interstellar gas that is readily accessible in absorption at radio/millimeter/submillimeter wavelengths. Accurate column densities are derived owing to the weak internal excitation, so relative molecular abundances are well known with respect to each other but not with respect to H2. Here we consider the use of proxies for hydrogen column densities N(H2) and N(H) = N(H I)+2N(H2) based on measurements of HCO+ absorption and CO emission and absorption, and we compare these with results obtained by others when observing H I, H2 and CO toward stars and active galactic nuclei. We consider the use of HCO+ as a proxy for H2 and show that the assumption of a relative abundance N(H2) = N(HCO+)/3 × 10-9 gives the same view of the atomic-molecular hydrogen transition that is seen in UV absorption toward stars. CO on the other hand shows differences between the radio and optical regimes because emission is always detected when N(HCO+) ≳ 6 × 1011 cm-2 or N(H2) ≳ 2 × 1020 cm-2. Wide variations in the integrated CO J = 1 - 0 brightness WCO and N(CO)/N(H2) imply equivalent variations in the CO-H2 conversion factor even while the ensemble mean is near the usual Galactic values. Gas/reddening ratios found in absorption toward stars, N(H)/E(B - V) = 6.2 × 1021 H cm-2 (mag)-1 overall or 6.8 × 1021 H cm-2 (mag)-1 for sightlines at E(B - V) ≤ 0.08 mag lacking H2 are well below the Galactic mean measured at low reddening and high Galactic latitude, 8.3 × 1021 H cm-2 (mag)-1.

Keywords: diffuse interstellar clouds; interstellar atomic gas; interstellar molecules
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 kinematics; galaxy dynamics