adsabs/SciX_UAT_keywords huggingface dataset:
Biases in Orbital Fitting of Directly Imaged Exoplanets with Small Orbital Coverage

The eccentricity of a planet's orbit and the inclination of its orbital plane encode important information about its formation and history. However, exoplanets detected via direct imaging are often only observed over a very small fraction of their period, making it challenging to perform reliable physical inferences given wide, unconstrained posteriors. The aim of this project is to investigate biases (deviation of the median and mode of the posterior from the true values of orbital parameters, and the width and coverage of their credible intervals) in the estimation of orbital parameters of directly imaged exoplanets, particularly their eccentricities, and to define general guidelines to perform better estimations of uncertainty. For this, we constructed various orbits and generated mock data for each spanning ∼0.5% of the orbital period. We used the Orbits For The Impatient algorithm to compute orbit posteriors and compared those to the true values of the orbital parameters. We found that the inclination of the orbital plane is the parameter that most affects our estimations of eccentricity, with orbits that appear near edge on producing eccentricity distributions skewed away from the true values and often bimodal. We also identified a degeneracy between eccentricity and inclination that makes it difficult to distinguish posteriors of face-on, eccentric orbits and edge-on, circular orbits. For the exoplanet-imaging community, we propose practical recommendations, guidelines, and warnings relevant to orbit fitting.

Keywords: exoplanet astronomy; orbit determination; bayesian statistics; exoplanets
TOI-532b: The Habitable-zone Planet Finder confirms a Large Super Neptune in the Neptune Desert orbiting a metal-rich M-dwarf host

We confirm the planetary nature of TOI-532b, using a combination of precise near-infrared radial velocities with the Habitable-zone Planet Finder, Transiting Exoplanet Survey Satellite (TESS) light curves, ground-based photometric follow up, and high-contrast imaging. TOI-532 is a faint (J ~ 11.5) metal-rich M dwarf with Teff = 3957 ± 69 K and [Fe/H] = 0.38 ± 0.04; it hosts a transiting gaseous planet with a period of ~2.3 days. Joint fitting of the radial velocities with the TESS and ground-based transits reveal a planet with radius of 5.82 ± 0.19 R⊕, and a mass of ${61.5}_{-9.3}^{+9.7}$ M⊕. TOI-532b is the largest and most massive super Neptune detected around an M dwarf with both mass and radius measurements, and it bridges the gap between the Neptune-sized planets and the heavier Jovian planets known to orbit M dwarfs. It also follows the previously noted trend between gas giants and host-star metallicity for M-dwarf planets. In addition, it is situated at the edge of the Neptune desert in the Radius-Insolation plane, helping place constraints on the mechanisms responsible for sculpting this region of planetary parameter space.

Keywords: extrasolar gaseous planets; radial velocity; transit photometry; hot neptunes
Measuring the β-decay Properties of Neutron-rich Exotic Pm, Sm, Eu, and Gd Isotopes to Constrain the Nucleosynthesis Yields in the Rare-earth Region

The β-delayed neutron-emission probabilities of 28 exotic neutron-rich isotopes of Pm, Sm, Eu, and Gd were measured for the first time at RIKEN Nishina Center using the Advanced Implantation Detector Array (AIDA) and the BRIKEN neutron detector array. The existing β-decay half-life (T 1/2) database was significantly increased toward more neutron-rich isotopes, and uncertainties for previously measured values were decreased. The new data not only constrain the theoretical predictions of half-lives and β-delayed neutron-emission probabilities, but also allow for probing the mechanisms of formation of the high-mass wing of the rare-earth peak located at A ≈ 160 in the r-process abundance distribution through astrophysical reaction network calculations. An uncertainty quantification of the calculated abundance patterns with the new data shows a reduction of the uncertainty in the rare-earth peak region. The newly introduced variance-based sensitivity analysis method offers valuable insight into the influence of important nuclear physics inputs on the calculated abundance patterns. The analysis has identified the half-lives of 168Sm and of several gadolinium isotopes as some of the key variables among the current experimental data to understand the remaining abundance uncertainty at A = 167-172.

Keywords: r-process; nucleosynthesis; nuclear physics
Magnetohydrodynamic Modeling Investigations of Kelvin-Helmholtz Instability and Associated Magnetosonic Wave Emission along Coronal Mass Ejections

Previous studies have suggested that the Kelvin-Helmholtz instability (KHI) and magnetohydrodynamic (MHD) wave emissions via the KHI along various shear flow boundaries in a solar-terrestrial environment may be possible. We expand upon these previous studies to investigate the linear and nonlinear evolution of the KHI and emission of MHD waves along the boundaries of coronal mass ejections (CMEs). Our results demonstrate that the KHI and MHD wave emission due to the KHI are possible along the CME boundaries during the KHI development. We found that magnetic field orientation in the region outside of the CME has strong effects on the strength of MHD wave emission. While a smaller parallel component of the magnetic field resulted in larger growth rates in the KHI development, a larger parallel component of the magnetic field resulted in stronger MHD wave emissions. For all cases we investigated, we identified emitted waves to be fast MHD waves. We suggest that these emitted MHD waves may be able to carry available kinetic energy from the CME flow to the outside of the CME, thereby contributing to solar coronal heating via energy dissipation.

Keywords: solar coronal mass ejections; ejecta; solar storm; solar corona; solar atmosphere; plasma astrophysics; magnetohydrodynamics; space plasmas; solar coronal waves; alfven waves; solar coronal heating
The Dark Matter Halo of M54

M54 is a prototype for a globular cluster embedded in a dark matter halo. Gaia Early Data Release 3 photometry and proper motions separate the old, metal-poor stars from the more metal-rich and younger dwarf galaxy stars. The metal-poor stars dominate the inner 50 pc, with a velocity dispersion profile that declines to a minimum around 30 pc then rises back to nearly the central velocity dispersion, as expected for a globular cluster at the center of a cold dark matter (CDM) cosmology dark matter halo. The Jeans equation mass analysis of the three separate stellar populations gives consistent masses that rise approximately linearly with radius to 1 kpc. These data are compatible with an infalling CDM dark matter halo reduced to ≃3 × 108 M ⊙ at the 50 kpc apocenter 2.3 Gyr ago, with a central globular cluster surrounded by the remnant of a dwarf galaxy. Tides gradually remove material beyond 1 kpc but have little effect on the stars and dark matter within 300 pc of the center. M54 appears to be a "transitional" system between globular clusters with and without local dark halos whose evolution within the galaxy depends on the time of accretion and orbital pericenter.

Keywords: globular star clusters; milky way galaxy; dark matter
Noise Reduction Methods for Large-scale Intensity-mapping Measurements with Infrared Detector Arrays

Intensity-mapping observations measure galaxy clustering fluctuations from spectral-spatial maps, requiring stable noise properties on large angular scales. We have developed specialized readouts and analysis methods for achieving large-scale noise stability with Teledyne 2048 × 2048 H2RG infrared detector arrays. We designed and fabricated a room-temperature low-noise ASIC Video8 amplifier to sample each of the 32 detector outputs continuously in sample-up-the-ramp mode with interleaved measurements of a stable reference voltage that remove current offsets and 1/f noise from the amplifier. The amplifier addresses rows in an order different from their physical arrangement on the array, modulating temporal 1/f noise in the H2RG to high spatial frequencies. Finally, we remove constant signal offsets in each of the 32 channels using reference pixels. These methods will be employed in the upcoming SPHEREx orbital mission that will carry out intensity-mapping observations in near-infrared spectral maps in deep fields located near the ecliptic poles. We also developed a noise model for the H2RG and Video8 to optimize the choice of parameters. Our analysis indicates that these methods hold residual 1/f noise near the level of SPHEREx photon noise on angular scales smaller than ~30'.

Keywords: near infrared astronomy; observational cosmology; astronomical instrumentation; cosmic background radiation
Bridging the Gap between Luminous Red Novae and Common Envelope Evolution: The Role of Recombination Energy and Radiation Force

Luminous red novae and their connection to common envelope evolution (CEE) remain elusive in astrophysics. Here, we present a radiation hydrodynamic model capable of simulating the light curves of material ejected during a CEE. For the first time, the radiation hydrodynamic model incorporates complete recombination physics for hydrogen and helium. The radiation hydrodynamic equations are solved with Guangqi. With time-independent ejecta simulations, we show that the peaks in the light curves are attributed to radiation-dominated ejecta, while the extended plateaus are produced by matter-dominated ejecta. To showcase our model's capability, we fit the light curve of AT 2019zhd. The central mass object of 6 M ⊙ is assumed based on observations and scaling relations. Our model demonstrates that the ejecta mass of AT 2019zhd falls within the range of 0.04–0.1 M ⊙. Additionally, we demonstrate that recombination energy and radiation force acceleration significantly impact the light curves, whereas dust formation has a limited effect during the peak and plateau phases.

Keywords: transient sources; common envelope evolution
The Prolific Thermonuclear X-Ray Bursts from the Outburst of the Newly Discovered Millisecond Pulsar MAXI J1816-195 Observed by Insight-HXMT and NICER

MAXI J1816-195 is a newly discovered accreting millisecond pulsar with prolific thermonuclear bursts, detected during its outburst in 2022 June by Insight-HXMT and NICER. During the outburst, Insight-HXMT detected 73 bursts in its peak and decay phase, serving as a prolific burst system found in the accreting millisecond pulsars. By analyzing one burst that was simultaneously detected by Insight-HXMT and NICER, we find a mild deviation from the conventional blackbody model. By stacking the Insight-HXMT light curves of 66 bursts that have similar profiles and intensities, a hard X-ray shortage is detected with a significance of 15.7σ in 30-100 keV. The shortage is about 30% of the persistent flux, which is low compared with other bursters. The shortage fraction is energy-dependent: larger in a higher energy band. These findings make the newly discovered millisecond MAXI J1816-195 a rather peculiar system compared with other millisecond pulsars and atoll bursters. In addition, based on the brightest burst, we derive an upper limit of the distance as 6.3 kpc, and therefore estimate the upper limit of the inner-disk radius of the accretion disk to be ~40 km. Assuming the radius as the magnetospheric radius, the derived magnetic field strength is about 7.1 × 108 G.

Keywords: x-ray bursters
HD 196390: A Tight Correlation of Differential Abundances with Condensation Temperature

Bedell et al. (2018) give precision differential abundances for 79 mostly G-dwarf stars. We correct these abundances for Galactic chemical evolution in a manner similar to that used by these authors but with parameters derived from linear fits to plots of [El/H] vs. age in lieu of [El/Fe]. We examine the resulting abundances for correlations with the 50% condensation temperature using values from both Lodders (2003) and Wood et al. (2019), and compare with the results of Bedell et al. HD 196390 is distinct in having the most significant correlation of the 79-star sample. We report statistics for a subset of stars with lower significance, but of some interest.

Keywords: stellar physics; stellar astronomy; solar physics; solar abundances
Two Homologous Quasi-periodic Fast-mode Propagating Wave Trains Induced by Two Small-scale Filament Eruptions

We present two homologous quasi-periodic fast-mode propagating (QFP) wave trains excited by two small-scale filament eruptions nearby a sunspot on 2017 September 12. By using observations from several ground-based and space-based instruments, it is found that the eruptions of two small-scale filaments resulted in some accompanying solar phenomena/activities (such as radio bursts, GOES C-class flares, coronal bright fronts, and QFP wave trains). The QFP wave trains run behind the main coronal bright fronts with a constant propagating speed of about 800 km s-1, while two main coronal bright fronts traveled away from the flare kernel obeying the power-law functions of $S(t)=894.9\ast {\left(t-7.43\right)}^{0.60}+76.8$ and S(t) = 705.3 ∗ (t - 19.12)0.47 + 57.5, respectively. The period of the first QFP wave train was estimated to be about 59 s, while the second QFP wave train has two periods of about 70 and 37 s. On the other hand, the intensity peaks of 94 and 335 Å passbands in the flare kernel exhibit some perturbations during the occurrences of the QFP wave trains. With the wavelet analysis and their synchronization, these perturbations and the QFP wave trains are tightly related phenomena, which suggests that they have a common exciting mechanism. Furthermore, we find that the emissions of the intensity peak mainly originate from the one footpoint of flare loops during the occurrence of the QFP wave trains. According to the above features, we conclude that the QFP wave trains are excited in the energy release process associated with magnetic reconnection and are closely related to the outflow of the magnetic reconnection.

Keywords: solar coronal waves; solar atmosphere; solar filament eruptions
Characterization of Thermal-infrared Dust Emission and Refinements to the Nucleus Properties of Centaur 29P/Schwassmann-Wachmann 1

We present analyses of Spitzer observations of 29P/Schwassmann-Wachmann 1 using 16 μm IRS "blue" peak-up (PU) and 24 and 70 μm MIPS images obtained on UT 2003 November 23 and 24 that characterize the Centaur's large-grain (10-100 μm) dust coma during a time of non-outbursting "quiescent" activity. Estimates of ϵfρ for each band (16 μm (2600 ± 43 cm), 24 μm (5800 ± 63 cm), and 70 μm (1800 ± 900 cm)) follow the trend between nucleus size versus ϵfρ that was observed for the WISE/NEOWISE comet ensemble. A coma model was used to derive a dust production rate in the range of 50-100 kg s-1. For the first time, a color temperature map of SW1's coma was constructed using the 16 and 24 μm imaging data. With peaks at ~140 K, this map implies that coma water-ice grains should be slowly sublimating and producing water gas in the coma. We analyzed the persistent 24 μm "wing" (a curved southwestern coma) feature at 352,000 km (90″) from the nucleus attributed by Stansberry et al. to nucleus rotation and instead propose that it is largely created by solar radiation pressure and gravity acting on micron-sized grains. We performed coma removal to the 16 μm PU image in order to refine the nucleus' emitted thermal flux. A new application of the Near Earth Asteroid Thermal Model at five wavelengths (5.730, 7.873, 15.80, 23.68, and 71.42 μm) was then used to refine SW1's effective radius measurement to R = 32.3 ± 3.1 km and infrared beaming parameter to η = 1.1 ± 0.2, respectively.

Keywords: comets; short period comets; comae; coma dust; infrared astronomy; infrared telescopes; dust continuum emission; centaur group
The Nearest Discovered Black Hole Is Likely Not in a Triple Configuration

HR 6819 was recently claimed to be a hierarchical triple system of a Be star in a wide orbit around an inner binary system of a black hole (BH) and a B III type star. We argue that this system is unlikely to be a hierarchical triple for three reasons. (I) Given that this system is discovered in a magnitude-limited Bright Star Catalog, the expected number of such systems in the Milky Way (MW) amounts to about 104, while the estimate for the MW budget for such systems is between 102 and 103 systems under generous assumptions. Such a large gap cannot be reconciled as it would otherwise likely overflow the MW budget for BHs. (II) The dynamical stability of this system sets lower bounds on the orbital separation of the outer Be star, while it not being resolved by Gaia places an upper limit on its projected sky separation. We show that these two constraints would imply a narrow range for the outer orbit without resorting to geometrical fine-tuning. (III) The triple system should have survived the stellar evolution prior to the formation of the BH in the inner binary. We perform numerical simulations starting with conservative initial conditions of this system and show that a small parameter space for BH progenitor star's mass loss, BH natal kicks, and initial orbital separation can reproduce HR 6819. Therefore, we propose this system is a chance superposition of a Be star with a binary.

Keywords: stellar dynamics; stellar evolutionary models; orbits; astrophysical black holes
Heliospheric Diffusion of Stochastic Parker Spirals in Radially Evolving Solar Wind Turbulence

We present a stochastic field line mapping model where the interplanetary magnetic field lines are described by a density distribution function satisfying a Fokker–Planck equation that is solved numerically. Due to the spiral geometry of the nominal Parker field and to the evolving nature of solar wind turbulence, the heliospheric diffusion of the magnetic field lines is both heterogeneous and anisotropic, including a radial component. The longitudinal distributions of the magnetic field lines are shown to be close to circular Gaussian distributions, although they develop a noticeable skewness. The magnetic field lines emanating from the Sun are found to differ, on average, from the spirals predicted by Parker. Although the spirals remain close to Archimedean, they are here underwound, on average. Our model predicts a spiral angle that is smaller by ∼5° than the Parker spiral angle at Earth's orbit for the same solar wind speed of V sw = 400 km s‑1. It also predicts an angular position on the solar disk of the best magnetically connected footpoint to an observer at 1 au that is shifted westward by ∼10° with respect to the Parker's field model. This significantly changes the angle of the most probable magnetic connection between possible sources on the Sun and observers in the inner heliosphere. The results have direct implications for the heliospheric transport of "scatter-free" electrons accelerated in the aftermath of solar eruptions.

Keywords: interplanetary turbulence; interplanetary magnetic fields
The Pan-STARRS Data-processing System

The Pan-STARRS data-processing system is responsible for the steps needed to downloaded, archive, and process all images obtained by the Pan-STARRS telescopes, including real-time detection of transient sources such as supernovae and moving objects including potentially hazardous asteroids. With a nightly data volume of up to 4 TB and an archive of over 4 PB of raw imagery, Pan-STARRS is solidly in the realm of Big Data astronomy. The full data-processing system consists of several subsystems covering the wide range of necessary capabilities. This article describes the Image Processing Pipeline and its connections to both the summit data systems and the outward-facing systems downstream. The latter include the Moving Object Processing System (MOPS) and the public database: the Published Science Products Subsystem.

Keywords: sky surveys; astronomy data analysis; astronomy databases; astronomy data reduction; photometry; astronomical techniques; astrometry
The Biermann Battery Driven by a Streaming Plasma

The Biermann battery is a promising generation mechanism of a seed magnetic field in the universe. We propose a new driving mechanism for the Biermann battery in an inhomogeneous plasma with a beam component. An inhomogeneous electron flow induced by the return current can make an electron pressure gradient that is not parallel to the density gradient. As a result, the magnetic field is generated by the Biermann battery. We demonstrate the new generation mechanism of the magnetic field by conducting three-fluid plasma simulations. By this mechanism, the first cosmic rays can generate the seed magnetic field with astrophysical scales at redshift around 20.

Keywords: cosmic magnetic fields theory; astrophysical magnetism; galaxy magnetic fields; magnetic fields; interplanetary magnetic fields; cosmic rays; plasma astrophysics; plasma physics
A Comparison of Properties of Quasars with and without Rapid Broad Absorption Line Variability

We investigate the correlation between rest-frame UV flux variability of broad absorption line (BAL) quasars and their variability in BAL equivalent widths (EWs) in a various timescale from <10 days to a few years in the quasar rest frame. We use the data sets of BAL EWs taken by the Sloan Digital Sky Survey Reverberation Mapping project and photometric data taken by the intermediate Palomar Transient Factory in the g and R bands and the Panoramic Survey Telescope and Rapid Response System in grizy bands. Our results are summarized as follows: (1) the distributions of flux variability versus BAL variability show weak, moderate, or a strong positive correlation; (2) there is no significant difference in flux variability amplitudes between BAL quasars with significant short timescale EW variability (called class S1) and without (class S2); (3) in all timescales considered in this paper, the class S1 quasars show systematically larger BAL variability amplitudes than those of the class S2 quasars; and (4) there are possible correlations between BAL variability and physical parameters of the quasars such as black hole masses (moderate positive), Eddington ratios, and accretion disk temperature (strong negative) in the class S2 quasars. These results indicate that the BAL variability requires changing in the ionizing continuum and an ancillary mechanism such as variability in X-ray shielding gas located at the innermost region of an accretion disk.

Keywords: high-luminosity active galactic nuclei; time domain astronomy; radio active galactic nuclei; active galactic nuclei