adsabs/SciX_UAT_keywords huggingface dataset:
Multistage Reconnection Powering a Solar Coronal Jet

Coronal jets are short-lived eruptive features commonly observed in polar coronal holes and are thought to play a key role in the transfer of mass and energy into the solar corona. We describe unique contemporaneous observations of a coronal blowout jet seen by the Extreme Ultraviolet Imager (EUI) on board the Solar Orbiter (SO) spacecraft and the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO). The coronal jet erupted from the south polar coronal hole, and was observed with high spatial and temporal resolution by both instruments. This enabled identification of the different stages of a breakout reconnection process producing the observed jet. We find bulk plasma flow kinematics of ~100-200 km s-1 across the lifetime of its observed propagation, with a distinct kink in the jet where it impacted and was subsequently guided by a nearby polar plume. We also identify a faint faster feature ahead of the bulk plasma motion propagating with a velocity of ~715 km s-1, which we attribute to untwisting of newly reconnected field lines during the eruption. A differential emission measure (DEM) analysis using the SDO/AIA observations revealed a very weak jet signal, indicating that the erupting material was likely much cooler than the coronal passbands used to derive the DEM. This is consistent with the very bright appearance of the jet in the Lyα passband observed by SO/EUI. The DEM was used to estimate the radiative thermal energy of the source region of the coronal jet, finding a value of ~2 × 1024 erg, comparable to the energy of a nanoflare.

Keywords: solar corona; solar coronal holes; solar filament eruptions; solar extreme ultraviolet emission
Evidence of Long-term Period Variations in the Exoplanet Transit Database (ETD)

We analyze a large number of citizen science data and identify eight hot Jupiter systems that show evidence for deviations from a constant orbital period: HAT-P-19 b, HAT-P-32 b, TrES-1 b, TrES-2 b, TrES-5 b, WASP-4 b, WASP-10 b, and WASP-12 b. The latter system is already well known to exhibit strong evidence for tidal orbital decay and serves as an important control for this study. Several other systems we identify have disputed period drifts in the literature, allowing the results here to serve as an independent analysis. The citizen science data are from the Exoplanet Transit Database (ETD), which is a global project established in 2008 by the Variable Star and Exoplanet Section of the Czech Astronomical Society. With over 400 planets and 12,000 contributed observations spanning 15 yr, the ETD is brimming with potential for studying the long-term orbital evolution of close-in hot Jupiters. We use our results to discuss prioritization of targets for follow-up investigations, which will be necessary to confirm the period drifts and their causes.

Keywords: exoplanets; exoplanet dynamics; transit timing variation method
6.7 GHz CH3OH Absorption toward the N3 Galactic Center Point Source

We present evidence of 6.7 GHz methanol (CH3OH) and 4.8 GHz formaldehyde (H2CO) absorption toward the Galactic Center (GC) point source "N3." Both absorption features are unresolved and spatially aligned with N3. The 6.7 GHz CH3OH contains a single-velocity component (centered at ∼10 km s-1), while the 4.8 GHz H2CO shows two-velocity components (centered at ∼-3 and +8 km s-1). We find that the velocities of these absorption components are similar to that of emission lines from other molecules (e.g., SiO and HC3N) detected toward this compact source (-13 to +25 km s-1; "N3 cloud"). The detection of these absorption features is a firm indication that some of the molecular gas in the N3 molecular cloud is on the near side of the continuum source. Analysis of the CH3OH absorption kinematics shows a relatively large velocity dispersion (3.8 km s-1) for the size scale of this feature (<0"1, <0.01 pc at the GC), when compared with other similarly sized GC clouds in the Larson line width-size relationship. Furthermore, this line width is closer to velocity dispersion measurements for size scales of 1.3 pc, which is roughly the width of the N3 cloud (25″; 1.0 pc). We argue that this relatively broad line width, over a small cross-sectional area, is due to turbulence through the depth of the cloud, where the cloud has a presumed line-of-sight thickness of ∼1 pc.

Keywords: galactic center; interstellar clouds; molecular gas
Jet Collimation and Acceleration in the Giant Radio Galaxy NGC 315

We study the collimation and acceleration of jets in the nearby giant radio galaxy NGC 315, using multifrequency Very Long Baseline Array observations and archival High Sensitivity Array and Very Large Array data. We find that the jet geometry transitions from a semi-parabolic shape into a conical/hyperbolic shape at a distance of ≈105 gravitational radii. We constrain the frequency-dependent position of the core, from which we locate the jet base. The jet collimation profile in the parabolic region is in good agreement with the steady axisymmetric force-free electrodynamic solution for the outermost poloidal magnetic field line anchored to the black hole event horizon on the equatorial plane, similar to the nearby radio galaxies M87 and NGC 6251. The velocity field derived from the asymmetry in brightness between the jet and counterjet shows gradual acceleration up to the bulk Lorentz factor of Γ ∼ 3 in the region where the jet collimation occurs, confirming the presence of the jet acceleration and collimation zone. These results suggest that the jets are collimated by the pressure of the surrounding medium and accelerated by converting Poynting flux to kinetic energy flux. We discover limb brightening of the jet in a limited distance range where the angular resolution of our data is sufficient to resolve the jet transverse structure. This indicates that either the jet has a stratified velocity field of fast-inner and slow-outer layers or the particle acceleration process is more efficient in the outer layer owing to the interaction with the surroundings on parsec scales.

Keywords: active galactic nuclei; radio galaxies; relativistic jets; very long baseline interferometry; magnetic fields; accretion
Arecibo Investigations of Pulsar B0823+26. I. Plasma Source Changes Configure Its Bright and Quiet Modes

The recently discovered 100X weaker quiescent (Q) mode in pulsar B0823+26 is X-ray quiet, unlike its usual bright (B) mode. Arecibo polarimetric observations were conducted to confirm the pulsar's orthogonal geometry and investigate the emission associated with its main pulse (MP), interpulse (IP), and postcursor (PC) components. Main results: (1) the pulsar's MP, PC, and IP are present in both modes and exhibit a two-pole orthogonal geometry. (2) The B-mode MP is dominated by core emission with weak conal outriders, whereas, the Q-mode double profile shows mainly residual conal emission with little core. The IP is conal in both modes. (3) Sporadic intrapulse emission trailing the PC is detected in the Q mode. (4) B0823+26 falls close to an $\dot{E}$ boundary of 1032.5 erg s-1 (or B12/P2 ∼ 2.5) between core- and conal-dominated profiles—which also represents a boundary between pair-plasma source configurations above the polar cap. For larger energies, the pair-formation front is central, flat, and generates backflow heating, whereas for smaller energies it is peripheral, lower, and produces little heating. (5) Apparently, the pulsar is able to assume both core- and conal-dominated "states" corresponding to its bright and weak modes. These circumstances appear to explain B0823+26's B-mode X-ray bright/core-dominated radio emission or Q-mode X-ray faint/conal radio emission—and why the IP is X-ray quiet in both modes. (6) These same considerations applied to B0943+10 may explain why its brighter radio mode was conal and X-ray quiet, while the weaker one was X-ray bright—because its peripheral sightline would miss most core radiation.

Keywords: pulsars; polarimetry; non-thermal radiation sources; proper motions
Photometric Recalibration of the SDSS Stripe 82 to a Few Millimagnitude Precision with the Stellar Color Regression Method and Gaia EDR3

By combining spectroscopic data from the LAMOST DR7, Sloan Digital Sky Survey (SDSS) DR12, and corrected photometric data from the Gaia EDR3, we apply the stellar color regression (SCR) method to recalibrate the SDSS Stripe 82 standard stars catalog of Ivezić et al. With a total number of about 30,000 spectroscopically targeted stars, we have mapped out the relatively large and strongly correlated photometric zero-point errors present in the catalog, ~2.5% in the u band and ~1% in the griz bands. Our study also confirms some small but significant magnitude dependence errors in the z band for some charge-coupled devices. Various tests show that we have achieved an internal precision of about 5 mmag in the u band and about 2 mmag in the griz bands, which is about five times better than previous results. We also apply the method to the latest version of the catalog (v4.2), and find modest systematic calibration errors of up to ~1% along the R.A. direction and smaller errors along the decl. direction. The results demonstrate the power of the SCR method when combining spectroscopic data and Gaia photometry in breaking the 1% precision barrier of ground-based photometric surveys. Our work paves the way for the recalibration of the whole SDSS photometric survey and has important implications for the calibration of future surveys. Future implementations and improvements of the SCR method under different situations are also discussed.

Keywords: flux calibration; calibration; stellar photometry; extinction
NEOWISE Observations of Distant Active Long-period Comets C/2014 B1 (Schwartz), C/2017 K2 (Pan-STARRS), and C/2010 U3 (Boattini)

Hyperactive comet activity typically becomes evident beyond the frost line (∼3–4 au) where it becomes too cold for water-ice to sublimate. If carbon monoxide (CO) and carbon dioxide (CO2) are the species that drive activity at sufficiently large distances, then detailed studies on the production rates of these species are extremely valuable to examine the formation of the solar system because these two species (beyond water) are next culpable for driving cometary activity. The NEOWISE reactivated mission operates at two imaging bandpasses, W1 and W2 at 3.4 μm and 4.6 μm, respectively, with the W2 channel being fully capable of detecting CO and CO2 at 4.67 μm and 4.23 μm in the same bandpass. It is extremely difficult to study CO2 from the ground due to contamination in Earth's atmosphere. We present our W1 and W2 photometry, dust measurements, and findings for comets C/2014 B1 (Schwartz), C/2017 K2 (Pan-STARRS), and C/2010 U3 (Boattini), hereafter, B1, K2, and U3, respectively. Our results assess CO and CO2 gas production rates observed by NEOWISE. We have determined: (1) comets B1 and K2 have CO2 and CO gas production rates of ∼1027 and ∼1029 molecules s‑1, respectively, if one assumes the excess emission is attributed to either all CO or all CO2; (2) B1 and K2 are considered hyperactive in that their measured Af ρ dust production values are on the order of ≳103 cm; and (3) the CO and CO2 production rates do not always follow the expected convention of increasing with decreased heliocentric distance, while B1 and K2 exhibit noticeable dust activity on their inbound leg orbits.

Keywords: long period comets; infrared astronomy; photometry; astronomy data analysis; comet volatiles
SN 2016ije: An SN 2002es-like Type Ia Supernova Exploded in a Metal-poor and Low-surface Brightness Galaxy

We have conducted photometric and spectroscopic observations of the peculiar Type Ia supernova (SN Ia) 2016ije that was discovered through the Tsinghua-NAOC Transient Survey. This peculiar object exploded in the outskirts of a metal-poor, low-surface brightness galaxy (i.e., M g = -14.5 mag). Our photometric analysis reveals that SN 2016ije is subluminous ( ${M}_{B,\max }$ = -17.65 ± 0.06 mag) but exhibits relatively broad light curves (Δm 15(B) = 1.35 ± 0.14 mag), similar to the behavior of SN 2002es. Our analysis of the bolometric light curve indicates that only 0.14 ± 0.04 M ⊙ of 56Ni was synthesized in the explosion of SN 2016ije, which suggests a less energetic thermonuclear explosion when compared to normal SNe Ia, and this left a considerable amount of unburned materials in the ejecta. Spectroscopically, SN 2016ije resembles other SN 2002es-like SNe Ia, except that the ejecta velocity inferred from its carbon absorption line (~4500 km s-1) is much lower than that from silicon lines (~8300 km s-1) at around the maximum light. Additionally, most of the absorption lines are broader than other 02es-like SNe Ia. These peculiarities suggest the presence of significant unburned carbon in the inner region and a wide line-forming region along the line of sight. These characteristics suggest that SN 2016ije might originate from the violent merger of a white dwarf binary system, when viewed near an orientation along the iron-group-element cavity caused by the companion star.

Keywords: supernovae; type ia supernovae
Detection of Vibrational Emissions from the Helium Hydride Ion (HeH+) in the Planetary Nebula NGC 7027

We report the detection of emission in the V = 1 - 0 P(1) (3.51629 μm) and P(2) (3.60776 μm) rovibrational lines of the helium hydride cation (HeH+) from the planetary nebula NGC 7027. These detections were obtained with the iSHELL spectrograph on NASA's Infrared Telescope Facility on Maunakea. They confirm the discovery of HeH+ reported recently by Güsten et al., who used the GREAT instrument on the SOFIA airborne observatory to observe its pure rotational J = 1 - 0 transition at 149.137 μm. The flux measured for the HeH+ V = 1 - 0 P(1) line is in good agreement with our model for the formation, destruction, and excitation of HeH+ in NGC 7027. The measured strength of the J = 1 - 0 pure rotational line, however, exceeds the model prediction significantly, as does that of the V = 1 - 0 P(2) line, by factors of 2.9 and 2.3 respectively. Possible causes of these discrepancies are discussed. Our observations of NGC 7027, covering the 3.26-3.93 μm spectral region, have led to the detection of more than 60 spectral lines including nine rovibrational emissions from CH+. The latter are detected for the first time in an astronomical source.

Keywords: interstellar medium; interstellar molecules; planetary nebulae; molecular physics; astrochemistry; interstellar emissions; infrared astronomy
TESS Hunt for Young and Maturing Exoplanets (THYME). III. A Two-planet System in the 400 Myr Ursa Major Group

Exoplanets can evolve significantly between birth and maturity, as their atmospheres, orbits, and structures are shaped by their environment. Young planets (<1 Gyr) offer an opportunity to probe the critical early stages of this evolution, where planets evolve the fastest. However, most of the known young planets orbit prohibitively faint stars. We present the discovery of two planets transiting HD 63433 (TOI 1726, TIC 130181866), a young Sun-like ( ${M}_{* }=0.99\pm 0.03$ ) star. Through kinematics, lithium abundance, and rotation, we confirm that HD 63433 is a member of the Ursa Major moving group (τ = 414 ± 23 Myr). Based on the TESS light curve and updated stellar parameters, we estimate that the planet radii are 2.15 ± 0.10 R⊕ and 2.67 ± 0.12 R⊕, the orbital periods are 7.11 and 20.55 days, and the orbital eccentricities are lower than about 0.2. Using High Accuracy Radial velocity Planet Searcher for the Northern hemisphere velocities, we measure the Rossiter-McLaughlin signal of the inner planet, demonstrating that the orbit is prograde. Since the host star is bright (V = 6.9), both planets are amenable to transmission spectroscopy, radial velocity measurements of their masses, and more precise determination of the stellar obliquity. This system is therefore poised to play an important role in our understanding of planetary system evolution in the first billion years after formation.

Keywords: young star clusters; exoplanet evolution; transits; exoplanet astronomy; stellar activity; stellar rotation; exoplanet dynamics
Mass Transfer as an Explanation for the Lifetime Travel Time Discrepancy in IT Librae

The eclipsing binary IT Librae is an unusual system of two B-type stars that is situated about 1 kpc above the Galactic plane. The binary was probably ejected from its birthplace in the disk, but the implied time of flight to its current location exceeds the evolutionary lifetime of the primary star. Here we present a study of new high-dispersion spectroscopy and an exquisite light curve from the Kepler K2 mission in order to determine the system properties and resolve the timescale discrepancy. We derive a revised spectroscopic orbit from radial-velocity measurements and determine the component effective temperatures through comparison of reconstructed and model spectra (T 1 = 23.8 ± 1.8 kK, T 2 = 13.7 ± 2.5 kK). We use the Eclipsing Light Curve code to model the K2 light curve, and from the inclination of the fit we derive the component masses (M 1 = 9.6 ± 0.6 M ⊙, M 2 = 4.2 ± 0.2 M ⊙) and mean radii (R 1 = 6.06 ± 0.16 R ⊙, R 2 = 5.38 ± 0.14 R ⊙). The secondary star is overluminous for its mass and appears to fill its Roche lobe. This indicates that IT Librae is a post-mass-transfer system in which the current secondary was the mass donor star. The current primary star was rejuvenated by mass accretion, and its evolutionary age corresponds to the time since the mass transfer stage. Consequently, the true age of the binary is larger than the ejection time of flight, thus resolving the timescale discrepancy.

Keywords: binary stars; high latitude field; b stars; eclipsing binary stars
Bridging the Gap between Intermediate and Massive Stars. I. Validation of MESA against the State-of-the-Art Monash Stellar Evolution Program for a 2M ⊙ AGB Star

One-dimensional stellar structure and evolution programs are built using different physical prescriptions and algorithms, which means there can be variations between models' predictions even when using identical input physics. This leads to questions about whether such deviations are physical or numerical; code validation studies are important and necessary tools for studying these questions. We provide the first direct comparison between the Monash stellar evolution program and MESA for a 2M ⊙ model evolved from the zero-age main sequence to the tip of the thermally pulsing asymptotic giant branch. We compare the internal structure of the two models at six critical evolutionary points and find that they are in excellent agreement with regard to characteristics like central temperature, central density, and the temperature at the base of the convective envelope during the thermally pulsing asymptotic giant branch. The H-exhausted core mass between the models differs by less than 4.2% throughout the entire evolution; the final values vary only by 1.5%. Surface quantities such as luminosity and radius vary by less than 0.2% prior to the asymptotic giant branch. During thermal pulses, the difference extends to 3.4%, largely due to uncertainties in mixing and the treatment of atmospheric boundary conditions. Given that the veteran Monash code is closed-source, the present work provides the first fully open-source computational analog. This increases accessibility to precision modeling on the asymptotic giant branch and lays the groundwork for higher-mass calculations that are performed with MESA but preserve the standards of the Monash code during the asymptotic giant branch.

Keywords: stellar evolution; stellar evolutionary models; asymptotic giant branch stars
Searching for Quasi-periodic Oscillations in Astrophysical Transients Using Gaussian Processes

Analyses of quasi-periodic oscillations (QPOs) are important to understanding the dynamic behavior in many astrophysical objects during transient events like gamma-ray bursts, solar flares, magnetar flares, and fast radio bursts. Astrophysicists often search for QPOs with frequency-domain methods such as (Lomb-Scargle) periodograms, which generally assume power-law models plus some excess around the QPO frequency. Time-series data can alternatively be investigated directly in the time domain using Gaussian process (GP) regression. While GP regression is computationally expensive in the general case, the properties of astrophysical data and models allow fast likelihood strategies. Heteroscedasticity and nonstationarity in data have been shown to cause bias in periodogram-based analyses. GPs can take account of these properties. Using GPs, we model QPOs as a stochastic process on top of a deterministic flare shape. Using Bayesian inference, we demonstrate how to infer GP hyperparameters and assign them physical meaning, such as the QPO frequency. We also perform model selection between QPOs and alternative models such as red noise and show that this can be used to reliably find QPOs. This method is easily applicable to a variety of different astrophysical data sets. We demonstrate the use of this method on a range of short transients: a gamma-ray burst, a magnetar flare, a magnetar giant flare, and simulated solar flare data.

Keywords: astrostatistics; bayesian statistics; astrostatistics techniques; model selection; x-ray transient sources; gamma-ray transient sources; magnetars; solar flares; gamma-ray bursts; time series analysis
Deep Synoptic Array Science: Discovery of the Host Galaxy of FRB 20220912A

We report the detection and interferometric localization of the repeating fast radio burst (FRB) source FRB 20220912A during commissioning observations with the Deep Synoptic Array (DSA-110). Two bursts were detected from FRB 20220912A, one each on 2022 October 18 and 2022 October 25. The best-fit position is (R.A. J2000, decl. J2000) = (23:09:04.9, +48:42:25.4), with a 90% confidence error ellipse with radii ±2″ and ±1″ in R.A. and decl., respectively. The two bursts are polarized, and we find a Faraday rotation measure that is consistent with the low value of +0.6 rad m-2 reported by CHIME/FRB. The DSA-110 localization overlaps with the galaxy PSO J347.2702+48.7066 at a redshift z = 0.0771, which we identify as the likely host. PSO J347.2702+48.7066 has a stellar mass of approximately 1010 M ⊙, modest internal dust extinction, and a star formation rate likely in excess of 0.1 M ⊙ yr-1. The host-galaxy contribution to the dispersion measure is likely ≲50 pc cm-3. The FRB 20220912A source is therefore likely viewed along a tenuous plasma column through the host galaxy.

Keywords: compact objects; radio interferometry; radio telescopes; radio transient sources
One-dimensional General Relativistic Particle-in-cell Simulations of Stellar-mass Black Hole Magnetospheres: A Semianalytic Model of Gamma-Rays from Gaps

In the absence of a sufficient amount of plasma injection into the black hole (BH) magnetosphere, the force-free state of the magnetosphere cannot be maintained, leading to the emergence of strong, time-dependent, longitudinal electric fields (i.e., spark gaps). Recent studies of supermassive BH magnetospheres using analytical methods and particle-in-cell (PIC) simulations propose the possibility of efficient particle acceleration and consequent gamma-ray emission in the spark gap. In this work, we perform 1D general relativistic PIC simulations to examine the gamma-ray emission from stellar-mass BH magnetospheres. We find that intermittent spark gaps emerge and particles are efficiently accelerated in a similar manner to the supermassive BH case. We build a semianalytic model of the plasma dynamics and radiative processes, which reproduces the maximum electron energies and peak gamma-ray luminosities of the simulation results. Based on this model, we show that the gamma-ray signals from stellar-mass BHs wandering through the interstellar medium could be detected by gamma-ray telescopes such as the Fermi Large Area Telescope or the Cherenkov Telescope Array.

Keywords: black holes; accretion; gamma-ray sources; plasma astrophysics