adsabs/SciX_UAT_keywords huggingface dataset:
Recovering Lost Light: Discovery of Supernova Remnants with Integral Field Spectroscopy

We present results from a systematic search for broad (≥ 400 km s‑1) Hα emission in integral field spectroscopy data cubes of ∼1200 nearby galaxies obtained with PMAS and MUSE. We found 19 unique regions that pass our quality cuts, four of which match the locations of previously discovered supernovae (SNe): one Type IIP and three Type IIn, including the well-known SN 2005ip. We suggest that these objects are young Supernova remnants (SNRs), with bright and broad Hα emission powered by the interaction between the SN ejecta and dense circumstellar material. The stellar ages measured at the locations of these SNR candidates are systematically lower by about 0.5 dex than those measured at the locations of core-collapse (CC) SNe, implying that their progenitors might be shorter lived and therefore more massive than a typical CCSN progenitor. The methods laid out in this work open a new window into the study of nearby SNe with integral field spectroscopy.

Keywords: supernova remnants; stellar feedback; interstellar medium; galaxies; core-collapse supernovae
Observation of Two Splitting Processes in a Partial Filament Eruption on the Sun: The Role of Breakout Reconnection

Partial filament eruptions have often been observed; however, the physical mechanisms that lead to filament splitting are not yet fully understood. In this study, we present a unique event of a partial filament eruption that undergoes two distinct splitting processes. The first process involves vertical splitting and is accompanied by brightenings inside the filament, which may result from internal magnetic reconnection within the filament. Following the first splitting process, the filament is separated into an upper part and a lower part. Subsequently, the upper part undergoes a second splitting, which is accompanied by a coronal blowout jet. An extrapolation of the coronal magnetic field reveals a hyperbolic flux tube structure above the filament, indicating the occurrence of breakout reconnection that reduces the constraining field above. Consequently, the filament is lifted up, but at a nonuniform speed. The high-speed part reaches the breakout current sheet to generate the blowout jet, while the low-speed part falls back to the solar surface, resulting in the second splitting. In addition, continuous brightenings are observed along the flare ribbons, suggesting the occurrence of a slipping reconnection process. This study presents, for the first time, the unambiguous observation of a two-stage filament-splitting process, advancing our understanding of the complex dynamics of solar eruptions.

Keywords: solar magnetic reconnection; solar flares; jets
Magnetic Fields in Low-mass Stars Increase Photometric Masses, Thereby Reducing Inferred Radius Inflation

Standard evolution models of a given age provide a relationship between stellar mass and T eff. Based on this, Cruz et al. have derived stellar masses and radii for a sample of Kepler stars using photometry alone: their radii are found to be inflated by up to 100% relative to standard models. However, magnetic fields distort the M-T eff relationship in a systematic way: here, we quantify this distortion, and show that radius inflations in the Cruz et al. stars are likely to be significantly smaller than 100%.

Keywords: stellar magnetic fields; stellar radii; starspots
The RR Lyrae Delay-time Distribution: A Novel Perspective on Models of Old Stellar Populations

The delay-time distribution (DTD) is the occurrence rate of a class of objects as a function of time after a hypothetical burst of star formation. DTDs are mainly used as a statistical test of stellar evolution scenarios for supernova progenitors, but they can be applied to many other classes of astronomical objects. We calculate the first DTD for RR Lyrae variables using 29,810 RR Lyrae from the OGLE-IV survey and a map of the stellar age distribution (SAD) in the Large Magellanic Cloud (LMC). We find that ∼46% of the OGLE-IV RR Lyrae are associated with delay times greater than 8 Gyr (main-sequence progenitor masses less than 1 M⊙), and consistent with existing constraints on their ages, but surprisingly about 51% of RR Lyrae appear to have delay times of 1.2-8 Gyr (main-sequence masses between 1 and 2 M⊙ at LMC metallicity). This intermediate-age signal also persists outside the Bar region, where crowding is less of a concern, and we verified that without this signal the spatial distribution of the OGLE-IV RR Lyrae is inconsistent with the SAD map of the LMC. Since an intermediate-age RR Lyrae channel is in tension with the lack of RR Lyrae in intermediate-age clusters (noting issues with small-number statistics), and noting the age-metallicity constraints on LMC stars, our DTD result possibly indicates that systematic uncertainties may still exist in SAD measurements of old stellar populations, perhaps stemming from the construction methodology or the stellar evolution models used. We describe tests to further investigate this issue.

Keywords: rr lyrae variable stars; large magellanic cloud; stellar populations; stellar evolution; stellar evolutionary models; horizontal branch; stellar ages; stellar pulsations; hertzsprung russell diagram
White-light Emission and Chromospheric Response by an X1.8-class Flare on 2012 October 23

On 2012 October 23, a strong white-light emission, associated with an X1.8-class flare, was observed by the Solar Optical Telescope on board the Hinode satellite. White-light kernels were clearly observed along the Ca II H ribbons. RHESSI also observed hard X-ray emissions that were almost located on the white-light kernels. The total energy of the white-light emission was ∼ 1027-28 erg, s-1 and the total energy of the accelerated electrons was almost of the same order when we used 40 keV as the lower energy cutoff. The white-light emission appears to have originated from nonthermal electrons in these energies. Moreover, the EUV imaging spectrometer on board the Hinode satellite performed a raster scan over this flaring active region and the flare occurred during the scan. Over the white-light kernels, we observed redshifts of a few tens of km s-1 in Fe XII. It appears that these EUV responses originated from some accelerated electrons due to the solar flare and they are considered to be the source of the white-light emission. In fact, the electron density of the white-light kernels was less than 1012 cm-3, which is sufficiently low for nonthermal electrons to penetrate into the photosphere.

Keywords: solar chromosphere; solar white-light flares; solar ultraviolet emission
The Effects of Oscillations and Collisions of Emerging Bipolar Regions on the Triggering of Solar Flares

The ability to predict the occurrence of solar flares in advance is important to humankind due to the potential damage they can cause to Earth's environment and infrastructure. It has been shown in Kusano et al. that a small-scale bipolar region (BR), with its flux reversed relative to the potential component of the overlying field, appearing near the polarity inversion line (PIL) is sufficient to effectively trigger a solar flare. In this study we perform further 3D magnetohydrodynamic simulations to study the effect that the motion of these small-scale BRs has on the effectiveness of flare triggering. The effect of two small-scale BRs colliding is also simulated. The results indicate that the strength of the triggered flare is dependent on how much of the overlying field is disrupted by the BR. Simulations of linear oscillations of the BR showed that oscillations along the PIL increase the flare strength while oscillations across the PIL detract from the flare strength. The flare strength is affected more by larger amplitude oscillations but is relatively insensitive to the frequency of oscillations. In the most extreme case the peak kinetic energy of the flare increased more than threefold compared to a non-oscillating BR. Simulations of torsional oscillations of the BR showed a very small effect on the flare strength. Finally, simulations of colliding BRs showed the generation of much stronger flares as the flares triggered by each individual BR coalesce. These results show that significantly stronger flares can result from motion of the BR along the PIL of a sheared field or from the presence of multiple BRs in the same region.

Keywords: active solar corona; solar flares; magnetohydrodynamical simulations
The Role of Inhomogeneities in Supernova Shock Breakout Emission

The breakout of a supernova blast wave from its progenitor star provides strong constraints on the star and its immediate surroundings. These surroundings are shaped by mass loss from the star and can include a wide variety of inhomogeneities. Here we present results of multidimensional radiation-hydrodynamics calculations of the interactions of the supernova blast wave with inhomogeneities in the immediate surroundings of a massive Wolf-Rayet star, calculating the effect these interactions have on the shock breakout signal from supernovae.

Keywords: supernovae; stellar dynamics; transient sources; x-ray sources
Breaking Giant Chains: Early-stage Instabilities in Long-period Giant Planet Systems

Orbital evolution is a critical process that sculpts planetary systems, particularly during their early stages where planet–disk interactions are expected to lead to the formation of resonant chains. Despite the theoretically expected prominence of such configurations, they are scarcely observed among long-period giant exoplanets. This disparity suggests an evolutionary sequence wherein giant planet systems originate in compact multiresonant configurations, but subsequently become unstable, eventually relaxing to wider orbits—a phenomenon mirrored in our own solar system's early history. In this work, we present a suite of N-body simulations that model the instability-driven evolution of giant planet systems, originating from resonant initial conditions, through phases of disk dispersal and beyond. By comparing the period ratio and normalized angular momentum distributions of our synthetic aggregate of systems with the observational census of long-period Jovian planets, we derive constraints on the expected rate of orbital migration, the efficiency of gas-driven eccentricity damping, and typical initial multiplicity. Our findings reveal a distinct inclination toward densely packed initial conditions, weak damping, and high giant planet multiplicities. Furthermore, our models indicate that resonant chain origins do not facilitate the formation of Hot Jupiters via the coplanar high-eccentricity pathway at rates high enough to explain their observed prevalence.

Keywords: exoplanet dynamics; exoplanet astronomy; exoplanet migration; exoplanet formation; dynamical evolution; planetary dynamics; planetary science
Proposed Host Galaxies of Repeating Fast Radio Burst Sources Detected by CHIME/FRB

We present a search for host galaxy associations for the third set of repeating fast radio burst (FRB) sources discovered by the CHIME/FRB Collaboration. Using the ~1' CHIME/FRB baseband localizations and probabilistic methods, we identify potential host galaxies of two FRBs, 20200223B and 20190110C at redshifts of 0.06024(2) and 0.12244(6), respectively. We also discuss the properties of a third marginal candidate host galaxy association for FRB 20191106C with a host redshift of 0.10775(1). The three putative host galaxies are all relatively massive, fall on the standard mass-metallicity relationship for nearby galaxies, and show evidence of ongoing star formation. They also all show signatures of being in a transitional regime, falling in the green valley, which is between the bulk of star-forming and quiescent galaxies. The plausible host galaxies identified by our analysis are consistent with the overall population of repeating and nonrepeating FRB hosts while increasing the fraction of massive and bright galaxies. Coupled with these previous host associations, we identify a possible excess of FRB repeaters whose host galaxies have M u - M r colors redder than the bulk of star-forming galaxies. Additional precise localizations are required to confirm this trend.

Keywords: radio transient sources; radio bursts
Coronal Magnetic Field Extrapolation and Topological Analysis of Fine-scale Structures during Solar Flare Precursors

Magnetic field plays an important role in various solar eruption phenomena. The formation and evolution of the characteristic magnetic field topology in solar eruptions are critical problems that will ultimately help us understand the origin of these eruptions in the solar source regions. With the development of advanced techniques and instruments, observations with higher resolutions in different wavelengths and fields of view have provided more quantitative information for finer structures. It is therefore essential to improve the method with which we study the magnetic field topology in the solar source regions by taking advantage of high-resolution observations. In this study, we employ a nonlinear force-free field extrapolation method based on a nonuniform grid setting for an M-class flare eruption event (SOL2015-06-22T17:39) with embedded vector magnetograms from the Solar Dynamics Observatory (SDO) and the Goode Solar Telescope (GST). The extrapolation results for which the nonuniform embedded magnetogram for the bottom boundary was employed are obtained by maintaining the native resolutions of the corresponding GST and SDO magnetograms. We compare the field line connectivity with the simultaneous GST/Hα and SDO/Atmospheric Imaging Assembly observations for these fine-scale structures, which are associated with precursor brightenings. Then we perform a topological analysis of the field line connectivity corresponding to fine-scale magnetic field structures based on the extrapolation results. The analysis results indicate that when we combine the high-resolution GST magnetogram with a larger magnetogram from the SDO, the derived magnetic field topology is consistent with a scenario of magnetic reconnection among sheared field lines across the main polarity inversion line during solar flare precursors.

Keywords: solar flares; solar active region magnetic fields; solar magnetic fields
Asteroseismic Determination of Stellar Rotation: On Synchronization in the Close Eclipsing Binaries AB Cas and OO Dra

A star's rotation rate is difficult to estimate without surface inhomogeneities such as dark or bright spots. This paper presents asteroseismic results to determine the rotation rates of δ Sct-type pulsating primary stars in two eclipsing binary systems, AB Cas and OO Dra. After removing the binarity-induced light variations from archival TESS data and carefully examining the combination frequencies, we identified 12 independent frequencies for AB Cas and 11 frequencies for OO Dra, with amplitudes higher than ~0.3 mmag, as δ Sct-type pulsation frequencies excited in each primary star. The theoretical frequencies for seismic analysis were obtained by fully considering rotation effects. Grid fitting for various stellar properties, such as mass, radius, metallicity, and rotation rate, yielded the best solutions for which the theoretical frequencies and stellar parameters agreed well with the observations. The rotation rate of the AB Cas primary was tightly constrained to 0.81 ± 0.01 day-1 (f rot/f orb = ${1.11}_{-0.02}^{+0.01}$ ), which is slightly faster than the synchronized rotation. In contrast, the rotation rate of 0.63 ± 0.01 day-1 for the OO Dra primary is lower than the synchronous value of approximately 0.81 day-1. Subsynchronous rotation is uncommon in short-period binaries, and its physical mechanism is not yet well understood. Our results show that asteroseismology can be used to measure the rotation rate of fast-rotating δ Sct stars precisely and thus provide a valuable constraint on rotation-orbit synchronization in close binary systems.

Keywords: asteroseismology; stellar rotation; delta scuti variable stars; eclipsing binary stars
Light Element Abundances and Multiple Populations in M53

We present results from a study of 94 red giant stars in the globular cluster M53. We use low-resolution spectra to measure the strength of CN and CH features at ∼3800 and 4300 Å, respectively. The strengths of these features are used to classify stars into a CN-enhanced and CN-normal population and to measure C and N abundances in all 94 stars. We find the red giant branch stars to be evenly split between the two populations identified, and observe the presence of CN-enhanced stars on the asymptotic giant branch. In addition, we identify five CH star candidates based on the strength of their CN and CH band features, and the presence of a P-branch in their CH band. We compare our identification of multiple populations to those based on the Na-O anticorrelation and pseudo-color indices in Hubble Space Telescope UV photometry, and find general agreement between all three methods. Our large sample size also allows us to study the radial distribution of each population, and we find that the CN-enhanced population is more centrally concentrated. We use our C and N measurements to compare the evolutionary changes in these elements as a function of magnitude between the two populations, and show that both populations experience similar evolutionary changes to the surface abundances of C and N. Finally, we calculate C+N+O abundances for each population and compare them to similar measurements made in M10; we find that in both clusters, CN-enhanced stars have a slightly enhanced C+N+O (Δ(C+N+O) ∼ 0.2 dex).

Keywords: globular star clusters; stellar evolution; stellar abundances
Desaturated EUV Flare Ribbons in an X-class Flare

This paper studies the energy dissipation of nonthermal electrons in the chromospheric flare ribbons during the peak time of a Geostationary Operational Environmental Satellite X-class flare (SOL2011-09-06) using desaturated Solar Dynamics Observatory/Atmospheric Imaging Assembly extreme-ultraviolet (EUV) narrow-band images. The temperature distribution in emission measure, called the differential emission measure (DEM), derived from the EUV fluxes from the flare ribbons shows an increase in the emission measure up to a temperature around 9 × 106 K, followed by a steep decline at higher temperatures. In contrast, the flare loop reaches temperatures up to 27 × 106 K. This result is in agreement with previously reported single-temperature measurements using soft X-ray filter images, as well as DEM distributions reported for smaller flares obtained from EUV line observations. The main difference between small and large flares appears to be an increased emission measure in the flare ribbons, while the ribbon peak temperature is similar for all flares. This is different from the flare loop temperatures, where the hottest temperatures occur in the largest flares. However, the physically relevant quantity for energy dissipation, the energy content of the heated plasma as a function of temperature, does not need to peak at the same temperature as the DEM. The poorly constrained source thickness in radial extent of the flare ribbons has a significant impact on the shape of the differential thermal energy distribution. In particular, if the highest temperatures occur over a wide radial extent as "evaporating" plasma starts expending, the largest amount of energy could potentially be hidden above the peak temperature of the DEM.

Keywords: solar flares; solar x-ray flares; solar extreme ultraviolet emission
From Supernova to Supernova Remnant: Comparison of Thermonuclear Explosion Models

Progress in the three-dimensional modeling of supernovae (SNe) prompts us to revisit the supernova remnant (SNR) phase. We continue our study of the imprint of a thermonuclear explosion on the SNR it produces, which we started with a delayed detonation model of a Chandrasekhar-mass white dwarf. Here we compare two different types of explosion models, each with two variants: two delayed detonation models (N100ddt, N5ddt) and two pure deflagration models (N100def, N5def), where the N number parameterizes the ignition. The output of each SN simulation is used as input to an SNR simulation carried on until 500 yr after the explosion. While all SNR models become more spherical over time and overall display the theoretical structure expected for a young SNR, clear differences are visible among the models, depending on the geometry of the ignition and on the presence or not of detonation fronts. Compared to N100 models, N5 models have a strong dipole component and produce asymmetric remnants. N5def produces a regular-looking, but offset remnant, while N5ddt produces a two-sided remnant. Pure deflagration models exhibit specific traits: a central overdensity, because of the incomplete explosion, and a network of seam lines across the surface, boundaries between burning cells. Signatures from the SN dominate the morphology of the SNR up to 100-300 yr after the explosion, depending on the model, and are still measurable at 500 yr, which may provide a way of testing explosion models.

Keywords: supernovae; type ia supernovae; supernova remnants
Quantitative Evaluation of Coronal Magnetic Field Models Using Tomographic Reconstructions of Electron Density

We introduce a new quantitative approach for assessing the quality of coronal magnetic field models. The method compares the location of the magnetic neutral line at a specified height in the magnetic field model with the locations of localized density peaks in the coronal electron density, as measured using coronal rotational tomography. This approach is flexible to the presence of pseudostreamers in the coronal magnetic field, as well as folds in the streamer belt. We present an example application during mid-2010 when the white-light streamer-belt structure is complex and the emergence of a large active region on the far side of the Sun presents a challenge for modeling the coronal magnetic structure.

Keywords: coronagraphic imaging; solar corona; model selection
Hidden Companions to Intermediate-mass Stars. XX. Discovery of a 0.58M ⊙, 7.4 au Companion to p Puppis

p Puppis is a nearby 3.1M ⊙ B8V star with astrometric evidence for a close companion in addition to its two wide companions at 1.3 kau (a white dwarf (WD)) and 38.7 kau (an F2V astrometric binary). Here we report on a VLTI/GRAVITY observation that revealed the close companion to be a 0.58M ⊙ star at a projected separation ρ = 100.2 mas ↔ 7.4 au, confirming the system to be a quintuple. The discovered companion explains the X-ray emission of p Pup detected by eROSITA. Moreover, we also find that the isochrone age of Myr of p Pup is incompatible with the minimum cooling age of 350 Myr for the 1.3 kau wide WD companion, suggesting that either they are not coeval or that the WD was formed through a non-trivial channel. *Based on observations collected at the European Southern Observatory, Chile, Program ID 112.25QQ.001.

Keywords: multiple stars; b stars; optical interferometry; wide binary stars