Sazuna/UAT_keywords huggingface dataset:
Laboratory Modeling of Supernova Remnants Collisions: Implications for Triggered Star Formation. Theoretical models of star formation consistently underestimate the rates observed in astronomical surveys. Stars form within giant molecular clouds, which fragment into dense clumps under the combined influences of turbulence, magnetic fields, radiation, and gravity. While some of these clumps collapse spontaneously, others require an external trigger, a mechanism estimated to account for 14%─25% of star formation in regions such as the Elephant Trunk Nebula. Laboratory astrophysics has emerged as a powerful approach for investigating such triggering processes, in particular those involving supernova remnants (SNRs). Recent experiments, guided by well-established scaling laws, have successfully replicated the dynamics of SNRs and their interactions with dense clumps or other SNRs. In this work, we present a comprehensive numerical study of these experimental configurations using the 3D radiation-hydrodynamics code TROLL. The simulations provide enhanced insight into the underlying physical mechanisms, accurately reproduce key experimental phenomena, and offer valuable comparisons with analytical models. This study underscores the strong synergy between laboratory experiments and numerical simulations, laying a robust foundation for future advancements in laboratory astrophysics. Furthermore, we propose a new experimental setup that offers improved scaling for the asymmetric collision observed in the DEM L316 system. Our findings also show that SNR collisions in dense environments can decrease the gravitational stability of dense clumps, thereby promoting their collapse and potentially triggering star formation.

Keywords: Supernova remnants, Hydrodynamical simulations, Laboratory astrophysics, Star formation
3D MHD Simulations of Coronal Loops Heated via Magnetic Braiding. I. Continuous Driving. The nature and detailed properties of the heating of the million-degree solar corona are important issues that are still largely unresolved. Nanoflare heating might be dominant in active regions and quiet Sun, although direct signatures of such small-scale events are difficult to observe in the highly conducting, faint corona. The aim of this work is to test the theory of coronal heating by nanoflares in braided magnetic field structures. We analyze a 3D MHD model of a multistrand flux tube in a stratified solar atmosphere, driven by twisting motions at the boundaries. We show how the magnetic structure is maintained at high temperature and for an indefinite time, by intermittent episodes of local magnetic energy release due to reconnection. We synthesize the optically thin emission with SDO/AIA and MUSE and compare the synthetic observations with the intrinsic coronal plasma properties, focusing on the response to impulsive coronal heating. Currents' buildup and their impulsive dissipation into heat are also investigated through different runs. In this first paper, we describe the proliferation of heating from the dissipation of narrow current sheets in realistic simulations of braided coronal flux tubes at unprecedented high spatial resolutions.

Keywords: Space plasmas, Solar magnetic reconnection, Solar coronal loops, Solar physics, Solar corona, Magnetohydrodynamical simulations
3D MHD Simulations of Coronal Loops Heated via Magnetic Braiding. II. Automatic Detection of Reconnection Outflows and Statistical Analysis of Their Properties. Recent observations of fast and bursty "nanojets" suggest novel diagnostics of nanoflare heating in the solar corona. The aim of this work is to investigate the presence and properties of reconnection outflows, similar to observed nanojets, in numerical simulations, and explore their relationship with the nanoflare properties. This work explores their potential as diagnostics for nanoflare heating in observations. We developed an algorithm of Reconnection Outflows Automatic Detection in 3D MHD simulations of coronal loops. We applied the algorithm to a 3D MHD-stratified coronal loop model heated by magnetic reconnection and analyzed the statistical properties of the jets produced at reconnection sites, over about 1 solar hr. The magnetic structure is maintained at a high temperature and for an indefinite time by intermittent episodes of local magnetic energy release due to reconnection.

Keywords: Space plasmas, Solar magnetic reconnection, Solar coronal loops, Solar physics, Solar corona, Magnetohydrodynamical simulations
Noisy Timing Behavior is a Feature of Central Compact Object Pulsars. We present a timing study of the three known central compact object (CCO) pulsars, isolated cooling neutron stars in supernova remnants, using observations from Chandra, XMM-Newton, and NICER spanning two decades. Relative to canonical young pulsars, CCOs are spinning down at a very slow rate  ∣ḟ∣&lt;10−15  s−2, implying a surface dipole magnetic field strength Bs &lt; 1011 G that is too weak to account for their X-ray-emitting hot spots. Two CCO pulsars with sufficiently long monitoring, 1E 1207.4−5209 and PSR J0821−4300, are seen to deviate from steady spin-down; their timing residuals can be modeled by one or more glitches in f and  ḟ  or alternatively by extreme timing noise. For the third CCO pulsar, PSR J1852+0040, the sparse temporal coverage was insufficient to detect such effects. Glitch activity and timing noise in large samples of rotation-powered pulsars correlate best with  ḟ , while the timing irregularities of the first two CCOs are extreme compared to pulsars of the same  ḟ . Nevertheless, timing activity in CCOs may arise from properties that they share with other young but more energetic pulsars: high internal temperature, strong buried magnetic field, and superfluid behavior. Alternatively, continuing low-level accretion of supernova debris is not ruled out as a source of timing noise in CCOs.

Keywords: Neutron stars, Pulsar timing method, Compact objects, Pulsars
Testing the Shock-cooling Emission Model from Star─Disk Collisions for Quasiperiodic Eruptions. Quasiperiodic eruptions (QPEs), the repeated outbursts observed in soft X-ray bands, have attracted broad interest, but their physical origin is under debate. One of the popular models, the star─disk collision model, suggests that QPEs can be produced through periodic collisions of an orbiting star with the accretion disk of a central black hole (BH). However, previous tests of the star─disk collision model mainly focus on the timing analysis. Other observed properties, such as peak luminosities Lp, durations te, and radiation temperatures Tp of the eruptions, are not systematically investigated. For a sample of six QPE sources and two QPE-like sources, we test the shock-cooling emission model from star─disk collisions by using these observables to derive the constraints on the stellar radius R⋆. We find that, except for two sources (eRO-QPE3 and eRO-QPE4), the rest of the sample either has no allowed R⋆ to simultaneously reproduce the observed Lp and te or the required R⋆ is too large to avoid being disrupted by the central BH. For the two exceptions, a stellar radius of the order of 1 R⊙ is necessary to satisfy all the constraints. Another issue with the simplest version of this model is that it predicts kTp ∼ 10 eV, one order of magnitude lower than the observed value.

Keywords: X-ray transient sources, Supermassive black holes, Tidal disruption
Circumbinary Disks in Post Common Envelope Binary Systems with Compact Objects. We conduct a population synthesis study using the binary population synthesis code COMPAS to explore the formation of circumbinary disks (CBDs) following the common envelope evolution (CEE) phase of a giant star and a neutron star (NS) or black hole (BH). We focus on massive binary systems that evolve into double compact object (DCO) binaries after the exposed core of the giant collapses to form a second NS or BH. A CBD around the binary system of the giant's core and the compact object alters the orbital evolution of the binary. We parameterize the conditions for CBD formation in post-CEE binaries and present characteristics of DCO progenitors that are likely or unlikely to form CBDs. We find that CBD formation is most common in BH─BH binaries and NS─NS binaries that are expected to merge within Hubble time. Furthermore, we find that the interaction of the CBD with the core—NS/BH system at the termination of the CEE reduces the expected rate of DCO mergers, regardless of whether these binaries tighten or expand due to this interaction. If the binary system loses angular momentum to the CBD, it may produce a luminous transient due to a merger between the NS/BH and the core of the giant rather than gravitational wave sources. Thus, accounting for post-CEE CBD formation and its interaction with the binary system in population synthesis studies is significant for obtaining reliable predictions of the gravitational wave event rates expected by current detectors.

Keywords: Neutron stars, Binary stars, Black holes, Transient sources, Gravitational wave sources
Galactic-scale Quasar Pairs from the Sloan Digital Sky Survey and Gaia DR3. We perform a systematic search for galactic-scale quasar pairs and small-scale (&lt;3″) lenses using the Sloan Digital Sky Survey (SDSS) DR16 quasar catalog and Gaia DR3, and identify 136 double quasar candidates from 1120 Gaia-resolved pairs after a magnitude and redshift cut of G &lt; 20.5 and z &gt; 0.5 (803 double quasars out of 2497 pairs without any cuts) with separations of  ∼0.″3─3″ , corresponding to projected physical separations of ∼3─30 kpc at the median redshift z = 1.7 for the sample. Candidate unobscured double quasars are selected as Gaia-resolved pairs around spectroscopically confirmed SDSS quasars (Lbol &gt; 1044.5 erg s−1) at 0.5 &lt; z ≲ 4.5. Gaia astrometry and SDSS spectral decomposition are used to exclude foreground star superpositions, which dominate (≳80% of) the initial Gaia-resolved pair sample. Correcting pair-resolving completeness, we measure an overall double quasar (lens and physical pairs combined) fraction of  5.7−0.3+0.3×10−4  (bootstrapping errors). The double quasar fraction measured in individual separation bins increases toward smaller separations, consistent with earlier findings. The dual quasar fraction also shows little redshift evolution for the luminous SDSS sample, in agreement with previous observations and simulation. However, the observed fraction is lower than simulation predictions by ∼0.8─1.6 dex, suggesting a significant population of obscured quasar pairs are missed in our search. Future wide-area space missions targeting both unobscured and obscured quasar pairs at subarcsecond resolutions will reveal the population of obscured quasar pairs and extend to much lower luminosities of active galactic nuclei.

Keywords: Double quasars, Black hole physics, Active galaxies
The Maximum Gravity Model for Partial Tidal Disruption Events: Mass Loss, Peak Fallback Rate, and Dependence on Stellar Properties. A star entering the tidal sphere of a supermassive black hole (SMBH) can be partially stripped of mass, resulting in a partial tidal disruption event (TDE). Here, we develop an analytical model for properties of these events, including the peak fallback rate,  Ṁpeak , the time at which the peak occurs, tpeak, and the amount of mass removed from the star, ∆M, for any star and any pericenter distance associated with the stellar orbit about the black hole. We compare the model predictions to 1276 hydrodynamical simulations of partial TDEs of main-sequence stars by a 106M⊙ SMBH. The model yields tpeak predictions that are in good agreement (to within tens of percent) with the numerical simulations for any stellar mass and age. The agreement for  Ṁpeak  is weaker due to the influence of self-gravity on the debris stream dynamics, which remains dynamically important for partial TDEs; the agreement for  Ṁpeak  is, however, to within a factor of ∼2─3 in the majority of cases considered, with larger differences for low-mass stars (M⋆ ≲ 0.5M⊙) on grazing orbits with small mass loss. We show that partial TDE light curves for disruptions caused by ∼106M⊙ SMBHs can span ∼20─100 days peak timescales, whereas grazing encounters of high-mass stars with high-mass SMBHs can yield longer peak timescales (t ≳ 1000 days), associated with some observed transients. Our model provides a significant step toward an analytical prescription for TDE light curves and luminosity functions.

Keywords: Black hole physics, Supermassive black holes, Hydrodynamics, Tidal disruption, Astrophysical black holes
COBIPLANE: A Systematic Search for Compact Binary Millisecond Pulsars at Low Galactic Latitudes. We present the main results obtained from the Compact Binary Pulsar Search in the Low-Latitude Neighborhood, an optical photometric survey designed to find new "spider" binary millisecond pulsars. We conducted observations targeting 30 unidentified sources from the 4FGL-DR3 Fermi Large Area Telescope catalog, selected for their pulsar-like γ-ray properties. Extending to Galactic latitudes as low as ±3°, this survey reaches closer to the Galactic plane than its predecessor survey, the Compact Binary Pulsar Search. We report the discovery of five optical variables coincident with the localizations of 4FGL J0821.5−1436, 4FGL J1517.9−5233, 4FGL J1639.3−5146, 4FGL J1748.8−3915, and 4FGL J2056.4+3142. These systems show optical flux modulation at the presumed orbital periods of 0.41576(6) days, 0.305(2) days, 0.204(7) days, 0.3(2) days, and 0.4395(1) days, respectively, and photometric temperatures of 4000─6000 K, consistent with the companion stars of the "redback" subtype of spider pulsar binaries. Based on their optical light curve shapes and X-ray properties characteristic for spider systems—namely, a luminosity of 1.5 × 1032(D/3.9 kpc)2 erg s−1 (0.3─10 keV) for 4FGL J1748.8−3915, and upper limits of ∼1031─1033 erg s−1 (0.2─12 keV) for the others—we classify these sources as new spider candidate systems.

Keywords: Close binary stars, Variable stars, High energy astrophysics, Millisecond pulsars
Hint of Dark Matter─Dark Energy Interaction in DESI DR2 and Current Cosmological Dataset?. We present new constraints on an interacting dark matter─dark energy scenario motivated by string compactification, where a scalar field adiabatically tracks the minimum of an effective potential sourced by dark matter density. In this study, we focus on the Chameleon dark energy model and numerically solve the Klein─Gordon equation using a shooting algorithm to determine precise initial conditions such that the field rests at effective potential minima today. We perform a comprehensive Markov Chain Monte Carlo (MCMC) analysis using a combination of datasets, including Planck, BAO (SDSS and DESI DR2), Pantheon+, and SH0ES. Our analysis shows a mild preference for a higher nonzero dark sector coupling, compared to earlier works on similar models, for two particular combinations of datasets: (i) Planck + DESI DR2 BAO +.Pantheon+ and (ii) Planck + SDSS BAO + Pantheon+ + SH0ES. Notably, the inclusion of DESI DR2 and SH0ES data increases the inferred interaction strength to β ∼ 0.3 (68% C.L.) and yields weak and positive evidence in favor of the model over ΛCDM, with  ∆χmin2=─4.75,─6.41  and ∆AIC= ─0.75, ─2.41, respectively. This model remains consistent with a phantom crossing at redshift z ∼ 0.5, in agreement with the trend indicated by DESI observations. However, due to the settlement of the scalar field at the minima of the effective potential at the present epoch, the effective dark energy equation of state asymptotically approaches weff → −1. leading to only weak evidence in favor of this model when analyzed using the DESI DR2 dataset.

Keywords: Cosmology, Dark matter, Dark energy
Inferring the Intrinsic Energy Function of FRB 20220912A. The statistical analysis of fast radio burst (FRB) samples from repeaters may suffer from a band-limited selection effect, which can bias the observed distribution. We investigated the impact of this selection bias on the energy function through simulations and then applied our analysis to the particular case of FRB 20220912A. Our simulations show that, in the sample of bursts observed by the Five-hundred-meter Aperture Spherical Telescope, assuming a unimodal intrinsic energy distribution, the band selection effect alone is insufficient to produce a bimodal energy distribution; only the bimodal central frequency distribution can achieve this. The bursts' energy of FRB 20220912A that primarily fell within the observing band showed no significant correlation with the central frequency. In contrast, bursts with higher central frequency tend to exhibit narrower bandwidth and longer duration. The distribution of the intrinsic energy can be modeled as a lognormal distribution with a characteristic energy of 8.13 × 1037 erg, and a power-law function with the index of 1.011 ± 0.028. In contrast to the initial energy function reported by Y.-K. Zhang et al., the low-energy peak vanishes, and the high-energy decline becomes steeper, which implies the low-energy peak is an observational effect. The bimodality of the energy distribution seems to originate from the intrinsic radiation mechanism.

Keywords: Neutron stars, Radio bursts, Non-thermal radiation sources, Radio transient sources
DeepVoid: A Deep Learning Void Detector. We present DeepVoid, an application of deep learning trained on a physical definition of cosmic voids to detect voids in density fields and galaxy distributions. By semantically segmenting the IllustrisTNG simulation volume using the tidal tensor, we train a deep convolutional neural network to classify local structure using a U-Net architecture for training and prediction. The model achieves a void F1 score of 0.96 and a Matthews correlation coefficient over all structural classes of 0.81 for dark matter particles in IllustrisTNG with interparticle spacing of λ = 0.33 h−1 Mpc. We then apply the machine learning technique of curriculum learning to enable the model to classify structure in data with significantly larger intertracer separation. At the highest tracer separation tested, λ = 10 h−1 Mpc, the model achieves a void F1 score of 0.89 and a Matthews correlation coefficient of 0.6 on IllustrisTNG subhalos.

Keywords: Cosmology, Large-scale structure of the universe, Convolutional neural networks, Voids, Cosmic web
On the Use of Field RR Lyrae as Galactic Probes. VIII. Early Formation of the Galactic Spheroid. We introduce a new photometric catalog of RR Lyrae (RRL) variables (∼300,000) mainly based on data available in public datasets. We also present the largest and most homogeneous spectroscopic dataset of RRLs and blue horizontal branch (BHB) stars ever collected. This includes radial velocity measurements (∼16,000) and iron abundances (∆S method for 8140 RRLs, plus 547 from literature). Elemental abundances based on high-resolution spectra are provided for 487 RRLs and 64 BHB stars. We identified candidate RRLs associated with the main Galactic components and their iron distribution function (IDF) becomes more metal rich when moving from the halo ([Fe/H] = −1.56) to the thick disk (TCD; [Fe/H] = −1.47) and thin disk (TND; [Fe/H] = −0.73). Furthermore, halo RRLs and RRLs in retrograde orbits are α enhanced ([α/Fe]=0.27, σ = 0.18), while TCD RRLs are either α enhanced ([Fe/H] ≤ −1.0) or α poor ([Fe/H] &gt; −1.0), and TND RRLs are mainly α poor ([α/Fe] = −0.01, σ = 0.20). We also identified RRLs associated with the main stellar streams—Gaia─Sausage─Enceladus (GSE); Sequoia, Helmi, and Sagittarius—and we found that their IDFs are quite similar to halo RRLs. However, GSE RRLs lack the metal-poor/metal-rich tails and their α-element distribution is quite compact. The iron radial gradient in Galactocentric distance for TND, TCD, and halo RRLs is negative and it decreases from −0.026, to −0.010, and to −0.002 dex kpc−1. The iron radial gradient based on dry halo (halo without substructures) RRLs is, within the errors, equal to the global halo. We also found a strong similarity between iron and [α/Fe] radial gradients of Milky Way RRLs and M31 globular clusters throughout the full range of galactocentric distances covered by the two samples. *Based in part on observations made with the Southern African Large Telescope (SALT): Program IDs: 2017-2-SCI-041, 2018-1-SCI-018, 2018-2-SCI-025, 2019-1-SCI-013, 2021-2-SCI-028, 2022-2-DDT-001, PI: B. Chaboyer). Based in part on data obtained in the Observatorios de Canarias del Instituto de Astrofisica de Canarias (IAC) with: the STELLA robotic telescope, an AIP facility jointly operated by AIP and IAC at the Teide Observatory in Tenerife, Spain; the Italian Telescopio Nazionale Galileo (TNG) operated by the Fundación Galileo Galilei of the INAF, the Nordic Optical Telescope (NOT) owned in collaboration by the University of Turku and Aarhus University and operated jointly by Aarhus University, the University of Turku and the University of Oslo, representing Denmark, Finland and Norway, the University of Iceland and Stockholm University, and the Mercator telescope operated by the Flemish Community, all at the Observatorio del Roque de los Muchachos of the IAC, La Palma, Spain (Program IDs: 101-MULTIPLE-4/21B, 107-MULTIPLE-4/22A, 120-MULTIPLE-2/23B, 165-Stella12/20A, PI: M. Monelli; Program ID: 108-MULTIPLE-2/25B, PI: M. Sánchez-Benavente).

Keywords: Milky Way dynamics, Chemical abundances, RR Lyrae variable stars, Milky Way evolution, Metallicity
Mapping the Galaxy Color─Star Formation Rate Relation with Manifold Learning and Infrared Image Stacking. Modern surveys present us with billions of faint galaxies for which we only have broadband images in ∼6─8 optical-to-near-infrared (NIR) filters. Galaxy star formation rates (SFRs) are difficult to estimate accurately without spectroscopic diagnostics or far-infrared (FIR) photometry, both of which are prohibitively expensive to obtain for large numbers of faint, high-redshift galaxies. Here we present the empirical relation between SFR and broadband optical-to-NIR colors learned from Spitzer MIPS and Herschel PACS/SPIRE imaging using an innovative stacking analysis that bins galaxies with similar optical-to-NIR spectral energy distributions using a self-organizing map (SOM). Stacking based on optical-to-NIR colors ensures that our FIR stacks are built from galaxies with similar intrinsic physical properties as opposed to stacking simply by stellar mass. We train a 40 × 40 SOM using 230,638 galaxies selected from the Cosmic Evolution Survey (COSMOS) field, and stack the mid-IR to FIR images from 24─500 μm. We are able to measure the median FIR luminosities from half of the SOM cells to calibrate the SFR. In addition to investigating the common structures of optical-to-NIR properties and FIR detections labeled on the SOM, we provide calibrated SFRs for nearly half of the galaxies in the COSMOS fields down to i-band magnitude ≤25.5, and present the evolution of the galaxy main sequence for low-mass galaxies to redshift z ∼ 2.5.

Keywords: Extragalactic astronomy, Star formation, Astronomy data analysis