adsabs/SciX_UAT_keywords huggingface dataset:
Statistical Investigation of Wave Propagation in the Quiet-Sun Using IRIS Spectroscopic Observations

In this analysis, we use spectroscopic observations of the quiet Sun made by the IRIS instrument and investigate wave propagation. We analyze various spectral lines formed in different atmospheric layers, such as the photosphere, chromosphere, and transition region. We examine the Doppler velocity time series at various locations in the quiet Sun to determine the dominant oscillation periods. Our results executing statistical analysis resemble those of the classical physical scenario, indicating that the photosphere is mainly characterized by the dominant 5 minute period, while the chromosphere is primarily associated with the 3 minute oscillation period. In the transition region, we observe a variety of oscillation periods, with dominant periods of 3, 8, and 12 minutes. We estimate the cutoff frequency by deducing the phase difference between two Doppler velocity time series obtained from spectral line pairs in different atmospheric layers formed at different temperatures. This reveals a significant correlation between 3 minute periods in the transition region and photospheric oscillations, suggesting that these oscillations in the transition region might propagate from the photosphere. Additionally, we analyze the phase difference between chromospheric oscillations and photospheric oscillations, demonstrating that only the 3 minute oscillations propagate upward. Based on the statistical analyses, we suggest the presence of magnetoacoustic waves in the solar atmosphere, some of which are propagating from the lower solar atmosphere upward, while some others are propagating downward. The transition region carries both long-period oscillations generated in situ and some photospheric oscillations that are also able to reach there from below.

Keywords: magnetohydrodynamics; solar oscillations; quiet sun; ultraviolet spectroscopy
A Serendipitous Observation of the Recently Discovered Cataclysmic Variable TUVO-21acq

The recently discovered non-magnetic cataclysmic variable TUVO-21acq was serendipitously observed in a quiescent state during an XMM-Newton observing campaign for the starburst galaxy NGC 4945. Data from this campaign was combined with archival serendipitous XMM observations to examine its X-ray and UV/optical characteristics. TUVO-21acq was found to have X-ray flux F X(0.4–3.0 keV) ∼ 1.3 × 10‑14 erg s‑1 cm‑2 and features similar to other quiescent dwarf novae, with X-ray luminosity L X(0.4–3.0 keV) ∼ 8 × 1030 erg s‑1 and a white dwarf mass ${M}_{\mathrm{WD}}={0.78}_{-0.27}^{+0.37}\,{M}_{\odot }$ . Its UV/optical spectrum was variable between observations, possibly due to changes in the accretion disk or the visibility of the bright spot.

Keywords: cataclysmic variable stars; dwarf novae
CLASSY. II. A Technical Overview of the COS Legacy Archive Spectroscopic Survey

The COS Legacy Archive Spectroscopic SurveY (CLASSY) is designed to provide the community with a spectral atlas of 45 nearby star-forming galaxies that were chosen to cover similar properties to those seen at high z (z > 6). The prime high-level science product of CLASSY is accurately coadded UV spectra, ranging from ~1000 to 2000 Å, derived from a combination of archival and new data obtained with HST's Cosmic Origins Spectrograph (COS). This paper details the multistage technical processes of creating this prime data product and the methodologies involved in extracting, reducing, aligning, and coadding far-ultraviolet and near-ultraviolet (NUV) spectra. We provide guidelines on how to successfully utilize COS observations of extended sources, despite COS being optimized for point sources, and best-practice recommendations for the coaddition of UV spectra in general. Moreover, we discuss the effects of our reduction and coaddition techniques in the scientific application of the CLASSY data. In particular, we find that accurately accounting for flux calibration offsets can affect the derived properties of the stellar populations, while customized extractions of NUV spectra for extended sources are essential for correctly diagnosing the metallicity of galaxies via C III] nebular emission. Despite changes in spectral resolution of up to ~25% between individual data sets (due to changes in the COS line-spread function), no adverse affects were observed on the difference in velocity width and outflow velocities of isolated absorption lines when measured in the final combined data products, owing in part to our signal-to-noise regime of S/N < 20. * Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the Data Archive at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.

Keywords: dwarf galaxies; ultraviolet astronomy; galaxy chemical evolution; galaxy spectroscopy; high-redshift galaxies; emission line galaxies
ALMA Observations of Lyα Blob 1: Multiple Major Mergers and Widely Distributed Interstellar Media

We present observations of a giant Lyα blob (LAB) in the SSA22 protocluster at z = 3.1, SSA22-LAB1, taken with the Atacama Large Millimeter/submillimeter Array. Dust continuum, along with [C II] 158 μm and CO(4-3) line emission have been detected in LAB1, showing complex morphology and kinematics across a ~100 kpc central region. Seven galaxies at z = 3.0987-3.1016 in the surroundings are identified in [C II] and dust continuum emission, with two of them potential companions or tidal structures associated with the most massive galaxies. Spatially resolved [C II] and infrared luminosity ratios for the widely distributed media (L[Cɪɪ]/LIR ≈ 10-2-10-3) suggest that the observed extended interstellar media are likely to have originated from star formation activity and the contribution from shocked gas is probably not dominant. LAB1 is found to harbor a total molecular gas mass Mmol = (8.7 ± 2.0) × 1010 M⊙, concentrated in the core region of the Lyα-emitting area. While (primarily obscured) star formation activity in the LAB1 core is one of the most plausible power sources for the Lyα emission, multiple major mergers found in the core may also play a role in making LAB1 exceptionally bright and extended in Lyα as a result of cooling radiation induced by gravitational interactions.

Keywords: interstellar medium; intergalactic medium; starburst galaxies; high-redshift galaxy clusters; circumgalactic medium
High-resolution Near-infrared Spectroscopy of Diffuse Sources around MWC 1080

To reveal the origins of diffuse H emissions observed around the Herbig star MWC 1080, we have performed a high-resolution near-infrared (NIR) spectroscopic observation using the Immersion Grating Infrared Spectrograph. In the NIR H and K bands, we detected various emission lines (six hydrogen Brackett lines, seven H2 lines, and an [Fe II] line) and compared their spatial locations with the optical (H and [S II]) and radio (13CO and CS) line maps. The shock-induced H2 and [Fe II] lines indicate the presence of multiple outflows, consisting of at least three associated young stars in this region. The kinematics of H2 and [Fe II] near the northeast (NE) cavity edge supports the idea that the NE main outflow from MWC 1080A is the blueshifted one with a low inclination angle. The H2 and [Fe II] lines near the southeast molecular region newly reveal that additional highly blueshifted outflows originate from other young stars. The fluorescent H2 lines were found to trace photodissociation regions formed on the cylindrical surfaces of the main outflow cavity, which are expanding outward with a velocity of about 1015 km s1. For the H emission, we identify its components associated with two stellar outflows and two young stars in addition to the dominant component of MWC 1080A scattered by dust. We also report a few faint H features located 0.4 pc away in the southwest direction from MWC 1080A, which lie near the axes of the NE main outflow and one of the newly identified outflows.

Keywords: herbig-haro objects; interstellar medium; young stellar objects; stellar jets; stellar winds; herbig ae/be stars; near infrared astronomy; high resolution spectroscopy; h i line emission
Observations of Magnetic Reconnection with Large Separatrix Angles and Separatrix Jets above the Solar Surface

We analyze six cases of magnetic reconnection with large separatrix angles and separatrix jets observed on the solar disk. The separatrix angle is defined as the angle between the two separatrices on the two sides of the outflow region. The plasma jets are observed immediately downstream of the separatrices. The morphological characteristics and magnetic field configurations of all magnetic reconnections are displayed. At the same time, we calculate several physical parameters of each case, which include the inflow velocity (from 2.3 to 24 km s-1), the outflow velocity (from 1.9 to 43 km s-1), the separatrix jet velocity (from 13 to 82 km s-1), the width (from 0.42 × 103 to 1.2 × 103 km) and length (from 1.4 × 103 to 4.3 × 103 km) of the current sheet, and the separatrix angle θsep (from 72° to 128°). We find that the outflow velocity, the separatrix jet velocity, and the width and length of the current sheet are positively related to the inflow velocity, but the separatrix angle does not depend on the inflow velocity and it is related to the initial magnetic field configuration before magnetic reconnection. Meanwhile, the velocities of the outflow and the separatrix jet decrease with increasing $\left|{\theta }_{{\rm{sep}}}-90^\circ \right|$ , indicating that when the separatrix angle is close to 90°, the jet and the outflow reach their maximum velocities. These observations are compared with the results of the theoretical model and the numerical simulation.

Keywords: solar magnetic reconnection; solar activity; solar magnetic fields
A Search for Neutron Star-Black Hole Binary Mergers in the Short Gamma-Ray Burst Population

Short gamma-ray bursts (SGRBs) are now known to be the product of the merger of two compact objects. However, two possible formation channels exist: neutron star-neutron star (NS-NS) or NS-black hole (BH). The landmark SGRB 170817A provided evidence for the NS-NS channel, thanks to analysis of its gravitational wave signal. We investigate the complete population of SGRBs with an associated redshift (39 events) and search for any divisions that may indicate that an NS-BH formation channel also contributes. Though no conclusive dichotomy is found, we find several lines of evidence that tentatively support the hypothesis that SGRBs with extended emission (EE; seven events) constitute the missing merger population: they are unique in the large energy-band sensitivity of their durations and have statistically distinct energies and host galaxy offsets when compared to regular (non-EE) SGRBs. If this is borne out via future gravitational wave detections, it will conclusively disprove the magnetar model for SGRBs. Furthermore, we identify the first statistically significant anticorrelation between the offsets of SGRBs from their host galaxies and their prompt emission energies.

Keywords: gamma-ray bursts; compact objects; black holes; neutron stars; transient sources
Infrared Spectroscopic Survey of the Quiescent Medium of Nearby Clouds. II. Ice Formation and Grain Growth in Perseus and Serpens

The properties of dust change during the transition from diffuse to dense clouds as a result of ice formation and dust coagulation, but much is still unclear about this transformation. We present 2-20 μm spectra of 49 field stars behind the Perseus and Serpens Molecular Clouds and establish relationships between the near-infrared continuum extinction (A K) and the depths of the 9.7 μm silicate (τ 9.7) and 3.0 μm H2O ice (τ 3.0) absorption bands. The τ 9.7/A K ratio varies from large, diffuse interstellar medium-like values (~0.55), to much lower ratios (~0.26). Above extinctions of A K ~ 1.2 (A V ~ 10; Perseus, Lupus, dense cores) and ~2.0 (A V ~ 17; Serpens), the τ 9.7/A K ratio is lowest. The τ 9.7/A K reduction from diffuse to dense clouds is consistent with a moderate degree of grain growth (sizes up to ~0.5 μm), increasing the near-infrared color excess (and thus A K), but not affecting the ice and silicate band profiles. This grain growth process seems to be related to the ice column densities and dense core formation thresholds, highlighting the importance of density. After correction for Serpens foreground extinction, the H2O ice formation threshold is in the range of A K = 0.31-0.40 (A V = 2.6-3.4) for all clouds, and thus grain growth takes place after the ices are formed. Finally, abundant CH3OH ice (~21% relative to H2O) is reported for 2MASSJ18285266+0028242 (Serpens), a factor of >4 larger than for the other targets.

Keywords: interstellar dust; interstellar dust extinction
Upward Overshooting in Turbulent Compressible Convection. III. Calibrate Parameters for One-dimensional Reynolds Stress Model

In this paper, we calibrate the coefficients for the one-dimensional Reynolds stress model (RSM) with the data generated from the three-dimensional (3D) numerical simulations of upward overshooting in turbulent compressible convection. It has been found that the calibrated convective and isotropic coefficients are almost the same as those calibrated in the pure convection zone. However, the calibrated diffusive coefficients differ significantly from those calibrated in the pure convection zone. We suspect that the diffusive effect induced by the boundary is stronger than by the adjacent stable zone. We have checked the validity of the downgradient approximation (DGA). We find that the prediction of the DGA on the third-order moments (TOMs) is unsatisfactory. However, the prediction on their derivatives is much better. It explains why the performance of the RSM is reasonable in application to the real stars. With the calibrated coefficients, we have solved the full set of nonlocal turbulent equations on RSM. We find that the RSM has successfully produced the thermal adjustment layer and turbulent dissipation layer, which were identified in the 3D numerical simulations. We suggest to use the inflection point of the auto-correlation of temperature perturbation and the Péclet number as the indicators on measuring the extents of the thermal adjustment layer and turbulent dissipation layer, respectively. This result may offer a practical guidance on the application of the RSM in 1D stellar structure and evolution models.

Keywords: stellar structures; stellar interiors; stellar cores; stellar convective zones; hydrodynamical simulations
A Possibly Short GRB 180418A and Phenomenology of Reverse-Shock Emission in the Optical Afterglows of Gamma-Ray Bursts

We present early-time ground-based optical follow-up observations of GRB 180418A, which was discovered by both Swift/BAT and Fermi/GBM. Its broadband afterglow was well monitored by Swift/XRT and ground-based optical telescopes. The optical light curve of GRB 180418A can be modeled by forward shock (FS) plus reverse shock (RS). We fit the light curves with standard external shock models and derive the physical properties of the outflow. It is found that the ratio R B ≡ ɛ B,r /ɛ B,f is 11.22, indicating a moderate degree of magnetization in the RS region. The reported duration of GRB 180418A, T 90, lies in the intermediate region between short and long gamma-ray bursts (GRBs). We further discuss the classification of GRB 180418A, and calculate ɛ = E γ,iso,52/E p,z,2 values of 0.026 and 0.018 (assuming the redshift z is 1.0 and 1.5, respectively), which is closer to short GRBs (SGRBs) in the ɛ-T 90,z plane. If GRB 180418A is an SGRB, it is the only reported SGRB thus far with RS emission in optical light curves. In order to compare the properties of GRB 180418A, we collected three SGRBs that may have RS emission (GRBs 060313, 090426, and 210207B) and also 22 long GRBs (LGRBs) with RS emission. We find that the parameters of LGRBs are in a wider range than those of SGRBs. Also, SGRBs appear to have very small R B values, but the results are generally similar to those of LGRBs. The fitting parameters of GRB 180418A are generally consistent with those of the other three SGRBs, implying that GRB 180418A may belong to the category of SGRBs.

Keywords: gamma-ray bursts
DRAGraces: A Pipeline for the GRACES High-resolution Spectrograph at Gemini

This paper describes the software Data Reduction and Analysis for GRACES (DRAGRACES), which is a pipeline reducing spectra from Gemini Remote Access to the CFHT ESPaDOnS Spectrograph (GRACES) at the Gemini North Telescope. The code is written in the IDL language. It is designed to find all the GRACES frames in a given directory, automatically determine the list of bias, flat, arc, and science frames, and perform the whole reduction and extraction within a few minutes. We compare the output from DRAGRACES with that of the Open source Pipeline for ESPaDOnS Reduction and Analysis (OPERA), a pipeline developed at the Canada-France-Hawaii Telescope (CFHT) that also can extract GRACES spectra. Both pipelines were developed completely independently, yet they give very similar extracted spectra. They both have their advantages and disadvantages. For instance, DRAGRACES is more straightforward and easy to use and is less likely to be derailed by a parameter that needs to be tweaked, while OPERA offers a more careful extraction that can be significantly superior when the highest resolution is required and when the signal-to-noise ratio is low. One should compare both before deciding which one to use for their science. Yet, both pipelines deliver a fairly comparable resolution power (R ∼ 52.8k and 36.6k for DRAGRACES and R ∼ 58k and 40k for OPERA in high- and low-resolution spectral modes, respectively), wavelength solution, and signal-to-noise ratio per resolution element. * First released on 2016 September 20.

Keywords: software documentation; astronomy data reduction; high resolution spectroscopy
X-Ray-to-radio Offset Inference from Low-count X-Ray Jets

Observations of positional offsets between the location of X-ray and radio features in many resolved, extragalactic jets indicates that the emitting regions are not cospatial, an important piece of evidence in the debate over the origin of the X-ray emission on kiloparsec scales. The existing literature is nearly exclusively focused on jets with sufficiently deep Chandra observations to yield accurate positions for X-ray features, but most of the known X-ray jets are detected with tens of counts or fewer, making detailed morphological comparisons difficult. Here we report the detection of X-ray-to-radio positional offsets in 15 extragalactic jets from an analysis of 22 sources with low-count Chandra observations, where we utilized the Low-count Image Reconstruction Algorithm. This algorithm has allowed us to account for effects such as Poisson background fluctuations and nearby point sources which have previously made the detection of offsets difficult in shallow observations. Using this method, we find that in 55% of knots with detectable offsets, the X-rays peak upstream of the radio, questioning the applicability of one-zone models, including the IC/CMB model for explaining the X-ray emission. We also report the nondetection of two previously claimed X-ray jets. Many, but not all, of our sources follow a loose trend of increasing offset between the X-ray and radio emission, as well as a decreasing X-ray-to-radio flux ratio along the jet.

Keywords: relativistic jets; active galactic nuclei; astronomy data analysis; x-ray astronomy; astronomical methods; high energy astrophysics
The Most Interesting Anomalies Discovered in ZTF DR17 from the SNAD-VI Workshop

The SNAD team has developed an adaptive learning algorithm, named Pine Forest (PF), to enhance anomaly detection in astronomical data. Recognizing the essential role of human engagement in the discovery process, PF presents outliers to a human expert for review, and filters out trees which disagree with the feedback provided. During the sixth annual SNAD workshop (https://snad.space/2023/), held in 2023 July, we applied PF to the Zwicky Transient Facility's DR17 data. Interesting discoveries include long-duration objects such as supernovae, along with fast transients like red dwarf flares and one microlensing event. As a result, new variable stars were identified and labeled in the SNAD knowledge database.

Keywords: supernovae; red dwarf flare stars; transient detection; outlier detection; astronomy data analysis
Two Luminous Post-AGB Stars in the Galactic Globular Cluster M19

We report the discovery of a luminous "yellow" post-asymptotic giant branch (PAGB) star in the globular cluster (GC) M19 (NGC 6273), identified during our uBVI survey of Galactic GCs. The uBVI photometric system is optimized to detect stars with large Balmer discontinuities, indicating very low surface gravities and high luminosities. The spectral energy distribution (SED) of the star is consistent with an effective temperature of about 6250 K and a surface gravity of $\mathrm{log}g=0.5$ . We use Gaia data to show that the star's proper motion and radial velocity are consistent with cluster membership. One aim of our program is to test yellow PAGB stars as candidate Population II standard candles for determining extragalactic distances. We derive a visual absolute magnitude of MV = - 3.39 ± 0.09 for the M19 star. This is in close agreement with the MV values found for yellow PAGB stars in the GCs ω Cen, NGC 5986, and M79, indicating a very narrow luminosity function. These objects are 4 mag brighter than RR Lyrae variables, and they can largely avoid the issues of interstellar extinction that are a problem for Population I distance indicators. We also identified a second luminous PAGB object in M19, this one a hotter "UV-bright" star. Its SED is consistent with an effective temperature of about 11,750 K and $\mathrm{log}g=2.0$ . The two objects have nearly identical bolometric luminosities, $\mathrm{log}L/{L}_{\odot }=3.24$ and 3.22, respectively.

Keywords: post-asymptotic giant branch stars; globular star clusters; late stellar evolution
A Semianalytic Model of the Pairwise Velocity Distribution between Dark Matter Halos

We study the probability distribution function (PDF) of relative velocity between two different dark matter halos (i.e., pairwise velocity) with high-resolution cosmological N-body simulations. We revisit a non-Gaussian framework to predict pairwise velocity statistics developed in Tinker. We investigate the pairwise velocity PDFs over a wide range of halo masses of 1012.5 ≲ M [h-1 M⊙] ≲ 1015 and redshifts of 0 < z < 1. At a given set of masses, redshift, and separation length between two halos, our model requires three parameters to set the pairwise velocity PDF, whereas previous non-Gaussian models in the literature assumed four or more free parameters. At length scales of 5 < r [h-1 Mpc] < 40, our model predicts the mean and dispersion of the pairwise velocity for dark matter halos with masses of 1012.5 ≲ M [h-1 M⊙] ≲ 1013.5 at 0.3 < z < 1 with a 5%-level precision. We demonstrate that our model of the pairwise velocity PDF provides an accurate mapping of the two-point clustering of massive-galaxy-sized halos at scales of O(10)h-1 Mpc between redshift and real space for a given real-space correlation function. For a mass-limited halo sample with masses greater than 1013.5 h-1 M⊙ at z = 0.55, our model can explain the monopole and quadrupole moments of the redshift-space two-point correlations with a precision better than 5% at the scales of 5-40 and 10-30 h-1 Mpc, respectively. Our model of the pairwise velocity PDF will give a detailed explanation of the statistics of massive galaxies at intermediate scales in redshift surveys.

Keywords: large-scale structure of the universe; cosmology; galaxy dark matter halos