Our aim is to increase the limited number of quasars behind M,31, necessary for probing the chemical content of the gas and for proper motion reference, with reliable and homogeneous redshift measurements from emission lines. We carried out spectroscopic follow-up of 32 quasar candidates. We confirm 23 quasars. Two are new discoveries (J004029.727+403705.68 and J004215.489+412031.52) and the rest have been reported elsewhere, but with somewhat deficient analysis; 16 spectra are published for the first time. We report new homogeneous redshifts for 34 quasars (from 40 spectra, adding 17 from the archives) and summarize all available information about bona fide quasars with reliable redshift, bringing their number to 124 within the μ_B=26m$/$ isophote. We carried out a comparison of redshifts from different sources and excluded some objects with redshifts derived from low-resolution spectra. We derived the reddening for them from the color excess with respect to dereddened counterparts with similar redshifts in the field. Comparisons of our reddenings with M,31 reddening maps found no significant correlations. Most QSOs behind M,31 show low reddening and do not probe high extinctions, probably due to a bias toward following up brighter and less extinct candidates, which underlines the need to identify fainter quasars behind nearby galaxies, especially behind higher extinction regions. Finally, the redshifts derived from low-resolution spectra must be treated with caution because they can contain significant errors.

Abstract We present an analysis of 22,656 narrow-line Seyfert 1 galaxies (NLSy1s) from the Sloan Digital Sky Survey (SDSS) DR17 (0.1 ≤ z ≤ 0.9), identifying a sample of spectroscopically anomalous sources. These anomalies were detected via the Spectroscopic Quasar Anomaly Detection ( SQuAD ) algorithm, which employed principal component analysis and hierarchical k -means clustering. Various physical diagnostic analyses were performed such as color excess ( E ( B − V ) ) calculations, Wide-field Infrared Survey Explorer color analysis, probing [O iii ] equivalent width as an inclination indicator, the Baldwin–Phillips–Terlevich (BPT) diagram, and eigenvector 1 diagram. We detected 620 anomalous NLSy1s classified into two groups. The first is 246 red NLSy1s, exhibiting host-galaxy-dominated spectra with a low-luminosity active galactic nucleus (AGN) core revealed by the emission line widths. The other set consists of 374 blue NLSy1s, which are highly luminous galaxies with enhanced AGN activity, bluer continua as compared to a typical NLSy1, and have stronger Fe ii emission. Finally, we identify a third group of 257 outliers, identified as intermediate Seyferts, which are a class of Seyfert galaxies identified by composite emission profiles and extremely strong emission lines paired with virtually no continuum. These sources also exhibit rare and high ionization emission lines unseen in any other NLSy1 spectra (e.g., [Ne v] λ 3345, Ne v λ 3426, Ne iii λ 3869, etc.). We conclude that the differentiating factor between red and blue NLSy1s is not dust obscuration or orientation effects, but intrinsic distinction in AGN activity. The resulting sample is presented as a value-added catalog.

ABSTRACT We present JWST/NIRSpec IFU observations of the $z=7.152$ galaxy system B14-65666, as part of the GA-NIFS survey. Line and continuum emission in this massive system ($\log _{10}(M_*/{\rm M}_{\odot })=9.8\pm 0.2$) is resolved into two strong cores surrounded by diffuse emission, as seen in recent JWST/NIRCam imaging. Our data set contains detections of [O ii]$\lambda \lambda 3726{,}3729$, [Ne iii]$\lambda \lambda 3869{,}3968$, Balmer lines, [O iii]$\lambda \lambda 4959{,}5007$, He i$\lambda 5875$, and weak [O iii]$\lambda 4363$. Each spectrum is fit with a model that consistently incorporates interstellar medium conditions (i.e. electron temperature, $T_{\rm e}$, electron density, $n_{\rm e}$, and colour excess, $E(B-V)$). The resulting line fluxes are used to constrain the gas-phase metallicity ($Z_{\rm g}\sim 0.2\mathrm{ -}0.3$ solar) and H$\beta$-based star formation rate for each region. Common line ratio diagrams (O32–R23, R3–R2, Ne3O2–R23) reveal that each line-emitting region lies at the intersection of low- and high-redshift galaxies, suggesting low ionization and higher metallicity compared to the predominantly lower-mass galaxies studied with the JWST/NIRSpec IFU so far at $z\gt 5.5$. Spaxel-by-spaxel fits reveal evidence for both narrow (FWHM $\lt 400$ km s$^{-1}$) and broad (FWHM $\gt 500$ km s$^{-1}$) line emission, the latter of which likely represents tidal interaction or outflows. Comparison to ALMA [C ii]158$\mu$m and [O iii]88$\mu$ m data shows a similar velocity structure, and we explore optical-far infrared diagnostics. The two core galaxies both lie on the mass-metallicity relation at $z\gt 4$, but show contrasting properties (e.g. $M_*$, $Z_{\rm g}$), suggesting distinct evolutionary pathways. Combining the NIRSpec IFU and ALMA data sets, our analysis opens new windows into the merging system B14-65666.

We present the first comprehensive spectroscopic and deep photometric study of the globular cluster candidate Patchick 126. The spectroscopic analysis is based on high-resolution near-infrared data obtained with the Immersion GRating INfrared Spectrometer (IGRINS) spectrograph, while the photometric analysis relies on Hubble Space Telescope (HST) observations from the (MGCS). We derived abundances for α-(O, Mg, Si, Ca, Ti), light-(C, N), odd-Z (Na, Al), iron-peak (Fe, Co, Cr, Ni, Mn, V), and s-process elements (Ce) for four red giant stars observed in both the H and K bands. Our results yield a mean metallicity of łangle ̊angle = -0.30 ± 0.03, with no evidence of intrinsic variation, and an α-enhancement of łangle ̊angle = +0.19 ± 0.02, consistent with the trends of metal-rich Galactic globular clusters. We detect an intrinsic C--N anti-correlation, but no Na-O or Al-Mg anti-correlations, in agreement with expectations for low-mass, metal-rich clusters. From the HST photometry in the F606W and F814W bands, we constructed deep colour-magnitude diagrams extending ∼ 2-3 magnitudes below the main-sequence turn-off. This depth allowed us to provide the first robust age estimate for the cluster. Applying the methods developed within the Cluster Ages to Reconstruct the Milky Way Assembly (CARMA) project, we derive an age of 11.9^ Hubble Missing Globular Cluster Survey Fe/H α/Fe +0.3 _ -0.4 Gyr. Independently, we obtain a photometric metallicity of Fe/H $= -0.28$, in excellent agreement with the spectroscopic results. The colour excess we derived, E(B-V) = 1.08, confirms that Patchick 126 is a heavily reddened cluster, located at a heliocentric distance of 7.8 kpc. Finally, from the orbital parameters, including energy, vertical angular momentum, circularity, and maximum vertical height, we find that Patchick 126 closely follows a disc-like orbit. Taken together, these results confirm that Patchick 126 is an in situ, low-mass globular cluster of the Milky Way, exhibiting properties that lie at the boundary between old-open and globular clusters.

Aims. We investigated the photometric and spectroscopic evolution of SN Ia 2025bvm to perform a detailed classification and provide an independent distance estimate for the host galaxy NGC 4156. Methods. We present UBVRI photometry for a period between days −16 and 80 relative to the B -band maximum. Six optical spectra were taken between days −3 and 28. We used different fitting methods to derive the basic photometric parameters. We determined the expansion velocities from the blueshift of the Si II absorption line and the equivalent widths of the interstellar Na I lines. Results. SN 2015bvm exhibits a photometric evolution typical for Type Ia supernovae; the Δ m 15 parameter and the rise time are both close to their mean values. The rising part of the light curves shows no signs of excess flux. The color curves indicate a significant color excess of E ( B − V ) tot = 0.22 ± 0.04 mag. The interstellar Na I lines in the host galaxy are stronger than expected for this value of dust extinction. SN 2025bvm is notable for its high expansion velocity at maximum light and the presence of a plateau in the velocity temporal evolution. We estimate a distance modulus of μ = 34.84 ± 0.10 mag, consistent with the value derived from the host galaxy redshift.

Abstract We present a detailed analysis of the early post-mass-transfer binary system HD 698 (V742 Cas), combining high-resolution optical spectroscopy, long-baseline interferometry, and radiative transfer modeling. Counter-phased RV curves reveal a circular orbit with a period of 55.927 ± 0.001 d and component masses of M Be = 7.48 ± 0.07 M ⊙ and M comp = 1.23 ± 0.02 M ⊙ . The Be primary is traced via broad H α wings, while narrow metallic absorption lines originate from a slowly rotating companion. The angular separation measured via interferometry implies a dynamical distance of 888 ± 5 pc. The spectral energy distribution is best reproduced with a color excess E ( B − V ) = 0.321 ± 0.016 due to interstellar reddening and a moderately dense viscous decretion disk with base density ρ 0 ≃ 5 × 10 −12 g cm −3 at r = R eq , declining radially as ρ ( r ) ∝ r − n with n = 3.0. The companion is found to be a luminous and inflated star with T eff , comp = 10 . 0 − 0.1 + 0.2 kK, R comp = 13 . 1 − 0.2 + 0.2 R ⊙ , and log L / L ⊙ = 3.19 , contributing significantly to the flux ( L comp / L Be ∼ 0.3). Spectral line mismatches provide further circumstantial evidence that the companion is hydrogen poor, consistent with a stripped-envelope star enriched by CNO processing. HD 698 thus belongs to the emerging class of Be + bloated O/B binaries, representing a short-lived, high-luminosity post-mass-transfer phase, when the stripped donor is still spectroscopically detectable before reaching the subdwarf phase.

Abstract We review the existing distance estimates to the black hole X-ray binary Swift J1727.8–1613, present new radio and near-UV spectra to update the distance constraints, and discuss the accuracies and caveats of the associated methodologies. We use line-of-sight H i absorption spectra captured using the MeerKAT radio telescope to estimate a maximum radial velocity with respect to the local standard of rest of 24.8 ± 2.8 km s −1 for Swift J1727.8−1613, which is significantly lower than that of a nearby extragalactic reference source. From this, we derive a near-kinematic distance of d near = 3.6 ± 0.3 (stat) ± 2.3 (sys) kpc as a lower bound after accounting for additional uncertainties given its Galactic longitude and latitude, ( l , b ) ≈ (8.6°, 10.3°). Near-UV spectra from the Hubble Space Telescope’s Space Telescope Imaging Spectrograph allows us to constrain the line-of-sight color excess to E ( B – V ) = 0.37 ± 0.01 (stat) ± 0.025 (sys). We then implement this in Monte Carlo simulations and present a distance to Swift J1727.8−1613 of 5 . 5 − 1.1 + 1.4 kpc, under the assumption that the donor star is an unevolved, main-sequence K4(±1)V star. This distance implies a natal kick velocity of 190 ± 30 km s −1 and therefore an asymmetrical supernova explosion within the Galactic disk as the expected birth mechanism. A lower distance is implied if the donor star has instead lost significant mass during the binary evolution. Hence, more accurate measurements of the binary inclination angle or donor star rotational broadening from future observations would help to better constrain the distance.

This study aims to determine the fundamental parameters of the binary system V1001,Cen, which remain poorly constrained. We conducted a photometric and spectroscopic study in the visual band of V1001,Cen, a system comprising two stellar components. Using Djurašević's models, we derived the physical parameters of both stars, the accretion disk around the gainer star, and the system's overall dimensions. Spectroscopic data from the CHIRON spectrometer allowed us to estimate the effective temperatures, semi amplitudes of radial velocity, and component masses. Disentangling the spectra using the Gonzalez Levato technique provided additional details about the stellar components. Evolutionary models were generated using the MESA code, and comparisons with Van Rensbergen's models were used to assess the system's evolutionary stage. The orbital period of V1001,Cen was determined to be $6.73 ± 0.01$ days, with a long period of $247.28 ± 10.0$ days. The color excess was estimated as E(B-V) = 0.6351 ± 0.0292 mag . Semi amplitudes of radial velocity were measured at mathrm and mathrm . The effective temperatures, determined using the spectrum code, are ± 250,K for the donor star and ± 2000,K for the gainer star. Masses were found to be ± 0.1,M_⊙ and ± 0.1,M_⊙ for the donor and gainer, respectively. The system, with an estimated age of 190 million years, is in its second phase of mass transfer, nearly conservative, with dot M M_⊙ yr^ . Mass transfer began 58 million years ago. The best fitting light curve model indicates an inclination angle of i = 68.!!^ ̧irc 3 ± 0.!!^ ̧irc 3, mathrm R_ g = 2.68 ± 0.1,R_⊙ mathrm R_ d = 6.47± 0.1,R_⊙ mathrm T_ g = 18,310± 500,K and mathrm T_ d = 8,750 ± 250,K parameters belonging to the gainer and donor, respectively

Interstellar ices play a fundamental role in the physical and chemical evolution of molecular clouds and star-forming regions, yet their large-scale distribution and abundance remain challenging to map. In this work, I present the ice color excess method (ICE), which parametrizes the peak optical depth (τ3.0max) of the prominent 3 μm absorption feature, which is predominantly caused by the presence of solid H2O. The method builds on well-established near-infrared color excess techniques and uses widely available infrared broadband photometry. Through detailed evaluation of passband combinations and a comprehensive error analysis, I constructed the ICE color excess metric Λ(W1 − I1). This parameter emerges as the optimal choice that minimizes systematic errors while leveraging high-quality, widely available photometry from Spitzer and WISE data archives. To calibrate the method, I compiled from the literature a sample of stars located in the background of nearby molecular clouds for which spectroscopically measured optical depths are available. The empirical calibration yielded a remarkably tight correlation between τ3.0max and Λ(W1 − I1). This photometric technique opens a new avenue for tracing the icy component of the interstellar medium on Galactic scales, providing a powerful complement to spectroscopic surveys, and enables new insights into the environmental dependence of the formation and evolution of icy dust grains.

ABSTRACT NGC 6791 is a remarkable stellar system that stands out among Galactic open clusters due to its dual distinction as one of the oldest and the most metal-rich clusters. This cluster is among the most thoroughly investigated open clusters, boasting a mass of approximately 4000 ${\rm M}_{\odot }$, an age of about 8 billion years, and a high metallicity of [Fe/H] $\approx 0.4$, making it the most metal-rich cluster identified in the Milky Way. This paper aims to revisit its kinematic, orbital, photometric properties, and stellar populations by using Gaia Data Release 3 (DR3) and BV photometry. To assess membership, we employed the pyupmaskpython package with the HDBSCAN algorithm. The cluster’s proper motions ($\mu _{\alpha }\cos \delta$, $\mu _{\delta }$) and parallax ($\varpi$) are −0.419 $\pm$ 0.12 mas yr$^{-1}$, −2.284 $\pm$ 0.21 mas yr$^{-1}$, and 0.192 $\pm$ 0.042 mas, respectively. Utilizing the PARSEC stellar isochrone fit, we derived the physical parameters of the cluster. The average cluster age and relaxation time are estimated to be 8.2 $\pm$ 0.5 Gyr and 153.9$\pm$ 12.54 Myr, respectively. For the Gaia data, the colour excess $E(G_{BP}-G_{RP})$ is determined to be 0.22 $\pm$ 0.04 mag, and the distance modulus is 13.1 $\pm$ 0.08 mag, corresponding to a distance of 4170 $\pm$ 262 pc. But for BV data, the distance modulus and the colour excess E(B − V) are 12.98 $\pm$ .08 and 0.17 $\pm$ 0.04 mag. The orbit of the cluster has been established. Finally, the mass function is well matched by the two Gaussian functions, which suggest that there are two stellar mass populations in NGC 6791 cluster.

Abstract VV 191 is a nearby (z ∼ 0.05), overlapping (occulting) galaxy pair, where a multiple-armed spiral galaxy is backlit by an elliptical galaxy. The overlap is used to derive and map dust attenuation in two James Webb Space Telescope NIRCam filters (F090W and F150W) and one visible-band Hubble Space Telescope Wide Field Camera 3 filter (F606W). We present maps of the attenuation in each filter, the ratio of total to selective attenuation with a near-infrared (NIR) color excess, R V I ˜ , and the NIR attenuation curve power-law index, α, approximated via Monte Carlo resampling methods. The maps trace the optically thin outer disk of foreground galaxy VV 191b at ∼100 pc physical resolution. We find the distributions of attenuation and R V I ˜ to be close to log-normal, and the distribution of α to be close to Gaussian throughout the disk and in high signal-to-noise ratio areas of VV191b. We analyze three spatially resolved handpicked regions in the far outer disk that are well backlit by the background galaxy.

This study presents a photometric analysis of the intermediate-age open cluster King 6, utilizing photometric data in 𝑈𝐵𝑉(𝑅𝐼)𝑐 passbands and 𝐽𝐻𝐾𝑠 from the 2𝑀𝐴𝑆𝑆 mission. Gaia DR3 kinematic data were used to estimate the membership probabilities, and 𝑇𝐸𝑆𝑆 data were employed to search for variable stars within the cluster. The cluster’s radius is estimated to be 9.′0 based on the stellar density profile, while optical and near-infrared color-color diagrams revealed color excesses of 𝐸(𝐵 − 𝑉) = 0.58 ± 0.03, 𝐸(𝐽 − 𝐾) = 0.24 ± 0.03, and 𝐸(𝑉 − 𝐾) = 1.53 ± 0.01 mag. The interstellar extinction law is normal in the direction of the cluster. The cluster′s estimated age is ∼251 Myr and the distance is 724 ± 5 pc. The mass function slope was found to be 𝑥 = 0.57 ± 0.28 by considering stars ≥ 1 M⊙. Our analysis indicates that the cluster was dynamically relaxed. Furthermore, we identified three new variable stars for the first time in the cluster region using 𝑇𝐸𝑆𝑆 data. These variables belong to the category of slow-pulsating B-type variables with periods of 46.70, 47.92, and 37.56 h.

Abstract The interaction between the relativistic jet and the circumburst medium produces a multiwavelength afterglow of a gamma-ray burst (GRBs). In this work, we present multiwavelength properties of GRB 250101A based on the observations of Swift, Fermi, and Mephisto. The spectral analysis of Swift/Swift Burst Alert Telescope (BAT) and Fermi/Gamma-ray Burst Monitor (GBM) reveals a soft prompt spectrum with a low-energy photon index of −1.18 and a peak energy of 33 keV, and the isotropic energy is 1.4 × 1052 erg. The prompt emission of GRB 250101A aligns with Type II GRBs in the Amati relation. Meanwhile, our analysis indicates that GRB 250101A is an X-ray-rich or X-ray-dominated GRB, with intrinsic properties suggesting that it is relatively softer than most classical GRBs. Optical observation with Mephisto, beginning 197 s post-trigger, shows a single power-law decay in uvgriz bands, with F ν,obs ∝ t −0.76 ν −1.21. The observed spectral index significantly exceeds theoretical predictions under standard afterglow models, suggesting a color excess of ∼0.216 mag. However, combining X-ray and optical afterglow, we find that GRB 250101A is more likely a “normal burst” rather than an “optical-dark burst,” and the dust extinction effect plays an important role in the optical blue bands. Furthermore, there is a structural change at T 0 + 2924 s in the optical light curve, indicating a density drop of ∼50% in the interstellar medium at a distance of ∼0.13 pc. Our analysis shows that this GRB clearly shows some unique characteristics in its observed X-ray-rich prompt emission as well as the circumburst environment, implying a special progenitor.

Aims. Expanding upon a recent investigation devoted to giant stars, we compare the radii derived from the asteroseismic scaling relations with those from surface brightness–colour relations (SBCRs) combined with the Gaia DR3 parallaxes for main-sequence (MS) stars. Methods. The atmospheric and asteroseismic parameters were sourced from the recently released KEYSTONE catalogue and matched to Gaia DR3 and TESS Input Catalog v8.2 to obtain precise parallaxes, V- and KS-band magnitudes, and colour excesses, E(B−V). We computed SBCR-based radii using two different SBCRs, and estimated their relative differences with respect to radius estimates from asteroseismic grid-based methods. Results. We find a good agreement between SBCR and asteroseismic radii, with mean relative differences in radii (Eg) in the range 2% to 3% and a standard deviation of about 3%, consistent with the expected variability of SBCRs. We find no dependence on parallax, and a mild dependence on [Fe/H] for one of the SBCRs tested. The relative difference in the estimated radii decreases as the mass increases, leading to a negative correlation between Eg and the estimated stellar mass, with a slope varying from −0.051±0.016 to −0.039±0.014 per solar mass, depending on the chosen SBCR. This change in slope led to a roughly 1.5% larger discrepancy in the Eg estimates for stars with masses below 1.0 M⊙. This larger discrepancy at the low-mass end supports conclusions drawn from giant star studies. This result is independently corroborated by the LEGACY sample, which uses Kepler photometry processed with the same pipeline as KEYSTONE. For the LEGACY sample we measure a mean relative offset in Eg of −1.4% with a standard deviation of 2.3%, and a dependence of Eg on mass with a slope of −0.052±0.011 per mass unit, both fully consistent with the KEYSTONE analysis. Conclusions. The analysis reveals a strong agreement between SBCR-based and asteroseismic radii for MS stars, but the apparent mass dependence still requires closer examination. This result is reassuring as it demonstrates the great accuracy and reliability of the radius estimates obtained through SBCRs, which, moreover, offer the significant advantage of being applicable to a large sample of stars with substantially lower time and costs compared to what is required by asteroseismology.

Abstract We investigate the relationships between infrared excess (IRX = L IR/L UV) and Balmer decrement (Hα/Hβ) as indicators of dust attenuation for 609 H ii regions at scales of ∼50–200 pc in NGC 628, utilizing data from AstroSat, the James Webb Space Telescope (JWST) and Multi Unit Spectroscopic Explorer. Our findings indicate that about three-fifths of the sample H ii regions reside within the regime occupied by local star-forming galaxies (SFGs) along the dust attenuation correlation described by their corresponding color excess parameters E(B − V)IRX = 0.51 E(B − V)Hα/Hβ . Nearly 27% of the sample exhibits E(B − V)IRX > E(B − V)Hα/Hβ , while a small fraction (∼13%) displays significantly lower E(B − V)IRX compared to E(B − V)Hα/Hβ . These results suggest that the correlation between the two dust attenuation indicators no longer holds for spatially resolved H ii regions. Furthermore, the ratio of E(B − V)IRX to E(B − V)Hα/Hβ remains unaffected by various physical parameters of the H ii regions, including star formation rate (SFR), SFR surface density, infrared luminosity (L IR), L IR surface density, stellar mass, gas-phase metallicity, circularized radius, and the distance to the galactic center. We argue that the ratio is primarily influenced by the evolution of the surrounding interstellar medium of the star-forming regions, transitioning from an early dense and thick phase to the late blown-away stage.

ABSTRACT We present a series of parameter recovery test results of the Bayesian analysis tool izi, which analyses emission lines from H ii regions and star-forming galaxies and returns the estimates of the gas metallicity $12 + \log ({\rm O}/{\rm H})$, ionization parameter $\log q$, and nebular emission-line colour excess $E(B-V)$. We created several mock data sets using izi to represent a few different ideal or realistic data sets and performed parameter estimation on the mock data with izi. We found that izi underestimated or overestimated the parameters by approximately $1 \sigma$ or greater when the model error was included, even when using all emission lines available in the model grids. We strongly recommend that izi users run parameter recovery tests adjusted for their data before interpreting the izi estimates. To encourage the appropriate use of izi, we also share a script for parameter recovery tests. The cause of izi’s biased estimation is the substantial model error in the likelihood term, which varies with the model parameters. We thus note that any parameter estimation with a substantial, varying model error in the likelihood term could return biased estimates for the model parameters, such as in the case of nebulabayes, another Bayesian analysis tool for photoionization emission lines. We also note two issues relevant to setting the $\log q$ prior using the observed line ratio [S iii] $\lambda \lambda 9068,9532$/[S ii] $\lambda 6717, \lambda 6731$ (the mismatch of line flux terms and violation of Bayes’ theorem) and propose a way to avoid the issues.

Abstract In this paper, we study how absorption-line systems affect the spectra and redshifts of quasi-stellar objects (QSOs), using catalogs of Mg ii absorbers from the early data release and first data release of the Dark Energy Spectroscopic Instrument. We determine the reddening effect of an absorption system by fitting an unreddened template spectrum to a sample of 50,674 QSO spectra that contain Mg ii absorbers. We find that reddening caused by intervening absorbers (v off > 3500 km s−1) has an average color excess of E ( B − V ) ¯ = 0.04 mag. We find that the E(B − V) tends to be greater for absorbers at low redshifts, or those having Mg ii absorption lines with higher equivalent widths, but shows no clear trend with v off for intervening systems. However, the E ( B − V ) ¯ of associated absorbers, those at v off < 3500 km s−1, shows a strong trend with v off, increasing rapidly with decreasing v off and peaking (∼0.15 mag) around v off = 0 km s−1. We demonstrate that Mg ii absorbers impact redshift estimation for QSOs by investigating the distributions of v off for associated absorbers. We find that at z > 1.5, these distributions broaden and bifurcate in a nonphysical manner. In an effort to mitigate this effect, we mask pixels associated with the Mg ii absorption lines and recalculate the QSO redshifts. We find that we can recover v off populations in better agreement with those for z < 1.5 absorbers and in doing so typically shift background QSO redshifts by Δz ≈ ± 0.005.

Abstract This study employs stellar parameters from spectroscopic surveys and Zhang et al. (2023) based on Gaia BP/RP (XP) spectra, along with photometric data from Galaxy Evolution Explorer (GALEX), UV/Optical Telescope (UVOT), and Gaia, to obtain extensive ultraviolet color excess information for the relevant bands of GALEX and UVOT. By considering the impact of stellar parameters (T eff, [Fe/H], and log g ) on intrinsic color indices and utilizing the blue-edge method combined with a random forest algorithm, an empirical relationship between stellar parameters and intrinsic ultraviolet color indices is established. By combining observed color indices, the study derives color excesses for 11,624,802 and 65,531 stars in the GALEX/near-UV and far-UV bands and for 336,633; 137,739; and 253,271 stars in the UVOT/uvw1, uvm2, and uvw2 bands, constructing corresponding ultraviolet extinction maps. Notably, the color excess data for the GALEX/near-UV band show a tenfold increase from previous results, with the extinction map covering approximately two-thirds of the sky at a resolution of 0 . ° 4. The typical uncertainties in the ultraviolet color excesses are 0.21 mag, 0.30 mag, 0.19 mag, 0.24 mag, and 0.21 mag for E NUV , G RP , E FUV , G RP , E u v w 1 , G RP , E u v m 2 , G RP , and E u v w 2 , G RP , respectively. By comparing the spatial distributions of R V derived from ultraviolet and Gaia optical band measurements with those obtained from infrared and optical data in previous works, it is evident that the R V distributions based on the ultraviolet data show noticeable differences, with some regions even exhibiting opposite trends. This suggests that a single-parameter R V extinction law may not be sufficient to simultaneously characterize the extinction behavior across infrared, optical, and ultraviolet bands.

We present a comprehensive study of the young open cluster King 13 using photometric and astrometric data from Gaia DR3 and 2MASS. Our analysis refines the cluster’s fundamental parameters, including its structure, kinematics, and evolutionary status. To assess membership, we employed thepyUPMASKPython package with the HDBSCAN algorithm. The primary emphasis of this study is our new approach to assign a membership probability at each radius, rather than applying a single value to the entire cluster. These probabilities are calculated based on the number of stars deduced from the King model. This revealed a dense core with an elongated halo aligned with the cluster’s tangent velocity. Cluster orbital analysis suggests the cluster moves in the Galactic plane toward the Galactic center, with its tidal tail aligned with orbital motion-likely due to Galactic tidal effects. We identified 1571 41 member stars with a total mass of 2658.4 61.5 M. The mass function (MF) for the cluster has been constructed using a step function with two power lows, and , rather than the single power low suggested by Salpeter. In this cluster, the and are found to be -3.70.4 and 2.3 0.15 , respectively. . The cluster’s physical parameters were derived using PARSEC stellar isochrones, estimating an age of 310 28 Myr and a relaxation time of 134 13 Myr, indicating dynamical stability. The proper motions (, ) and parallax () were measured as -2.64 0.36 mas yr, -0.89 0.25 mas yr, and 0.245 0.05 mas, respectively. The corresponding distance of the cluster, derived from the parallax, is 4082 231 pc. The derived distance modulus is 13.11 1.03 mag ( 4187 262 pc), with color excess values of 1.17 0.07 mag (Gaia) and 0.44 0.03 mag (2MASS), further validating our results. Additionally, 46 member stars with radial velocity data allowed us to compute the cluster’s orbit using the galpy package. Our findings highlight the presence of a tidal tail directed toward the center of the Galaxy and underscore the role of Galactic tidal forces in shaping King 13’s morphology, reinforcing its importance in the evolution of open clusters.

While δ Scuti stars --- intermediate-mass stars pulsating with periods of $<0.3$ d --- are the most numerous class of κ-mechanism pulsators in the instability strip, the short periods and small peak-to-peak amplitudes have left them understudied and under-utilized. Recently, large-scale time-domain surveys have significantly increased the number of identified δ Scuti stars, enabling more comprehensive investigations into their properties. Notably, the Tsinghua University–Ma Huateng Telescopes for Survey (TMTS), with its high-cadence observations at 1-minute intervals, has identified thousands of δ Scuti stars, greatly expanding the sample of these short-period pulsating variables. This study makes use of multiband photometric time-series data to refine the period-luminosity (P-L) relations of δ Scuti stars and show how observed P-L relations can be used to simultaneously infer dust obscuration and distance. Using spectroscopy, we also study the dependence of the P-L relations on metallicity. Using the δ Scuti stars from the TMTS catalogs of Periodic Variable Stars, we cross-matched the dataset with Pan-STARRS1, 2MASS, and WISE to obtain photometric measurements across optical (g, r, i, z, and y), near-infrared (J, H, and K_s), and mid-infrared (W1, W2, and W3) bands, respectively. Parallax data, used as Bayesian priors, were retrieved from Gaia DR3, and line-of-sight dust extinction priors were estimated from a 3D dust map. Using PyMC we performed a simultaneous determination of the 11-band P-L relations of δ Scuti stars. The simultaneous determination of multiband P-L relations of δ Scuti stars not only yields precise measurements of these relations, but also greatly improves constraints on the distance moduli and color excesses, as evidenced by the reduced uncertainties in the posterior distributions. Furthermore, our methodology enables an independent estimation of the color excess through the P-L relations, offering a potential complement to existing 3D dust maps. Moreover, by cross-matching with LAMOST DR7, we investigated the influence of metallicity on the P-L relations. Our analysis reveals that incorporating metallicity might reduce the intrinsic scatter at longer wavelengths. However, this result does not achieve 3σ significance, leaving open the possibility that the observed reduction is attributable to statistical fluctuations. We introduce an innovative approach to studying the P-L relations of δ Scuti stars, facilitating more comprehensive investigations into their utility as distance indicators and their significance in understanding stellar evolution. Our extensible methodology also enables the inference of dust extinction using pulsating stars beyond δ Scuti stars. Although the inclusion of metallicity in the P-L relations appears to reduce intrinsic scatter at longer wavelengths, further analysis is required to fully understand the impact of metal abundances on the properties of δ Scuti stars.