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The aim of this work is to establish the present accuracy and convergence of available estimates of galactic extinction. We determine the galactic interstellar extinction in selected high-latitude areas of the sky based on Gaia DR3 astrometry and photometry and spectroscopic data from the LAMOST survey. For this purpose, we choose 42 northern high-latitude sky areas surrounding supernovae that allowed establishing the accelerated expansion of the universe. We compare our results with the estimates accepted in that paper and find that they agree well, within observational errors. Simultaneously, the estimates for galactic extinction by other authors along the same sightlines show systematic differences, which can cause the distance to the extragalactic object to change by ±3–5%. [ABSTRACT FROM AUTHOR]

New high-precision photometric measurements of the V957 Cep system ( , , , B6 V+B8 V), as well as an integrated approach to determining orbital parameters based both on photometric solutions of the light curves and the study of the course of residual deviations of the minima timings from the linear formula made it possible for the first time to accurately measure the apsidal motion rate: /year, which coincided with the theoretical value under the condition of the orbital and axial rotation synchronism: /year. The physical parameters of the component stars were obtained: K, , , K, M2 = 3.0 ± , . This set of parameters corresponds to stars of zero age, recently descended to ZAMS. The secondary component is a pulsating variable star of the Cephei type. [ABSTRACT FROM AUTHOR]

The aim of this work is to establish the present accuracy and convergence of available estimates of galactic extinction. We determine the galactic interstellar extinction in selected high-latitude areas of the sky based on Gaia DR3 astrometry and photometry and spectroscopic data from the LAMOST survey. For this purpose, we choose 42 northern high-latitude sky areas surrounding supernovae that allowed establishing the accelerated expansion of the universe. We compare our results with the estimates accepted in that paper and find that they agree well, within observational errors. Simultaneously, the estimates for galactic extinction by other authors along the same sightlines show systematic differences, which can cause the distance to the extragalactic object to change by ±3–5%.

The extinction curve of interstellar dust in the dense molecular cloud cores is crucial for understanding dust properties, particularly size distribution and composition. We investigate the infrared extinction law in four nearby isolated molecular cloud cores—L429, L483, L673, and L1165—across the 1.2–8.0 μ m wavelength range, using deep near-infrared and mid-infrared photometric data from UKIRT Infrared Deep Sky Survey and Spitzer Space Telescope. These observations probe an unprecedented extinction depth, reaching A _V ∼ 40–60 mag in these dense cloud cores. We derive color-excess ratios E ( K − λ )/ E ( H − K ) by fitting color–color diagrams of ( K − λ ) versus ( H − K ), which are subsequently used to calculate the extinction law A _λ / A _K . Our analysis reveals remarkably similar and exceptionally flat infrared extinction curves for all four cloud cores, exhibiting the most pronounced flattening reported in the literature to date. This flatness is consistent with the presence of large dust grains, suggesting significant grain growth in dense environments. Intriguingly, our findings align closely with the Astrodust model for a diffuse interstellar environment proposed by Hensley and Draine. This agreement between dense core observations and a diffuse medium model highlights the complexity of dust evolution and the need for further investigation into the processes governing dust properties in different interstellar environments.

Investigating the extinction law in regions of high dust extinction, such as the Pillars of Creation within the M16 region, is crucial for understanding the densest parts of the interstellar medium (ISM). In this study, we utilize observations from the Near-Infrared Camera and the Mid-Infrared Instrument onboard the James Webb Space Telescope (JWST) to analyze the color-excess ratios E (F090W − λ )/ E (F090W − F200W) across a wavelength range of 0.9–7.7 μ m. Our method involves performing linear regression on color–color diagrams to derive these ratios. The enhanced detection capabilities of JWST data allow us to probe the distinct extinction law to the densest regions in M16 corresponding to an extinction depth up to A _V ∼ 60 mag. Remarkably, the resultant color-excess ratio curve exhibits a flatter profile than predicted by typical dust extinction models with R _V = 5.5 for dense ISM environments. Moreover, we observe that the mid-infrared extinction law diverges from the near-infrared power law, showing a tendency for the slope to flatten as the wavelength increases. These findings have significant implications for our understanding of the dust properties in dense interstellar environments.

The interstellar extinction law is important for interpreting observations and inferring the properties of interstellar dust grains. Based on the 993 prism/CLEAR spectra from the James Webb Space Telescope (JWST), we investigate the 0.6–5.3 μ m interstellar dust extinction law. We propose a pair method to obtain the reddening curves based only on JWST observed spectra. Most of the high-extinction sources are toward the young star cluster Westerlund 2. The infrared 1.0–5.3 μ m reddening curves agree with the power law A _λ ∝ λ ^− ^α well. We determine an average value of α = 1.98 ± 0.15, which is consistent with the average value of the Galaxy. We find that α may be variable and independent of R _V . With the derived α , we convert the reddening curves into the extinction curves and establish the nonparameterized α -dependent extinction curves in the wavelength range of 0.6–5.3 μ m. At λ < 1 μ m, the derived extinction law is not well described by the parameterized power-law-type curve. Our nonparameterized α -dependent extinction curves are suitable for the extinction correction of JWST-based photometry and spectra measurements at 0.6–5.3 μ m. We also provide the extinction coefficients for the JWST NIRCam bandpasses with different α .

We present new three-dimensional (3D) interstellar extinction maps in the and Gaia filters within 2 kpc of the Sun, a 3D differential extinction (dust spatial distribution density) map along lines of sight in the same space, a 3D map of variations in the ratio of the extinctions in the and Gaia filters within 800 pc of the Sun, and a 2D map of total Galactic extinction through the entire dust half-layer from the Sun to extragalactic space for Galactic latitudes . The 3D maps have a transverse resolution from 3.6 to 11.6 pc and a radial resolution of 50 pc. The 2D map has an angular resolution of 6.1 arcmin. We have produced these maps based on the Gaia DR3 parallaxes and Gaia, Pan-STARRS1, SkyMapper, 2MASS, and WISE photometry for million stars. We have paid special attention to the space within 200 pc of the Sun and high Galactic latitudes as regions where the extinction estimates have had a large relative uncertainty so far. Our maps estimate the extinction within the Galactic dust layer from the Sun to an extended object or through the entire dust half-layer from the Sun to extragalactic space with a precision mag. This gives a high relative precision of extinction estimates even at high Galactic latitudes, where, according to our estimates, the median total Galactic extinction through the entire dust half-layer from the Sun to extragalactic objects is mag. We have shown that the presented maps are among the best ones in data amount, space size, resolution, precision, and other properties. [ABSTRACT FROM AUTHOR]

Dust extinction is one of the fundamental measurements of dust grain sizes, compositions, and shapes. Most of the wavelength-dependent variations seen in Milky Way extinction are strongly correlated with the single parameter R (V) = A (V)/ E (B − V). Existing R (V)-dependent extinction relationships use a mixture of spectroscopic and photometry observations, and hence do not fully capture all the important dust features or continuum variations. Using four existing samples of spectroscopically measured dust extinction curves, we consistently measure the R (V)-dependent extinction relationship spectroscopically from the far-ultraviolet (FUV) to mid-infrared for the first time. Linear fits of A (λ)/ A (V) dependent on R (V) are done using a method that fully accounts for their significant and correlated uncertainties. These linear parameters are fit with analytic wavelength-dependent functions to determine the smooth R (V) (2.3–5.6) and wavelength (912 Å–32 μ m) dependent extinction relationship. This relationship shows that the FUV rise, 2175 Å bump, and the three broad optical features are dependent on R (V), but the 10 and 20 μ m features are not. Existing literature relationships show significant deviations compared to this relationship especially in the FUV and infrared (IR). Extinction curves that clearly deviate from this relationship illustrate that this relationship only describes the average behavior versus R (V). We find tentative evidence that the relationship may not be linear with R (V)−1 especially in the ultraviolet (UV). For the first time, this relationship provides measurements of dust extinction that spectroscopically resolve the continuum and features in the UV, optical, and IR as a function of R (V), enabling detailed studies of dust grain properties and full spectroscopic accounting for the effects of dust extinction on astrophysical objects. [ABSTRACT FROM AUTHOR]

Cosmological surveys must correct their observations for the reddening of extragalactic objects by Galactic dust. Existing dust maps, however, have been found to have spatial correlations with the large-scale structure of the Universe. Errors in extinction maps can propagate systematic biases into samples of dereddened extragalactic objects and into cosmological measurements such as correlation functions between foreground lenses and background objects and the primordial non-Gaussianity parameter f NL. Emission-based maps are contaminated by the cosmic infrared background, while maps inferred from stellar reddenings suffer from imperfect removal of quasars and galaxies from stellar catalogs. Thus, stellar-reddening-based maps using catalogs without extragalactic objects offer a promising path to making dust maps with minimal correlations with large-scale structure. We present two high-latitude integrated extinction maps based on stellar reddenings, with a point-spread functions of FWHMs 6.′1 and 15′. We employ a strict selection of catalog objects to filter out galaxies and quasars and measure the spatial correlation of our extinction maps with extragalactic structure. Our galactic extinction maps have reduced spatial correlation with large-scale structure relative to most existing stellar-reddening-based and emission-based extinction maps. [ABSTRACT FROM AUTHOR]

The λ 21 cm H i emission that is used to trace the gas-to-dust ratio at high Galactic latitudes has contributions from material beyond the Milky Way disk, with uncertain and likely subsolar metallicity and dust content. These contributions can be isolated kinematically and their presence is clear for sightlines with small mean reddening 〈 E ( B − V )〉 ≲ 0.03 mag, which have mean ratios 〈 N (H i )〉/〈 E ( B − V )〉 that are 20%–50% above the high-latitude Galactic average 〈 N (H i )〉/〈 E ( B − V )〉 = 8.3 × 10 ^21 cm ^−2 mag ^−1 . By mapping N (H i ) and E ( B − V ) across H i high-velocity cloud complexes and the Magellanic Clouds, we show that the reddening of this kinematically isolated gas is on average 5 times smaller per H i than the high-latitude average. However, the aggregate contribution of this gas is small and 〈 N (H i )〉/〈 E ( B − V )〉 = 8.3 × 10 ^21 cm ^−2 mag ^−1 is the appropriate value for Galactic gas seen at high latitude using the H i and reddening measures employed here and in our previous work.

We present a direct measurement of extinction curves using corrected Gaia XP spectra of the common sources in Gaia DR3 and LAMOST DR7. Our analysis of approximately 370,000 high-quality samples yielded a high-precision average extinction curve for the Milky Way. After incorporating infrared photometric data from Two Micron All Sky Survey and Wide-field Infrared Survey Explorer, the extinction curve spans wavelengths from 0.336 to 4.6 μ m. We determine an average R _55 of 2.730 ± 0.007, corresponding to R _V = 3.073 ± 0.009, and a near-infrared power-law index α of 1.935 ± 0.037. Our study confirmed some intermediate-scale structures within the optical range. One new feature was identified at 540 nm, and its intensity exhibited a correlation with extinction. This extinction curve can be used to investigate the characteristics of dust and enhance the extinction correction of Milky Way stars. A Python package for this extinction curve is available.

At first light, the Thirty Meter Telescope (TMT) near-infrared (NIR) instruments will be fed by a multiconjugate adaptive optics instrument known as the Narrow Field Infrared Adaptive Optics System (NFIRAOS). NFIRAOS will use six laser guide stars to sense atmospheric turbulence in a volume corresponding to a field of view of 2′, but natural guide stars (NGSs) will be required to sense tip/tilt and focus. To achieve high sky coverage (50% at the north Galactic pole), the NFIRAOS client instruments use NIR on-instrument wave front sensors that take advantage of the sharpening of the stars by NFIRAOS. A catalog of guide stars with NIR magnitudes as faint as 22 mag in the J band (Vega system), covering the TMT-observable sky, will be a critical resource for the efficient operation of NFIRAOS, and no such catalog currently exists. Hence, it is essential to develop such a catalog by computing the expected NIR magnitudes of stellar sources identified in deep optical sky surveys using their optical magnitudes. This paper discusses the generation of a partial NIR Guide Star Catalog (IRGSC), similar to the final IRGSC for TMT operations. The partial catalog is generated by applying stellar atmospheric models to the optical data of stellar sources from the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS) optical data and then computing their expected NIR magnitudes. We validated the computed NIR magnitudes of the sources in some fields by using the available NIR data for those fields. We identified the remaining challenges of this approach. We outlined the path for producing the final IRGSC using the Pan-STARRS data. We have named the Python code to generate the IRGSC as irgsctool , which generates a list of NGS for a field using optical data from the Pan-STARRS 3pi survey and also a list of NGSs having observed NIR data from the UKIRT Infrared Deep Sky Survey if they are available. irgsctool is available in the public domain on this GitHub public repository ( https://github.com/sshah1502/irgsc ), while the generated and validated IRGSC for the 20 test fields and additional Pan-STARRS Medium Deep Survey fields can be found on Zenodo.

We conducted a photometric and kinematic analysis of the young open cluster NGC 2345 using CCD UBV data from 2 m Himalayan Chandra Telescope, Gaia Data Release 3, Two Micron All-Sky Survey, and the Photometric All-Sky Survey data sets. We found 1732 most probable cluster members with membership probability higher than 70%. The fundamental and structural parameters of the cluster are determined based on the cluster members. The mean proper motion of the cluster is estimated to be ${\mu }_{\alpha }\cos \delta $ = −1.34 ± 0.20 and μ _δ = 1.35 ± 0.21 mas yr ^−1 . Based on the radial density profile, the estimated radius is ∼12.′8 (10.37 pc). Using color–color and color–magnitude diagrams, we estimate the reddening, age, and distance to be 0.63 ± 0.04 mag, 63 ± 8 Myr, and 2.78 ± 0.78 kpc, respectively. The mass function slope for main-sequence stars is determined as 1.2 ± 0.1. The mass function slope in the core, halo, and overall region indicates a possible hint of mass segregation. The cluster’s dynamical relaxation time is 177.6 Myr, meaning ongoing mass segregation, with complete equilibrium expected in 100–110 Myr. Apex coordinates are determined as −40.°89 ± 0.12, − 44.°99 ± 0.15. The cluster’s orbit in the Galaxy suggests early dissociation into field stars due to its close proximity to the Galactic disk.

The far-infrared (FIR) opacity of dust in dark clouds within the Ophiuchus molecular cloud is investigated through multiwavelength infrared observations from UKIDSS, Spitzer, and Herschel. Employing the infrared color excess technique with both near-infrared and mid-infrared photometric data, a high-resolution extinction map in the K band ( A _K ) is constructed for three dark clouds: L1689, L1709, and L1712. The derived extinction map has a resolution of $1^{\prime} $ and reaches a depth of A _K ∼ 3 mag. The FIR optical depths τ _250 at a reference wavelength of 250 μ m are obtained by fitting the Herschel PACS and SPIRE continuum data at 100, 160, 250, 350, and 500 μ m using a modified blackbody model. The average dust opacity per unit gas mass at 250 μ m, r κ _250 , is determined through a pixel-by-pixel correlation of τ _250 with A _K , yielding a value of approximately 0.09 cm ^2 g ^−1 , which is about 2–3 times higher than the typical value in the diffuse interstellar medium. Additionally, an independent analysis across 16 subregions within the Ophiuchus cloud indicates spatial variations in dust opacity, with values ranging from 0.07 to 0.12 cm ^2 g ^−1 . Although the observed trend of increasing dust opacity with higher extinction implies grain growth, our findings indicate that rapid grain growth has clearly not yet occurred in the dark clouds studied in this work.

The Milky Way dust extinction curve in the near-infrared (NIR) follows a power-law form, but the value of the slope, β _NIR , is debated. Systematic variations in the slope of the Milky Way UV extinction curve are known to be correlated with variations in the optical slope (through R _V ), but whether such a dependence extends to the NIR is unclear. Finally, because of low dust column densities, the NIR extinction law is poorly understood at high Galactic latitudes where most extragalactic work takes place. In this paper, we construct extinction curves from 56,649 stars with Sloan Digital Sky Survey (SDSS) and Two Micron All Sky Survey photometry, based on stellar parameters from SDSS spectra. We use dust maps to identify dust-free stars, from which we calibrate the relation between stellar parameters and intrinsic colors. Furthermore, to probe the low-dust regime at high latitudes, we use aggregate curves based on many stars. We find no systematic variation of β _NIR across low-to-moderate dust columns (0.02 < E ( B − V ) ≲ 1), and report average β _NIR = 1.85 ± 0.01, in agreement with the law in the 2019 Fitzpatrick et al. study, but steeper than the Cardelli et al. and 1999 Fitzpatrick laws. Star-to-star scatter in β _NIR is relatively small (σ( β _NIR ) = 0.13). We also find no intrinsic correlation between β _NIR and R _V (there is an apparent correlation that is the result of the correlated uncertainties in the two values). These results hold for typical sightlines; we do not probe very dusty regions near the Galactic Center, nor rare sightlines with R _V > 4. Finally, we find R _H = 0.345 ± 0.007 and comment on its bearing on Cepheid calibrations and the determination of H _0 .

We present a new version of our analytical model of the spatial interstellar extinction variations within the nearest kiloparsec from the Sun. This model treats the three-dimensional (3D) dust distribution as a superposition of three overlapping layers: (1) the layer along the Galactic midplane, (2) the layer in the Gould Belt, and (3) the layer passing through the Cepheus and Chamaeleon dust cloud complexes. In each layer the dust density decreases exponentially with increasing distance from the midplane of the layer. In addition, there are sinusoidal longitudinal extinction variations along the midplane of each layer. We have found the most probable values of 29 parameters of our model using four data sets: the 3D stellar reddening maps by Gontcharov and Mosenkov (2017), Lallement et al. (2019), and Green et al. (2019) and the extinctions inferred by Anders et al. (2022) for 993 291 giants from the Gaia Early Data Release 3. All of the data give similar estimates of the model parameters. The extinction for a star or a point in space is predicted by our model with an accuracy from to 0.37 for high and low Galactic latitudes, respectively. The natural fluctuations of the dust medium dominate in these values. When ignoring the fluctuations of the medium, the average extinction for an extended object (a galaxy, a star cluster, a dust cloud) or a small region of space is predicted by our model with an accuracy from to 0.15 for high and low Galactic latitudes, respectively. Green et al. (2019) and Anders et al. (2022) give in unison an estimate of for the extinction at high latitudes across the whole Galactic dust half-layer above or below the Sun with the natural fluctuations of the medium . If such a high estimate is subsequently confirmed, then it will require to explain how a substantial amount of dust ended up far from the Galactic midplane. Our model is a step in this explanation. [ABSTRACT FROM AUTHOR]

We determine the interstellar extinction in the selected high-latitude areas of the sky based on Gaia EDR3 astrometry and photometry and spectroscopic data from RAVE survey. We approximate the results with the cosecant law in each area thus deriving the parameters of the barometric formula for different lines of sight. The distribution of the parameters over the entire sky is described using spherical harmonics. As a result, we get a mathematical description of the interstellar visual extinction for different lines of sight and distances from the Sun which can be used for estimating interstellar extinction.

Distance dependences of interstellar extinction () for a number of high-latitude areas of the southern sky were obtained using the data of the RAVE DR6 spectroscopic survey and the Gaia DR2/EDR3 astrometric survey. These dependencies were approximated by the classical barometric function (cosecant law). Function parameters were then approximated by spherical functions. The resulting analytical 3D model of interstellar extinction AV can be used to estimate the values of for the stars in the Galaxy with known parallaxes, as well as the total (galactic) extinction values in a given direction. [ABSTRACT FROM AUTHOR]

Interstellar-dust extinction law is essential for interpreting observations. In this work, we investigate the ultraviolet (UV)–mid-infrared (IR) extinction law of the Taurus molecular cloud and its possible variations. We select 504,988 dwarf stars (4200 K ≤ T _eff ≤ 8000 K) and 4757 giant stars (4200 K ≤ T _eff ≤ 5200 K) based on the stellar parameters of Gaia DR3 as tracers. We establish the T _eff –intrinsic color relations and determine the intrinsic color indices and color excesses for different types of stars. In the determination of color excess ratios (CERs), we analyze and correct the curvature of CERs and derive the UV–mid-IR CERs of 16 bands. We consider different effective wavelengths for different types of stars when converting CERs to relative extinction and obtain the extinction law with a better wavelength resolution. In addition, we analyze the possible regional variation of extinction law and derive the average extinction law of R _V = 3.13 ± 0.32 for the Taurus molecular cloud. Only 0.9% of subregions have deviations >3 σ , indicating limited regional variation in the extinction law. We also discuss the effect of Gaia T _eff overestimation on the determination of the Taurus extinction law and find that the effect is negligible.

Dust extinction is one of the fundamental measurements of dust grain sizes, compositions, and shapes. Most of the wavelength-dependent variations seen in Milky Way extinction are strongly correlated with the single parameter R ( V ) = A ( V )/ E ( B − V ). Existing R ( V )-dependent extinction relationships use a mixture of spectroscopic and photometry observations, and hence do not fully capture all the important dust features or continuum variations. Using four existing samples of spectroscopically measured dust extinction curves, we consistently measure the R ( V )-dependent extinction relationship spectroscopically from the far-ultraviolet (FUV) to mid-infrared for the first time. Linear fits of A ( λ )/ A ( V ) dependent on R ( V ) are done using a method that fully accounts for their significant and correlated uncertainties. These linear parameters are fit with analytic wavelength-dependent functions to determine the smooth R ( V ) (2.3–5.6) and wavelength (912 Å–32 μ m) dependent extinction relationship. This relationship shows that the FUV rise, 2175 Å bump, and the three broad optical features are dependent on R ( V ), but the 10 and 20 μ m features are not. Existing literature relationships show significant deviations compared to this relationship especially in the FUV and infrared (IR). Extinction curves that clearly deviate from this relationship illustrate that this relationship only describes the average behavior versus R ( V ). We find tentative evidence that the relationship may not be linear with R ( V ) ^−1 especially in the ultraviolet (UV). For the first time, this relationship provides measurements of dust extinction that spectroscopically resolve the continuum and features in the UV, optical, and IR as a function of R ( V ), enabling detailed studies of dust grain properties and full spectroscopic accounting for the effects of dust extinction on astrophysical objects.

Cosmological surveys must correct their observations for the reddening of extragalactic objects by Galactic dust. Existing dust maps, however, have been found to have spatial correlations with the large-scale structure of the Universe. Errors in extinction maps can propagate systematic biases into samples of dereddened extragalactic objects and into cosmological measurements such as correlation functions between foreground lenses and background objects and the primordial non-Gaussianity parameter f _NL . Emission-based maps are contaminated by the cosmic infrared background, while maps inferred from stellar reddenings suffer from imperfect removal of quasars and galaxies from stellar catalogs. Thus, stellar-reddening-based maps using catalogs without extragalactic objects offer a promising path to making dust maps with minimal correlations with large-scale structure. We present two high-latitude integrated extinction maps based on stellar reddenings, with a point-spread functions of FWHMs 6.′1 and 15′. We employ a strict selection of catalog objects to filter out galaxies and quasars and measure the spatial correlation of our extinction maps with extragalactic structure. Our galactic extinction maps have reduced spatial correlation with large-scale structure relative to most existing stellar-reddening-based and emission-based extinction maps.

Precise interstellar dust extinction laws are important to infer the intrinsic properties of reddened objects and correctly interpret observations. In this work, we attempt to measure the optical–infrared extinction laws of the Large and Small Magellanic Clouds (LMC and SMC) by using red supergiant (RSG) stars and classical Cepheids as extinction tracers. The spectroscopic RSG samples are constructed based on the APOGEE spectral parameters, Gaia astrometric data, and multiband photometry. We establish the effective temperature–intrinsic color relations for RSG stars and determine the color excess ratio (CER) E ( λ − G _RP )/ E ( G _BP − G _RP ) for the LMC and SMC. We use classical Cepheids to derive base relative extinction ${A}_{{G}_{\mathrm{RP}}}/E({G}_{\mathrm{BP}}-{G}_{\mathrm{RP}})$ . The results are 1.589 ± 0.014 and 1.412 ± 0.041 for the LMC and SMC. By combining CERs with ${A}_{{G}_{\mathrm{RP}}}/E({G}_{\mathrm{BP}}-{G}_{\mathrm{RP}})$ , the optical–infrared extinction coefficients ${A}_{\lambda }/{A}_{{G}_{\mathrm{RP}}}$ are determined for 16 bands. We adjust the parameters of R _V -dependent extinction laws and obtain average extinction laws for the LMC and SMC of R _V = 3.40 ± 0.07 and R _V = 2.53 ± 0.10, respectively, which are consistent with Gordon et al. In the optical bands, the adjusted R _V extinction curves agree with the observations with deviations less than 3%.

Asteroseismology has become widely accepted as a benchmark for accurate and precise fundamental stellar properties. It can therefore be used to validate and calibrate stellar parameters derived from other approaches. Meanwhile, one can leverage large-volume surveys in photometry, spectroscopy, and astrometry to infer stellar parameters over a wide range of evolutionary stages, independently of asteroseismology. Our pipeline, SEDEX ( https://github.com/Jieyu126/SEDEX ), compares the spectral energy distribution predicted by the MARCS and BOSZ model spectra with 32 photometric bandpasses, combining data from nine major, large-volume photometric surveys. We restrict the analysis to targets with available spectroscopy from the APOGEE, GALAH, and RAVE surveys to lift the temperature−extinction degeneracy. The cross-survey atmospheric parameter and uncertainty estimates are homogenized with artificial neural networks. Validation of our results with CHARA interferometry, Hubble Space Telescope CALSPEC spectrophotometry, and asteroseismology shows that we achieve high precision and accuracy. We present a catalog of improved interstellar extinction ( ${\sigma }_{{A}_{V}}\simeq $ 0.14 mag) and stellar radii ( σ _R / R ≃ 7.4%) for ∼1.5 million stars in the low-to-high-extinction ( A _V ≲ 6 mag) fields observed by the spectroscopic surveys. We derive global extinctions for 184 Gaia DR2 open clusters and confirm the differential extinction in NGC 6791 and NGC 6819, which have been subject to extensive asteroseismic analysis. Furthermore, we report 36,854 double-lined spectroscopic main-sequence binary candidates. This catalog will be valuable for providing constraints on detailed modeling of stars and for constructing 3D dust maps of the Kepler field, the TESS Continuous Viewing Zones, and the PLATO long-duration observation fields.

Despite the impressive advances in Galactic structure studies, thanks to the large astronomical surveys, there remain several open questions. Although at low distances, optical surveys can bring us important information, the potential of NIR surveys, combined with the optical data, should be considered. In the present work, we explore the stellar distribution through the most recent NIR surveys toward low latitudes (|b| < 2° for 20° ≤ ℓ ≤ 346°) in the Galactic disk, such as 2MASS (entire plane), UKIDSS (20° ≤ ℓ ≤ 231°), and VVV-PSF data (295° ≤ ℓ ≤ 346°), avoiding directions toward the Galactic bar and bulge. Our final compilation contains nearly 140 million stars. We used this sample to perform total star counts at different longitudes, obtaining longitudinal profiles that are compared with those of other authors. For some directions, we obtained the stellar density as a function of distance to investigate the stellar distribution in the Galactic disk. As an example, the variation of the counts toward the Scutum arm tangential direction reveals the stellar content of two spiral arms, e.g., Sagittarius and Scutum. These are the preliminary results of a study that will cover a large extension of the Galactic disk.

Interstellar dust extinction curves provide valuable information about dust properties, including the composition and size of the dust grains, and are essential to correct observations for the effects of interstellar dust. In this work, we measure a representative sample of near-infrared (NIR; 0.8–5.5 μ m) spectroscopic extinction curves for the first time, enabling us to investigate the extinction at wavelengths where it is usually only measured in broad photometric bands. We use IRTF/SpeX spectra of a sample of reddened and comparison stars to measure 15 extinction curves with the pair method. Our sample spans A ( V ) values from 0.78 to 5.65 and R ( V ) values from 2.43 to 5.33. We confirm that the NIR extinction curves are well fit by a power law, with indices and amplitudes differing from sight line to sight line. Our average diffuse NIR extinction curve can be represented by a single power law with index α = 1.7, but because of the sight line-to-sight line variations, the shape of any average curve will depend on the parental sample. We find that most of the variation in our sample can be linked to the ratio of total-to-selective extinction R ( V ), a rough measurement of the average dust grain size. Two sight lines in our sample clearly show the ice extinction feature at 3 μ m, which can be fitted by a modified Drude profile. We find tentative ice detections with slightly over 3 σ significance in two other sight lines. In our average diffuse extinction curve, we measure a 3 σ upper limit of A (ice)/ A ( V ) = 0.0021 for this ice feature.

The results of the spectral and photometric studies of two Be/X-ray binaries, 1H1936+541 and 1H2202+501, are presented. The spectral class of the optical component of the 1H1936+541 system was determined for the first time, and the spectral class of the optical component of the 1H2202+501 system was refined. According to the results, the optical components of the systems 1H1936+541 and 1H2202+501 are Be stars of the spectral types B1Ve and B3Ve, respectively. These findings, as well as the well-known spectral type distribution of Be stars, can testify to the fact that the object 1H1936+541 belongs to X-ray binary systems. At the same time, taking into account the fact that a very small number of Be/X-ray binaries of the spectral type B3 is known so far, the object 1H2202+501 cannot unambiguously be classified as a Be/X-ray binary. The rotational speeds of the main components of these systems are 246 ± 11 km/s for 1H1936+541 and 111 ± 8 km/s for1H2202+501; the range of the tilt angles of their rotation axes is within 49°–82° and 21°–28°, respectively. Additionally, using the B and V band photometric observations and spectral classes obtained, the interstellar extinction values E(В – V), as well as the distances to the objects, were estimated. In particular, for 1H2202+501, the value of E(В – V) is 0.36 ± 0.03m, and the distance r ranges from 0.8 to 1.6 kpc. For the 1H1936+541 system, the following values were obtained: E(В – V) = 0.23 ± 0.03m and r = 2.1–3.6 kpc. The comparison of the distances to the objects with the data from the GAIA DR2 catalog (http://gea.esac.esa.int/archive/) revealed the coincidence of the corresponding values within the limits of errors. [ABSTRACT FROM AUTHOR]

The properties of red clump giants in the central regions of the Galactic bulge are investigated in the photometric Z and Y bands of the infrared VVV (VISTA/ESO) survey and the [3.6], [4.5], [5.8], and [8.0] μm bands of the GLIMPSE (Spitzer/IRAC) Galactic plane survey. The absolute magnitudes for objects of this class have been determined in these bands for the first time: MZ = −0.20 ± 0.04, MY = −0.470 ± 0.045, M[3.6] = −1.70 ± 0.03, M[4.5] = −1.60 ± 0.03, M[5.8] = −1.67 ± 0.03, and M[8.0] = −1.70 ± 0.03. A comparison of the measured magnitudes with the predictions of theoretical models for the spectra of the objects under study has demonstrated good mutual agreement and has allowed some important constraints to be obtained for the properties of bulge red clump giants. In particular, a comparison with evolutionary tracks has shown that we are dealing predominantly with the high-metallicity subgroup of bulge red clump giants. Their metallicity is slightly higher than has been thought previously, [M/H] ≃ 0.40 (Z ≃ 0.038) with an error of [M/H] ≃ 0.1 dex, while the effective temperature is 4250± 150 K. Stars with an age of 9-10 Gyr are shown to dominate among the red clump giants, although some number of younger objects with an age of ~8 Gyr can also be present. In addition, the distances to several Galactic bulge regions have been measured, as D = 8200-8500 pc, and the extinction law in these directions is shown to differ noticeably from the standard one. [ABSTRACT FROM AUTHOR]