- ID:
- ivo://CDS.VizieR/J/ApJS/240/31
- Title:
- M-subdwarf research. I. LAMOST DR4 spectra obs.
- Short Name:
- J/ApJS/240/31
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We propose a revision of the system developed by Lepine+ (2007ApJ...669.1235L) for spectroscopic M-subdwarf classification. Based on an analysis of subdwarf spectra and templates from Savcheva+ (2014ApJ...794..145S), we show that the CaH1 feature originally proposed by Gizis (1997, J/AJ/113/806) is important in selecting reliable cool subdwarf spectra. This index should be used in combination with the [TiO5, CaH2+CaH3] relation provided by Lepine+ to avoid misclassification results. In the new system, the dwarf-subdwarf separators are first derived from a sample of more than 80000 M dwarfs and a "labeled" subdwarf subsample, and these objects are all visually identified from their optical spectra. Based on these two samples, we refit the initial [TiO5, CaH1] relation and propose a new [CaOH, CaH1] relation supplementing the [TiO5, CaH1] relation to reduce the impact of uncertainty in flux calibration on classification accuracy. In addition, we recalibrate the {zeta}TiO/CaH parameter defined in Lepine+ to enable its successful application to Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) spectra. Using this new system, we select candidates from LAMOST Data Release 4 and finally identify a set of 2791 new M-subdwarf stars, covering the spectral sequence from type M0 to M7. This sample contains a large number of objects located at low Galactic latitudes, especially in the Galactic anti-center direction, expanding beyond previously published halo- and thick disk-dominated samples. Besides, we detect magnetic activity in 141 objects. We present a catalog for this M-subdwarf sample, including radial velocities, spectral indices and errors, and activity flags, with a compilation of external data (photometric and Gaia Data Release 2 astrometric parameters).
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1652. M-Subdwarfs
- ID:
- ivo://CDS.VizieR/J/AJ/113/806
- Title:
- M-Subdwarfs
- Short Name:
- J/AJ/113/806
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a spectroscopic classification system for M-dwarfs and M-subdwarfs based on quantitative measures of TiO and CaH features in the region 6200 - 7400 Angstroms. Our sample of cool stars covers the range from solar metallicity stars to the most extreme subdwarfs known. Using synthetic spectra computed by Allard and Hauschildt (1995), we derive metallicities for the stars. Stars are classified as dwarfs (M V), subdwarfs (sdM), or extreme subdwarfs (esdM). These classifications correspond to [m/H] = 0.0, -1.2, and -2.0 respectively. Our metallicity scale agrees with theoretical HR diagrams and HST globular cluster measurements. We discuss some nearby subdwarfs of particular interest in light of our metallicity scale. We include photometry compiled from the literature.
- ID:
- ivo://CDS.VizieR/J/A+A/564/A90
- Title:
- M subdwarfs VLT/UVES high resolution spectra
- Short Name:
- J/A+A/564/A90
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- M subdwarfs are metal poor and cool stars. They are important probes of the old galactic populations. However, they remain elusive due to their low luminosity. Observational and modeling efforts are required to fully understand their physics and to investigate the effects of metallicity in their cool atmospheres. We perform a detailed study of a sample of subdwarfs to determine their stellar parameters and constrain the stat-of-the art atmospheric models. We present UVES/VLT high resolution spectra of three late-K subdwarfs and 18 M subdwarfs. Our atlas covers the optical region from 6400{AA} up to the near infrared at 8900{AA}. We show spectral details of cool atmospheres at very high resolution (R~40000) and compare with synthetic spectra computed from the recent BT-Settl atmosphere models. Our comparison shows that molecular features (TiO, VO, CaH), and atomic features (FeI, TiI, NaI, KI) are well fitted by current models. We produce an effective temperature versus spectral type relation all over the subdwarf spectral sequence. Thanks to the high resolution of our spectra, we perform a detailed comparison of line profiles of individual elements such as FeI, CaII, TiI, and are able to determine accurate metallicities of these stars. These determinations contribute to calibrate the relation between metallicity and molecular band strength indices from low-resolution spectra. This work shows that the new generation of models are able to reproduce various spectral features of M subdwarfs. Working with these high resolution spectra allowed us to disentangle the atmospheric parameters (effective temperature, gravity, metallicity), which is not possible when using low resolution spectroscopy or photometry.
- ID:
- ivo://CDS.VizieR/J/A+A/575/A9
- Title:
- M17-SW datacubes in C and CO lines
- Short Name:
- J/A+A/575/A9
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We probe the column densities and masses traced by the ionized [CII] and neutral [CI] atomic carbon with spectrally resolved maps, and compare them to the diffuse and dense molecular gas traced by [CI] and low-J CO lines toward the star-forming region M17 SW. We mapped a 4.1pcx4.7pc region in the [CI] 609{mu}m line using the APEX telescope, as well as the CO isotopologues with the IRAM 30m telescope. Data are analyzed based on velocity channel maps that are 1km/s wide. We correlate their spatial distribution with that of the [CII] map obtained with SOFIA/GREAT. Optically thin approximations were used to estimate the column densities of [CI] and [CII] in each velocity channel.
- ID:
- ivo://CDS.VizieR/V/98
- Title:
- MSX Infrared Astrometric Catalog
- Short Name:
- V/98
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The MSX Infrared Astrometric Catalog has been contructed as a tool for improving the pointing accuracy of infrared observations. The catalog contains 177,860 astrometric stars, 61,242 which have been identified with their infrared counterparts from IRAS catalogs and the Catalog of Infrared Observations through position and color matching. Infrared flux densities are predicted for 6 wavelength bands between 4 and 22um. The catalog identifications are complete to within the spatial coverage of current surveys for those astrometric stars brightest in the infrared. By predicting fluxes of astrometric stars without IR identifications we are able to extend the catalog to areas of the sky which were incomplete in the IRAS catalogs. Furthermore, by retaining stars below the brightness limit of current surveys we are able to provide better spatial coverage to help point or position the next generation of infrared telescopes.
- ID:
- ivo://CDS.VizieR/J/ApJS/244/8
- Title:
- M-type stars in LAMOST DR5
- Short Name:
- J/ApJS/244/8
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new catalogs of M giant and M dwarf stars from the Large Sky Area Multi-Object Fibre Spectroscopic Telescope (LAMOST) data release 5 (DR5). In total, 39796 M giants and 501152 M dwarfs are identified from the classification pipeline. The template-fitting results contain M giants with 7 temperature subtypes from M0 to M6, M dwarfs with 18 temperature subtypes from K7.0 to M8.5, and 12 metallicity subclasses from dMr to usdMp. We cross-matched our M-type catalog with the Two Micron All-Sky Survey (2MASS) and Wide-field Infrared Survey Explorer (WISE) catalog to obtain infrared magnitude and colors. Adopting the distances derived from the parallaxes in Gaia DR2, the M_G_ versus (G_bp_-G_rp_)_0_ diagram shows that there are also early-type stars and white dwarf-M dwarf binaries included in our M-type stars sample, with a contamination rate of about 4.6% for M giants and 0.48% for M dwarfs. We found that CaH spectral indices are an efficient selection criteria for carbon stars. A total of 289 carbon stars were identified from the M giants sample, and further confirmed by LAMOST spectra.
- ID:
- ivo://CDS.VizieR/J/MNRAS/394/21
- Title:
- Multi-epoch spectroscopy of SN 1994W
- Short Name:
- J/MNRAS/394/21
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a multi-epoch quantitative spectroscopic analysis of the Type IIn supernova (Type IIn SN) 1994W, an event interpreted by Chugai et al. (2004MNRAS.352.1213C) as stemming from the interaction between the ejecta of a SN and a 0.4M_{sun}_ circumstellar shell ejected 1.5yr before core collapse.
- ID:
- ivo://CDS.VizieR/J/A+A/399/813
- Title:
- Multiple merging events in Abell 521
- Short Name:
- J/A+A/399/813
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a detailed spatial and dynamical analysis of the central ~2.2Mpc(Ho=75km/s/Mpc) region of the galaxy cluster Abell 521 (z=0.247), based on 238 spectra (of which 191 new measurements) obtained at the 3.6m Telescope of the European Southern Observatory and at the Canada-France-Hawaii Telescope. From the analysis of the 125 galaxies that are confirmed members of the cluster, we derive a location ("mean" velocity) of C_BI_=74019^{+112}^_{-125}_km/s and detect a complex velocity distribution with high velocity scale ("dispersion", S_BI_=1325^{+145}^_{-100}_km/s), but clear departure from a single Gaussian component. When excluding a possible background group of four galaxies, the velocity dispersion remains still large (~1200 km/s).
- ID:
- ivo://CDS.VizieR/J/ApJ/852/108
- Title:
- Multiwavelength obs. of gamma-ray NOVA Sco 2012
- Short Name:
- J/ApJ/852/108
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- It has recently been discovered that some, if not all, classical novae emit GeV gamma-rays during outburst, but the mechanisms involved in the production of gamma-rays are still not well understood. We present here a comprehensive multiwavelength data set-from radio to X-rays-for the most gamma-ray-luminous classical nova to date, V1324 Sco. Using this data set, we show that V1324 Sco is a canonical dusty FeII-type nova, with a maximum ejecta velocity of 2600km/s and an ejecta mass of a few x10^-5^M_{sun}_. There is also evidence for complex shock interactions, including a double-peaked radio light curve which shows high brightness temperatures at early times. To explore why V1324 Sco was so gamma-ray luminous, we present a model of the nova ejecta featuring strong internal shocks and find that higher gamma-ray luminosities result from higher ejecta velocities and/or mass-loss rates. Comparison of V1324 Sco with other gamma-ray-detected novae does not show clear signatures of either, and we conclude that a larger sample of similarly well-observed novae is needed to understand the origin and variation of gamma-rays in novae.
- ID:
- ivo://CDS.VizieR/J/A+A/545/A97
- Title:
- 0.8-6{mu}m calibrated spectrum of 55 Cnc
- Short Name:
- J/A+A/545/A97
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The ACME Spectra project provides absolutely calibrated, mostly empirical spectra of exoplanet host stars for use in analysis of the stars and their planets. Spectra are obtained from ground-based telescopes and are tied directly to calibrated ground- and space-based photometry. The spectra remain only "mostly" empirical because of telluric absorption, but interpolation of stellar models over the gaps in wavelength coverage provides continuous stellar spectra. Among other uses, the spectra are suitable for precisely converting observed secondary eclipses (occultations) into absolute flux units with minimal recourse to models. In this paper, I introduce ACME's methods and present a calibrated spectrum of the nearby, super-Earth hosting star 55 Cancri that spans the range from 0.81-5.05um.
