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1691. Mrk 996 optical spectroscopy
ID:
ivo://CDS.VizieR/J/A+A/561/A64
Title:
Mrk 996 optical spectroscopy
Short Name:
J/A+A/561/A64
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present an integral field spectroscopic study with the Gemini Multi-Object Spectrograph (GMOS) of the unusual blue compact dwarf (BCD) galaxy Mrk 996. We show through velocity and dispersion maps, emission-line intensity and ratio maps, and by a new technique of electron density limit imaging that the ionization properties of different regions in Mrk 996 are correlated with their kinematic properties.
1692. Mrk 926 spectra
ID:
ivo://CDS.VizieR/J/A+A/657/A122
Title:
Mrk 926 spectra
Short Name:
J/A+A/657/A122
Date:
22 Feb 2022
Publisher:
CDS
Description:
Mrk926 is known to be a highly-variable AGN. Furthermore, it is known to show very broad-line profiles. We intended to study the continuum and line profile variations of this object with high temporal resolution in order to determine its broad-line region (BLR) structure, and to derive its black hole (BH) mass. We carried out a high-cadence spectroscopic variability campaign of Mrk926 with the 10m HET telescope, aided by photometric V-band data taken with the C18 telescope at the Wise Observatory, over a period of about five months. We extracted spectroscopic continuum and line light curves, and computed cross-correlation functions (CCFs) as well as velocity-resolved CCFs with respect to the combined spectroscopic and photometric V-band light curve. The continuum luminosity of Mrk926 showed a drastic decrease during our campaign. The luminosity dropped to less than 50% of its original luminosity within 2.5 months only. Furthermore, the spectra of Mrk926 show complex and very broad Balmer line profiles including outer Balmer satellites ranging from +/-5000 to +/-13000km/s. The integrated H{alpha}, H{beta} and HeI_5876_ line light curves are delayed relative to the continuum light curve. The Ha and Hb lines show two velocity-delay structures in the central part of their line profile (within +/-5000km/s) at ~10 and ~57 light-days, and at ~5 and ~48 light-days, respectively. These structures might be interpreted as the upper and lower half of an ellipse in the velocity-delay plane, that might be the signature of a line-emitting ring, inclined by ~50{deg} to the line of sight, orbiting the black hole at radii R of 33.5 and 26.5 light-days. We determined continuum luminosities log({lambda}*L_({lambda})_/erg/s) of 43.68 to 44.13 which are in good agreement with the established R_(BLR)-L_(AGN) relation. Adopting delays of 33.5 and 26.5 days for Ha and Hb, respectively, we derive a black hole mass of 1.1+/-0.2*10^8^M_{sun}_ which indicates a low Eddington ratio decreasing from 8 to 3 percent during our campaign. The Balmer satellite components show a higher correlation coefficient with respect to the continuum than the central line profile, and their response to the continuum variations is of the order of only 3-5 days. We attribute this to the central line segment and the Balmer satellites having different, spatially distinct regions of origin.
1693. MS bands of SiC_2_ in LMC carbon stars
ID:
ivo://CDS.VizieR/J/MNRAS/355/1196
Title:
MS bands of SiC_2_ in LMC carbon stars
Short Name:
J/MNRAS/355/1196
Date:
21 Oct 2021
Publisher:
CDS
Description:
From a sample of 304 carbon stars in the central parts of the Large Magellanic Cloud (LMC), ~27 per cent have Merrill-Sanford (MS) bands of the SiC2 molecule. The data are based on a uniform set of spectra taken with 2dF on the Anglo-Australian Telescope, and give useful statistics on the incidence of MS bands and on their correlation (or otherwise) with other properties. All of these are red stars, cooler than 3100 K. The proportion of stars showing the bands is highest amongst the coolest stars, but not all very cool stars show the bands. There is no evidence that MS bands are more common in J-type stars (carbon stars with a high ^13^C/^12^C ratio) than in N-type carbon stars, at least within this sample of LMC stars. There is no apparent correlation with stellar variability, or between the photospheric temperature [as measured by (J-K)] and the occurrence of the 'hot' MS bands from excited molecular states.
1694. M82 spectral maps
ID:
ivo://CDS.VizieR/J/A+A/578/A49
Title:
M82 spectral maps
Short Name:
J/A+A/578/A49
Date:
21 Oct 2021
Publisher:
CDS
Description:
M82 is one of the nearest and brightest starburst galaxies. It has been extensively studied in the past decade and by now is considered the prototypical extragalactic photon-dominated region (PDR) and a reference for studying star formation feedback. Our aim is to characterize the molecular chemistry in M82 at spatial scales of giant molecular clouds (GMCs), ~100pc, to investigate the feedback effects of the star formation activity.
1695. M-subdwarf research. I. LAMOST DR4 spectra obs.
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).
1696. 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.
1697. M subdwarfs VLT/UVES high resolution spectra
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.
1698. M17-SW datacubes in C and CO lines
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.
1699. MSX Infrared Astrometric Catalog
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.
1700. M-type stars in LAMOST DR5
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.

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