Extension of the C star rotation curve of the Milky Way to 24 kpc

Demers and Battinelli published, in 2007 the rotation curve of the Milky Way based on the radial velocity of carbon stars outside the Solar circle. Since then we have established a new list of candidates for spectroscopy. The goal of this paper is to determine the rotation curve of the galaxy, as far as possible from the galactic center, using N type carbon stars. The stars were selected from their dereddened 2MASS colours, then the spectra were obtained with the Dominion Astrophysical Observatory and Asiago 1.8 meter telescopes. This publication adds radial velocities and Galactrocentric distances of 36 carbon stars, from which 20 are new confirmed. The new results for stars up to 25 kpc from the galactic center, suggest that the rotation curve shows a slight decline beyond the Solar circle.Comment: 13 pages, 3 figures, 1 table; accepted for publication in Astrophysic

Cool carbon stars in the halo: new very red or distant objects

The goal of this paper is to present and analyse a new sample of cool carbon (C)stars located in the halo. Twenty three new C stars were discovered. Spectra are typical of N-type stars with C2 and CN bands and sometimes Halpha in emission. ... Four objects are particularly red with J-K > 3, with 2 located at more than 5 kpc. from the Galactic plane. Eight additional objects with similar properties are found in the literature and our previous works. These 12 C stars could be useful to study mass loss at low metallicity. Two objects are at distances of 95 and 110 kpc. They are located in the region with galactocentric Z < -60 kpc in which the model of Law et al. predicts the Sgr stream to have a loop. (Abstact abridged)Comment: 16 pages, 12 figures, accepted by A

The Digitized First Byurakan Survey Data Base. Late-Type Stars Candidates. New Confirmations. I

International audienceThe Digitized First Byurakan Survey (DFBS) is the digitized version of the First Byurakan Survey (FBS, or Markarian survey). The FBS was the first systematic survey of the extragalactic sky. This objective-prism survey was carried out in 1965-1980 by B.E.Markarian and his colleagues using the 1 m Schmidt telescope of the Byurakan Astrophysical Observatory and resulted in discovery of 1517 UVX-excess (Markarian) galaxies. FBS low-resolution spectral plates have been used for a long time to search and study faint Late-Type Stars (LTS, M-type and C stars) at high Galactic latitudes. A total of 18 lists of the FBS LTS were published between 1990 and 2016. We report newly confirmed C and M giants, and also large amount of M dwarfs based on the Gaia DR3 BP/RP low-resolution spectroscopic data base. Some of the newly confirmed M dwarfs presents binary systems. Some of them are new eclipsing binaries. In our previous studies of the DFBS spectral plates, all were presented as LTS candidates. Gaia high-accuracy astrometric and photometric data and Transiting Exoplanet Survey Satellite (TESS) data are used to characterize these new confirmed LTS. TESS phase-dependent light curves show rotational modulations and flares for many new M dwarfs. This confirmations of the large number of completely new objects represents a very significant extension in the census of M giants, faint N-type Asymptotic Giant Branch C stars, CH-type C giants at high Galactic latitudes, and M dwarfs in the solar vicinity. Some objects are located more than 7 kpc from the Galactic plane. Ultimately, we aim to present value-added catalog and update the FBS LTS catalog. Note that a large amount of the blue stellar objects with UVX-excess and numerous of emission line objects were also detected

TYC 1417-891-1 and TYC 1478-742-1: Eclipsing Variable Stars. The Gaia EDR3 and TESS Photometric Data

International audienceBased on the TESS (Transiting Exoplanet Survey Satellite) phase dependent light curves, we confirm the eclipsing type variability nature for two G-type dwarfs: TYC 1417-891-1 and TYC 1478-742-1. Both objects show EA (Algol-type) light curves morphology. Orbital period for TYC 1417-891-1 is P ≈ 8.0 day and for TYC 1478-742-1, P ≈ 13.6 day. We present Gaia EDR3 and TESS catalogue important physical parameters as well as LAMOST spectra. Both objects are relatively bright and are located at a distance of 260.59 (±3.21) pc (TYC 1417-891-1) and 117.42 (±0.74) pc (TYC 1478-742-1). The TESS light curve of TYC 1478-742-1 shows also flares as well. We discuss possible nature of the secondary and faint objects around these stars

New Carbon Stars Confirmed in the Digitized First Byurakan Survey Database

Published in Astrofizika, 62, 4, 643-647, November 2019International audienc

Revised and updated catalogue of Byurakan-IRAS stars

Context.Five lists of late-type stars were published in Astrophysics in 1997–2001, found in the First Byurakan Survey low-dispersion spectroscopic plates as optical identifications of unidentified IRAS sources. These identifications were carried out in the region with \delta> +61\degr and |b|> 15 \degr with a surface of 1504 deg2. As a result, the catalogue of the Byurakan-IRAS Stars (BIS) was compiled. Its preliminary version has been available at the CDS since 2003. Aims.We revised and updated the BIS catalogue with the new data from recently published optical and infrared catalogues to give access to all available data and make further comparative studies of the properties of these objects possible. Methods.We made cross-correlations of the BIS catalogue with the MAPS, USNO-B1.0, and 2MASS, added updated SIMBAD data for the BIS objects, and provided accurate DSS1 and DSS2 positions and revised photometry. We also checked the objects for proper motion and variability. A refined classification from low-dispersion spectra in the Digitized First Byurakan Survey (DFBS) was carried out. Results.The revised and updated catalogue of 276 Byurakan-IRAS stars (BIS) is presented. Conclusions.The BIS catalogue can be used to study a complete sample of IRAS-selected stars and to investigate individual objects

Investigation of Long-Period Variables in the Catalina Southern Catalog: New Carbon Stars and False Objects

International audienceAs part of our ongoing study of the evolved giants in the galactic halo, we consider the sample of 1286 long-period variables (LPVs) in the southern hemisphere provided by the Catalina Sky Survey experiment. These LPVs have periods P > 80 days and amplitudes >0.2 mag. First, by using the Hamburg/ESO spectral survey, we aim to determine the spectral type as either M-type or C-type for objects located in the imprint of this survey, |b| > 30°. Of 135 LPVs obeying this selection, we classified 93, and found only two new carbon stars. Secondly, we consider faint LPVs. We discovered that many lie at ~1 arcmin from a bright Mira catalogued in the General Catalog of Variable Stars (GCVS) with identical period. We study these suspicious cases in detail, and conclude that for as many as 56 faint Catalina LPVs, their variability is due to contamination by light from the bright, neighboring GCVS Mira: an instrumental artefact. We conclude that when dealing with distant, faint Miras in the Catalina catalog, researchers should pay attention to the polluting effects of neighbouring bright and variable objects