Investigation of DFBS late type stars at high galactic latitudes

Abstract

We study in this thesis relatively bright late-type giants found in the First Byurakan Survey (FBS) data base. We present the 2nd version of the catalogue of FBS LTS with new data (FBS LTS v2), 1471 objects. It is a homogeneous and complete database for high- Galactic late-type stars, including M and C types. Since 2007, all FBS low-resolution spectral plates are digitized. All DFBS spectral plates are analyzed with FITSView and SAO Image ds9 and numerous relatively faint LTS were discovered. We have made cross-correlation with DFBS, USNO-B1.0, 2MASS, AllWISE, IRAS PSC/FSC, AKARI, ROSAT BSC/FSC, GCVS, SDSS and added updated SIMBAD data. For numerous new detected objects, we present accurate DSS2 positions, approximate spectral subtypes refined from the DFBS low-dispersion spectra, luminosity classes estimated from 2MASS colours, and available proper motions for 1471 FBS LTS. The Revised and Updated Catalogue v2 lists a large number of completely new objects, which promise to extend very significantly the census of M giants, faint N-type AGB carbon stars, CH-type carbon giants at high Galactic latitudes, also M dwarfs in the Solar vicinity up to 16.0m-17.0m in visual. Phase dependent light-curves from large sky area variability data bases such as Catalina Sky Survey (CSS) and All-Sky Automated Survey for Supernovae (ASAS-SN), and the early installment of the third Gaia data release (Gaia EDR3) photometric and astrometric data have been used to characterize our sample of 1100 M-type giants found and 130 C-type stars at high latitudes. We show the behaviour of our sample stars in a Gaia DR2 color–absolute magnitude diagram (CaMD), the Gaia-2MASS-diagram, including two alternative versions, and the logP-K-diagram. In this way we explore the potential of these diagrams and their combination for the analysis and interpretation of datasets of LPVs. We show the possibility to classify stars into M- and C-types and to identify the mass of the bulk of the sample stars.