A total of 18 lists of the First Byurakan Survey of Late-Type Stars (FBS LTS) were published between 1990 and 2016. The stars were found on FBS low-dispersion spectroscopic plates. A systematic search and selection were carried out on a surface of ∼16 000 deg2 on almost the whole area of the FBS. As a result, the ‘Revised and Updated Catalogue of the First Byurakan Survey of Late-Type Stars’ was generated (FBS LTS v1; 1045 objects). We present the second version of the catalogue of FBS LTS with new data (FBS LTS v2), comprising 1471 objects. It is a homogeneous and complete data base for high-Galactic-latitude, late-type stars, including M and C types. Since 2007, all FBS low-resolution spectral plates have been digitized. All digitized FBS (DFBS) spectral plates have been analysed with FITSView and SAO Image ds9, and numerous relatively faint LTSs have been discovered. We have performed cross-correlations 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 LTSs. The Revised and Updated Catalogue v2 lists a large number of completely new objects, which promises to extend very significantly the census of M giants, faint N-type asymptotic giant branch carbon stars, CH-type carbon giants at high Galactic latitudes, and M dwarfs in the Solar vicinity up to 16.0–17.0 mag in the visual. Some important data from Gaia DR2 and supplementary spectra from the Byurakan Astrophysical Observatory 2.6-m and LAMOST telescopes are presented.

International audienceThe goal of this paper is to present an optical variability study of the comparatively faint carbon (C) stars which have been discovered by searching the First Byurakan Survey (FBS) low-resolution (lr) spectral plates at high Galactic latitudes using recent wide-area variability databases. The light curves from the Catalina Sky Survey (CSS) and Northern Sky Variability Survey (NSVS) databases were exploited to study theit variability nature. In this paper, first in this series, the variability classes are presented for 54 N-type Asymptotic Giant Branch (AGB) C stars. One finds that 9 stars belongs to the group of Mira-type, 43 are Semi-Regular (SR), and 2 stars are Irregular (Irr)-type variables. The variability types of 27 objects has been established for the first time. K-band absolute magnitudes, distances, and height from the Galactic plane were estimated for all of them. We aim to better understand the nature of the selected C stars through spectroscopy, 2MASS photometric colors, and variability data. Most of the tools used in this study are developed within the framework of the Astronomical Virtual Observatory

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