Search and study of extremely red objects in the DFBS database

The Digitized First Byurakan Survey (DFBS) is the digitized version of the famous Markarian survey (or the First Byurakan Survey, FBS). Using the BSpec extraction software written by one of the authors (GC), we started to search for faint and very red objects in the DFBS database, which is now available online. Among the extremely red objects we expect mainly stars of late M8-M9 sub-types or very late N-type Carbon stars close to the FBS detection limit. However, some high-redshift QSOs may be found as well. The criteria for searching of such objects in the DFBS are based on spectral length (l<40pix, compared to the total length of l=10^7pix). To avoid misselection, we have excluded objects near the plate limit, as due to the low sensitivity of the photographic emulsion in blue, all such spectra are short. On the other hand, very bright stars show longer spectra even when their spectral type is late, so the criteria must be weakened to l<50pix. We obtained the first list of candidate objects for the DFBS zone with central DEC=+39° with their positions, B and R magnitudes, and other spectral data. Our purpose is to complete the selection procedure for such objects, based on all FBS sky area coverage and investigation of these objects at high Galactic latitudes. Cross-correlations with X-ray, optical, IR, and radio catalogs have been made. The preliminary results will be reported.