Abstract Title: *
A search for new variable objects in the field of OB81 association in M31 galaxy

Authors: *
Mitko Churalski, Petko Nedialkov and Antoniya Valcheva

Institution: *
Department of Astronomy, Sofia University

Preferred format: *
Oral

Abstract Text: *
We perform an astrometry with accuracy of ~0.05 arcsec for 678 stars with UB photometry in
the 5.6'х5.6' field of OB81 association in M31 galaxy. Their photometry was carried out on CCD
images, obtained with the NAO-Rozhen 2-meter telescope in Aug. 2000 (Kurtev 2002). The
comparison with the Aug 2000- Sept. 2002 stellar photometry within the same field, published in
the M31 UBVRI catalog (Massey et al. 2016) showed no zero-point difference in B-band,
whereas in U-band, a systematic difference of 0.13 ± 0.03 mag emerged. Thirteen candidates
for variable objects have been detected at level, greater than 3 sigma. Five of them are known
variables of the delta Cep type and one star has been detected as IR variable by WISE mission.
The remaining 7 candidates are newly detected variables, but only one of them at detection
level, greater than 4 sigma.