VRc photometry of new variable stars detected in a field from the photographic plate collection of Sternberg Institute

A. Zheleznyak^#1, V. Shevchenko^#1,2, I. Slyusarev^#1,2, A. M. Zubareva^#3,4, V. Checha^#2, A. V. Lapko^#2

#1. Institute of Astronomy, Kharkiv Karazin National University, Kharkiv, Ukraine; #2. Department of Astronomy and Space Informatics, Kharkiv Karazin National University, Kharkiv, Ukraine; #3. Institute of Astronomy, Russian Academy of Sciences, Moscow, Russia; #4. Sternberg Astronomical Institute, Lomonosov Moscow State University, Moscow, Russia.

Received:   23.01.2015;   accepted:   16.11.2015
(E-mail for contact: shevchenko@astron.kharkov.ua)

Comments:


1. MinII = 16^m.43.

2. MinII = 15^m.54.

3. M–m = 0.35 P.

4. MinII = 16^m.43.

5. We observed only one minimum and one maximum of brightness.

6. MinII = 16^m.6.

7. We observed the star on one night only. If our assumption about EW type is correct, the time interval covered and the shape of the light curve correspond to a period close to 0^d.408.

Remarks:
A field centered at β Cassiopeiae is one of those included in the program of digitizing the Sternberg Institute's plate collection (Kolesnikova et al. 2008). Several variable stars were suspected of variability in the field as a result of this program. We participate in CCD checks of suspected variables; the results will be presented elsewhere. In the course of this work, we found seven new variable stars in the field. Observations were carried out in 2013 and 2014 at Chuguev Observational Station of the Astronomical Institute of Kharkiv Karazin National University (KhNU) with the 70-cm reflector as a part of research programs for students (Shevchenko et al. 2013). The telescope is equipped with a FLI 47-10 Peltier-cooled CCD camera (1027×1056 pixels, pixel size 13×13 μm). Images were taken in V and R bands of the Johnson–Cousins photometric system. Original CCD frames were calibrated for dark current and flat field in the standard manner. The methods of CCD observations and reductions were described by Krugly et al. (2002) and Tereschenko et al. (2010). The method for detecting variable stars was described by Zheleznyak and Kravtsov (2003). The brightness measurements of stars on CCD images were made using the aperture photometry package (ASTPHOT) developed by Mottola et al. (1995). The absolute calibrations of the magnitudes were performed with standard star sequences from Landolt (1992). The accuracy of the resultant absolute photometry is within 0.01–0.03 mag.

References:
Kolesnikova, D. M., Sat, L. A., Sokolovsky, K. V., et al., 2008, Acta Astron., 58, 279.
Krugly, Yu. N., Belskaya, I. N., Shevchenko, V. G., et al., 2002, Icarus, 158, 294.
Landolt, A. U. 1992. Astron. J., 104, 340.
Mottola, S., de Angelis, G., di Martino, M., et al., 1995, Icarus, 117, 62.
Shevchenko, V., Drobjazko, N., Slyusarev, I., et al., 2013, Perem. Zvezdy Prilozh., 13, No. 7.
Tereschenko, I. À., Shevchenko, V. G., Krugly, Yu. N., 2010, Kinemat. Phys. Cel. Bodies, 26, 89.
Zheleznyak, A. P., Kravtsov, V. V., 2003, Astron. Letters, 29, 599.