BVIc Photometry for 14 Blue Variables

L. N. Berdnikov^#1, E. N. Pastukhova^#2

#1. Sternberg Astronomical Institute, Lomonosov State University, Moscow, Russia #2. Institute of Astronomy, Russian Academy of Sciences, Moscow, Russia

Received:   19.09.2013;   accepted:   20.04.2015
(E-mail for contact: leonid.berdnikov@gmail.com, pastukhova@sai.msu.ru)

Comments:


1. B–V = 0.07, J–K = –0.072.

2. B–V = 0.18, J–K = 0.013.

3. B–V = 0.15, J–K = –0.017.

4. B–V = –0.08, J–K = –0.043.

5. B–V = –0.04, J–K = –0.001.

6. B–V = 0.05, J–K = –0.041.

7. B–V = 0.00, J–K = 0.026.

8. B–V = 0.02, J–K =–0.006.

9. B–V = 0.10, J–K = – 0.012.

10. B–V = 0.14, J–K = 0.129.

11. B–V = 0.21, J–K = 0.100.

12. B–V = 0.28, J–K = 0.044.

13. B–V = 0.03, J–K = –0.050.

14. B–V = 0.28, J–K = 0.679:.

Remarks:
In 2006–2012, we performed photometric observations of selected variable stars classified as Cepheids in the ASAS-3 Catalog (Pojmanski 2002) with the 76-cm telescope of the South African Astronomical Observatory (SAAO, Republic of South Africa). Observations were made with a photoelectric photometer on JD 2454000–2454479, and a SBIG ST-10XME CCD camera was used on the rest of the days. Photoelectric observations are marked with circled dots on the light curves. We used BVI filters of the Kron–Cousins system (Cousins 1976). Analysis of observations revealed that all 14 stars were too blue for Cepheids: their mean B–V colors were between –0.04 and +0.28 mag, and J–H colors (drawn from 2MASS catalogue, Skrutskie et al. 2006) were between –0.07 and +0.10 mag. These variables are not identified with X-ray sources, and they have small amplitudes, which increase from B band to I band; for some of them, the time of minimum on the B-band light curve coincides with that of maximum in V and I. It is difficult to classify these variable stars according to known types of the GCVS (Samus et al. 2007–2013), hence we give one-wave periods for all objects, 1.5 to 6 days, but, most likely, these variables are eclipsing binaries. If it is so, the periods should be doubled.

Acknowledgments: Our studies are supported by grants from the Russian Foundation for Basic Research (grants No. 11-02-00495, 13-02-00203 and 13-02-00664) and from the Program "Transitional and Explosive Processes in Astrophysics" of the Presidium of Russian Academy of Science. We would like to thank the administration of the SAAO for allocation of telescope time.

References:
Cousins, A.W.J., 1976, Mem. R. Astron. Soc., 81, 25
Pojmanski, G., 2002, Acta Astronomica, 52, 397
Samus, N.N., Durlevich, O.V., Kazarovets, E V., Kireeva, N.N., Pastukhova E.N., et al., 2007–2013, General Catalogue of Variable Stars, Centre de Données Astronomiques de Strasbourg, B/gcvs
Skrutskie, M.F., Cutri, R.M., Stiening, R., et al., 2006, Astron. J., 131, 1163