New Variable Stars in the Open Cluster NGC 7129

A. A. Popov, V. V. Krushinsky, E. A. Avvakumova, A. F. Punanova, I. S. Zalozhnih, A. Y. Burdanov
Kourovka Astronomical Observatory of Ural State University, Yekaterinburg, Russia

Received:   19.04.2011;   accepted:   13.07.2011
(E-mail for contact: apopov66@gmail.com)

Comments:


1. I = 14.38 – 14.72.

2. R = 16.92 – 17.67; I = 15.96 – 16.72.

3. R = 12.77 – 12.89; I = 11.20 – 11.24.

4. R = 13.05 – 13.41; I = 10.84 – 11.02.

5. R = 14.40 – 14.55; I = 12.27 – 12.33.

6. IRAS 21419+6543.

7. R = 15.62 – 16.48; I = 14.86 – 15.39.

8. R = 12.29 – 12.56; I = 10.27 – 10.41.

9. R = 10.85 – 10.97.

10. I = 14.09 – 14.22.

11. X-ray source SS2009 NGC7129-S3-X1. A T Tau variable according to Kun et al. (2009).

12. R = 16.06 – 17.38; I = 14.78 – 16.10.

13. X-ray source SS2009 NGC7129-S3-X2. R = 14.27 – 14.50; I = 13.36 – 13.50.

14. X-ray source SS2009 NGC7129-S3-X9.

15. X-ray source SS2009 NGC7129-S3-X20.

16. X-ray source SS2009 NGC7129-S3-X25. A T Tau variable according to Magakian et al. (2004).

17. X-ray source SS2009 NGC7129-S3-X29. I = 14.89 – 15.07.

18. X-ray source SS2009 NGC7129-S2-X1. A T Tau variable according to Magakian et al. (2004). R = 16.73 – 17.83; I = 15.70 – 16.38.

19. X-ray source SS2009 NGC7129-S3-X30. A T Tau variable according to Kun et al. (2009). R = 15.21 – 15.47; I = 14.10 – 14.26.

20. X-ray source SS2009 NGC7129-S2-X4.

22. X-ray source SS2009 NGC7129-S2-X9. R = 12.83 – 12.96; I = 12.41 – 12.51.

23. O'Connell effect is possible. R = 13.63 – 13.89; I = 12.82 – 13.04.

25. IRAS 21404+6608. A T Tau variable according to Kun et al. (2009). R = 14.37 – 14.94; I = 13.17 – 13.63.

26. R = 13.08 – 13.20; I = 10.93 – 10.99.

27. I = 15.45 – 15.64.

28. I = 10.32 – 10.39.

Remarks:
Photometric observations of the young open cluster NGC 7129 were performed between October 22, 2009 and November 20, 2010 in the Kourovka Astronomical Observatory of Ural State University. We used one of the MASTER robotic telescopes (Lipunov 2004), equipped with the Apogee AltaU16 4096 x 4096 Peltier-cooled CCD camera, its pixel size being 9 x 9 μm. The observations were carried out in the VRI filters of the Johnson–Cousins system. The initial reductions (dark subtraction and flat-fielding) and photometry were performed using the IRAF V2.14 software package. Photometry of 2300 stars was made in a small area (75' x 45') of the frame. The photometric uncertainty was from 0.007 to 0.06 mag for 700 stars with magnitudes from 11 to 16. We found 23 new variable stars and obtained new photometric data for 5 known variable stars, the results are presented in the Table. We also observed the previously known variables V373 Cep, V350 Cep, and Cl NGC7129 SV1 (Semkov 2003), our results are in general agreement with data available for these stars. The suspected variable NSV 13871 showed no brightness variations in excess of photometry errors, i.e. it is found constant within 0.02 mag.

From our observations, we classify three stars as eclipsing binaries of EA, EB, EW types and two stars, as probable BY-type rotating variables by the shape of their light curves. To determine the periods, we used the period-search software developed by Dr. V.P. Goranskij for Windows environment. For classification of the other objects, we use their (J–H) and (H–K) color indices from the 2MASS survey. The stars v233, v884, v1108, v1111, v1196, v1245, v1258, v1309, v1350, v1361, v1388, v1572, v1895, v2068 exhibit a significant infrared excess. They are located in the area of classical T Tau stars in the (J–H) vs (H–K) diagram (Meyer et al. 1997). Five of these stars were previously classified as T Tau variables based on the presence of H_α emission in their spectra (Stelzer & Scholz 2009; Kun et al. 2009; Magakian et al. 2004). We believe that the nine other stars with similar positions in the diagram are also Orion variables. The slowly pulsating stars v526, v579, v596, v990, v1054, v1412, v2042, v2105 are located in the area of giant stars in the (J–H) vs (H–K) diagram. We classified this stars as SR: or LB: variables. Our classification of IN and SR stars is only provisional. Lond series of observations are needed to improve classification of these stars. The star coordinates were taken from the 2MASS catalog. The information on X-ray sources was taken from Stelzer and Scholz (2009). The spectral types are from Kun et al. (2009).

In our light curves, the V magnitudes are plotted as black squares; R magnitudes, as red triangles; and I magnitudes, as blue crosses. DV and DR in the panels are magnitude shifts applied respectively to the V- and R-band data.

Acknowledgements: This study was financially supported by the State Agency for Science and Innovation of the Ministry of Education and Science of the Russian Federation (state contracts No. 02.740.11.0249 and No. 02.740.11.0247), by the State Agency for Education of the Ministry of Education and Science of the Russian Federation (state contracts No. 540 and No. 919).

References:
Kun, M., Balog, Z., Kenyon, S.J., et al., 2009, Astrophys. J. Suppl., 185, 451
Lipunov, V.M., Krylov, A.V., Kornilov, V.G., et al., 2004, Astron. Nachr., 325, 580
Magakian, T.Yu., Movsessian, T.A., Nikogossian, E.H., 2004, Astrophysics, 47, 519
Meyer, M.R., Calvet, N., Hillenbrand, L.A., 1997, Astron. J., 114, 288
Semkov, E.H., 2003, IBVS, No. 5406
Stelzer, B., Scholz, A., 2009, Astron. Astrophys., 507, 227