| Article in PDF |
"Peremennye Zvezdy", Prilozhenie, vol. 15, N 7 (2015) |
| #1. Kourovka Astronomical Observatory of Ural Federal University, Yekaterinburg,
Russia;
#2. Institute of Astronomy, Russian Academy of Sciences, Moscow, Russia; #3. Sternberg Astronomical Insitute, Lomonosov Moscow State University, Moscow, Russia; #4. Irkutsk State University, Irkutsk, Russia. |
| ISSN 2221–0474 |
Received: 9.09.2014; accepted: 19.11.2015
(E-mail for contact: apopov66@gmail.com)
|
Comments:
1. Twice longer period is also possible.
2. Twice longer period is also possible.
3. Twice longer period is also possible.
4. MinII = 14m.49.
5. MinII = 11m.45.
6. MinII = 14m.79.
7. We observed only two brightness minima.
8. Former transiting exoplanet candidate of spectral type G8V (Burdanov et al. 2013) is an eclipsing binary with secondary minimum 0.009 mag deep. A secondary eclipse was revealed during photometric follow-up observations.
9. MinII = 16m.46.
10. Twice longer period is also possible.
11. MinII = 10m.95:.
12. MinII = 13m.14. Combined brightness of two close stars, 2MASS J20280965+5026039 and 2MASS J20280935+5026078 (TF1-07140), was measured. The first one probably varies.
13. MinII = 14m.52.
14. We observed only one decrease of brightness.
15. MinII = 13m.94:. Twice longer period is also possible.
16. MinII = 14m.51.
17. Twice longer period is also possible.
18. MinII = 12m.05.
19. MinII = 15m.19.
20. Orbital eccentricity is possible.
21. MinII = 14m.13.
22. MinII = 15m.41.
23. MinII = 13m.46. O'Connell effect.
24. We observed only one decrease of brightness.
25. MinII = 14m.85. Twice shorter period is also possible.
26. Twice longer period is also possible.
27. Twice longer period is also possible.
28. We observed only one decrease of brightness.
29. MinII = 12m.71. There is an orbital eccentricity.
30. MinII = 15m.18.
31. MinII = 14m.18. O'Connell effect.
32. MinII = 13m.21.
33. MinII = 14m.83.
34. MinII = 14m.57. O'Connell effect.
35. MinII = 14m.49. O'Connell effect.
36. Twice longer period is also possible.
37. MinII = 17m.10:. Orbital eccentricity is possible.
38. MinII = 13m.35. There is an orbital eccentricity.
39. Twice longer period is also possible.
40. Twice longer period is also possible.
41. We observed only one decrease of brightness.
42. MinII = 15m.7.
43. MinII = 13m.47:. O'Connell effect.
44. Twice longer period is also possible.
45. MinII = 15m.40.Remarks:
Kourovka Planet Search (KPS) is a project aimed at finding new transiting exoplanets using the Master-II-URAL telescope. Our pilot observations were obtained during short and bright summer nights of 2012 at the Kourovka Astronomical Observatory of the Ural Federal University. We observed the first 2 × 2 square degree target field in Cygnus centred at α = 20h30m.0, δ = +50°30'.0 (J2000.0).
Main part of observations were carried out during May–August, 2012 with additional sets in December, 2012, March–May, 2013 and July–August, 2013 with the Master-II-URAL robotic telescope.
The system consists of two parallel optical telescopes (40-cm aperture, 1:2.5 focal ratio) installed on the same mount and equipped with two Peltier cooled Apogee Alta U16M CCD cameras. The image scale is 1.85''/px. Observations can be performed simultaneously in two filters of the Johnson–Cousins BVRI photometric system (Lipunov et al. 2010).
Our main observational set lasted for 36 nights in R band with 50-second exposures. There were several additional observational nights were in December, 2012 in R and V bands with 180-second exposures. The longest additional observational set was conducted during March–May, 2013 for 16 nights in B and V bands with 120-second exposure times. We carried out our final set in 2013 July–August with 120-second exposures in V and R bands.
Astrometric reductions of all frames were performed using the Astrometry.net console application (Lang et al. 2010). All objects were identified using 2MASS catalogue (Skrutskie et al. 2006). Initial photometric reductions and aperture photometry were performed in the IRAF package (Tody 1986). We used the Astrokit console application (Burdanov et al. 2014) for data post-processing. The program performs high-precision differential CCD photometry for thousands of stars and uses Robust Median Statistic criterion (Rose & Hintz 2007) to search for variable-star candidates. The photometric precision for stars from 10 to 16 mag was 0.01–0.12 mag, 0.008–0.05 mag, and 0.007–0.09 mag for B, V, and R bands respectively.
From initial sample of 21500 stars, we selected 370 variable objects whose light curves were inspected by eye. To determine periods of variability, we used the light curve analysis tool by Kirill Sokolovsky. This application implements Lafler & Kinman (1965) and Deeming (1975) methods to search for periods as well as transforms Julian Dates to Heliocentric Julian Dates.
All variable objects were divided into five groups according to their light-curve shape: 1) Algol-type eclipsing binaries (EA); 2) β Lyrae and W Ursae Majoris eclipsing binaries (EB and EW); 3) δ Sct low-amplitude pulsating variable stars with short periods; 4) giant stars (objects with IR excess slowly changing brightness with a big amplitude) 5) all other objects that do not form any special type. We plan to publish a paper about each type of objects described before and also about validation of discovered transiting exoplanet candidates. In this paper we will discuss the first group of objects, Algol- type eclipsing binaries.
In this paper, we provide figures that consist of two panels. Star's instrumental magnitude as a function of Julian Date is given in the left panel and phase folded light curve is given in the right panel. When we could not define a period, we provide only the light curve as a function of Julian Date. In the figures, we used red colour for R band, green colour for V band, and blue colour for B band data. The B-band photometric precision is worse than in the two other filters, thus we provide it only in cases when B-band observations helped to determine the varaible's period. For the sake of visibility, we shifted stars' magnitudes in V and B bands by (V–R) and (B–R) values. Colour indices are provided on top of each figure. If there is a suspicion for a given star to have an eccentric orbit, then phase 0.5 on such light curves is marked with a vertical dashed line.
Acknowledgements:
This work was supported by Russian Foundation for Basic Research grants 14-02-31338 and 14-02-31056 (partially). This work was partially supported by the Russian Ministry of Education and Science (contract No. 01201465056 and state order No. 3.615.2014/K).
The authors wish to thank Dr. Kirill Sokolovsky for providing his on-line light curve analysis tool.
This research made use of Aladin (Bonnarel et al. 2000), SIMBAD database (operated at the Centre de Données astronomiques de Strasbourg), the International Variable Star Index (VSX) database (operated at AAVSO, Massachusetts, USA), PyRAF (product of the Space Telescope Science Institute, operated by AURA for NASA), and the NASA/IPAC Extragalactic Database (NED) (operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration).References:
Bonnarel, F., Fernique, P., Bienaymé, O., et al. 2000, Astron. and Astrophys. Suppl., 143, 33
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Burdanov, A. Y., Krushinsky, V. V., Popov, A. A., 2014, Astrophysical Bulletin, 69, p. 368
Deeming, T. J., 1975, Astrophys. and Space Science, 36, 137
Lafler, J., Kinman, T. D., 1965, Astroph. J. Suppl., 11, 216
Lang, D., Hogg, D. W., Mierle K., et al., 2010, Astron. J., 139, 1782
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