Peremennye Zvezdy

Article in PDF
"Peremennye Zvezdy",
Prilozhenie
,
vol. 15, N 7 (2015)

Variable Stars in Cygnus Discovered with Kourovka Planet Search. Rart I: Eclipsing binaries of Algol type

A. A. Popov#1, A. Y. Burdanov#1, A. M. Zubareva#2,#3, V. V. Krushinsky#1, E. A. Avvakumova#1, K. Ivanov#4
#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)


#NameOtherCoord (J2000)TypeMaxMinSystemPeriodEpoch (JD)typeSpCommentL.CurveFind.ChartData
1 2MASS 20242458+495902020 24 24.59, +49 59 02.0EA14.8015.06R2.51352456168.159min Comm. 1TF1-00113_lc.pngTF1-00113_fc.pngTF1-00113.txt
2 2MASS 20243133+504243820 24 31.33, +50 42 43.8EA14.0014.20R6.9442456169.312min Comm. 2TF1-00307_lc.pngTF1-00307_fc.pngTF1-00307.txt
3 2MASS 20250078+493805420 25 00.78, +49 38 05.5EA15.6216.18R1.28032456124.296min Comm. 3TF1-01236_lc.pngTF1-01236_fc.pngTF1-01236.txt
4 2MASS 20250871+495714120 25 08.71, +49 57 14.2EA14.4314.58R0.681752456141.320min Comm. 4TF1-01491_lc.pngTF1-01491_fc.pngTF1-01491.txt
5 2MASS 20252662+502651920 25 26.62, +50 26 52.0EA11.3411.46R5.269482456161.481min Comm. 5TF1-02042_lc.pngTF1-02042_fc.pngTF1-02042.txt
6 2MASS 20253905+512330120 25 39.06, +51 23 30.1EA14.6014.84R2.996:2456154.338min Comm. 6TF1-02426_lc.pngTF1-02426_fc.pngTF1-02426.txt
7 2MASS 20254651+502323020 25 46.52, +50 23 23.1EA15.3215.78R 2456161.300min Comm. 7TF1-02680_lc.pngTF1-02680_fc.pngTF1-02680.txt
8 2MASS 20260213+500603220 26 02.14, +50 06 03.2EA12.4212.47R0.846762456062.817minG8VComm. 8TF1-03154_lc.pngTF1-03154_fc.pngTF1-03154.txt
9 2MASS 20261094+510555620 26 10.94, +51 05 55.6EA15.6716.60R0.5460132456140.341min Comm. 9TF1-03437_lc.pngTF1-03437_fc.pngTF1-03437.txt
10 2MASS 20264315+512355520 26 43.16, +51 23 55.5EA15.0515.62R1.313362456131.386min Comm. 10TF1-04428_lc.pngTF1-04428_fc.pngTF1-04428.txt
11 2MASS 20264501+505846120 26 45.02, +50 58 46.2EA10.9110.97R5.6122456162.260min Comm. 11TF1-04470_lc.pngTF1-04470_fc.pngTF1-04470.txt
12 2MASS 20280965+502603920 28 09.65, +50 26 03.9EA13.0213.20R3.842456131.40min Comm. 12TF1-07149_lc.pngTF1-07149_fc.pngTF1-07149.txt
13 2MASS 20282625+504255720 28 26.25, +50 42 55.7EA14.4014.92R1.227952456124.312min Comm. 13TF1-07690_lc.pngTF1-07690_fc.pngTF1-07690.txt
14 2MASS 20283375+494309020 28 33.76, +49 43 09.0EA11.6811.94R 2456496.300min Comm. 14TF1-07903_lc.pngTF1-07903_fc.pngTF1-07903.txt
15 2MASS 20284275+505639220 28 42.75, +50 56 39.3EA13.8714.02R1.64762456160.338min Comm. 15TF1-08198_lc.pngTF1-08198_fc.pngTF1-08198.txt
16 2MASS 20284845+495637220 28 48.46, +49 56 37.3EA14.4214.58R5.36932456168.304min Comm. 16TF1-08373_lc.pngTF1-08373_fc.pngTF1-08373.txt
17 2MASS 20285270+504044620 28 52.70, +50 40 44.7EA14.9015.23R4.232456141.38min Comm. 17TF1-08499_lc.pngTF1-08499_fc.pngTF1-08499.txt
18 2MASS 20290715+511518020 29 07.15, +51 15 18.1EA11.9712.34R0.720572456134.296min Comm. 18TF1-08954_lc.pngTF1-08954_fc.pngTF1-08954.txt
19 2MASS 20292815+494117220 29 28.16, +49 41 17.2EA14.8015.42R2.72902456149.308min Comm. 19TF1-09612_lc.pngTF1-09612_fc.pngTF1-09612.txt
20 2MASS 20293182+501616520 29 31.82, +50 16 16.6EA14.1414.27R7.352:2456169.354min Comm. 20TF1-09724_lc.pngTF1-09724_fc.pngTF1-09724.txt
21 2MASS 20293524+494812220 29 35.25, +49 48 12.3EA13.9214.34R1.001772456270.196min Comm. 21TF1-09824_lc.pngTF1-09824_fc.pngTF1-09824.txt
22 2MASS 20295378+501355120 29 53.78, +50 13 55.2EA14.8515.68R1.27132456124.224min Comm. 22TF1-10473_lc.pngTF1-10473_fc.pngTF1-10473.txt
23 2MASS 20300448+503625320 30 04.49, +50 36 25.3EA13.2813.67R1.045972456140.311min Comm. 23TF1-10841_lc.pngTF1-10841_fc.pngTF1-10841.txt
24 2MASS 20301347+511301120 30 13.48, +51 13 01.2EA13.9014.23R 2456148.32min Comm. 24TF1-11148_lc.pngTF1-11148_fc.pngTF1-11148.txt
25 2MASS 20311210+493701820 31 12.10, +49 37 01.9EA14.6214.88R2.64902456272.178min Comm. 25TF1-13176_lc.pngTF1-13176_fc.pngTF1-13176.txt
26 2MASS 20311925+494418720 31 19.25, +49 44 18.8EA13.8714.02R2.60582456160.244min Comm. 26TF1-13412_lc.pngTF1-13412_fc.pngTF1-13412.txt
27V0745 Cyg2MASS 20314369+505213320 31 43.70, +50 52 13.4EA11.8812.28:R2.28312454298.624min Comm. 27TF1-14190_lc.pngTF1-14190_fc.pngTF1-14190.txt
28 2MASS 20315610+495507220 31 56.11, +49 55 07.3EA13.7514.00R 2456150.3min Comm. 28TF1-14601_lc.pngTF1-14601_fc.pngTF1-14601.txt
29 2MASS 20321743+505347920 32 17.43, +50 53 47.9EA12.5412.85R10.8992456375.473min Comm. 29TF1-15295_lc.pngTF1-15295_fc.pngTF1-15295.txt
30 2MASS 20324567+505205620 32 45.68, +50 52 05.6EA14.6415.38R1.68512456131.364min Comm. 30TF1-16208_lc.pngTF1-16208_fc.pngTF1-16208.txt
31 2MASS 20331729+511855620 33 17.29, +51 18 55.7EA13.9714.27R0.602422456135.400min Comm. 31TF1-17274_lc.pngTF1-17274_fc.pngTF1-17274.txt
32 2MASS 20333229+502857320 33 32.30, +50 28 57.3EA13.1413.32R2.28912456161.377min Comm. 32TF1-17750_lc.pngTF1-17750_fc.pngTF1-17750.txt
33 2MASS 20335379+503504020 33 53.80, +50 35 04.0EA14.7014.90R2.46:2456169.31min Comm. 33TF1-18473_lc.pngTF1-18473_fc.pngTF1-18473.txt
34 2MASS 20340397+495213620 34 03.98, +49 52 13.6EA14.1614.61R0.771222456141.383min Comm. 34TF1-18819_lc.pngTF1-18819_fc.pngTF1-18819.txt
35 2MASS 20340645+501648820 34 06.46, +50 16 48.8EA13.9214.58R0.487702456133.395min Comm. 35TF1-18913_lc.pngTF1-18913_fc.pngTF1-18913.txt
36 2MASS 20341922+494043020 34 19.23, +49 40 43.0EA15.8016.46R2.6362:2456403.401min Comm. 36TF1-19369_lc.pngTF1-19369_fc.pngTF1-19369.txt
37 2MASS 20343391+500030320 34 33.92, +50 00 30.4EA16.5018.2R5.53442456169.305min Comm. 37TF1-19832_lc.pngTF1-19832_fc.pngTF1-19832.txt
38 2MASS 20344126+511117120 34 41.27, +51 11 17.1EA13.2313.36R5.7:2456403.4min Comm. 38TF1-20107_lc.pngTF1-20107_fc.pngTF1-20107.txt
39 2MASS 20344804+503510920 34 48.04, +50 35 10.9EA13.9714.82R5.012456141.39min Comm. 39TF1-20328_lc.pngTF1-20328_fc.pngTF1-20328.txt
40 2MASS 20345474+504734420 34 54.75, +50 47 34.4EA16.4018.2R7.14:2456141.28min Comm. 40TF1-20573_lc.pngTF1-20573_fc.pngTF1-20573.txt
41 2MASS 20345937+494210920 34 59.37, +49 42 10.9EA14.4014.58R 2456134.4min Comm. 41TF1-20712_lc.pngTF1-20712_fc.pngTF1-20712.txt
42 2MASS 20350000+504439520 35 00.01, +50 44 39.6EA15.5316.0R0.618822456133.376min Comm. 42TF1-20734_lc.pngTF1-20734_fc.pngTF1-20734.txt
43 2MASS 20350181+494525220 35 01.82, +49 45 25.3EA13.3313.78:R6.92:2456135.99min Comm. 43TF1-20787_lc.pngTF1-20787_fc.pngTF1-20787.txt
44 2MASS 20352554+503328520 35 25.54, +50 33 28.6EA15.5815.83R0.9912456161.311min Comm. 44TF1-21392_lc.pngTF1-21392_fc.pngTF1-21392.txt
45 2MASS 20353462+502821820 35 34.63, +50 28 21.8EA15.1716.2R1.139142456400.433min Comm. 45TF1-21500_lc.pngTF1-21500_fc.pngTF1-21500.txt

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
Burdanov, A. Y., Popov, A. A., Krushinsky, V. V., Ivanov, K., 2013, Perem. Zvezdy, 33, 2
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
Lipunov, V., Kornilov, V., Gorbovskoy, E., et al., 2010, Advances in Astronomy, article id. 349171
Rose, M. B., Hintz, E. G., 2007, Astron. J., 134, 2067
Skrutskie, M. F., Cutri, R. M., Stiening, R., et al., 2006, Astron. J., 131, 1163
Tody, D., 1986, Instrumentation in astronomy VI, Proceedings of the Meeting, Tucson, AZ, Mar. 4–8. Part 2, Vol. 627, 733
Woźniak, P. R., Vestrand, W. T., Akerlof, C. W., et al., 2004, Astron. J., 127, 2436



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