Peremennye Zvezdy

Peremennye Zvezdy (Variable Stars) 35, No. 1, 2015

Received 29 January; accepted 11 February.

Article in PDF

New Double-Mode RR Lyrae Variables II

A. V. Khruslov

Institute of Astronomy, Russian Academy of Sciences, Moscow, Russia; e-mail: khruslov@bk.ru


We present a new study of 56 known RR Lyrae variable stars from the Catalina surveys periodic variable star catalog. We analyzed all observations available for these stars in the Catalina Surveys and SuperWASP online public archives using the period-search software developed by Dr. V.P. Goranskij for Windows environment. According to these data, the stars are double-mode RR Lyrae variables, pulsating in the first-overtone and fundamental modes.

1. Introduction

According to the International Variable Star Index (VSX, AAVSO), about 600 double-mode RR Lyrae variable stars are currently known in our Galaxy, usually pulsating in the fundamental and first overtone radial modes (most of them, outside globular clusters). During the recent years, automated data surveys resulted in a considerable progress in the identification of stars of this type. The author of the present paper, with his co-authors, earlier discovered 56 double-mode RR Lyrae variable stars, pulsating in the fundamental and first-overtone radial modes ( Khruslov 2007, 2010, 2011, 2012ab; Khruslov, Huemmerich, and Bernhard 2013; Antipin and Khruslov 2013; Huemmerich and Khruslov 2014; Khruslov 2014). In this article, I present the discovery of additional 56 double-mode RR Lyrae variable stars, pulsating in the first-overtone and fundamental modes.

2. Results

I studied 56 known RR Lyrae variable stars from the Catalina surveys periodic variable star catalog (Drake et al. 2014), analyzing all observations available for them in the Catalina Surveys (Drake et al. 2009) and SuperWASP (Butters et al. 2010) online public archives using the period-search software developed by Dr. V.P. Goranskij for Windows environment. The SuperWASP observations are available as FITS tables, which were converted into ASCII tables using the OMC2ASCII program as described by Sokolovsky (2007). In the Catalina surveys periodic variable star catalog, all these variables are designated as RRC stars. Our analysis of the available data demonstrates that the variables are double-mode RR Lyrae variables, pulsating in the first-overtone and fundamental modes.

Light curves, finding charts, and data (CSS, SSS, MLS, 1SWASP) are available online in the html version of this paper as a zip-archive. The light curves are given in the format displayed in Fig. 1. Top panels present data folded with the fundamental-mode and first-overtone periods. Bottom panels show the same curves after prewhitening the other oscillation (if the frequencies and were excluded, it is also noted). These light curves are given for all data series.

Fig. 1. The light curve of USNO-B1.0 1155-0026482 (No. 3).

Along with the light curves, we present power spectra of the RR Lyrae variables, for the raw data and after subtraction of the first-overtone (or fundamental mode) oscillations, as shown in Fig. 2. The structure of the power spectra shows that the secondary periods are real.

The stars' period ratios, , are typical of radially pulsating double-mode RR Lyrae stars. The Petersen diagram for double-mode RR Lyrae variables from this paper is displayed in Fig. 3.

In five cases, the periods presented in the Catalina surveys periodic variable star catalog are wrong. For Nos. 18, 28, and 56, the catalog period is a one-day alias of the real first overtone period; for Nos. 12 and 29, the catalog period is a one-day alias of the real fundamental mode period.

Fig. 2. The power spectra of USNO-B1.0 1155-0026482 (No. 3) for the frequencies and .

Fig. 3. The Petersen diagram for the program double-mode RR Lyrae stars.

Information on the studied stars is presented in Tables 1-4. Table 1 contains numbers from the GSC and USNO-B1.0 catalogs; equatorial coordinates (J2000); magnitude at maximum and minimum in the Catalina surveys photometric system; period previously known for the star, according to the Catalina surveys periodic variable star catalog. Asterisks mark the presence of additional information on the star, as explained in Comments. The tabulated coordinates of the variables were drawn from either the GSC2.3 (Lasker et al. 2008) or 2MASS (Skrutskie et al. 2006) catalogs.

Table 1. Positions, magnitudes, and periods

No. Name Coordinates (J2000) CSS mag , days
1 USNO-B1.0 1201-0009113 0039 3838 +300940 8 16.91-17.67 03951946
2 GSC 1206-01674 01 53 42.59 +15 52 15.6 14.64-15.19 0.4205069
3 USNO-B1.0 1155-0026482 02 15 54.78 +25 34 39.6 15.71-16.48 0.357762
4 USNO-B1.0 1012-0025337 02 48 18.04 +11 12 40.5 15.94-16.65 0.418635
5 USNO-B1.0 1538-0156471 07 01 44.47 +63 53 02.7 15.98-16.57 0.3566511
6 USNO-B1.0 1021-0178560 08 09 35.30 +12 09 00.3 16.55-17.33 0.3713580
7 USBO-B1.0 1211-0158004* 08 14 29.85 +31 11 15.3 16.86-17.60 0.3508887
8 USNO-B1.0 0994-0170746 08 16 52.42 +09 27 56.7 16.47-17.29 0.3582525
9 USNO-B1.0 1087-0165074 08 24 26.28 +18 42 28.7 16.51-17.38 0.3765145
10 USNO-B1.0 1142-0160444 08 45 29.36 +24 16 31.2 17.55-18.47 0.3597362
11 USN0-B1.0 0998-0182783 08 48 38.26 +09 51 14.9 16.73-17.48 0.3560988
12 USNO-B1.0 0995-0182765 08 52 13.29 +09 32 16.1 18.1-19.0 0.3281944
13 USNO-B1.0 1265-0169434* 08 58 09.48 +36 31 21.4 16.61-17.44 0.3558720
14 USNO-B1.0 0971-0212517 09 16 37.72 +07 11 25.3 16.55-17.30 0.404839
15 USNO-B1.0 1061-0174839 09 43 11.02 +16 09 53.5 16.70-17.49 0.3791779
16 USNO-B1.0 1083-0199119 09 55 44.88 +18 23 07.8 16.54-17.37 0.3753066
17 USNO-B1.0 1220-0203005 09 57 25.89 +32 01 17.6 17.51-18.31 0.3889338
18 USNO-B1.0 1119-0202036 10 06 44.06 +21 56 59.4 17.5-18.4 0.283598
19 USNO-B1.0 0903-0190606 10 23 08.54 +00 23 30.4 18.4-19.3 0.354036
20 USNO-B1.0 1059-0190499 10 23 47.66 +15 59 12.3 17.3-18.1 0.3745709
21 USNO-B1.0 1326-0262115 10 24 57.50 +42 40 22.2 17.02-17.73 0.4086693
22 USNO-B1.0 0972-0231646 10 34 06.66 +07 12 07.9 17.40-18.25 0.3504379
23 USNO-B1.0 0875-0290446 10 42 07.92 -02 29 56.8 17.11-17.91 0.4200851
24 USNO-B1.0 0866-0219758 10 44 18.73 -03 18 50.9 16.79-17.68 0.3636318
25 USNO-B1.0 1076-0231367 11 03 51.80 +17 36 09.9 17.58-18.49 0.358411
26 USNO-B1.0 1139-0181861 11 16 44.95 +23 59 28.2 17.50-18.44 0.4130053
27 USNO-B1.0 1072-0234586 11 19 22.51 +17 13 23.7 16.87-17.60 0.3646734
28 USNO-B1.0 0877-0319036 11 28 45.50 -02 16 00.7 17.2-18.1 0.2570875
29 USNO-B1.0 1129-0228008 11 33 27.98 +22 59 21.5 16.81-17.62 0.324888
30 USNO-B1.0 1075-0239855 11 45 17.70 +17 31 16.1 16.91-17.64 0.40805
31 USNO-B1.0 1038-0192883 11 46 31.44 +13 51 59.4 17.39-18.33 0.3511538
32 USNO-B1.0 0783-0261258 12 12 50.62 -11 39 08.5 16.80-17.55 0.3614389
33 GSC 5533-00078 12 27 26.34 -13 00 28.3 15.19-15.75 0.3642299
34 USNO-B1.0 1005-0208522 12 38 15.56 +10 35 31.3 17.34-18.31 0.3700176
35 USNO-B1.0 0997-0233324* 12 53 47.39 +09 43 09.1 15.66-16.24 0.3690403
36 USNO-B1.0 1041-0224476 13 08 47.87 +14 10 12.2 16.75-17.51 0.34526
37 USNO-B1.0 0990-0227417 13 21 53.28 +09 01 31.4 17.8-18.7 0.3547121
38 USNO-B1.0 1162-0217838 13 23 22.11 +26 13 43.7 17.46-18.33 0.3544163
39 USNO-B1.0 1244-0215132 14 21 58.72 +34 27 24.4 16.16-16.78 0.3564981
40 USNO-B1.0 1240-0222201 14 44 01.00 +34 02 43.6 16.59-17.42 0.4070824
41 USNO-B1.0 1247-0222564 15 03 58.26 +34 46 47.4 17.02-17.87 0.357288
42 USNO-B1.0 0965-0243978* 15 08 17.61 +06 32 13.2 16.82-17.46 0.4119803
43 USNO-B1.0 1308-0273169 16 46 47.65 +40 51 16.5 16.40-17.08 0.3739999
44 USNO-B1.0 1147-0245047 16 48 59.11 +24 43 55.6 16.53-17.21 0.4011456

Table 1 Positions, magnitudes, and periods (continued)

No. Name Coordinates (J2000) CSS magn. , days
45 USNO-B1.0 1116-0277997 16 57 09.73 +21 40 02.0 16.57-17.50 0.3648103
46 USNO-B1.0 1108-0268087 16 57 40.31 +20 53 33.7 16.08-16.65 0.3744385
47 USNO-B1.0 1057-0629220 21 48 53.46 +15 45 20.6 17.66-18.49 0.3558251
48 USNO-B1.0 1035-0607825 21 56 54.02 +13 31 24.7 16.13-16.70 0.406222
49 USNO-B1.0 1063-0609449 22 17 47.44 +16 19 29.8 17.21-17.98 0.4070613
50 GSC2.3 N09A000095* 22 27 17.66 +25 20 08.4 14.66-15.13 0.402694
51 USNO-B1.0 1016-0656702* 22 34 30.58 +11 39 12.6 16.81-17.43 0.3888151
52 USNO-B1.0 1233-0612339* 22 40 00.25 +33 22 37.6 14.51-15.11 0.357745
53 USNO-B1.0 1092-0590255 22 43 20.23 +19 14 33.1 16.58-17.32 0.35608
54 USNO-B1.0 1161-0575560 22 51 17.35 +26 10 54.5 17.10-17.75 0.3715164
55 USNO-B1.0 0989-0604703 22 55 42.42 +08 59 36.2 15.41-16.07 0.3492836
56 GSC 2255-01669* 23 49 00.58 +27 03 16.4 13.62-14.29 0.2682041

Light elements of all oscillations: the first-overtone period , fundamental period , first-overtone and fundamental mode epoch of maxima, period ratio , periods of the frequencies () and () are collected in Table 2.

Table 2. Light elements

No. , d , d Epoch, JD Epoch, JD , d , d
1 0.395196 0.529664 2455000.332 2455000.237 0.7461 - -
2 0.420513 0.564048 2455000.275 2455000.250 0.7455 0.240908 -
3 0.357769 0.480781 2455000.023 2455000.148 0.7441 0.2051257 1.39816
4 0.418642 0.561570 2455000.406 2455000.035 0.7455 0.2398406 1.6450
5 0.356657 0.479216 2455000.248 2455000.414 0.7443 - -
6 0.371362 0.498566 2455000.240 2455000.335 0.7449 0.212834 1.45553
7 0.350894 0.472146 2455000.542 2455000.636 0.7432 0.201293 -
8 0.358253 0.481136 2455000.062 2455000.200 0.7446 0.205350 1.40272
9 0.376512 0.505835 2455000.245 2455000.107 0.7443 0.215849 1.47280
10 0.359741 0.482865 2455000.095 2455000.370 0.7450 - -
11 0.356102 0.478487 2455000.337 2455000.235 0.7442 - -
12 0.364073 0.489181 2455000.358 2455000.336 0.7443 0.20873 1.4234
13 0.355872 0.478181 2455000.037 2455000.374 0.7442 0.204029 1.3912
14 0.404849 0.542956 2455000.070 2455000.087 0.7456 0.231921 1.59165
15 0.379178 0.509437 2455000.256 2455000.007 0.7443 0.217380 1.48303
16 0.375307 0.503529 2455000.277 2455000.423 0.7454 0.215033 1.47384
17 0.388921 0.521624 2455000.140 2455000.023 0.7456 - -

Table 2. Light elements (continued)

No. , d , d Epoch, JD Epoch, JD , d , d
18 0.395859 0.530969 2455000.092 2455000.210 0.7455 0.226780 1.55578
19 0.354037 0.475673 2455000.165 2455000.205 0.7443 - -
20 0.374572 0.502380 2455000.260 2455000.287 0.7456 - -
21 0.408675 0.548171 2455000.454 2455000.486 0.7455 0.234125 -
22 0.350447 0.471002 2455000.082 2455000.224 0.7440 0.200940