New Double-Mode RR Lyrae Variables III

Peremennye Zvezdy (Variable Stars) 35, No. 4, 2015 Received 8 July; accepted 24 September. A. V. Khruslov Institute of Astronomy, Russian Academy of Sciences, Moscow, Russia; e-mail: khruslov@bk.ru We present a new study of 123 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 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.

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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 112 double-mode RR Lyrae variable stars, pulsating in the fundamental and first-overtone radial modes ( Khruslov 2007, 2010, 2011, 2012a,b, 2014, 2015; Khruslov et al. 2013; Antipin and Khruslov 2013; Huemmerich and Khruslov 2014). In this article, I present the discovery of 123 more double-mode RR Lyrae variable stars, pulsating in the first-overtone and fundamental modes.

2. Results

I studied 123 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) online public archives using the period-search software developed by Dr. V.P. Goranskij for Windows environment. In the Catalina surveys periodic variable star catalog, all these variables are called RRC stars. According to our data, 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) 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.

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 is shown in Fig. 2. The structure of the power spectra shows that the secondary periods are real.

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

There are several cases of wrong periods in the Catalina surveys periodic variable star catalog: for Nos. 1, 5, 19, 22, 55, and 72, the period given by them is a one-day alias of the true first overtone period; for Nos. 42 and 87, the period is a one-day alias of the true fundamental mode period.

The star designations are from the USNO-B1.0 catalog (Monet et al. 2003). The tabulated coordinates of the variables were drawn from either the GSC2.3 (Lasker et al. 2008) or 2MASS (Skrutskie et al. 2006) catalogs.

For all stars,the Catalina Sky Survey (CSS) data were used in the analysis. Additionally, we used the Mount Lemmon Survey (MLS) data for Nos. 8, 10, 13, 16, 28, and 32 and the Siding Spring Survey (SSS) data for Nos. 34, 61, 118, and 123.

Information on the studied stars is presented in Tables 1-3. Table 1 contains numbers from the 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.

Light elements of all oscillations: the first-overtone period , the fundamental period , the first-overtone and fundamental mode epoch of maxima (expressed as JD - 2455000), period ratio , periods of the frequencies () and () are collected in Table 2.

Table 3 presents semi-amplitudes of all the oscillations in Catalina surveys data: semi-amplitudes of first-overtone () and fundamental mode () oscillations, for the () and () frequencies; asterisks mark the presence of comments to Tables 1-3.

Comments:

8. MLS magnitudes are given in Table 1. From CSS data, , , .

10. MLS magnitudes are given in Table 1. The CSS data are for combined brightness of two stars, USNO-B1.0 1053-0034367 and USNO-B1.0 1053-0034364, ; the pair is unresolved, and the measured amplitudes are strongly underestimated. In the MLS data, the pair is resolved: MLSJ031325.6+152146 = USNO-B1.0 1053-0034367 varies, while MLSJ031325.3+152142 = USNO-B1.0 1053-0034364 is a constant star.

13. MLS magnitudes are given in Table 1. MLS data are in the JD 2454096-2456666 time range. The brightness level is higher in the CSS data, possibly because of a faint companion, so the CSS amplitudes can be somewhat underestimated.

16. MLS magnitudes are given in Table 1. From CSS data, , , .

28. MLS magnitudes are given in Table 1. From CSS data, , , .

32. MLS magnitudes are given in Table 1. From CSS data, , , , .

35. Additional non-radial pulsation with the light elements: , .

37. Additional non-radial pulsation with the light elements: , .

66. Also detected is the interaction frequency : days, = 0.069.

75. The known RRAB star CSSJ143432.6+010218 = USNO-B1.0 0910-0235475 is in to the north-west.

101. GSC 5183-01440.

109. GSC 5216-00603.

112. An additional non-radial pulsation is possible, with the light elements: , .

114. There are two objects with identical coordinates in the Catalina Surveys Periodic Variable Star Catalog (Drake et al. 2014); the period of the second of them is given as 0.3974071 days.

Acknowledgments: The author wishes to thank Dr. V.P. Goranskij for providing his software. This study was supported by the Russian Foundation for Basic Research (grant 13-02-00664) and by the Programme "Transitionary and Violent Processes in Astrophysics" of the Presidium of Russian Academy of Sciences.

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