Peremennye Zvezdy

Peremennye Zvezdy (Variable Stars) 35, No. 2, 2015

Received 06 March; accepted 12 March.

A Photometric Study of the Double-Mode High-Amplitude Scuti Variable Star QS Draconis

A. V. Khruslov[1], A.V. Kusakin[2]

  1. Institute of Astronomy, Russian Academy of Sciences, Moscow, Russia; e-mail:

  2. Fesenkov Astrophysical Institute, Almaty, Kazakhstan; e-mail:

We present the results of our new observations of QS Draconis, a recently discovered double-mode high-amplitude Scuti variable, HADS(B) type. We analyzed our CCD photometry for this star, improved the frequencies and and pulsation amplitudes, detected the interaction frequencies , , , and .

Article in PDF

1. Introduction

In this paper, we present the results of our study of QS Draconis, a double-mode high-amplitude  Scuti variable star, HADS(B) type. Its coordinates in the GCVS catalog (Samus et al. 2007-2012) are 15213469, +61 29 22 7 (J2000.0).

The variability of QS Dra (GSC 4181-00046) was discovered by one of the autors (Khruslov 2007) from the publicly available data of the Northern Sky Variability Survey (NSVS, Wozniak et al. 2004). The variable was classified as a double-mode high-amplitude Scuti variable star, DSCT(B) type, pulsating in the fundamental and first overtone modes. Khruslov (2007) suggested the following light elements:

(fundamental mode) and

(first overtone mode).

The period ratio is typical of double-mode HADS stars (Petersen & Christensen-Dalsgaard 1996).

In the present paper, we use a much longer series of observations that makes it possible to improve the periods and to detect new interaction frequencies, , , , and .

2. Observations

Our CCD observations in the Johnson bands were performed at the Tien Shan Astronomical Observatory of the V.G. Fesenkov Astrophysical Institute, at the altitude of 2750 m above the sea level. The time span of the observations is JD 2456364-2456783. The observatory has two Zeiss 1000-mm telescopes. Most of our observations were performed with the eastern Zeiss 1000-mm reflector (the focal length of the system was mm before JD 2456500 and 6650 mm after this date; the detector was an Apogee U9000 D9 CCD camera). During the three last nights (JD 2456774, 2456781 and 2456783), we used the newly introduced western Zeiss 1000-mm reflector (the focal length of the system was 13250 mm, the detector being an Apogee F16M CCD camera).

Reductions were performed using the MaxIm DL aperture photometry package. The finding chart (Fig. 1) identifies the variable star, comparison star, and check star. The comparison star was GSC 4181-00052, 15211604 +61 28 45 2 (J2000.0), and the check star, GSC 4181-00443, 15220416 +61 34 18 8 (J2000.0). The magnitudes of the comparison star are and (Johnson's system) in the AAVSO Photometric All-Sky Survey (APASS, catalog. The -band magnitudes could be presented only as magnitude differences with respect to the comparison star.

Fig. 1. The finding chart of QS Draconis.

Our observations are available online in the html version of this paper.

3. Results

We analyzed the time series using Deeming's method implemented in the WinEfk code written by V.P. Goranskij. Using our observations of QS Dra, we improved the frequencies and , detected oscillations corresponding to interaction between and : , , , and . The results are presented in Tables 1 and 2. Table 1 presents light elements of the oscillations and . The epochs are given separately for each of the three bands because of their being obviously different, especially for in the band (the difference is 5 per cent of the period). The improvement of the elements was carried out using the -band observations, in agreement with the NSVS data; we used the improved NSVS epochs , . Table 2 presents all detected frequencies and their amplitudes in , , and bands.

Table 1. Light elements of the oscillations and

Mode Period, d Epoch, HJD 2456565+
0.09442318 0.0738 0.0777 0.0783
0.07304432 0.0552 0.0555 0.0563

Table 2. Detected frequencies

Mode Frequency, c/d Period, d Semi-amplitude, mag
10.590620 0.09442318 0.1188 0.1073 0.0814
13.690318 0.07304432 0.1152 0.1041 0.0852
24.28086 0.0411847 0.0336 0.0272 0.0223
3.0998 0.3226 0.0234 0.0196 0.0155
21.18128 0.0472115 0.0204 0.0112 0.0088
34.87155 0.02867667 0.0107 0.0040 0.0038

Fig. 2. The power spectra of QS Dra for the frequencies and , band.

The light curves of QS Draconis in the , and bands are displayed in Figs. 3, 4, 5. Along with the light curves, we present power spectra of QS Draconis, for the raw data and after subtraction of the fundamental-mode oscillations (see Fig. 2).

The star varies within the following range: the -band range is 1271 - 1337; the -band range is from 1263 to 1316. The amplitude in the  band is 043 (range from to ).

Figure 6 exhibits light-curve variations from one cycle to another during the same night, typical of high-amplitude double-mode  Scuti variables.

Acknowledgments: The authors are grateful to Dr. V. P. Goranskij for providing light-curve analysis software. We wish to thank M. A. Krugov, N. V. Lichkanovsky, I. V. Rudakov, R. I. Kokumbaeva, and W. Mundrzyjewski for their assistance during the observations. This study was supported by the Russian Foundation for Basic Research (grant 13-02-00664), the Programme "Transitional and Outburst Processes in the Universe" of the Presidium of Russian Academy of Sciences, and the program "Studies of Physical Phenomena in Star-forming Regions and Nuclear Zones of Active Galaxies" of the Ministry of Education and Science (Republic of Kazakhstan).

Fig. 3. The light curves of QS Dra, band. Upper panels: raw data; lower panels: the folded light curves with the other oscillation pre-whitened.

Fig. 4. The light curves of QS Dra, band.

Fig. 5. The light curves of QS Dra, band.

Fig. 6. Observations of QS Dra acquired during a single night of April 8, 2014 (JD 2456756).


Khruslov, A.V., 2007, Perem. Zvezdy Prilozh., 7, No. 25

Petersen, J.O., Christensen-Dalsgaard, J., 1996, Astron. and Astrophys., 312, 463

Samus, N.N., Durlevich, O.V., Kazarovets, E.V., et al., 2007-2012, General Catalogue of Variable Stars, Centre de Donnees Astronomiques de Strasbourg, B/gcvs

Wozniak, P.R., Vestrand, W.T., Akerlof, C.W., et al., 2004, Astron. J., 127, 2436

Main Page | Search
Astronet | SAI | INASAN

Report problems