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Peremennye Zvezdy (Variable Stars) 35, No. 2, 2015 Received 06 March; accepted 12 March.
A Photometric Study of the Double-Mode High-Amplitude
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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 15
21
34
69, +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,
http://www.aavso.org/download-apass-data) catalog. The 
-band
magnitudes could be presented only as magnitude differences with
respect to the comparison star.
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
and
| Mode | Period, d | Epoch, HJD 2456565+ | ||
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|
|
||
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0.09442318 | 0.0738 | 0.0777 | 0.0783 |
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0.07304432 | 0.0552 | 0.0555 | 0.0563 |
Table 2. Detected frequencies
| Mode | Frequency, c/d | Period, d | Semi-amplitude, mag | ||
|
|
|
|||
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10.590620 | 0.09442318 | 0.1188 | 0.1073 | 0.0814 |
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13.690318 | 0.07304432 | 0.1152 | 0.1041 | 0.0852 |
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24.28086 | 0.0411847 | 0.0336 | 0.0272 | 0.0223 |
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3.0998 | 0.3226 | 0.0234 | 0.0196 | 0.0155 |
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21.18128 | 0.0472115 | 0.0204 | 0.0112 | 0.0088 |
|
34.87155 | 0.02867667 | 0.0107 | 0.0040 | 0.0038 |
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
12
71 - 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).
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Fig. 3.
The light curves of QS Dra, |
References:
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