Comments:
1. The variability of USNO-A2.0 0900-06705094 was discovered by Kraus et al. (2007,
MG1 646352),
log P =
0.153.
The AAVSO Variable Star Index (VSX; www.aavso.org/vsx/) suggests type RRC, without
light elements.
According to data from Catalina Surveys, it is actually a double-mode RR Lyrae star,
type RR(B), with the light elements tabulated below.
| Mode |
Frequency, c/d |
Semi-amplitude, SV mag |
Period, days |
Epoch, JD |
| f1 |
2.301936 |
0.155 |
0.434417 |
2454800.820 |
| f0 |
1.720318 |
0.053 |
0.581288 |
2454801.000 |
| f1 + f0 |
4.022186 |
0.022 |
0.248621 |
2454800.608 |
| f1 – f0 |
0.581649 |
0.021 |
1.71925 |
2454801.90 |
P1/P0 = 0.7473.
J – K = 0.362 (2MASS).
2. The variability of USNO-A2.0 0900-06907148 was discovered by Kraus et al. (2007,
MG1 666086),
log P =
0.65.
The AAVSO Variable Star Index suggests type RRC, without
light elements.
According to data from Catalina Surveys, it is actually a double-mode RR Lyrae star,
type RR(B), with the light elements tabulated below.
| Mode |
Frequency, c/d |
Semi-amplitude, SV mag |
Period, days |
Epoch, JD |
| f1 |
2.781804 |
0.151 |
0.359479 |
2454800.634 |
| f0 |
2.069973 |
0.105 |
0.483098 |
2454800.541 |
| f1 + f0 |
4.85178 |
0.049 |
0.206110 |
2454800.574 |
P1/P0 = 0.7441.
J – K = 0.203 (2MASS).
3. The variability of GSC 0293-01052 was discovered by Kraus et al. (2007, MG1
698628),
log P =
0.3.
The AAVSO Variable Star Index suggests type RRAB, without
light elements.
According to data from Catalina Surveys, it is actually a double-mode RR Lyrae star,
type RR(B), with the light elements tabulated below.
| Mode |
Frequency, c/d |
Semi-amplitude, SV mag |
Period, days |
Epoch, JD |
| f1 |
2.558644 |
0.163 |
0.390832 |
2454800.880 |
| f0 |
1.906836 |
0.095 |
0.524429 |
2454800.650 |
P1/P0 = 0.7453.
J – K = 0.265 (2MASS).
4. The variability of GSC 0310-00922 was discovered by Kraus et al. (2007, MG1
716004),
log P = 2.474.
The AAVSO Variable Star Index suggests type RRAB, without
light elements.
According to data from Catalina Surveys, it is actually a double-mode RR Lyrae star,
type RR(B), with the light elements tabulated below.
| Mode |
Frequency, c/d |
Semi-amplitude, SV mag |
Period, days |
Epoch, JD |
| f1 |
2.953372 |
0.149 |
0.338596 |
2454800.060 |
| f0 |
2.193093 |
0.142 |
0.455977 |
2454800.145 |
| f1 + f0 |
5.14655 |
0.047 |
0.194305 |
2454800.070 |
| f1 – f0 |
0.760375 |
0.038 |
1.31514 |
2454801.05 |
P1/P0 = 0.7426.
J – K = 0.255 (2MASS).
5. The variability of GSC 0321-00872 was discovered by Kraus et al. (2007, MG1
738552),
log P = 2.874.
The AAVSO Variable Star Index suggests type RRAB, without
light elements.
According to data from Catalina Surveys, it is actually a double-mode RR Lyrae star,
type RR(B), with the light elements tabulated below.
| Mode |
Frequency, c/d |
Semi-amplitude, SV mag |
Period, days |
Epoch, JD |
| f1 |
2.653780 |
0.150 |
0.376821 |
2454800.570 |
| f0 |
1.976957 |
0.089 |
0.505828 |
2454800.750 |
| f1 + f0 |
4.630744 |
0.032 |
0.215948 |
2454800.627 |
| f1 – f0 |
0.676773 |
0.027 |
1.47760 |
2454801.40 |
P1/P0 = 0.7450.
J – K = 0.132 (2MASS).
6. The variability of USNO-A2.0 0900-08468794 was discovered by Kraus et al. (2007,
MG1 816948),
log P = 2.449.
The AAVSO Variable Star Index suggests type RRC, without
light elements.
According to data from Catalina Surveys, it is actually a double-mode RR Lyrae star,
type RR(B), with the light elements tabulated below.
| Mode |
Frequency, c/d |
Semi-amplitude, SV mag |
Period, days |
Epoch, JD |
| f1 |
2.803500 |
0.177 |
0.356697 |
2454800.751 |
| f0 |
2.087055 |
0.065 |
0.479144 |
2454800.609 |
P1/P0 = 0.7444.
7. The variability of V2220 Sgr was discovered by Hoffmeister (1963).
The variable is listed in the GCVS as an RR star without light elements.
According to data from SuperWASP, it is actually a double-mode RR Lyrae star, type
RR(B), with the light elements tabulated below.
| Mode |
Frequency, c/d |
Semi-amplitude, mag |
Period, days |
Epoch, JD |
| f1 |
2.51345 |
0.341 |
0.39786 |
2454300.879 |
| f0 |
1.87434 |
0.184 |
0.53352 |
2454300.810 |
| f1 + f0 |
4.38781 |
0.087 |
0.227904 |
2454300.825 |
| f1 – f0 |
0.63902 |
0.080 |
1.5649 |
2454301.06 |
P1/P0 = 0.7457.
J – K = 0.184 (2MASS).
When plotting the phased light curves for the identified frequencies,
f1 and f0, I also subtracted variations of the mean
brightness in the 1SWASP data, probably of instrumental origin
(corresponding to the frequency f = 1 in the power spectra).
Remarks:
I present a new investigation of seven known RR Lyrae variable stars.
I analyzed all observations available for these stars 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.
According to these data, the variables are double-mode RR Lyrae variables, pulsating
in the first-overtone and fundamental modes.
Their period ratios, P1/P0, are typical of radially pulsating
double-mode RR Lyrae stars.
Along with the light curves, I present power spectra of the RR Lyrae variables, for
the raw data and after subtraction of the first-overtone oscillations.
The structure of the power spectra shows that the secondary periods are real.
The SuperWASP observations are available as FITS tables which were converted into
ASCII tables using the OMC2ASCII program as described by Sokolovsky (2007).
When reducing the SuperWASP observations, I rejected nights with large scatter of
data points, probably due to weather or instrumental errors.
The tabulated coordinates of the variables were drawn either from the 2MASS catalog
or from the GCVS (Samus et al. 2007–2012).
Acknowledgements: Thanks are due to Dr. K.V. Sokolovsky for his advice concerning
data retrieving. The author wishes to thank Dr. V.P. Goranskij for providing his
software.
I am grateful to Dr. A.L. Kraus for providing access to the
MG1 Variable Star Catalog (MG1-VSC).
References:
Butters, O.W., West, R.G., Anderson, D.R., et al., 2010, Astron. Astrophys.,
520, L10
Drake, A.J., Djorgovski, S.G., Mahabal, A., et al., 2009, Astrophys. J., 696, 870
Hoffmeister, C., 1963, Veröff. Sternwarte Sonn., 6, 1
Kraus, A.L., Craine, E.R., Giampapa, M.S., et al.,2007, Astron. J., 134, 1488
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
Sokolovsky, K.V., 2007, Perem. Zvezdy Prilozh., 7, No. 30
