Peremennye Zvezdy

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"Peremennye Zvezdy",
Prilozhenie
,
vol. 10, N 16 (2010)

Three New Double-Mode Cepheids, Pulsating in the First and Second Overtone Modes

A. V. Khruslov
Tula, Russia

ISSN 2221–0474

Received:   8.03.2010;   accepted:   17.05.2010
(E-mail for contact: khruslov@bk.ru)


#NameOtherCoord (J2000)TypeMaxMinSystemPeriodEpoch (JD)typeSpCommentL.CurveFind.ChartData
1 GSC 4064-0017904 10 05.43, +61 46 38.2CEP(B)13.213.75R(see Comments)(see Comments)max Comm. 11.PNG NSVS 2030690 NSVS 2058214
2 TYC 5992 02251 107 43 42.49, -20 50 20.3CEP(B)9.529.68V(see Comments)(see Comments)max Comm. 22.PNG ASAS 074343-2050.3
3NSV 6647TYC 8690 02031 114 23 45.70, -58 29 25.0CEP(B)11.311.8V(see Comments)(see Comments)max Comm. 33.PNG ASAS 142346-5829.4

Comments:


1. 

The variability of GSC 4064-00179 = NSVS 2030690 = NSVS 2058214 was discovered by Khruslov (2005) from ROTSE-I/NSVS data (Wozniak et al. 2004; also see http://skydot.lanl.gov/nsvs). The variable was classified as a CWB Cepheid with the period of 1.1136 d. This variability type was chosen because of the variable's position at a distance from the galactic plane (b = +7.4 deg) somewhat larger than typical of classical Cepheids and a period somewhat too short. At that time, I analyzed only the ROTSE data without photometric correction flags (higher precision data). Now I performed a repeated analysis of the NSVS data, also retaining those with photometric correction flags and thus considerably increasing the number of data points. In this analysis, I rejected all observations with uncertainties in excess of 0.15 mag (plotted as small dots). As a result, I was able to reveal two periodicities of the star, characteristic of double-mode Cepheids.

ModeFrequency, c/d Semi-amplitude, Rmag Period, days Epoch, HJD
f1 0.8982 0.172 1.1133 2451497.64
f2 1.1181 0.046 0.8944 2451498.18

The period ratio P2/P1 = 0.8034 is typical of beat Cepheids pulsating in the first and second overtone modes.
J-H = 0.493 (2MASS).



2. 

The variability of TYC 5992 02251 1 = ASAS 074343-2050.3 was reported by Pojmanski (2002). ASAS 074343-2050.3, listed in the ASAS catalog of variable stars as a first-overtone Cepheid (period 0.73629 d), is actually a double-mode Cepheid.

ModeFrequency, c/d Semi-amplitude, V mag Period, days Epoch, HJD
f1 1.358192 0.041 0.736273 2453455.43
f2 1.685727 0.010 0.593216 2453455.40
f1+f2 3.04395 0.005 0.328521 2453455.40

The period ratio P2/P1 = 0.8057 is typical of beat Cepheids pulsating in the first and second overtone modes.
B-V = 1.233 (Tycho2).
TYC 5992 02251 1 is a close visual double star 2MASS 07434278-2050155 (J=9.437, J-H = 0.259) and 2MASS 07434249-2050204 (J=8.234, J-H = 0.443), and thus the tabulated amplitude is too low. The brighter of the stars probably varies, its J-H color index is more typical of Cepheids.



3. 

The variability of NSV 6647 = TYC 8690 02031 1 = ASAS 142346-5829.4 was reported by Strohmeier et al. (1964). The star, listed in the ASAS catalog of variable stars as an RRAB variable (period 0.631294 d), is actually a double-mode Cepheid.

ModeFrequency, c/d Semi-amplitude, V mag Period, days Epoch, HJD
f1 1.584103 0.190 0.631272 2453556.358
f2 1.972822 0.029 0.506888 2453556.358

The period ratio P2/P1 = 0.8030 is typical of beat Cepheids pulsating in the first and second overtone modes.
B-V = 0.848 (Tycho2), J-H = 0.351 (2MASS).

Remarks:
I present a new investigation of three known pulsating variables.

I re-analysed the ASAS-3 and ROTSE-I/NSVS data (Wozniak et al. 2004) using the period-search software developed by Dr. V.P. Goranskij for Windows environment. According to the data, the stars are double-mode Cepheids, pulsating in the first and second overtone modes. The period ratios, P2/P1, are typical of double-mode variables pulsating in the first and second overtone modes. The tabulated coordinates of the variables were drawn from the Tycho2 and 2MASS catalogs.

References:
Khruslov, A.V., 2005, PZP, 5, No. 3
Pojmanski, G., 2002, Acta Astronomica, 52, 397
Strohmeier, W., Knigge, R., Ott, H., 1964, IBVS, No. 74
Wozniak, P.R., Vestrand, W.T., Akerlof, C.W., et al., 2004, Astron. J., 127, 2436



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