Journal "Peremennye Zvezdy"

"Peremennye Zvezdy",
Prilozhenie,
vol. 11, N 17 (2011)

Unusual Variability of TYC 5978 00472 1

A. V. Khruslov
Tula, Russia

Received: 29.01.2011; accepted: 22.04.2011
(E-mail for contact: khruslov@bk.ru)

Star Name:	TYC 5978 00472 1, ASAS 072641–2208.9, NSVS 15394646, NSVS 15276801, NSVS 17947858
Coordinates (J2000):	07 26 41.41, –22 08 53.7
Variability type:	SRD: + E:;	Limits, System:	10.2 – 10.7 (V);
Period:	(see Remarks) d;	Epoch:	JD (see Remarks)

Remarks:

TYC 5978 00472 1 = ASAS 072641-2208.9 is listed in the ASAS-3 catalog of variable stars (Pojmanski 2002) as a "miscellaneous" variable star with the period of 0.249024 days.

I re-analyzed the ASAS-3 observations (additionally taking into account the sparse NSVS data (Wozniak et al. 2004)) using the period-search software developed by Dr. V.P. Goranskij for Windows environment. The star's brightness variations were found to be a superposition of two periodic components: a long-period (presumably pulsational) one and a much-shorter-period one, resembling, by its light curve shape, ellipsoidal variations of a binary system with a hint to a narrow eclipse at the primary minimum. The following light elements were determined:

	Period, day	Epoch, JD
pulsating component, P₁	312	2453700.
eclipsing component, P₂	8.2958	2453707.98

The star is not catalogued as a visual double star, and Schmidt photographs of the field available in data archives show its image not very different from those of single stars. The companion 2MASS 07264120-2208486 is much fainter than the variable (by 4–5 mag) and does not contribute much to the photometric data. There are no known X-ray sources at the position of the variable.

In our opinion, the star is a hierarchical multiple system or an optical system. It contains an ellipsoidal binary (with narrow eclipses) and a pulsating star. The amplitudes of both variations are larger than the observed combined-brightness amplitude. The presence of a Mira in the system is improbable taking into account the color indices (J–K = 0.303 in 2MASS; B–V = 0.056 in Tycho-2).

The unusual brightness variations of TYC 5978 00472 1 make its spectroscopy very desirable.

The tabulated coordinates are from the Tycho-2 catalog.

References:

Pojmanski, G., 2002, Acta Astronomica, 52, 397
Wozniak, P.R., Vestrand, W.T., Akerlof, C.W., et al., 2004, Astron. J., 127, 2436

Light Curve
Unusual Variability of TYC 5978 00472 1

The phased light curves. ASAS-3 data, top: folded with the periods P1 and P2; Bottom: the same curves after prewhitening the other variation. NSVS data are shown after the ASAS data; top: the raw data folded with the period P1; bottom: the data, with the period P1 prewhitened, folded with the period P2.

Unusual Variability of TYC 5978 00472 1

A. V. Khruslov Tula, Russia

A. V. Khruslov
Tula, Russia