New Variable Stars in Two Fields in the Southern Hemisphere

T. Kryachko^#1, A. Samokhvalov^#2, S. A. Korotkiy^#3, D. G. Lambas^#4

#1. Astrotel Observatory, Karachay-Cherkessia, Russia; #2. Surgut, Russia; #3. Ka-Dar Scientific Center and Public Observatory, Moscow, Russia; #4. Instituto de Astronomía Teórica y Experimental, Conicet-UNC, Córdoba, Argentina

Received:   4.12.2010;   accepted:   11.03.2011
(E-mail for contact: bredfild@mail.ru, sav@surgut.ru, astro_stas@mail.ru, dgl@oac.uncor.edu)

Comments:


1. Period 0^d.3351 is also possible. Primary minima:

HJD(TT)	±
2455477.8099	0.0008
2455481.8315	0.0007
2455483.8408	0.0007

Min_II=14^m.36.

2. Periods 0^d.3053 or 0^d.4396 are also possible. Min_II=16^m.65.

3. Primary minima:

HJD(TT)	±
2455478.8477	0.0008
2455483.8329	0.0005

Min_II=15^m.66.

4. A close pair of two stars: USNO-A2.0 0525-03533089 and USNO-A2.0 0525-03533312. USNO-A2.0 0525-03533089 varies.

5. Maxima:

HJD(TT)	±
2455480.8375	0.0007
2455481.8357	0.0009
2455482.8317	0.0007

6. Maxima:

HJD(TT)	±
2455475.6092	0.0008
2455481.5989	0.0008

7. Periods 1^d.6383 or 2^d.47 are also possible. Infrared colors J–H=0.537, H–K=0.127, J–K=0.664 (2MASS) are consistent with the K spectral type (Bessell and Brett 1988) and BY: classification.

Remarks:
During observations of two fields in the southern hemisphere (see the following table) we discovered seven new variable stars.

Field	α	δ	Number of images	JD start	JD end
1	06h 50m 29s	–36° 11′ 01″	316	2455475	2455486
2	23h 12m 35s	–28° 30′ 31″	486	2455475	2455486

Our observations were carried out in Tolar Grande, Argentina, using the 80-mm f/6 ED refractor, equipped with an unfiltered SBIG ST-2000XM CCD camera. All images were taken with 5-minute exposure times. For basic reductions for dark current, flat fields and bias we used MaxIm DL software. For search and photometry of new variable stars, we applied VaST software by Sokolovsky and Lebedev (2005).

The comparison stars for two fields were the following:

Field	Comparison star	α	δ	R1	R2	Rcomp
1	USNO-A2.0 0525-03545983	06h 50m 29s.28	–36° 22′ 17″.2	13m.47	13m.33	13m.40
2	USNO-A2.0 0600-44465807	23h 13m 40s.95	–28° 21′ 34″.6	12m.45	12m.44	12m.445

The coordinates of the variable and comparison stars in the tables were drawn from the 2MASS catalogue (Skrutskie et al. 2006). The R₁ and R₂ magnitudes of the comparison stars were drawn from the USNO-B1.0 catalogue (Monet et al. 2003). Unfiltered magnitudes were calibrated using the R_comp magnitudes from the last table. For search for periods and epochs of extrema, we use Peranso software (www.peranso.com).

Acknowledgements: We would like to thank S. V. Antipin for helpful discussion.

References:
Bessell, M.S., Brett, J.M., 1988, PASP, 100, 1134
Monet, D.G., Levine, S.E., Casian, B., et al., 2003, Astron. J., 125, 984
Skrutskie, M.F., Cutri, R.M., Stiening, R., et al., 2006, Astron. J., 131, 1163
Sokolovsky, K., Lebedev, A., 2005, in 12th Young Scientists' Conference on Astronomy and Space Physics, Kyiv, Ukraine, April 19-23, 2005, eds.: Simon, A.; Golovin, A., p.79