New Variable Stars Discovered by the NMW Survey

K. V. Sokolovsky^#1,2, S. A. Korotkiy^#3

#1 Astro Space Center of Lebedev Physical Institute, Russian Academy of Sciences, Profsoyuznaya Str. 84/32, 117997 Moscow, Russia; #2 Sternberg Astronomical Institute, Moscow State University, Universitetskii pr. 13, 119992 Moscow, Russia; #3 Ka-Dar Astronomy Foundation, Kuzminki, P.O. Box 82, 142717 Moscow Region, Russia

Received:   28.05.2013;   accepted:   11.04.2014
(E-mail for contact: kirx@scan.sai.msu.ru)

Comments:


1. LS I +61 166 = 2MASS J00462520+6139111, J–Ks = 0.359 ± 0.030. Listed in the catalog of galactic OB stars (Reed 2003). NSVS data show a clear flaring event.


2. IRAS 00439+6001, J–Ks = 1.409 ± 0.025.


3. IRAS 00491+6456 = 2MASS J00521297+6512262, J–Ks = 1.379 ± 0.043.


4. IRAS 01009+6301 = 2MASS J01040483+6317106, J–Ks = 1.487 ± 0.457.


5. IRAS 01086+6248, J–Ks = 1.527 ± 0.029.


6. 2MASS J01165972+6332056, J–Ks = 0.635 ± 0.035. The star does not appear to be blended on both NMW and DSS2 images, so the estimated variability amplitude is expected to be reliable. Stability of the period and lightcurve shape over the 12-year-long interval separating the NSVS and NMW observations favors the DCEPS classification. However, Y Oph, a DCEPS star with a close period of 17^d.1 has a larger amplitude of 0^m.59 (V) and earlier spectral class F8Ib–G3Ib. If the newly discovered variable is a member of a binary system, that could explain the small variability amplitude and late spectral type. An alternative classification of this object as a spotted BY Dra-type variable cannot be excluded.


7. 2MASS J01220620+6232404, J–Ks = 0.312 ± 0.031.


8. 2MASS J01244042+6308297, J–Ks = 0.192 ± 0.031.


9. J–Ks = 1.341 ± 0.030.

Remarks:
Two 7.8° × 5.9° fields in Cassiopeia (136 images centered at α = 00:59:05, δ = +63:31:01, J2000) and Puppis (92 images centered at α = 08:14:06, δ = –24:00:00, J2000) are investigated using the New Milky Way (NMW) survey archive (Sokolovsky, Korotkiy & Lebedev 2013). The images are obtained with an unfiltered wide-field camera (F=135mm f/2.0 lens + ST8300M CCD) operated by the Ka-Dar Observatory in Karachay-Cherkessia, Russia. VaST software (Sokolovsky & Lebedev 2005) is used for image processing. The magnitude scale is calibrated using V magnitudes of Tycho-2 (Hog et al., 2000) stars in the field of view. The NSVS (Woźniak et al. 2004) and ASAS-3 (Pojmanski 2002) data are used to supplement the NMW survey photometry. Coordinates of the newly identified variable stars are drawn from the Tycho-2 catalog with the exception of 2MASS J00465096+6017454, 2MASS J01115454+6304596, and 2MASS J08160470-2307275 for which the positions are taken from the 2MASS catalog (Skrutskie et al. 2006). The suggested spectral classification is based on 2MASS infrared colors (Bessell & Brett 1988). The online lightcurve analysis tool developed by one of the authors (KVS) was used for period analysis.

Acknowledgements: The authors are grateful to Dr. Alexandra Zubareva for comments that helped to improve this work. KVS is partly supported by the RFBR grant 13-02-00664.

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