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    MisV1097 is a blue W UMa-type eclipsing variable    

March 3, 2003
Pejcha, O.; Yoshida, S.; Greaves, J.; Ohkura, N.

Ondrej Pejcha revealed that MisV1097 is a blue W UMa-type eclipsing variable.

MisV1097, R.A. 01h15m28s.73, Decl. +41o19'59".3 (J2000.0), is a new variable star discovered in the course of the MISAO Project from Nobuo Ohkura's unfiltered CCD images between 2000 September and December.

MisV1097 on Ohkura's images

It is also recorded in the Guide Star Catalog 1.1 and the USNO-A2.0 as follows.

GSC 2808-00139 01h15m28s.75 +41o19'59".1 Error:0.2" Mag:12.41 MagError:0.40 Band:6 Class:0 Plate:02RY Flag:F Epoch:04 AUG 1984

USNO-A2.0 1275.00747331 01h15m28s.736 +41o19'59".40 Mag(R):12.5 Mag(B):13.1

The observations suggest that it is a short periodic variable with a range of 12.4 - 13.2 mag.

Observations from Ohkura's images

Seiichi Yoshida investigated the DSS images and found that MisV1097 is bright in any bands on the DSS 1 and the DSS 2 images. Especially, it is very bright on the DSS 2 Bj-band image, which implies that MisV1097 is blue.

DSS 2 images (5x5 arcmin)

MisV1097 is also recorded in the 2MASS catalog. The 2MASS J-Ks color is 0.160 mag. This is the bluest value among all MisV stars recorded in the 2MASS catalog until MisV1118.

John Greaves reported that the USNO-B1.0 B1-R1 color is 0.4 mag, which implies that Johnson B-V color is around 0.2 mag. It means the spectral class of MisV1097 may be A or early F.

Ondrej Pejcha observed MisV1097 in V and I bands for 4 hours on Feb. 14, 2003 at Brno Observatory, and succeeded to obtain the light curves. The curves show a nice symmetric minimum of an eclipse, and revealed that MisV1097 is a W UMa-type (EW) eclipsing variable.

Light curves by Pejcha (differential against GSC 2808 707)

Comparison star and check stars of Pejcha's observations

Based on these light curves, John Greaves pointed out that the period is probably about 0.5 to 0.6 days.

The difference between V and I from Ondrej Pejcha's observations shows that MisV1097 is much bluer than the comparison star and two check stars. Here are the relative V-I color of MisV1097 and the comparison star against the two check stars at Feb. 14.7335.

              V-I against   V-I against
              check star 1  check star 2
  MisV1097      -0.588        -0.152
  Comp. star    +0.356        +0.792

The GCVS description on EW type says, "The components generally belong to spectral types F-G and later." But it also says on KE subgroup of EW-type stars as, "Contact systems of early (O-A) spectral type, both components being close in size to their inner critical surfaces."

Therefore MisV1097 is probably an EW/KE type variable star.

Note that the color of MisV1097 in standard system is not obtained. Multi-color photometry using standard filters is encouraged.

The Digitized Sky Surveys were produced at the Space Telescope Science Institute under U.S. Government grant NAG W-2166.

The DSS images are obtained at the Astronomical Image On-line Access Interface (http://dss.mtk.nao.ac.jp/).

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