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[vsnet-newvar 1854] MisV1097 is a blue W UMa-type eclipsing variable



Dear colleagues,

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

Please see the following web page for information in details on
MisV1097.

  http://vsnet.aerith.net/misao/report/variable/MisV1097.html

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.

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.

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.

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.

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.

Best regards,

--
Seiichi Yoshida
comet@aerith.net
http://vsnet.aerith.net/


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