[vsnet-chat 7270] Mira Variable V2010 Cyg and Another Adjoining New Mira Variable MisV1340

[Seiichi Yoshida]

Dear colleagues,

  Mira Variable V2010 Cyg and Another Adjoining New Mira Variable MisV1340
  http://www.aerith.net/misao/report/variable/MisV1340.html

Seiichi Yoshida, MISAO Project, discovered a new Mira type variable
MisV1340 from unfiltered CCD images taken by Nobuo Ohkura, Okayama,
Japan; and Ken-ichi Kadota, Ageo, Saitama, Japan.

  http://www.aerith.net/misao/data/misv.cgi?1340

This star is adjoining to a Mira type variable V2010 Cyg discovered by
Lennart Dahlmark.

The variability of this star was found already in 2000 in the course
of the MISAO Project. But we found the position was extremely close to
a Mira type variable V2010 Cyg = LD 162 with a range of 13.0 - <15.2
mag(V). 

In fact, this star is a northern component of double stars with
similar brightness lying north-south direction with a separation of 20
arcsec. And the southern component is registered as V2010 Cyg = LD
162.

Based on the measurements using the old system in 2000, no significant
variation of the southern star was detected from the MISAO Project
images. Therefore, we judged the identification of V2010 Cyg was wrong
and the northern star, not the southern star, must be variable. We
judged the following identification will be correct.

  Variable star of the MISAO Project = V2010 Cyg = LD 162

John Greaves and Brian Skiff researched the IBVS papers and commented
on this identification.

The coordinates published in the Dahlmark's discovery paper (IBVS
3855) are inaccurate. But in the chart, the southern star is marked as
a variable.

The southern star is USNO-A1.0 1200.14807721 (R.A. 20h09m44s.155,
Decl. +31o58'49".18). In the revision paper by Skiff & Williams (IBVS
4450), this USNO-A1.0 coordinates are published as a accurate position
of V2010 Cyg.

However, the resolution in the original chart is not very good. In
addition, no variability of the southern star is found between the
DSS2 R images in 1991 and 1992, on the other hand, the variability of
the northern star is evident. So it seemed correct that the mark in
the original paper was a mistake and the northern star was a real
variable.

Therefore, we did not announce this star as one of our new variable
stars in 2000. Instead, we reported the revision of V2010 Cyg's
coordinates [vsnet-id 299].

However, in 2006, we concluded our identification above was wrong. We
concluded both of the double stars are variable, the original position
of V2010 Cyg was correct, and our star, the northern star, is a new
variable star.

The reasons for our conclusion are as follows.

Based on the measurements using the latest system, the brightness of
the southern star seems also slightly variable. So probably the
variations of both of the double stars are detected. But because the
resolution is nearly limit, we cannot affirm if the variation is real
or not only based on the MISAO Project images.

The double stars are very bright on the 2MASS images. The northern
star is recorded in the infrared catalog MSX5C. The USNO-A2.0 color of
the southern star is very reddish as B-R = 4.6 mag. Therefore both of
the double stars are likely red variables.

The NSVS detected the following Mira type variable at the position of
the double stars.

  NSVS 2009441+315858  20h09m44s.126 +31o58'58".22  Mag:12.819  MagError:0.070  MagRange:1.160  Period:567

The NSVS position is exactly the center between the double stars lying
north-south direction. So the NSVS could not deblend the double stars
and must have measured the blended brightness. The light curve is
available as follows.

  http://skydot.lanl.gov/nsvs/star.php?num=8484079&mask=32004
  http://skydot.lanl.gov/nsvs/star.php?num=8467488&mask=32004

Although the light curve shows a Mira type variation, it is
asymmetric, that is, there is a large difference between the first and
the last maximum brightness. This implies that two Mira type light
curves are combined. 

Skiff re-examined the Dahlmark's chart and confirmed that it clearly
marks the southern star. 

These facts derive the following two conclusions.

- Dahlmark's V2010 Cyg is the southern star.

- Variation of the northern star was detected by the MISAO Project.

Therefore, we announce the northern star as another new Mira type
variable MisV1340 adjoining to a Mira type variable V2010 Cyg.

Best regards,

--
Seiichi Yoshida
comet at aerith.net
http://www.aerith.net/