[vsnet-chat 4568] MisV and 2MASS identifications

[Seiichi Yoshida <comet@aerith.net>]

Dear colleagues,

# Continued from the following two mails:
  Subject: [vsnet-id 458] Re: MisV1089 ID
  Subject: [vsnet-chat 4542] Re: re MisV0380
  Subject: [vsnet-newvar 945] Re: [vsnet-id 458] Re: MisV1089 ID

Dr. Skiff wrote in [vsnet-chat 4542]:
>      Another point in regard to 2MASS IDs (per vsnet-id 456) is to look at
>  the J-K color, not simply the magnitudes.  As Kato-san noted, the usual
> red variables found by MISAO are very bright, even saturated in 2MASS, so
> the JHK magnitudes are typically in the 5 to 8 range.  More importantly,
> the J-K color (forget H) for red variables will be at least 1.2 or greater.
> Thus many of the IDs with comparatively blue colors (J-K < 1.0 roughly)
> appearing in vsnet-id 456 are wrong if they apply to red variables.  For a
> rough correspondence, the J-K value is comparable to V-R in the visible.
> Thus a K0III is J-K about 0.6, M0III is about 1.0, carbon stars much redder.

I classified the possible 2MASS identifications based on the J-K
color. The J-K value is added at the end of each line.

Kato-san wrote in [vsnet-newvar 945]:
>    I have examined the case of MisV0035.  There is a much brighter 2MASS
> star, but is slightly offset from the original MISAO position.

Now I completely agree on you. Probably the catalogued position of
MisV0035 is not good. I tried to search bright red 2MASS objects
within 10 arcsec of some MisV stars which were identified with faint
blue 2MASS objects in my last mail, and found some have bright ones a
bit away from the catalogued position. So here I rejected those ones.

1) Faint blue stars (J-K < 1.0, J > 10)

MisV1097  0.3"  2MASS 011528.730 +411959.02 (2000.0) 11.808 11.682 11.648  0.160
MisV0002  0.6"  2MASS 072403.510 +412602.31 (2000.0) 12.232 11.796 11.727  0.505
MisV1095  0.5"  2MASS 002649.502 +414908.81 (2000.0) 10.746 10.161  9.987  0.759

MisV1061  0.2"  2MASS 210017.978 +275255.92 (2000.0) 11.325 11.195 11.113  0.212
MisV0814  0.6"  2MASS 053333.785 +344323.24 (2000.0) 12.667 12.393 12.283  0.384
MisV1105  0.6"  2MASS 201438.659 +415614.26 (2000.0) 12.495 12.135 12.043  0.452
MisV0665  0.8"  2MASS 184323.844 -212036.95 (2000.0) 11.243 10.848 10.789  0.454
MisV0779  0.2"  2MASS 210938.019 +381245.75 (2000.0) 11.030 10.434 10.307  0.723
MisV0049  1.5"  2MASS 180113.908 -302036.81 (2000.0) 10.696 10.085  9.892  0.804

MisV0002 is an ecliptic type. MisV1095 is also an ecliptic
type. MisV1097 is a short periodic type. So their identifications must
be correct. They are not red variable.

The other 6 stars are interesting. The type are uncertain. They have
no bright 2MASS objects within 10 arcsec. So probably the
identifications are correct. Probably they are not red variable
stars.

Actually, all of them, except ofr MisV0049, are identified with GSC
stars, and the GSC magnitude is as bright as the MISAO's unfiltered
CCD magnitude. So they are not red variable. 

  MisV1061 (12.0-12.7 mag) = GSC 2180-00207 (12.73 mag)
  MisV0814 (13.3-14.5 mag) = GSC 2412-00713 (14.55 mag)
  MisV1105 (13.4-14.2 mag) = GSC 3159-01247 (13.93 mag)
  MisV0665 (13.0-14.2 mag) = GSC 6292-01507 (12.89 mag)
  MisV0779 (12.8-14.2 mag) = GSC 3168-02233 (12.87 mag)

MisV0049 is 13.9-15.1C mag. So considering the difference between the
unfiltered CCD magnitude and the 2MASS magnitude, I think the
identification is correct and it is a red variable, although the J-K
is smaller than 1.0.

2) Bright blue stars (J-K < 1.0, J < 10)

MisV1024  1.6"  2MASS 200135.611 +335902.75 (2000.0)  7.312  5.861  6.583  0.729

This is very interesting. MisV1024 is identified with IRAS 19596+3350
and S-type star NSS 49. So it must be a red variable. However, the
2MASS J-K value is very small. I do not know why.

3) Faint red stars (J-K > 1.1, J > 10)

MisV0603  0.2"  2MASS 180105.946 -115941.89 (2000.0) 13.765 12.909 12.619  1.146
MisV1069  0.4"  2MASS 195258.818 +492237.62 (2000.0) 10.819 10.042  9.630  1.189
MisV0371  1.8"  2MASS 185732.835 -185517.19 (2000.0) 10.208  9.390  9.014  1.194
MisV0332  0.1"  2MASS 190143.025 +285755.33 (2000.0) 10.339  9.443  9.140  1.199
MisV0257  0.9"  2MASS 200312.473 +322157.00 (2000.0) 13.801 12.427 12.081  1.720

All these stars are very faint variable stars. So I think the
identifications are correct. The faint 2MASS magnitude seems to
reflect the faint unfiltered CCD magnitude.

Best regards,

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

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