[vsnet-chat 3886] Info on a LMC star

["Sebastian Otero" <varsao@fullzero.com.ar>]

Dear friends:

Observing some variables in the LMC, I used one B spectral type star as a
comparison and then found that the published V values suggested variability
and furthermore, they had nothing to do with my observation...

When I looked for the star in the Tycho and Tycho 2 catalogues, I noticed
that there are two stars close from each other labelled with different names
but sharing some particular features:

Tycho recorded  TYC 9167-00383-1, position 5h 39m 05.52s -69º 29' 22.5" , Vt
12.36 and B-V -0.49 ,
while Tycho 2 doesn't include that star but do include  TYC 9167-00759-1 ,
position 5h 38m 58.85s -69º 29' 22.0" , Vt 11.72 and  B-V -0.41

The Tycho Input Catalogue agrees with the Tycho 2 entry and gives a rough
9.8 V magnitude.
From Tycho numbers I see there is a great error, since a color index bluer
than -0.4 is impossible and the UBV measurements are +0.12.
Searching in the Washington Double Star catalogue, I found there is a double
star near the same position. Magnitudes mentioned are 10.8 and 12.8. It is
DM-69 468 which turns out to be HD 269927.
The question is: Is HD 269927 the same star as TYC 9167-00759-1 ?
And what is TYC 9167-00383-1? A mistake?  Or both Tycho 1 and Tycho 2 stars
are the individual components of the WDSC pair?

At the time of my observation there was no other star that could be
misidentified nearby. At least not a 10 or 11 magnitude one.

Measurements:

V measurements in the GCPD are 10.96, B-V 0.12  and 10.64 (They are for the
AB pair, so it's supposedly the brighter I should be observing.)   SIMBAD
lists the object as V= 10.69, B-V 0.11.
My observation last night is 10.3, comparing the star with nearby stars that
looked okay and with good PEP(V) values.

Some clarification?

Thanks,
Sebastian.


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