[vsnet-sequence 90] Problems with southern RCB sequences.

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

While observing RS Telescopii and V Coronae Australis I have found several
problems with the sequences.
The main problem lies near RS Tel. It is a V= 9.46 star, B-V= 1.4, according
to Tycho 2. I have estimated it as near 9.25.
It is GSC 8358 1769.
Being so close to the variable now that it is bright, it is a very useful
comparison.
Note that I have always seen it very much brighter than the V= 9.68 star
(B-V= 0.0) that lies very near( GSC 8358 1679) but in the past RS Telescopii
wasn't bright enough to use it.

Then I found another confirmation to my discrepance. When I made two
different estimates with different comparison stars, the results were very
different:

946 (8) V (1) 968 =  9.66
946 (1) V (1) 1012= 9.79

1012 is GSC 8358 383 (B-V= 0.1).

After estimating (with several other comparison stars) the brightness of GSC
8358 1769 as 9.25, I obtained the following:

925 (8) V (1) 968 =  9.63
925 (1) V (1) 1012= 9.68

That's better. Obviously we need photometry of all these fields.

V CrA doesn't have a good sequence too, but there is not an outstanding
error.
GSC 7915 745 (V= 9.22 , B-V= 1.5) looks 0.1 mag. brighter.
GSC 7915 395 (V= 9.55 , B-V= 0.5) looks a little fainter (9.6)

It was a surprise to find that for this field all I observed is in agreement
with Tycho 1 values and not with Tycho 2. (??)

All I want to comment is that we are in need of good sequences down here....

Cheers,
Sebastian


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