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Hi Sebastian and readers,
Some 10 years ago I used to roam the LMC field with my 5" apogee refractor
and monitored a rather largish (?) number of probable variables. Most of them
were classified as S Dor and S Dor:.
After a while I got the impression that most bright stars around that
region got a life of their own and seem to vary.
Without a steady magnitude reference platform I got confused and
gradually lost interest.
A few of those variables kept my interest alive for a while, ao HD(E)
269858 which had a (probable S Dor type) outburst ongoing and evolved around
magnitude 9.2. It's nice to see that this S Dor ? variable is recently reported
on. I see it around 10.3, a full magnitude fainter than in the early
nineties.
Another such unpublished variable (if it is indeed one) was in the field of
S Dor itself at (2000) coordinates 051805-6914. It was documented to be at 11.5
and my estimates gave it around 12.6, I think I must have a look again.
Another interesting target was HD 269582 (S Dor: / Z And:). A range of
10.3-11.8 was given. I saw it around 12.4 then. Possibly it is
fainter still now.
I could go on for a few more but I rather stop here.
Some speculation: most of those 'stars' are bluish and are becoming partly
obscured and reddened by nebulous environments. Possibly that is what
causes their variability to a certain (possibly total) extent. B-V-R
measures over time would certainly reveal this possibility.
Happy observing to all,
Berto Monard
Pretoria
>>> "Sebastian Otero" <varsao@fullzero.com.ar> 12/25/00 09:50PM >>> 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. --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://vsnet.grisoft.com). Version: 6.0.219 / Virus Database: 103 - Release Date: 05/12/00 |
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