[vsnet-chat 5437] Precise position of TZ Vel

["Mati Morel" <morel@ozemail.com.au>]

While working through a list of old, but still poorly identified southern
variables (announced in Union Obs. Circ. 48 (1920)), I had a bit of trouble
with the Mira variable TZ Velorum. The discovery note says that it is the
"middle star of three, others 12.5 (mag)". My Guide8 display shows no such
configuration, so the GCVS position was probably off.  TZ Vel did not appear
to be in the GSC, nor did it show up on various photos I checked.  Finally I
found a bright star in the USNO-A2.0 cat., about 10s of RA to the east. Its
mags. are r = 8.6. b = 13.3, V =104, position 9:30:27.35 -53:8:47.2.  This
must be be TZ Vel, but where were the 12.5 mag companions?  A look at the
DSS image soon made things clear.
1).  The companions are GSC 8584-01180 (13.0) and 8584-4631 (13.8),
separation about 20", and somewhat fainter than expected.  There is a faint
star halfway between them.
2). The USNO-A2.0 position (above) is slightly off, probably skewed by one
or more companions just to the east.

Checking the GSC 2.2 catalogue turned up the position of the faint star
referred to in 1).  Its photometry is R = 16.19, B = 18.05 (yielding an
approx. V =16.9).  I take this to be TZ Vel, position 9:30:26.71 -53:8:46.3
(2000),  in very good agreement with the note in UOC48.

As a matter of interest, TZ Vel was picked and followed by Vello Tabur.  His
uncalibrated light curve can be found at
http://vsnet.tip.net.au/~vello/varstar
The small scale of his images (50"/pixel) are not suited for determining
accurate positions, but his light curve suggests a period of about 370d,
rather than 237.4d.

Regards,
Mati Morel
morel@ozemail.com.au

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