[vsnet-chat 2338] Position of UX Ara

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

UX Ara is another one of those neglected southern variables, but may be
worth watching more than most others.
According to the GCVS, UX Ara = CoD-51 10588 (10) = CPD-51 10055 (10.0).
This DM star
coincides with an IR source IRAS 16514-5150 and can be identified with an
USNO-A2.0
star at (J2000) 16h55m22.52s -51 55'35.25".   Not listed in GSC.
Turning to the main table of the GCVS, the position given for UX Ara is 41"
south of
the DM star and coincides with GSC 8339.01540 (13.3) at 16h55m22.54s -51
56'16.3".

Which id. is the correct counterpart for UX Ara?  DM star or GSC star?
Fortunately, back in August 1985, Bill Liller in Chile photographed UX Ara mear 
maximum. By 1985 September 19.00 UT it had grown steadily brighter, to
magnitude 8.5
on 2415 Pan Film with orange filter. From a very low dispersion spectrogram
its spectral
type was estimated as early M (very uncertain), suggesting that the visual
magnitude
was about 9.0.
Liller also saw UX Ara in early May 1984, when it briefly reached about
visual magn.
10.5 (yellow filter).
Copies of blow-ups of red and IR UK Schmidt plates (exposed 1980 July 18)
clearly
show that the northern component, ie CoD -51 10588, has a large IR excess,
consistent
with a red star as observed by Liller. 
UX Ara is evidently a long-period Mira variable, reaching magn. 10vis at times.
Its position is (2000) 16h55m22.52s - 51 55'35.25".  It has no GSC number.
The erroneous GCVS position has resulted in mistaken ids. in other places: - 
eg Guide7; Gareth Williams coordinate file for 4600 variables (vsnet 1779).

I thank Rob McNaught, who many years ago, provided me with copies of Liller's
correspondence and copies of UK Schmidt plate blow-ups. I commend Bill
Liller for
his diligence in picking up this star as a by-product of NovaSearch.

P.s. It is interesting to speculate what could have happened if Bill Liller
had not
picked up UX Ara. Hypothetically, if some other diligent observer had found
variability
in GSC 8339.01540 and not found any other variables in the vicinity, then
all the
modern reference works (GCVS, Guide7 and Williams VS id. file) would all
have pointed
towards the GSC star as UX Ara. The "real" UX Ara would have been overlooked.
All hypothetical of course, but the above scenario has much in common with the
GM Sgr/ Goranskij's star debacle.

P.p.s. The GCVS range for UX Ara is 11.8 - 12.6p. I suspect that the max. figure
refers to UX Ara, but the "12.6" refers to the GSC star, when UX Ara was
invisible.
Regrads,
 





 
/Mati

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