[vsnet-alert 10370] (fwd) V532 Oph: likely RCB star

[Taichi Kato]

   According to AAVSO discussion, Patrick Wils has pointed out that
V532 Oph is likely an R CrB-type object.  The object was rising in
2006, bright (V around 11.7) in 2007, faint again in 2008.

===

From: Patrick Wils <patrickwils at yahoo.com>

V532 Oph is classified as a long period (>6000 days) eclipsing variable, based o
n the observation of a single eclipse (bottom light curve of <http://articles.ad
sabs.harvard.edu/cgi-bin/nph-iarticle_query?bibcode=1942AnHar.109....1S&db_key=A
ST&page_ind=9&plate_select=NO&data_type=GIF&type=SCREEN_GIF&classic=YES> = SVS 4
57).  The ASAS light curve is a bit more intriguing: <http://www.astrouw.edu.pl/
cgi-asas/asas_variable/173242-2151.7,asas3,0,0,500,0,0>.

2MASS has J=9.05, Ks=8.56 (from 30 May 1998, before the ASAS data), while DENIS 
has J=13.45, K=9.33 (for 8 October 1998).  If these values are reliable it has f
aded by more than 4 magnitudes in about 4 months and also has considerably redde
ned.  The NSVS database (from 1999) has no data for it, while a number of 13th m
ag stars in the neighbourhood were observed, suggesting it was fainter than mag 
13.5 at the time, and also ASAS (starting from 2000) has it faint at the beginni
ng (first positive data point dates from June 2002).  Finally there are also MAC
HO images from July 2000 with the star very faint or not visible at all.  

The light curve and infrared data suggest V532 Oph is an RCB type variable.  The
 current ASAS data indicates that it was faint, but is brightening again at the 
moment.  Multi-colour photometry of this star is encouraged.

Patrick