[vsnet-alert 14824] PNV_J180645.2-360458

[Hiroyuki Maehara]

 Shigehisa Fujikawa (Kagawa, Japan) reported his discovery of an unusual
variable star (or possible nova?) in Sgr. His observations and a follow-up
observation by K. Itagaki (Yamagata, Japan) are as follows (measured by
H. Kaneda, Hokkaido, Japan):

2012 Jul 23.517     12.5  (S. Fujikawa; f=105mm lens + CCD)
         23.519     12.6  (S. Fujikawa; f=105mm lens + CCD)
         30.554     12.2  (S. Fujikawa; f=105mm lens + CCD)
         30.555     12.0  (S. Fujikawa; f=105mm lens + CCD)
     Aug  1.553     11.5  (S. Fujikawa; f=105mm lens + CCD)
          1.605     11.3  (S. Fujikawa; f=400mm lens + Canon EOS X2 DSLR camera)
          2.467     11.3  (K. Itagaki; 60cm telescope + CCD)
          2.491     11.5  (S. Fujikawa; f=400mm lens + Canon EOS X2 DSLR camera)

 The object is located at R.A. =  18h 06m 45.23s, Decl. = -36d 04' 58.5" 
(equinox 2000.0; measured from 6 CCD images obtained by K. Itagaki with 
60cm telescope). There is a faint object in the 2MASS catalog
(2MASS J18064523-3604583 Jmag=15.11) at this position.

 H. Kaneda pointed that this object was detected by ASAS. According to 
ASAS data, this object brightened slowly during 2003-2005 and it was
at almost constant brightness (V~12mag) during 2005-2008. The object
showed short fadings (time-scale of a few tens of days) in the 2009
observing season. 
http://www.astrouw.edu.pl/cgi-asas/asas_variable/180645-3604.9,asas3,0,0,500,0,0
Note: there is a mag~13-14 star at 18:06:45.67, -36:04:55.1 (J2000.0), 
about 6 arcseconds NE of this object.

The long-term variation of the object is similar to those of V4334 Sgr 
and FG Sge (or very slow nova?). Could someone perform spectroscopy of
the object? This object was at Vmag=11.2 (B-V=1.1) on Aug. 3.50.

object                   YYYYMMDD(UT)   mag      code
PNV_J180645.2-360458     20120803.49784 9.87Ic   Mhh.VSOLJ
PNV_J180645.2-360458     20120803.49878 10.54Rc  Mhh.VSOLJ
PNV_J180645.2-360458     20120803.50007 11.22V   Mhh.VSOLJ
PNV_J180645.2-360458     20120803.50229 12.33B   Mhh.VSOLJ
PNV_J180645.2-360458     20120803.50539 11.23y   Mhh.VSOLJ