[vsnet-alert 9772] Re: OT_J111218-353837 (new optical transient)

[arne]

Masayuki Suzuki wrote:
>>> "Pi of the Sky automatic trigger has detected a new object on the sky
>>> at (2000) RA = 11 12 18, DEC = -35 38 37. No known variable star or
>>> minor planet is present at this position.
>>
>>
>>   The images definitely show the outbursting nature of the object.
>> To my eyes, the field looks blank down to the 20 mag.
>> No ROSAT source is present.
>> The object again looks like an outbursting dwarf nova with
>> a very large amplitude.  Further detailed observations are strongly
>> urged.
>>
>>   Please use the name OT_J111218-353837 for reporting in the meantime.
> 
> 
> 
> 
> I took images of OT_J111218-353837 remotely (Mayhill, NM) with 0.25-m 
> f/3.4 reflector + CCD on Dec. 23.47 UT .
> 
> OT_J111218-353837
> RA= 11h 12m 17.41s, DEC= -35o 38' 28.9" (equinox 2000.0)
> V mag = 12.9  (Dec. 23.47 UT)
> 
> 
We also obtained images on 071223 from SRO, with astrometry
  11:12:17.40  -35:38:28.8  J2000
UCAC2 reductions, errors less than 0.1arcsec; essentially identical
to Suzuki-san's measurements.

This is about 12arcsec from the position
11 12 18, DEC = -35 38 37
originally reported from the Pi of the Sky team.
This rules out the R=13 nearby companion as the progenitor,
and comes close to the GSC2.3 star mentioned by Brian Skiff at
11 12 17.44 -35 38 30.1
However, this is about an arcsec error.  I don't know the accuracy
of GSC2.3 or SuperCOSMOS at this faint level, but this star and the
OT are probably identical.

The rough photometry is
    V    B-V   V-Rc  R-I   V-Ic
  12.91 -0.03  0.06  0.03  0.08

So no evidence of any Halpha emission.  With an 8-magnitude outburst
amplitude and the high galactic latitude, I'd consider this to be
a cataclysmic binary, probably WZ Sge subclass.
Arne