(cba:news) FW: AAVSO Special Notice #208: Optical transient in Pegasus]

Joe Patterson jop at astro.columbia.edu
Sat May 8 15:59:33 EDT 2010

Dear CBAers,

This is potentially a SENSATIONAL object, if it is a dwarf nova, not a 
classical.  Probably pretty damn interesting if it's some third class of 
object, too.  Anything that erupts violently to 8th magnitude 
frantically deserves our attention... and in particular OUR attention.

You might have to do aperture photometry to include both stars in the 
double.  I'd consider that the safe approach, although if you're well 
acquainted with your local capabilities re psf fitting, telescope drive, 
etc., make your own judgment.  Also check all available news sources for 
the doubtless rapidly evolving information on this star.

Could this be a true challenger to WZ Sagittae's supremacy?  GW Lib and 
V455 And were mighty impressive, but fell somewhat short.  The heart 
starts to beat faster...


Great follow-on to CR Boo in the night-time sky.  BTW I hope that 
southerners will consider this target, too.  +21 doesn't look good, but 
the nights are long, so maybe?

Subject: AAVSO Special Notice #208: Optical transient in Pegasus

AAVSO Special Notice #208

Optical transient in Pegasus
May 8, 2010

CBET 2273 (D.W.E. Green, editor) reports the discovery of a bright
transient in Pegasus by Dae-Am Yi (Yeongwol-kun, Gangwon-do, Korea).
The object was discovered at magnitude 10.8 on 2010 May 6.77 (JD
2455323.27) on an image taken with a Canon 5D + 93-mm camera lens. The
object brightened to magnitude 8.4 as observed on 2010 May 7.76
(2455324.26) on an image taken with a 400-mm lens. The transient object
appears to be concident with GSC 2197:886 on discovery images, but this
identification is not yet proven. The GSC star has a NOMAD catalog V
magnitude of 13.84 and is a close double with a separation of about 3
arcseconds. Based upon an examination of the POSS-I and POSS-II plates
by Arne Henden, it is possible that the double is composed of two
unassociated stars, one with a high proper motion. Observations of this
field are strongly encouraged both to obtain astrometry of the source
and to follow the progress of this outburst. It was noted by H. Yamaoka
(Kyushu University) that there is a bright ROSAT X-ray source within
seven arcseconds of the GSC star, and so the object may be a cataclysmic
variable of some kind.

CBET 2273 gives the coordinates of the GSC star for the object, which are

RA: 21 38 06.571 , Dec: +26 19 57.33

Charts for this object may be plotted using AAVSO VSP:



Please promptly submit all observations to the AAVSO using the name
"VSX J213806.5+261957".

This AAVSO Special Notice was prepared by M. Templeton.


Information on submitting observations to the AAVSO may be found at:


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