[vsnet-alert 13976] XMMSL1 J063045.9-603110 (ATEL)

[Taichi Kato]

The Astronomer's Telegram                   http://www.astronomerstelegram.org

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ATEL #3811							     ATEL #3811

Title:	XMMSL1 J063045.9-603110 : A new bright soft X-ray transient
		from the XMM-Newton Slew Survey
Author:	A M Read (University of Leicester), R D Saxton (ESAC), P Esquej
		(CAB, CSIC-INTA)
Queries:	amr30 at star.le.ac.uk
Posted:	17 Dec 2011; 16:09 UT
Subjects:X-ray, Transient

We report the discovery of XMMSL1 J063045.9-603110, a new X-ray transient,

found in an XMM-Newton slew from 1st December 2011. The source position

(2000.0) is RA:06 30 45.9 DEC:-60 31 10 with an 8'' 1 sigma error circle.

The source is bright and point-like. The (0.2-2 keV) count rate was 32.6
ct/s 
in the EPIC-pn detector (medium filter). The slew data were severely affected

by pile-up, and a significantly higher count rate would have been seen
using a 
faster, smaller window observing mode. A fit to the rudimentary slew spectrum,

extracted from a 10"-60" annulus to counter the effects of pile-up, yields
an 
absorption of nH=1.1E21 cm-2 and a black-body temperature of 85eV. This
gives 
rise to an absorbed (0.2-2 keV) flux of 4.0E-11 erg/cm2/s, which is over
200 
times greater than the upper limit calculated from the ROSAT All Sky Survey

using the same spectral parameters. XMM-Newton has slewed over this position

twice previously, resulting in upper limits of <0.52 ct/s (14/08/2002)
and 
<1.76 ct/s (18/11/2008). There have been no dedicated XMM-Newton pointings
at 
this position.  

There are no obvious longer-wavelength counterparts, the nearest bright
object 
being USNO-B1.0*0294-0048878, with magnitudes of r=14.3, b=16.1, J=13.8,

H=13.4, K=13.4. Its distance of 19" however places it well outside the

nominal slew error circle (8"). A small number of very faint objects are
also 
observed, but these are still over 17" away. The spectral softness and
lack 
of a prior known counterpart is suggestive of it possibly being a new nova.
We 
welcome further observations to ascertain the true nature of the object.