XMMSL1 J063045.9-603110 : A new bright soft X-ray transient from the XMM-Newton Slew Survey
ATel #3811; A M Read (University of Leicester), R D Saxton (ESAC), P Esquej (CAB, CSIC-INTA)
on 17 Dec 2011; 16:09 UT
Credential Certification: Dr. Andy Read (amr30@star.le.ac.uk)
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.
