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XMMSL1 J162940.2-112024 : A new X-ray transient from the XMM-Newton Slew Survey

ATEL # 1689; A M Read (Leicester), R D Saxton (ESAC), P Esquej (MPE)
on 2 Sep 2008; 14:02 UT
Password Certification: Dr. Andy Read (

Subjects: X-ray, Request for Observations, Transients

We report the discovery of XMMSL1 J162940.2-112024, a new X-ray transient, found in an XMM-Newton slew from 20th August 2008. The source position (2000.0) is RA:16 29 40.2 DEC:-11 20 24 with an 8'', 1 sigma error circle. No other XMM-Newton slew has covered this sky position.

The source is bright and point-like. The (0.2-2 keV) count rate was 3.1 ct/s in the EPIC-pn detector, whilst the (0.2-10 keV) count rate was 4.9 ct/s. A power law fit to the rudimentary slew spectrum, using a fixed Galactic absorption out of our galaxy at this position (nH=1.4E21 cm-2), yields a spectral slope of 1.8. This gives rise to an unabsorbed (0.2-2 keV) flux of 1.2E-11 erg/cm2/s, a factor 60 greater than the upper limit calculated from the ROSAT All Sky Survey using the same spectral parameters.

Though the slew spectrum appears roughly similar to that of an AGN, its position suggests that it may be a foreground object, such as a flare star, CV or Nova. Two catalogued optical sources lie within the error circle: USNO-B1.0*0786-0301344, R1=16.7, B1=19.5, and USNO-B1.0*0786-0301348, R1=18.4, B1=19.7. We welcome further observations to ascertain the true nature of the object.

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