[vsnet-alert 13511] 1RXS J202406.6+260918 X-ray brightening (in May)

[Taichi Kato]

1RXS J202406.6+260918 X-ray brightening (in May).  Observations are encouraged!

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

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ATEL #3485							     ATEL #3485

Title:	A soft X-ray flare from XMMSL1 J202406.4+260926
Author:	Richard Saxton (XMM SOC / ESAC, Madrid Spain), Andrew Read
		(Leicester University, U.K.), Pilar Esquej (Centro de Astrobiologia,
		CSIC-INTA,Torrejon de Ardoz, Spain)  
Queries:	richard.saxton at sciops.esa.int
Posted:	15 Jul 2011; 07:23 UT
Subjects:X-ray, Request for Observations, Transient

We report the discovery of a large, 15 ct/s, soft X-ray flux from 
XMMSL1 J202406.4+260926 in an XMM-Newton slew on May 22nd 2011. 
The source position, RA:20 24 06.4 DEC:+26 09 26 (1-sigma error 
radius of 8") has been observed in two earlier slews in 2005 
and 2009, without detecting the source (upper limits of 0.8 and 0.7 ct/s

respectively). A very faint object, 1RXS J202406.6+260918, is catalogued

in the ROSAT ALL-Sky Survey with a count rate of 0.032 c/s, which equates

to a flux 60x fainter than that seen on May 22nd. 

A rudimentary slew spectrum, made from the 70 photons of the XMM-Newton
slew 
detection, is consistent with a background AGN but only if the intrinsic

flux (0.2-2 keV) is high (1-2x10E-10 ergs/s/cm2) and the power-law slope
quite 
steep (2.7-4.1). We consider it more likely that the source lies in  
our galaxy, and tentatively identify it with the brightest optical object

in the error circle, USNO-B1.0 1161-0489239, with B1 mag=14.55, R1 mag=12.96.

We welcome further observations, particulary with optical telescopes, 
to ascertain the true nature of the object.

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Password Certification: Richard Saxton (richard.saxton at sciops.esa.int)
http://www.astronomerstelegram.org/?read=3485
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