X-ray Transients in M31
ATel #97; A. K.H. Kong, M. R. Garcia, F. A. Primini, J. E. McClintock and S. S. Murray (Harvard-Smithsonian Center for Astrophysics)
on 6 Jun 2002; 18:38 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Albert Kong (akong@cfa.harvard.edu)
Subjects: X-ray, Binary, Black Hole, Neutron Star, Transient
A bright X-ray transient was detected by Chandra on 2002 June 2 with a
series of 5 HRC-I snapshots. The new source CXOU J004154.6+405648
(R.A.=00h41m54s.64, Dec.=+40d56m48s.0, +/- 1", J2000) is discovered at a
luminosity (0.3-10 keV) of 1.5 x 1038 erg/s (assuming an
absorbed power-law
model with photon index = 2 and NH = 1021
cm-2 at a
distance of 780
kpc). It was not detected in previous HRC and ACIS images taken
between 1999 and 2002. In a merged 38ks ACIS-S image of this region, we
derived a 3-sigma detection limit of 1.5 x 1035 erg/s. A ROSAT
source (1RXS
J004154.1+405648) in the ROSAT all-sky survey catalogue
(1-sigma error circle of 13") is found within 10" from this new transient.
Using the count rate of the ROSAT source, we derived a luminosity of 5 x
1037 erg/s. However, this source is not listed in the M31 PSPC
catalogs (Supper et al. 1997,2001) that used data after the all-sky
survey. If this new transient is indeed associated with the ROSAT source
observed in 1991 then it joins the small but growing list of recurrent
transients found in M31.
The recurrent transient CXOM31 J004309.8+411901 (source r3-16 in Kong et
al. 2002; astro-ph/0203243)
described in ATEL#79 was also observed by
Chandra ACIS-I on 2002 June 3. It was seen at 4 x 1037 erg/s in
2002 January, but is about 20 times fainter at 2 x 1036 erg/s
in the 2002 June data.
