X-ray Transients in M31
ATel #76; A. Kong, M. Garcia, S. Murray, F. Primini, J. McClintock and R. Di Stefano (Harvard-Smithsonian Center for Astrophysics)
on 12 Sep 2001; 23:47 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Albert Kong (akong@cfa.harvard.edu)
Subjects: X-ray, Transient
A bright X-ray transient in M31 was detected in a 5000-sec Chandra ACIS-I
observation on 2001 Aug 31.54 UT. The new transient (CXOU
J004305.5+411703) is located at R.A. = 00h43m05s.55, Decl = +41o17'03''.3
(equinox 2000.0; based on the aspect solution, with uncertainty of ~1'').
The energy spectrum can be fitted with a power-law model with a photon
index of 1.5; the 0.5-10 keV luminosity is estimated to be 2.7 x
1038 erg/s (assuming a distance of 780 kpc). There is second
transient (CXOU
J004242.1+411424) located at R.A. = 00h42m42s.1, Decl = +41o14'24''.7
(equinox 2000.0; with uncertainty of ~1''). This source is not detected
below 1 keV, with estimated 0.5-10 keV luminosity of 7 x 1036
erg/s (assuming a power-law spectrum with NH=1021
cm-2 and a photon
index of 1.2). Both sources did not show up in the
previous Chandra observation on 2001 June 10. Observations of the new
X-ray transients at other wavelengths are encouraged.
The super-soft transient observed by XMM (XMMU J004308.5+411820, IAUC # 7659 ) in 2001 June is not detected in our observation. The other
transient discovered in the June XMM observation (XMMU J004245.2+411721)
is only present just above the 2-sigma level at
1036 erg/s (0.5-10 keV; assuming a power-law spectrum with
photon
index of 1.5), corresponding to an order of magnitude fainter than in
2001 June.
