Central Bureau for Astronomical Telegrams

Central Bureau for Astronomical Telegrams -- Image credits

IAUC 7291: X-RAY TRANSIENT IN M31; XTE J1859+226

The following International Astronomical Union Circular may be linked-to from your own Web pages, but must not otherwise be redistributed (see these notes on the conditions under which circulars are made available on our WWW site).

Read IAUC 7290 SEARCH Read IAUC 7292

View IAUC 7291 in .dvi or .ps format.
IAUC number 

                                                  Circular No. 7291
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)
BMARSDEN@CFA.HARVARD.EDU or DGREEN@CFA.HARVARD.EDU (science)
URL http://cfa-www.harvard.edu/iau/cbat.html  ISSN 0081-0304
Phone 617-495-7244/7440/7444 (for emergency use only)


X-RAY TRANSIENT IN M31
     S. S. Murray, M. R. Garcia, and F. A. Primini, Harvard-
Smithsonian Center for Astrophysics, report:  "We have discovered a
bright new x-ray transient located 13" west of the radio nucleus of
M31.  A 15 000-s observation with the Chandra ACIS-I detector,
centered on Oct. 13.23 UT, shows a new source at R.A. = 0h42m42s.18,
Decl. = +41o16'08".4 (equinox 2000.0; 90-percent error radius 2".0),
with a luminosity of about 10**38 erg/s in the Chandra bandpass
0.5-10 keV.  This position is derived from a plate solution using
eight globular clusters detected in the Chandra image and positions
referenced to the HST Guide Star Catalog (Magnier et al. 1993, A.Ap.
272, 695).  The last ROSAT HRI observation of this region in Jan.
1996 shows no source at this location, to an upper limit of 5 x
10**35 erg/s.  Observations at other wavelengths are encouraged in
order search for a possible counterpart."


XTE J1859+226
     D. Dal Fiume, Istituto TeSRE, CNR Bologna, communicates
(together with F. Frontera, M. Orlandini, L. Amati, S. Del Sordo,
L. Stella, T. Belloni, D. Ricci, M. Capalbi, and M. R. Daniele, on
behalf of a large collaboration):  "BeppoSAX observed the transient
source XTE J1859+226 on Oct. 15.086-15.405 UT for about 14 000 s in
the MECS and HPGSPC and for 7000 s in the PDS.  The source was
clearly detected up to 200 keV.  The 2-200-keV spectrum is roughly
approximated by an absorbed power law with photon index of about
-2.8 and N_H about 8 x 10**21 cm**-2.  This spectral slope is
consistent with that measured with BATSE (IAUC 7282) and steeper
than that measured with RXTE (IAUC 7274).  The source flux was 1.2
x 10**-8 erg s**-1 cm**-2 (560 mCrab) in the energy band 2-10 keV,
and was 3.3 x 10**-9 erg s**-1 cm**-2 (190 mCrab) in the energy
band 20-100 keV.  A power-spectral-density estimate shows a
prominent quasiperiodic oscillation (QPO) centered at 5.49 +/- 0.04
Hz (FWHM = 0.7 +/- 0.1 Hz) both in the MECS and in the HPGSPC data,
with a fractional r.m.s. amplitude of about 5 percent in the band
1.5-10 keV.  A less-prominent QPO peak is observed near about 0.6
Hz only in the HPGSPC data, while we do not find evidence for the
0.45-Hz QPO observed by RXTE (IAUC 7274).  These timing and
spectral characteristics are reminiscent of a blackhole candidate
in outburst.  Additional BeppoSAX observations are planned."

                      (C) Copyright 1999 CBAT
1999 October 26                (7291)            Daniel W. E. Green

Read IAUC 7290 SEARCH Read IAUC 7292

View IAUC 7291 in .dvi or .ps format.

Our Web policy. Index to the CBAT/MPC/ICQ pages.

Valid HTML 4.01!