Central Bureau for Astronomical Telegrams
IAUC 7010: XTE J1550-564
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 7011
.dvi or
.ps format.
Circular No. 7010
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
Phone 617-495-7244/7440/7444 (for emergency use only)
XTE J1550-564
M. H. Finger, Universities Space Research Association; S. W.
Dieters, University of Alabama, Huntsville; and R. B. Wilson,
Marshall Space Flight Center, NASA, report for the BATSE/Compton
Observatory team: "A quasiperiodic oscillation (QPO) in the flux of
this transient x-ray source is seen in power spectra of the BATSE
20-50-keV discriminator rates. On Sept. 9.0 UT, the QPO was
centered on 271 +/- 2 mHz, and it had a FWHM of 30 +/- 5 mHz and a
fractional rms of 19.2 +/- 2.5 percent. The QPO was first detected
on Sept. 7.45 near 55 mHz and has been steadily increasing in
frequency, reaching 350 mHz by Sept. 9.3. The QPO appears to have
reached the Nyquist frequency (488 mHz) of our discriminator rates
before the end of Sept. 9, and is no longer detectable in them."
C. A. Wilson, B. A. Harmon, W. S. Paciesas, and M. L.
McCollough, Marshall Space Flight Center, NASA, report for the
BATSE team: "The x-ray transient XTE J1550-564 (IAUC 7008) is being
detected with BATSE in the band 20-100 keV. The outburst was first
visible between Sept. 6.9 and 7.0 UT. Average 20-100-keV flux
levels are (in 10E-8 erg cmE-2 sE-1): Sept. 6.0-7.0, < 0.1;
7.0-8.0, 1.26 +/- 0.08, 8.0-8.6, 1.90 +/- 0.12; 8.6-9.0, 2.42 +/-
0.11. The spectrum is adequately fit by a power law. On Sept. 7,
it extends beyond 200 keV and softens significantly during the
intensity rise. Average photon number indices are: Sept. 7.0-8.0,
-2.11 +/- 0.09, 8.0-8.6, -2.62 +/- 0.11; 8.6-9.0, -2.73 +/- 0.09."
D. Campbell-Wilson, V. McIntyre, R. Hunstead, and A. Green,
University of Sydney, report observations at 843 MHz with the
Molonglo Observatory Synthesis Telescope (MOST): "We detect a
likely radio counterpart to the x-ray transient XTE J1550-564 in
images obtained on Sept. 9 and 10. The source is located at R.A. =
15h50m59s.1, Decl. = -56o28'39'' (equinox 2000.0), with estimated
errors of 5'' in each coordinate, coincident with the possible
optical counterpart reported on IAUC 7009. Archival MOST images
obtained on 1992 Apr. 10 and 1998 June 14 show no radio source at
this position to 3-sigma levels of 4.5 and 3.9 mJy, respectively.
Preliminary flux densities are 10 mJy on Sept. 9.18 and 16 mJy on
Sept. 10.16 UT (mid-exposure) with estimated errors of 2.5 mJy;
image quality in these short observations is affected by sidelobes
of the strong supernova remnant G326.3-1.8 immediately to the
northeast."
(C) Copyright 1998 CBAT
1998 September 11 (7010) Daniel W. E. Green
Read IAUC 7011
.dvi or
.ps format.
Our Web policy. Index to the CBAT/MPC/ICQ pages.
