Central Bureau for Astronomical Telegrams

Central Bureau for Astronomical Telegrams -- Image credits

IAUC 7008: XTE J1550-564; XTE J1906+09

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 7007  SEARCH Read IAUC 7009

View IAUC 7008 in .dvi or .ps format.
IAUC number

                                                 Circular No. 7008
Central Bureau for Astronomical Telegrams
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)
URL http://cfa-www.harvard.edu/iau/cbat.html
Phone 617-495-7244/7440/7444 (for emergency use only)

XTE J1550-564
     D. A. Smith, Massachusetts Institute of Technology (MIT), on
behalf of the RXTE/ASM teams at MIT and Goddard Space Flight Center
(GSFC), reports:  "A transient x-ray source has been detected with
the RXTE/ASM near R.A. = 15h50m41s, Decl. = -56o27'.6 (equinox
2000.0).  The source was first detected at an intensity of about 70
mCrab (2-12 keV; 5-sigma significance) in an observation at Sept.
7.0927 UT.  At Sept. 7.4282, the source was observed to have a
strength of 170 +/- 20 mCrab.  Crossed lines of position were
obtained; from these, the source is estimated to be located within
a region (90-percent confidence) defined by a box of width 4'.3 and
length 11'.0 with corners at R.A. = 15h51m31s, -56o33'.4; 15h50m19s,
-56o26'.1; 15h49m52s, -56o19'.3; 15h50m57s, -56o25'.1."
     F. E. Marshall, GSFC; and E. A. Smith, Hughes STX and GSFC,
write:  "An RXTE PCA observation on Sept. 7.72 UT of the transient
XTE J1550-564 shows a highly-variable source with an average 2-10-
keV flux of 6 x 10E-8 erg sE-1 cmE-2.  Aperiodic variability of
about a factor of two was seen on timescales of less than a second.
The source is likely to be a black-hole transient."

XTE J1906+09
     T. Takeshima and R. H. D. Corbet, Goddard Space Flight Center
(GSFC) and Universities Space Research Association; and J. H.
Swank, GSFC, on behalf of the RXTE Science Operations Center,
report:  "During a series of pointed observations of SGR 1900+14
with the Proportional Counter Array on RXTE, a coherent pulsation
at period of 89.178 +/- 0.003 s (not barycenter-corrected) was
detected, in addition to 5.16-s pulsations (IAUC 7001, 7002, 7003,
7004, 7005), in data obtained on Aug. 31.34-31.52, Sept. 1.24-1.52,
and 2.41-2.52 UT.  However, the 89-s pulsations were not seen in
observations on Aug. 29.41-29.59 and 30.28-30.46.  This period and
the 2-10-keV pulse profile are consistent with those reported by
Marsden et al. (1998, Ap.J. 502, L129) for XTE J1906+09.  The
average pulsed PCA count rates were 1.6, 2.5, and 4.3 counts/s
(2-10 keV) in the three observations, respectively.  As SGR 1900+14
pulses at a 5.16-s period, XTE J1906+09 with its 89-s period is
probably a transient pulsar and not associated with the soft
gamma-ray repeater itself.  Offset pointed observations with the
PCA are scheduled to attempt to determine the source position."

                      (C) Copyright 1998 CBAT
1998 September 8               (7008)            Daniel W. E. Green

Read IAUC 7007  SEARCH Read IAUC 7009

View IAUC 7008 in .dvi or .ps format.

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

Valid HTML 4.01!