New outburst of SAX J1808.4-3658
ATel #110; C. B. Markwardt (U. Maryland & NASA/GSFC), J. M. Miller (CfA) & R. Wijnands (University of St. Andrews)
on 15 Oct 2002; 02:31 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Craig B. Markwardt (craigm@lheamail.gsfc.nasa.gov)
Subjects: X-ray, Binary, Neutron Star, Transient, Pulsar
SAX J1808.4-3658
The authors report the discovery of a new
outburst of the first known millisecond accreting pulsar SAX
J1808.4-3658. In RXTE PCA scans of the galactic center performed on
Oct 13.279 (UT), an X-ray source whose position is consistent with SAX
J1808.4-3658 was detected with a flux of 65 mCrab (2-10 keV). On Oct
9.5 the PCA flux was less than 0.5 mCrab. Two minutes of pointed data
were obtained, in which X-ray pulsations were detected at the
frequency 400.953 +/- 0.008 Hz (barycentered). This frequency is
consistent with the known pulsar spin frequency and orbital Doppler
modulation. The RXTE ASM instrument detected the source on Oct 14.30
and 14.37 at fluxes of 105 and 76 mCrab, respectively. In its 1998
outburst, the source also exhibited fast radio and optical transients,
and so multiwavelength observing is encouraged. Additional RXTE
PCA observations are taking place.
