SAX J1819.3-2525 (GM Sgr) Brightens to 12 Crab
ATel #43; D. A. Smith, A. M. Levine, and E. H. Morgan (MIT)
on 15 Sep 1999; 17:25 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Donald A. Smith (dasmith@space.mit.edu)
Subjects: X-ray, Transient
Referred to by ATel #: 44, 45
SAX J1819.3-2525 (GM Sgr)
D. A. Smith, A. M. Levine and E. H. Morgan (MIT) report on behalf of
the RXTE All-Sky Monitor (ASM) team at MIT and NASA/GSFC:
On 1999 Sep. 15.420 (UT), SAX J1819.3-2525 (= XTE J1819-254), an X-ray
transient likely to be associated with the variable star GM Sgr (IAUC
7119 ), was measured by the ASM to have an intensity of 1.55+-0.04 Crab
(2-12 keV; estimated error is based solely on counting statistics).
Subsequent measurements over the following hours showed a rapid
increase in X-ray intensity: 1.32+-0.04 Crab (Sep. 15.422), 1.43+-0.04
Crab (Sep. 15.423), 2.41+-0.04 Crab (Sep. 15.488), 3.74+-0.05 Crab
(Sep. 15.489), 10.0+-0.2 (Sep. 15.701), and 12.2+-0.2 (Sep. 15.703).
The spectrum is harder than that of the Crab Nebula. These results
were obtained following receipt of the report from T. Kato of the
optical brightening of GM Sgr (vsnet-alert 3475).
