Swift and RXTE Discovery of a New X-ray Transient, SWIFT J1729.9-3437
ATel #2747; C. B. Markwardt (NASA/GSFC), H. A. Krimm (USRA & NASA/GSFC), J. H. Swank (NASA/GSFC)
on 20 Jul 2010; 03:01 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Craig B. Markwardt (craigm@lheamail.gsfc.nasa.gov)
Subjects: X-ray, Gamma Ray, Request for Observations, Binary, Black Hole, Neutron Star, Transient, Pulsar
Referred to by ATel #: 2749
We report the discovery of a new X-ray transient, designated SWIFT
J1729.9-3437, based on Swift BAT all-sky monitoring and RXTE PCA
monitoring scans of the galactic center region.
Swift BAT detected a new source
starting on 2010-07-13 at a count rate (15-50 keV) of
0.0033 ± 0.0009 ct/cm2/s (~15 mCrab) and rising steadily to 0.0055 ± 0.0013 ct/cm2/s (~25 mCrab) on 2010-07-18. The cumulative
significance for the past eight days is 8.1 sigma.
The best-fit
BAT position is R.A. = 262.503, Decl. = -34.640 degrees (J2000), with 3.0 arcmin
position uncertainty (95% confidence).
Independently, RXTE PCA monitoring scans of the galactic center region
detected a new transient source. The position of the source is
consistent with the Swift BAT position. After reprocessing the PCA data
retrospectively with that position, the source was detected at 2-10 keV
fluxes of 10 and 12 mCrab on dates 2010-07-14.7 and 2010-07-18.6,
respectively, indicating a rising flux. Before that time, the flux was
less than 1 mCrab (2-10 keV).
Given that the 2-50 keV spectrum appears harder than the Crab, it is
possible that the source is an accreting X-ray pulsar or a black hole
system in the "low hard" state.
Follow-up observations have been requested for Swift and RXTE.
