[ Previous | Next | ADS ]

Swift detects a flare from IGR J16418-4532

ATel #7454; P. Romano (INAF-IASFPA), S. D. Barthelmy (GSFC), H. A. Krimm (CRESST/GSFC/USRA), P. A. Evans (U Leicester), N. Gehrels (NASA/GSFC), J. A. Kennea (PSU), C. Gronwall (PSU), D. Malesani (DARK/NBI), K. L. Page (U Leicester), B. Sbarufatti (INAF-OAB/PSU), M. H. Siegel (PSU)
on 28 Apr 2015; 13:43 UT
Credential Certification: Pat Romano (romano@ifc.inaf.it)

Subjects: X-ray, Gamma Ray, Binary, Transient, Pulsar

The Swift Burst Alert Telescope (BAT) triggered on the high mass X-ray binary IGR J16418-4532 on 2015 April 27 at 14:18:02 UT (image trigger 639199). Swift immediately slewed to the target.

Using the data set from T-239 to T+963 s from recent telemetry downlinks, we report that this is a very weak source in BAT, and as such a description of the mask-weighted light curve is problematic. The time-averaged spectrum from T+0.0 to T+376 s is best fit by a simple power-law model with a photon index of 3.18 +/- 0.78. The fluence (same time interval) in the 15-150 keV band is (4.4 +/- 1.6)E-7 erg cm-2. All quoted errors are at the 90% c.l.

The XRT began observing the field at 14:25:34.6 UT, 452 s after the BAT trigger. The XRT light curve shows the descending part of a flare that reached about 4 counts s-1. The mean XRT/PC spectrum (T+461 to 1025 s) can be fit by an absorbed power-law model with a photon index of 0.7+/-0.6 and an absorbing column density of NH=(6+3-2)E22 cm-2. The average 0.3-10 keV observed (unabsorbed) flux is 3.5E-10 (4.7E-10) erg cm-2 s-1.

The historical light curve from the BAT hard X-ray transient monitor (Krimm et al, 2013, ApJS, 209, 14; 15-50 keV) can be found at http://swift.gsfc.nasa.gov/docs/swift/results/transients/weak/IGRJ16418-4532 .

Scaled Map Transient Analysis for IGR J16418-4532