GCN Circular 19473
Subject
GRB 160530A: discovery with the Compton Spectrometer and Imager
Date
2016-05-30T22:47:40Z (8 years ago)
From
John Tomsick at SSL at UCB <jtomsick@ssl.berkeley.edu>
John A. Tomsick (UC Berkeley/Space Sciences Laboratory) reports on behalf
of the Compton Spectrometer and Imager (COSI) team:
COSI is a large field of view (1/4-sky) gamma-ray (0.1-10 MeV) instrument on
a Superpressure Balloon flight that began on May 16.
A likely Gamma-ray Burst (GRB 160530A) was detected by COSI in both the
cesium iodide shields and the germanium strip detectors (GeDs). The GRB
started at 2016 May 30, 07:03:46 UT and lasted until 07:04:23 UT (based on
the shield rates). During the burst, the light curve shows several large amplitude
fluctuations.
Based on the GeD rates and assuming a Band function with alpha=1.0,
beta=2.5, and E_break = 150 keV, we calculated a preliminary burst fluence of
1.3E-5 erg/cm2. This value may be revised in the future using the spectral
capabilities of the GeDs.
The position of the GRB is R.A. = 120.2 deg, Decl. = -26.2 deg (J2000, 90%
confidence error radius = 1.5 degrees), which corresponds to Galactic coordinates
of l = 243.9 deg, b = 2.1 deg. Due to the proximity to the Galactic plane, a Galactic
origin cannot be ruled out.
We searched the SIMBAD database for possible counterparts, and three known
gamma-ray sources are present in the COSI error region: GRB 080516,
2FGL J0758.0-2615c, and 3FGL J0755.2-2633 are, respectively, 0.4, 0.6, and
1.3 degrees from the center of the COSI error circle.
Follow-up observations with Swift/XRT are underway (see P.A. Evans et al., GCN
Circ. 19472) to search for an afterglow that may allow us to improve the position
and provide a definitive classification of the COSI burst.