[vsnet-grb-info 21327] Swift Trigger 872470: further Swift analysis

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  23426
SUBJECT: Swift Trigger 872470: further Swift analysis
DATE:    18/11/19 16:06:35 GMT
FROM:    Valerio D'Elia at ASDC  <valerio.delia at ssdc.asi.it>

V. D’Elia (SSDC), A. Y. Lien (GSFC/UMBC), M. H. Siegel (PSU) report on behalf of the Swift team:

We performed further analysis of the Swift data of the BAT trigger 872470 (D’Aì et al. GCN Circ. 23425)

The ground analysis using the BAT data set from T-239 to T+963 sec shows nothing significant in the BAT light curves. Also, the BAT image significance decreases to ~ 1.4 sigma.

The Swift/XRT began settled observations of the field 1033 s after the BAT trigger. The total exposure time is 2.8 ks, and data are entirely in Photon Counting (PC) mode. No X-ray sources have been detected in the BAT error circle. The 3-sigma upper limit at the BAT position is 6E-3 cts/s corresponding to a 0.3-10 keV observed flux of 2e-13 erg cm^-2 s^-1 (assuming a typical GRB spectrum).

The Swift/UVOT began settled observations of the field 1074 s after the BAT trigger. No optical afterglow consistent with the BAT position is detected in the initial UVOT exposures to a limiting magnitude in the white filter of 20.4.

We thus conclude that this trigger was indeed due to particle background near the SAA and is not an astrophysical event

This circular is an official product of the Swift team.