GRB 220306B: Swift detection of a burst
Abstract
At 18:15:37 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 220306B (trigger=1095288). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 5.378, +71.354 which is RA(J2000) = 00h 21m 31s Dec(J2000) = +71d 21' 14" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a complex structure with a duration of about 15 sec. The peak count rate was ~2600 counts/sec (15-350 keV), at ~0 sec after the trigger. The XRT began observing the field at 18:17:03.3 UT, 85.9 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source located at RA, Dec 5.38628, 71.36313 which is equivalent to: RA(J2000) = 00h 21m 32.71s Dec(J2000) = +71d 21' 47.3" with an uncertainty of 4.0 arcseconds (radius, 90% containment). This location is 34 arcseconds from the BAT onboard position, within the BAT error circle. This position may be improved as more data are received; the latest position is available at https://www.swift.ac.uk/sper. We cannot determine whether the source is fading at the present time. A power-law fit to a spectrum formed from promptly downlinked event data gives a column density consistent with the Galactic value of 4.07 x 10^21 cm^-2 (Willingale et al. 2013). UVOT took a finding chart exposure of 150 seconds with the White filter starting 89 seconds after the BAT trigger. No credible afterglow candidate has been found in the initial data products. The 2.7'x2.7' sub-image covers 100% of the XRT error circle. The typical 3-sigma upper limit has been about 19.6 mag. The 8'x8' region for the list of sources generated on-board covers 100% of the XRT error circle. The list of sources is typically complete to about 18 mag. No correction has been made for the expected extinction corresponding to E(B-V) of 0.578. Burst Advocate for this burst is R. Caputo (regina.caputo AT nasa.gov). Please contact the BA by email if you require additional information regarding Swift followup of this burst. In extremely urgent cases, after trying the Burst Advocate, you can contact the Swift PI by phone (see Swift TOO web site for information: http://www.swift.psu.edu/)
- Publication:
-
GRB Coordinates Network
- Pub Date:
- March 2022
- Bibcode:
- 2022GCN.31697....1C