GRB 210104A: Swift detection of a burst with a bright optical counterpart
Abstract
At 11:26:59 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 210104A (trigger=1015873). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 103.705, +64.661 which is RA(J2000) = 06h 54m 49s Dec(J2000) = +64d 39' 39" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a multi-peaked structure with a duration of about 40 sec. The peak count rate was ~16000 counts/sec (15-350 keV), at ~21 sec after the trigger. The XRT began observing the field at 11:28:01.8 UT, 62.7 seconds after the BAT trigger. XRT found a bright, uncatalogued X-ray source located at RA, Dec 103.7707, 64.6743 which is equivalent to: RA(J2000) = 06h 55m 4.97s Dec(J2000) = +64d 40' 27.5" with an uncertainty of 5.3 arcseconds (radius, 90% containment). This location is 111 arcseconds from the BAT onboard position, within the BAT error circle. No event data are yet available to determine the column density using X-ray spectroscopy. The initial flux in the 2.5 s image was 1.41e-09 erg cm^-2 s^-1 (0.2-10 keV). UVOT took a finding chart exposure of nominal 150.0 seconds with the White filter starting 70 seconds after the BAT trigger. There is a candidate afterglow in the list of sources generated on-board at RA(J2000) = 06:55:05.25 = 103.77188 DEC(J2000) = +64:40:34.0 = 64.67611 with a 90%-confidence error radius of about 1.10 arc sec. This position is 6.7 arc sec. from the center of the XRT error circle. The estimated magnitude is 15.52. No correction has been made for the expected extinction corresponding to E(B-V) of 0.04. Burst Advocate for this burst is E. Troja (eleonora.troja 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:
- January 2021
- Bibcode:
- 2021GCN.29233....1T