GCN Circular 24129
Subject
GRB 190326A: Swift XRT and UVOT follow-up observations
Event
Date
2019-04-18T17:20:09Z (7 years ago)
From
Boris Sbarufatti at PSU <bxs60@psu.edu>
B. Sbarufatti (PSU), P. Kuin (MSSL/UCL) and M. H. Siegel (PSU) report on behalf of the Swift-XRT team:
Swift has performed XRT and UVOT follow-up observations of BAT detected GRB 190326A (Siegel et al. GCN Circ. 24009), after it came out of the Sun observing constraint.
The data were collected between T0+18.91 days and T0+18.98 days, for a total exposure of 1.9 ks in Photon Counting (PC) mode for XRT and with the UVW1 filter for UVOT.
No uncatalogued X-ray sources have been detected. The 3-sigma upper limit at the BAT refined position (Markwardt et al. GCN Circ. 24020) is 1.95E-2 ct s^-1, corresponding to a 0.3-10 keV observed flux of 9.75E-13 erg cm^-2 s^-1 (assuming a typical GRB spectrum).
The UVOT also does not detect any new source at the BAT refined position.
Preliminary 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first finding chart (FC) exposure and subsequent exposures are:
Filter T_start(ks) T_stop(ks) Exp(ks) Mag
uvw1 1633 1640 1.89 >20.47
The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.10 in the direction of the burst (Schlegel et al. 1998).
The BAT refined analysis pointed out that the unusually soft spectrum hinted at a possible SGR nature for the source.
However, a non detection at T+18.9 days is consistent with the expected behavior of a short GRB, and we conclude that it is more likely that the event was a Gamma Ray Burst.
This circular is an official product of the Swift XRT and UVOT teams.