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GCN Circular 24419

Subject
GRB 190501A: Swift XRT and UVOT Observations
Date
2019-05-07T13:10:39Z (5 years ago)
From
Frank Marshall at Swift/UVOT <marshall@milkyway.gsfc.nasa.gov>
Phil Evans (U. Leicester) and F.E. Marshall (NASA/GSFC)
report on behalf of the Swift team:

Swift-XRT has performed follow-up observations of the AGILE-detected
burst GRB 190501A (Ursi et al. GCN Circ. 24360), collecting 2.9 ks of
Photon Counting (PC) mode data between T0+146.7 ks and T0+157.7 ks.
The XRT field-of-view covers about 7% of the AGILE/GRID
95%-confidence error region (Verrecchia et al. GCN Circ. 24363) and none of
the IPN 3-sigma error region (Hurley et al. GCN Circ. 24732).

No uncatalogued X-ray sources have been detected. The 3-sigma upper
limit in the field ranges from ~0.003 to ~0.004 ct s^-1, corresponding
to a 0.3-10 keV observed flux of 1.2e-13 to 1.7e-13 erg cm^-2 s^-1
(assuming a typical GRB spectrum).

Three previously-catalogued X-ray sources have been detected, however
their status as catalogued objects makes them unlikely to be the
afterglow.

The results of the XRT-team automatic analysis of the XRT observations,
including a position-specific upper limit calculator, are available at
http://www.swift.ac.uk/ToO_GRBs/00020892.

The Swift/UVOT began settled observations of the field of GRB 190501A
146672 s after the AGILE trigger.
No optical afterglow consistent with the AGILE/GRID position
is detected in the initial UVOT exposures.
The UVOT images cover about 4% of the 95%-confidence
AGILE/GRID error region and none of the IPN 3-sigma error region.
Preliminary 3-sigma upper limits using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the initial exposures are:

Filter         T_start(s)   T_stop(s)      Exp(s)         Mag

white           147234       153893          933         >21.8
v               147796       154103          761         >20.0
u               146672       157636         1167         >20.7

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.03 in the direction of the burst
(Schlegel et al. 1998).

This circular is an official product of the Swift team.
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