TITLE:   GCN CIRCULAR
NUMBER:  39345
SUBJECT: GRB 250215A: Swift/UVOT Upper Limits
DATE:    25/02/16 15:30:21 GMT
FROM:    Mike Siegel at PSU/Swift MOC <mhs18@psu.edu>

M.H. Siegel (PSU) reports on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 250215A detected by Fermi,
the Einstein Probe and INTEGRAL (GCN Circ. 39327; Wang et al., GCN Circ. 39329; Barria
et al., GCN Circ. 39331) 19.5 ks after the trigger.  The afterglow reported in the XRT
(Page et al., GCN Circ. 39336) and optical/IR (Liu et al., GCN Circ. 39330; Xie et al.,
GCN Cic. 39333; Malesani et al., GCN Circ. 39339) is not detected in the single U-band
exposure. This is consistent with the redshift of z=4.61 reported by Sanchez-Ramirez
et al. (GCN Circ. 39343).

Preliminary 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011,
AIP Conf. Proc. 1358, 373) for the initial exposure is:

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

u              9504         16104          1704           >21.06

The magnitudes in the table are not corrected for the Galactic extinction due to the reddening
of E(B-V) = 0.056 in the direction of the burst (Schlegel et al. 1998).