[vsnet-grb-info 21866] GRB 190311A: Swift/UVOT Detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  23965
SUBJECT: GRB 190311A: Swift/UVOT Detection
DATE:    19/03/13 16:33:25 GMT
FROM:    Mike Siegel at PSU/Swift MOC  <mhs18 at psu.edu>

M. H. Siegel (PSU) and E. Troja (NASA/GSFC/UMCP)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 190311A
88 s after the BAT trigger (Troja et al., GCN Circ. 23946).
A source consistent with the XRT position (Goad et al., GCN Circ. 23950)
is detected in the initial UVOT exposures. This source is consistent
with the initial transient reported by UVOT, Mondy (Pozanenko et al., GCN
Circ. 23947), Next (Zhu et al., GCN Circ. 23948), MASTER (Gorbovskoy, GCN
Circ. 23949), TSHAO (Belkin et al., 23951), GMG (Mao et al., GCN Circ. 23954)
and OAO (Peris et al., GCN Circ. 23959). The source faded below detection by the second
orbit.

The preliminary UVOT position is:
    RA  (J2000) =  14:08:15.71 = 212.06546 (deg.)
    Dec (J2000) = +53:30:02.9  =  53.50080 (deg.)
with an estimated uncertainty of 0.49 arc sec. (radius, 90% confidence).

Preliminary detections using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early exposures are: 

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

white               88          238          147         19.59 +/- 0.10
white             5678         7314          393            >21.42
white            51260        58205         2454            >22.45
u                  301          550          246         19.85 +/- 0.20
u                 6704        18770         1081            >21.08
b                 6910        19082          493            >20.89
v                 6089        12525         1164            >20.42
uvw1              6500        28478         1676            >20.98
uvm2              6294        23285         1557            >20.87
uvw2              5884         7521          393            >20.16

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.01 in the direction of the burst
(Schlegel et al. 1998).