TITLE:   GCN CIRCULAR
NUMBER:  32656
SUBJECT: GRB 221009: Swift/UVOT Detection
DATE:    22/10/10 12:41:35 GMT
FROM:    Paul Kuin at MSSL  <npkuin@gmail.com>

N. P. M. Kuin (UCL-MSSL) and S. Dichiara (PSU) report on behalf

of the Swift/UVOT team:


The Swift/UVOT began settled observations of the field of

GRB 221009 179 s after the BAT trigger (Dichiara et al.,

GCN Circ. 32632, and 32633).  This GRB was initially reported as being

a new bright hard X-ray transient and named SwiftJ1913.1+1946.

Further analysis shows this is a GRB (Kennea et al, GCN Circ.

32635, and 32651).

The  preliminary UVOT position was reported in the Dichiara et al. GCN.

The GRB was also detected by Fermi (Veres et al. GCN Circ 32636;

Bissaldi et al. GCN Circ. 32637; Lesage etal. GCN Circ. 32642),

IPN (Svinkin et al.,  GCN Circ. 32641); Agile (Ursi et al. GCN

Circ 32650). A redshift of 0.151 has been reported by de Ugarte

Postigo et al. (GCN Circ. 32648), and optical detections were

reported also (MASTER: Lipunov et al., GCN Circ. 32634 and 32639;

Liverpool Telescope photometry and spectrum: Perley GCN Circ

32638;  VVS: Broens, GCN Circ. 32640; BOOTES-2/TELMA: Hu et al., GCN

Circ. 32644; Mondy: Belkin et al. GCN Circ. 32645; MeerLICHT: de Wet et al.

GCN Circ. 32646; Nanshan/NEXT photometry and Xinglong-2.16m

spectroscopy Xu et al. GCN Circ. 32647; Al Khatim Observatory:

Odeh, GCN Circ. 32649; REM: Brivio et al. GCN Circ. 32652). Near IR

was reported for PRIME by Durbak et al. GCN Circ. 32654 and radio

AMI-LA: Bright et al. GCN Circ. 32653 and ATA:Farah et al.  GCN Circ. 32655.

Pre-discovery limits from ZTF: Karambelkar et al. GCN Circ. 32643.


Preliminary detections and 3-sigma upper limits 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              179          329          147         16.68 +/- 0.03
v                  668          688           20         15.55 +/- 0.10
b                  593          613           20         17.05 +/- 0.11
u                  337          587          246         17.68 +/- 0.06
w1                 718         1293           58        >18.2
w2                 817         1219           39        >19.1

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 1.563 in the direction of the burst
(Schlegel et al. 1998).