TITLE:   GCN CIRCULAR
NUMBER:  15973
SUBJECT: GRB 140311A: Swift/UVOT Upper Limits
DATE:    14/03/12 19:27:01 GMT
FROM:    Stephen Holland at STScI  <sholland@stsci.edu>

S. T. Holland (STScI) and J. L. Racusin (NASA/GSFC) report on behalf
of the Swift/UVOT team:

    The Swift/UVOT began settled observations of the field of GRB
140311A 9540 s after the BAT trigger (Racusin et al. 2014, GCNC
15944). We do not detect any new source consistent with the Nansan
afterglow position (Xu et al. 2014, GCNC 15947) in any of the UVOT
exposures. Preliminary 3-sigma upper limits, using the UVOT
photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373),
for the summed exposures are presented below.

---------------------------------------------------
Filter        TSTART     TSTOP   Exposure       Mag
---------------------------------------------------
v            11,358     11,533        171     >19.0
b            37,852     38,759        885     >21.3
uvw1         40,124     40,366        238     >19.8
uvw2         10,542     11,352        886     >21.2
white          9540     10,446        885     >22.0
---------------------------------------------------

    The quoted upper limits have not been corrected for the expected
extinction due to the Galactic reddening along the line of sight to
this burst of E(B-V) = 0.03 mag (Schlafly et al. 2011, ApJS, 737,
103). The non-detection in the UVOT data is consistent with a redshift
of z = 4.95 (Tanvir et al, 2014, GCNC 15961).