GRB 100511A

A.Daikyuji, N.Ohmori, Y.Nisioka, K.Noda, M.Yamauchi
(University of Miyazaki)

We have observed the field covering the error circle of
GRB GRB100511A (Swift trigger 421695)
with the unfiltered CCD camera on the 30-cm telescope
at University of Miyazaki.
The observation was started 14:19:42 UT, about two and
a half hours after the Swift trigger time.
We have compared our data of 30 sec exposures
with the USNO-A2.0 catalog,
There is no new source at the reported position.

the upper limits are as follows:
--------------------------------------------------------------
Start(UT) End(UT) Num. of frames Limit (mag.)
--------------------------------------------------------------
14:19:42 14:20:12 1 14.9
14:19:42 15:02:15 26 16.0
---------------------------------------------------------------

Adria C. Updike, Dieter H. Hartmann (Clemson University), G. Grant
Williams (MMTO), and Peter A. Milne (Steward Observatory) report:

We observed the field of Swift trigger 421695 (Sbarufatti et al., GCN
10737
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 ) with the 0.6m Super-LOTIS telescope located at KPNO beginning 21
seconds after the trigger.  Within the BAT error circle, we detect no new
sources to a limiting magnitude of R = 17.5 (as compared to the USNO B1.0
catalog) in our first 3 minutes of stacked exposures.

P. N. Bhat (UAH)  
report on behalf of the Fermi GBM Team:

"At 00:49:56.23 UT on 11 May 2010, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 100511A (trigger 295231798 / 100511035).
The Fermi Observatory executed a maneuver following this trigger and
tracked the burst location for the next 5 hours, subject to
Earth-angle constraints.

The on-ground calculated location, using the GBM trigger
data, is RA = 109.29, DEC = -4.65 (J2000 degrees,
equivalent to 07 h 17.2 m, -4 d 39 '), with an uncertainty
of 1.0 degree (radius, 1-sigma containment,
statistical only; there is additionally a systematic
error which is currently estimated to be 2 to 3 degrees).
 
The angle from the Fermi LAT boresight is 43 degrees.

The GBM light curve shows several pulses
with a duration (T90) of about 38 s (50-300 keV).
The time-averaged spectrum from T0-7.4 s to T0+52 s is
adequately fit by a power law function with an exponential
high energy cutoff.  The power law index is -1.32 +/- 0.02 and
the cutoff energy, parameterized as Epeak, is
946.6 (+134/-110) keV

(C-stat 1777 for 863 d.o.f.).

The event fluence (8-1000 keV) in this time interval is
(7.08 +/- 0.05)E-06 erg/cm^2. The 1-sec peak photon flux
measured starting from T0+25 s in the 8-1000 keV band
is 8.81 +/- 0.18 ph/s/cm^2.

A Band function fits the spectrum equally well
(C-stat 1776 for 862 d.o.f.) with Epeak= 882.5 +166/-115 keV,
alpha = -1.3 +/- 0.02 and beta = -2.43 (+0.24/-1.71).

The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog."