GRB 110318A

B. Sbarufatti (INAF-OAB/IASFPA), S. D. Barthelmy (GSFC),
M. M. Chester (PSU), P. D'Avanzo (INAF-OAB), V. D'Elia (ASDC),
P. A. Evans (U Leicester), N. Gehrels (NASA/GSFC),
J. M. Gelbord (PSU), C. Gronwall (PSU), C. Guidorzi (U Ferrara),
S. T. Holland (CRESST/USRA/GSFC), J. A. Kennea (PSU),
R. Margutti (INAF-OAB), A. Melandri (INAF-OAB),
K. L. Page (U Leicester), P. Romano (INAF-IASFPA),
C. J. Saxton (UCL-MSSL), M. H. Siegel (PSU),
E. Sonbas (GSFC/USRA/Adiyaman Univ.) and C. A. Swenson (PSU) report on
behalf of the Swift Team:

At 13:14:19 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 110318A (trigger=449542).  Swift did not slew to the burst
because of the Sun observing constraint. 
The BAT on-board calculated location is 
RA, Dec 338.274, -15.282, which is 
   RA(J2000)  =  22h 33m 06s
   Dec(J2000) = -15d 16' 55"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve shows two main peaks
with a duration of about 20 sec.  The peak count rate
was ~7000 counts/sec (15-350 keV), at ~2 sec after the trigger. 

Due to a Sun observing constraint, Swift cannot slew to the BAT
position until 05:00 UT on 2011 April 11. There will thus be no XRT or
UVOT data for this trigger before this time. 

Burst Advocate for this burst is B. Sbarufatti (boris.sbarufatti AT brera.inaf.it). 
Please contact the BA by email if you require additional information
regarding Swift followup of this burst. In extremely urgent cases, after
trying the Burst Advocate, you can contact the Swift PI by phone (see
Swift TOO web site for information: http://www.swift.psu.edu/too.html.)

S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (GSFC/UMBC),
N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC),
D. M. Palmer (LANL), T. Sakamoto (GSFC/UMBC), B. Sbarufatti (INAF-OAB/IASFPA),
M. Stamatikos (OSU), J. Tueller (GSFC), T. N. Ukwatta (MSU)
(i.e. the Swift-BAT team):
 
Using the data set from T-114 to T+595 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 110318A (trigger #449542)
(Sbarufatti, et al., GCN Circ. 11798
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 ).  The BAT ground-calculated position is
RA, Dec = 338.292, -15.278 deg, which is 
   RA(J2000)  =  22h 33m 10.0s 
   Dec(J2000) = -15d 16' 40.9" 
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 27%.
 
The mask-weighted light curve shows a small precursor peak between T-8 and
T-2 sec.  The main peak starts at ~T-1 sec, peaks at ~T+1 sec, and ends
at ~T+15 sec.  T90 (15-350 keV) is 16.0 +- 1.7 sec (estimated error
including systematics).
 
The time-averaged spectrum from T-13.0 to T+10.6 sec is best fit by a power law
with an exponential cutoff.  This fit gives a photon index 1.05 +- 0.23, 
and Epeak of 94.3 +- 23.7 keV (chi squared 43.1 for 56 d.o.f.).  For this
model the total fluence in the 15-150 keV band is 4.9 +- 0.2 x 10^-6 erg/cm2
and the 1-sec peak flux measured from T+1.95 sec in the 15-150 keV band is
8.0 +- 0.5 ph/cm2/sec.  A fit to a simple power law gives a photon index
of 1.58 +- 0.05 (chi squared 59.4 for 57 d.o.f.).  All the quoted errors
are at the 90% confidence level. 
 
The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/449542/BA/

G. Fitzpatrick (UCD) reports on behalf of the Fermi GBM Team:�


"At 13:14:16.70 UT on 18th March 2011, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 110318 (trigger 322146858 / 110318552),�
which was also detected by the Swift/BAT (Sbarufatti et al. 2011,�
GCN 11798
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 ). The GBM on-ground location is consistent with the Swift�
position.


The angle from the Fermi LAT boresight is 70 degrees.


The GBM light curve consists of single peak
with a duration (T90) of about 12 s (50-300 keV).�
The time-averaged spectrum from T0-1 s to T0+10 s is �
fit well with �a power law function with an exponential
high-energy cutoff. �The power law index is -0.86 +/- 0.04 and
the cutoff energy, parameterized as Epeak, is 114.70 +/- 3.72 keV


A Band function fits the spectrum equally well with Epeak= 107.00 +/- 5.18
keV, alpha =-0.80 +/- 0.05, and beta = -2.74 +/- 0.25.


The event fluence (10-1000 keV) in this time interval is�
(8.05 +/- 0.15)E-6 erg/cm^2. The 1-sec peak photon flux measured�
starting from T0-1 s in the 8-1000 keV band�
is 10.97 +/- 0.29 ph/s/cm^2.


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

[GCN OPS NOTE(19mar11): Per author's request, the citation
for GCN Circ 11798
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  was corrected.]