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GCN Circular 7748

Subject
GRB 080517, Swift-BAT refined analysis
Date
2008-05-18T19:34:04Z (16 years ago)
From
Ann M. Parsons at NASA/GSFC/Swift <Ann.M.Parsons@nasa.gov>
C. Markwardt (GSFC/UMD), S. D. Barthelmy (GSFC), W. Baumgartner (GSFC/ 
UMBC),
J. Cummings (GSFC/UMBC), E. Fenimore (LANL), N. Gehrels (GSFC), H. Krimm
(GSFC/USRA), K. McLean (GSFC/UMD), D. Palmer (LANL), A. Parsons (GSFC),
T. Sakamoto (GSFC/UMBC), G. Sato (GSFC/ISAS), M. Stamatikos (GSFC/ORAU),
J. Tueller (GSFC), T. Ukwatta (GWU)  (i.e. the Swift-BAT team):

Using the data set from T-240 to T+962 sec from the recent telemetry  
downlink,
we report further analysis of BAT GRB 080517 (trigger #311874)  
(Parsons, et al.,
GCN Circ. 7742).

The BAT ground-calculated position is RA, Dec = 102.274, 50.741 deg  
which is
    RA(J2000)  =  06h 49m 05.8s
    Dec(J2000) = +50d 44' 28.5"
with an uncertainty of 2.4 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 50%.

The mask-weighted lightcurve shows a single, FRED-like peak rising  
quickly to
its maximum at ~T+4.4 sec with a roughly exponential decay down to  
background
at ~T+60 sec. T90 (15-350 keV) is 64.6 +- 27.2 sec (estimated error  
including
systematics).

The time-averaged spectrum from T-0.9 to T+68.3 sec is best fit by a  
simple
power-law model.  The power law index of the time-averaged spectrum is
1.54 +- 0.33.  The fluence in the 15-150 keV band is 5.6 +- 1.2 x 10^-07
erg/cm2. The 1-sec peak photon flux measured from T+3.88 sec in the
15-150 keV band is 0.6 +- 0.2 ph/cm2/sec.  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/311874/BA/

This burst satisfies Sakamoto/Ukwatta Swift-BAT possible high-z criteria
(Ukwatta et al. arXiv:0802.3815).
1) PL photon index = 1.54 (PL photon index < 2)
2) 1-s peak photon flux = 0.627459 (1-s peak photon flux < 1.0 ph/cm2/s)
3) Light curve variance = 6.818773e-05 (Variance < 0.0001)
4) T90/(Peak photon flux) = 103.0 (T90/(Peak photon flux) > 100)
Based on a limited sample of bursts, these criteria yield an 85%  
chance it
has a redshift greater than 3.5. As noted in the initial Swift circular
(Parsons, et al., GCN Circ. 7742), the observed X-ray absorption implies
that the burst is most likely at z<4.8.
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