GRB 080517

A. M. Parsons (GSFC), A. P. Beardmore (U Leicester),
D. N. Burrows (PSU), J. R. Cummings (NASA/UMBC),
P. A. Evans (U Leicester), N. Gehrels (NASA/GSFC),
S. T. Holland (CRESST/USRA/GSFC), E. A. Hoversten (PSU),
C. B. Markwardt (CRESST/GSFC/UMD), F. E. Marshall (NASA/GSFC),
P. T. O'Brien (U Leicester), K. L. Page (U Leicester),
D. M. Palmer (LANL) and E. Troja (U Leicester/INAF-IASFPA) report on
behalf of the Swift Team:

At 21:22:51 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 080517 (trigger=311874).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 102.255, +50.731 which is 
   RA(J2000) = 06h 49m 01s
   Dec(J2000) = +50d 43' 51"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a single-peaked
structure with a duration of about 20 sec.  The peak count rate
was ~500 counts/sec (15-350 keV), at ~0 sec after the trigger. 

The XRT began observing the field at 21:24:57.5 UT, 125.5 seconds after
the BAT trigger. Using promptly downlinked data we find a fading,
uncatalogued X-ray source with an enhanced position: RA, Dec 102.24274,
50.73512 which is equivalent to:
   RA(J2000)  = 06h 48m 58.26s
   Dec(J2000) = +50d 44' 06.4"
with an uncertainty of 2.7 arcseconds (radius, 90% containment). This
location is 31 arcseconds from the BAT onboard position, within the BAT
error circle. We note that a known, 18th magnitude optical source lies
within our error circle; this is identified as a galaxy, EO0691-0008689,
in the APM-North survey. 

A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density in excess of the Galactic value (8.12e+20
cm^-2, Kalberla et al. 2005), with an excess column of 2.5
(+1.70/-1.44) x 10^21 cm^-2 (90% confidence). The relation of Grupe et
al. (2007) implies that this burst has a redshift z<4.8, although high
redshift fits to the absorbed XRT spectrum are possible if paired with
an anomalously large column. A summary of the promptly downlinked data
is given at http://www.swift.ac.uk/sper/311874/. 

UVOT took a finding chart exposure of 100 seconds with the White   
(160-650 nm)  filter starting 130 seconds after the BAT trigger. A   
400 second exposure with the V filter was taken starting 236 seconds  
 after the BAT trigger.  There is no evidence for an afterglow, 
however there is a known object within the XRT error circle visible
in the UVOT images. The 2.7'x2.7' sub-image covers 100% of the XRT
error circle.  The typical  3-sigma upper limit has been about 18.5
mag in both  images. No  correction has been made for the expected
extinction  corresponding  to E(B-V) of 0.11. 

Burst Advocate for this burst is A. M. Parsons (parsons AT milkyway.gsfc.nasa.gov). 
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.)

R.J. Smith (Liverpool JMU), A. Gomboc (Univ. of Ljubljana, Slovenia),
A. Melandri, C. Guidorzi, M. Burgdorf, C.G. Mundell, I.A. Steele, D. 
Carter, A. Monfardini, C.J. Mottram, S. Kobayashi, D. Bersier (Liverpool 
JMU) report:

The 2-m Liverpool Telescope started observing the field of GRB 080517 
(Parsons et al. GCN 7742
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 ) at 3 min after the trigger time.

No optical transient has been located in our images to the following 
magnitude limits:

Filter      t_mid (min from GRB)    Exp (s)       Lim
------------------------------------------------------------------
R             16.08                  120          19.6
I             18.93                  120          19.2
------------------------------------------------------------------
Magnitudes were calibrated vs the USNOB1 catalogue.

In particular, comparison with Digitized Sky Survey images shows no 
obvious additional optical source in the vicinity of the known, 
moderately bright object noted to be within the XRT error circle.

Observations stopped one hour after the burst time. No further 
observations are currently planned.

P.A. Evans, M.R. Goad, J.P. Osborne and A.P. Beardmore (U. Leicester) 
report on behalf of the Swift-XRT team.

Using 88 s of overlapping XRT Photon Counting mode and UVOT
data for GRB 080517, we find an astrometrically corrected X-ray
position (using the XRT-UVOT alignment and matching UVOT field sources
to the USNO-B1 catalogue): RA, Dec = 102.24189, +50.73496 which is equivalent
to:

RA (J2000): 06h 48m 58.05s
Dec (J2000): +50d 44' 05.8"

with an uncertainty of 1.8 arcsec (radius, 90% confidence).

This position may be improved as more data are received. The latest position
can be viewed at http://www.swift.ac.uk/xrt_positions. Position enhancement is
described by Goad et al. (2007, A&A, 476, 1401
http://www.swift.ac.uk/xrt_positions/Goad.pdf), the current algorithm is an
extension of this method.

This circular was automatically generated, and is an official product of the
Swift-XRT team.

P. A. Evans (U. Leicester) and A.M. Parsons (GSFC) report on behalf of the 
Swift-XRT team:

We have analysed the first two snapshots of Swift-XRT data obtained for 
GRB 080517 (Parsons et al, GCN Circ. 7742
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 ), comprising 3.3 ks in Photon 
Counting (PC) mode, starting 144 s after the BAT trigger. The 
UVOT-enhanced XRT position was given in Evans et al. (GCN Circ. 7744
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 )

The light curve can be described as a broken power-law, with an initial
decay of 2.47 (+0.25/-0.23), with a break at T+~1100s to a slope of 0.57
(+0.25/-0.74).

A spectrum obtained from all of the PC data can be modelled with an
absorbed power-law, with gamma=1.91 (+0.36/-0.34) and an absorption
column of 1.41 (+0.10/1.11) e21 cm^-2, in excess of the Galactic
value of 8.12e20 cm^-2 (Kalberla et al. 2005). The observed
(unabsorbed) flux in this spectrum is 6.07 (8.12) e-12 erg cm^-2
s^-1. The counts to  observed flux conversion is 5.93e-11 erg cm^-2
count^-1.

If the light-curve continues to decay at alpha=0.57  the count rate at 
24 hours is predicted to be 1.6e-3 count s-1, corresponding to an 
observed (unabsorbed) flux of 7.10 (9.49) e-14 erg cm^-2 s^-1.

This is an official product of the Swift-XRT team.

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
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 ).

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
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 ), the observed X-ray absorption implies
that the burst is most likely at z<4.8.