GRB 080303

P. D'Avanzo, D. Fugazza, L.A. Antonelli, S. Covino, L.  Calzoletti, S. 
Campana, G.  Chincarini, M.L. Conciatore, S. Cutini, V. D'Elia, F. 
D'Alessio, F.  Fiore, P. Goldoni, D. Guetta,  C. Guidorzi, G.L. Israel, 
E. Maiorano, N. Masetti, A. Melandri, E. Meurs, L. Nicastro, E. Palazzi, 
E. Pian, S. Piranomonte, L.  Stella, G.  Stratta, G. Tagliaferri, G. 
Tosti, V.Testa, S.D. Vergani,  F. Vitali report on behalf of the REM team:

The robotic 60-cm REM telescope located at La Silla (Chile) observed 
automatically the field of the GRB 080303  on March 03 09:13:30 UT 
(about 180 seconds after the burst).

We detect an afterglow candidate inside the XRT error box down at the 
following coordinates (J2000):

R.A.= 07:28:13.91
Dec.: -70:14:00.3

with an uncertainty of 0.4". The object has H~15.9.

Further analysis is in progress.

T. Sakamoto (NASA/UMBC), W. H. Baumgartner (GSFC/UMBC),
A. P. Beardmore (U Leicester), G. Cusumano (INAF-IASFPA),
P. A. Evans (U Leicester), N. Gehrels (NASA/GSFC), C. Gronwall (PSU),
E. A. Hoversten (PSU), N. P. M. Kuin (MSSL), J. Mao (INAF-OAB),
A. Moretti (INAF-OAB), P. T. O'Brien (U Leicester),
S. R. Oates (UCL-MSSL), J. P. Osborne (U Leicester),
K. L. Page (U Leicester), D. M. Palmer (LANL),
D. Perez (U Leicester), P. Romano (INAF-IASFPA),
M. Stamatikos (NASA/ORAU), R. L. C. Starling (U Leicester),
G. Stratta (ASDC), G. Tagliaferri (INAF-OAB),
E. Troja (U Leicester/INAF-IASFPa) and H. Ziaeepour (UCL-MSSL) report
on behalf of the Swift Team:

At 09:10:35 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 080303 (trigger=304549).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 112.073, -70.240 which is 
   RA(J2000) = 07h 28m 18s
   Dec(J2000) = -70d 14' 23"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a FRED-like 
structure with a duration of about 30 sec.  The peak count rate
was ~2600 counts/sec (15-350 keV), at ~0 sec after the trigger. 

The XRT began observing the field at 09:11:47.7 UT, 72.4 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
fading, uncatalogued X-ray source with an enhanced position: RA, Dec
112.05892, -70.23448 which is equivalent to:
   RA(J2000)  = 07h 28m 14.14s
   Dec(J2000) = -70d 14' 04.1"
with an uncertainty of 2.6 arcseconds (radius, 90% containment). This
location is 26 arcseconds from the BAT onboard position, within the BAT
error circle. 

A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density consistent with the Galactic value of
1.26e+21 cm^-2 (Kalberla et al. 2005), so we cannot constrain the
redshift at this time using the relation from Grupe et al. (2007). A
summary of the promptly downlinked data is given at
http://www.swift.ac.uk/sper/304549/. 

The initial flux in the 2.5 s image was 4.53e-10 erg cm^-2 s^-2 (0.2-10
keV). 

UVOT took a finding chart exposure of 100 seconds with the White
(160-650 nm) filter starting 80 seconds after the BAT trigger. There
is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image
at
    RA(J2000) =	07:28:14.14 = 112.0589  
    DEC(J2000) = -70:14:01.7 = -70.2338 
with a 1-sigma error radius of about 0.6 arc sec. This
position is 2.4 arc sec. from the center of the XRT error circle. The
estimated magnitude is 18.4 with a 1-sigma error of about 0.5 mag. A
400s V band image was taken beginning 186 s after the burst. The
estimated magnitude is 18.3 with a 1 sigma error of 0.5 magnitudes. 
At 986 s after the burst the source is undetected in a 108 s V band
exposure. The typical limiting magnitude is 18.0 magnitudes in an
exposure of this length. No correction has been made for the expected
extinction corresponding to E(B-V) of 0.19. 

Burst Advocate for this burst is T. Sakamoto (Taka.Sakamoto AT 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.)

A.C. Gilmore and P.M. Kilmartin (University of Canterbury's Mt John Observatory 
report:

We observed a fading source inside the XRT error box at coordinates (2000.0) 
R.A. = 07:28:14.10
Dec.: -70:14:01.4
Uncertainty ~0.5" in poor seeing.

Unfiltered R magnitudes from comparison with USNO A2.0 stars
 U.T.   R
09:28  18.1
09:40  18.5
09:48  19.0
10:02  19.2
10:13  19.4
10:28  19.9 

Observations with Mt John's 1.0-metre f/8 McLellan reflector.

This message may be cited.

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

Using 1194 s of overlapping XRT Photon Counting mode and UVOT
data for GRB 080303, 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 = 112.05899, -70.23431 which is equivalent
to:

RA (J2000): 07h 28m 14.16s
Dec (J2000): -70d 14' 03.5"

with an uncertainty of 1.7 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).

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

GRB080303: Swift XRT refined analysis

J. Mao (INAF-OAB), A. Moretti (INAF-OAB), T. Sakamoto (NASA/UMBC),
C. Guidorzi (Univ. Bicocca & INAF-OAB) report on behalf of the Swift-XRT 
team:

We have analysed the Swift-XRT data obtained for
BAT GRB 080303 (trigger #304549, Sakamoto, et al., GCN Circ. 7351
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 ).
The data consist of 105 s in Windowed Timing (WT) mode, starting 80 s
after the BAT trigger and 206 s in Photon Counting (PC) mode.
The UVOT-enhanced XRT position was given in Evans et al. (GCN Circ. 7356
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 ).

The light-curve shows a simple power-law with a slope of alpha=1.65 � 0.05.

The spectrum formed from all the WT data can be modeled with a power-law 
of photon index
Gamma = 1.88 � 0.12, with an absorbing column of NH = (1.32 � 0.03)e21 
cm^-2 (in excess
with respect to the Galactic value of 8.97e20 cm^-2). The spectrum 
formed from the PC data
can be modeled with a power-law of photon index Gamma = 1.81 � 0.17, 
with an absorbing
column of NH = (5.72 � 4.77)e20 cm^-2.

If the light-curve continues to decay with a slope of 1.65, the 
afterglow at 24 hour will be with
an expected count rate of 1.5e-4 count s^-1. This corresponds to an 
observed (unabsorbed) flux
of 7E-15(9e-15) erg cm-2 s-1.

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

M. Schubel, T. Brennan, D. Reichart, M. Nysewander, A. LaCluyze, K. Ivarsen, J. A. Crain, A. Foster, J. Haislip, J. Styblova, and A. Trotter report:

Skynet observed the localization of GRB 080303 (Sakamoto et al., GCN 7351
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 ) with two of the 16" PROMPT telescopes at CTIO beginning 45 seconds after the burst (30 seconds after notification) in VRI.

We detect the afterglow (D'Avanzo et al., GCN 7350
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 ) in R and I.  At 182 seconds after the burst we measure I ~ 16.2 mag, and at 242 seconds we measure R ~ 17.0 mag (calibrated to 5 USNO B1 stars).

T. Sakamoto (GSFC/UMBC), S. D. Barthelmy (GSFC), J. Cummings (GSFC/UMBC),
E. Fenimore (LANL), N. Gehrels (GSFC), H. Krimm (GSFC/USRA), 
C. Markwardt (GSFC/UMD), K. McLean (GSFC/UMD), D. Palmer (LANL),
A. Parsons (GSFC), 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 080303 (trigger #304549)
(Sakamoto, et al., GCN Circ. 7351
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 ).  The BAT ground-calculated position is
RA, Dec = 112.019, -70.231 deg which is 
   RA(J2000)  = 7h 28m 4.6s 
   Dec(J2000) = -70d 13' 53" 
with an uncertainty of 1.6 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 80%.
 
The mask-weighted light curve shows a FRED-like peak T-1 sec, peaking at 
T+0.5 sec, and ending at T+20 sec.  There is also an extended emission until 
T+~90 sec.  T90 (15-350 keV) is 67 +- 20 sec (estimated error including systematics).
 
The time-averaged spectrum from T-0.2 to T+73.2 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.54 +- 0.25.  The fluence in the 15-150 keV band is 6.6 +- 1.0 x 10^-7 erg/cm2.  
The 1-sec peak photon flux measured from T+0.06 sec in the 15-150 keV band
is 1.4 +- 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/304549/BA/

A.A. Breeevld (MSSL/UCL) and T. Sakamoto (GSFC/UMBC) report on behalf 
of the Swift UVOT team:

The Swift/UVOT observed the burst GRB080303 (Sakamoto et al. GCN circ 
7351
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 ) starting with the finding chart exposure in white, 81s after the 
BAT trigger. The afterglow is detected at the enhanced XRT position 
(Evans et al. GCN circ 7356
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 ) in all filters except uvm2. In white it is 
detectable until at least 6600s after the trigger. The brightness 
increases until about 700s after the burst, then fades with an 
estimated temporal slope in the v filter of alpha= 0.9

The initial UVOT magnitudes (in the UVOT photometric system; Breeveld 
et al. GCN circ 6614
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 ) and 3 sigma upper limts from single exposures are 
as follows:

Filter	   Tstart(s)    Tstop(s)    Exp(s)   Mag      error(mags)
white    81            180             99.8      18.48    0.08
              682           691             9.8        18.19    0.19
              836           845             9.8        18.46    0.24
              880           979             99.8      18.88    0.11
             5195          5394          199.8    20.79    0.38
             6632           6831         199.8    20.72    0.35
v         187             586             399.8    18.03   0.08
             722             741            19.8       17.74   0.3
             987            1095           108.1    19.06    0.3
             5607          5806           199.8    19.76   0.38
b           667           676               9.8       18.59   0.36
               821           830              9.7         >18.74  (UL)
             4991          5190           199.8      >20.86  (UL)
             6427          6626           199.8     20.26   0.27
u           642             661             19.8     18.23    0.32
               797           816              19.8     17.99    0.26
             4785          4984            199.8    19.4     0.22
             6221          6420            199.8    20.33    0.41
uvw1    618            637             19.8        >18.1  (UL)
               771            790             19.7      17.83    0.38
              4581          4780            199.8   19.84    0.43
              6016          6215             199.8      >20.18 (UL)
uvm2    593            612               19.8        >17.58 (UL)
               746            765               19.8         >17.61 (UL)
               4375          4574            199.8       > 19.69 (UL)
                5811         6010            199.8      >19.76  (UL)
uvw2     698              717             19.8       >18.01 (UL)
                 851            870              19.8       17.82   0.37
               5401          5600            199.7       19.76 0.33
               6838          6875              37.6        >18.7  (UL)

The values quoted above are not corrected for the expected Galactic 
extinction corresponding to a reddening of E(B-V)=0.192 mag in the 
direction of the burst (Schlegel et al. 1998).

Aquib Moin (Curtin Institute of Radio Astronomy / Australia Telescope
National Facility), Steven Tingay (Curtin Institute of Radio Astronomy),
Chris Phillips (Australia Telescope National Facility), Gregory Taylor
(University of New Mexico), Mark Wieringa (Australia Telescope National
Facility) and Ralph Martin (Perth Observatory) report:

We observed the BAT refined position of the GRB 080303 (GCN 7359
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 ) at 4.8
and 8.456 GHz with the Australia Telescope Compact Array (ATCA) on May
31, 2008 between 04:09:05 UT and 14:19:35 UT.

We did not detect a radio source at the BAT position of the GRB 080303
(GCN 7359
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 ). The radio flux density at the GRB position is -0.384 +/-
0.303 mJy at 4.8 GHz, and 0.078 +/- 0.250 mJy at 8.6 GHz (1-sigma).

The Australia Telescope Compact Array (/ Parkes telescope / Mopra
telescope / Long Baseline Array) is part of the Australia Telescope
which is funded by the Commonwealth of Australia for operation as a
National Facility managed by CSIRO.

See field image at:

http://astronomy.ivec.org/dokuwiki/doku.php/grb/grb_080303_field_image