GRB 080328

M. Perri (ASDC), D. N. Burrows (PSU), S. Campana (INAF-OAB),
P. A. Evans (U Leicester), N. Gehrels (NASA/GSFC),
C. Guidorzi (INAF-OAB), C. B. Markwardt (CRESST/GSFC/UMD),
K. L. Page (U Leicester), D. M. Palmer (LANL),
D. Perez (U Leicester), P. Romano (INAF-IASFPA),
R. L. C. Starling (U Leicester), G. Stratta (ASDC),
D. E. Vanden Berk (PSU), P. A. Ward (MSSL-UCL) and
H. Ziaeepour (UCL-MSSL) report on behalf of the Swift Team:

At 08:03:04 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 080328 (trigger=307931).  Swift slewed immediately to the 
burst.  The BAT on-board calculated location is 
RA, Dec 80.479, +47.524 which is 
   RA(J2000) = 05h 21m 55s
   Dec(J2000) = +47d 31' 26"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a multi-peaked
structure with a duration of about 110 sec.  The peak count rate
was ~9500 counts/sec (15-350 keV), at ~10 sec after the trigger. 

The XRT began observing the field at 08:04:44.0 UT, 99.4 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
fading, uncatalogued X-ray source with an enhanced position: RA, Dec
80.48189, 47.51035 which is equivalent to:
   RA(J2000)  = 05h 21m 55.65s
   Dec(J2000) = +47d 30' 37.3"
with an uncertainty of 2.6 arcseconds (radius, 90% containment). This
location is 49 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
3.38e+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/307931/. 

The initial flux in the 2.5 s image was 1.08e-08 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of nominal 400 seconds with the V filter
starting 216 seconds after the BAT trigger. There is a candidate afterglow in
the list of sources generated on-board at
  RA(J2000)  =	05:21:55.85 =  80.4827
  DEC(J2000) = +47:30:39.2  =  47.5109
with a 1-sigma error radius of about 0.6 arc sec. This position is 2.8 arc sec. 
from the center of the XRT error circle. The estimated magnitude is 17.7 with a
1-sigma error of about 0.5 mag. No correction has been made for the expected
extinction of about 1.9 magnitudes. 

Burst Advocate for this burst is M. Perri (perri AT asdc.asi.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.)

C. Guidorzi (INAF-OAB),, A. Gomboc (U. Ljubljana), D. Bersier, C.G. 
Mundell, I.A. Steele, R.J. Smith, D. Carter, S. Kobayashi, M. Bode 
(Liverpool JMU), P. O'Brien, N. Bannister, N. Tanvir (U. Leicester) 
report:

The 2-m Faulkes North Telescope (Hawaii) automatically reacted to the
Swift burst GRB080328 (trigger=307931, Perri et al. GCN 7525
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 ).

Observations started about 167 s after the trigger time. We confirm
the detection of the optical counterpart by UVOT.

From the first 3x10 s exposure frames in R, we estimate a temporal
decay index between 167 and 240 s after the trigger time of
alpha = 1.4 +/- 0.2.

Filter  Tstart(s)  Exposure(s)    Mag
-----------------------------------------------
    R       167           10      16.96 +/- 0.02
    R       198           10      17.26 +/- 0.02
    R       230           10      17.44 +/- 0.02
-----------------------------------------------

Magnitudes are calibrated with respect to USNOB1 R2 in the R filter.
A systematic error on absolute magnitudes of ~0.3 must be included.

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

Using 855 s of overlapping XRT Photon Counting mode and UVOT
data for GRB 080328, 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 = 80.48231, +47.51063 which is equivalent
to:

RA (J2000): 05h 21m 55.75s
Dec (J2000): +47d 30' 38.3"

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), 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. Ward (MSSL-UCL), P. Schady (MSSL-UCL) and M. Perri (ASDC) report on  
behalf of the Swift-UVOT team

The Swift/UVOT observed the field of GRB 080328 starting 110s after  
the BAT trigger (Perri et al., GCN 7525
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 ). The afterglow is detected at

RA:      05h 21m 55.87s
DEC:  +47d 30' 39.4"

only in the white and v filters, with an error radius of 0.6 arcsec  
(90% confidence).
The afterglow is seen to decay in both these filters, and has the  
following magnitudes and 3-sigma upper limits (in the UVOT photometric  
system, Poole et al. (2008, MNRAS, 383, 627)).

Filter	Tstart(s) 	Exp(s)	 Magnitude

white	110		99.8	17.84 +/- 0.05
white	867		99.8	20.43 +/- 0.27
white	5611	399.8	> 21.60
v		217		399.8	17.90 +/- 0.08
v		973		399.8	19.25 +/- 0.20
v		6023	399.8	> 20.00 	

The afterglow is not detected in any other filters, perhaps due to the  
high Galactic extinction value of  E(B-V) = 0.58 mag. The following  
are the 3-sigma upper limits for these filters.

Filter	Tstart(s) 	Exp(s)	 Magnitude

b		851		493.6      > 20.96
u 		673		338.5   	> 20.59
uvw1	648		362.8  	> 20.54
uvm2	623		393.2	> 20.38
uvw2	728		498.5  	> 20.88

The values quoted above are not corrected for Galactic extinction  
corresponding to a reddening of E(B-V) = 0.58 mag in the direction of  
the burst (Schlegel et al. 1998).

M. Perri and G. Stratta (ASDC) report on behalf of the Swift XRT team:

We have analysed the first 3 orbits of Swift XRT data of the BAT GRB
080328 (Perri et al., GCN Circ. 7525
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 ). The data consist of 151 s in
Windowed Timing (WT) mode, from  T+108s to T+259s, and of
6.9 ks in Photon Counting (PC) mode thereafter.

The best XRT position is the UVOT-enhanced position reported by
Beardmore et al. (GCN Circ. 7527
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 ).

The early 0.3-10 keV X-ray light curve in WT mode shows a rapid decay.
Starting from T+260s up to T+13.7ks the curve is well fit by a broken
power-law model with decay indices alpha1=-0.57 (+0.09) (-0.06),
alpha2=-1.10 (+/-0.05) and a temporal break at (1.7+/-0.3) ks.

The WT X-ray spectrum is well fit by an absorbed power-law model
with a photon index of 2.1 (+/-0.1), a column density of
(4.2+/-0.4)e21 cm**-2 and an average observed 0.3-10 keV flux
of 9.3e-10 erg/cm**2/s. The PC X-ray spectrum during the first orbit,
from  T+260s to T+2106s, is also well fit by an absorbed power-law
model with a photon index of 2.2 (+/-0.1) and a column density of
(5.0+/-0.6)e21 cm**-2. The observed 0.3-10 keV flux for this spectrum
is 1.5e-10 erg/cm**2/s. We note the Galactic column density in the
direction of the source is 3.4e21 cm**-2.

Assuming the X-ray emission continues to decline at the same rate, we
predict a 0.3-10 keV XRT count rate of 0.03 count/s at T+24hr, which
corresponds to an observed 0.3-10 keV flux of about
1.4e-12 erg/cm**2/s.

This circular is an official product of the Swift XRT Team.

H. Krimm (GSFC/USRA), S. D. Barthelmy (GSFC), J. Cummings (GSFC/UMBC),
E. Fenimore (LANL), N. Gehrels (GSFC), C. Markwardt (GSFC/UMD),
K. McLean (GSFC/UMD), D. Palmer (LANL), A. Parsons (GSFC), M. Perri (ASDC),
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-120 to T+183 sec from the recent telemetry
downlink, we report further analysis of BAT GRB 080328 (trigger
#307931) (Perri, et al., GCN Circ. 7525
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 ).  The BAT ground-calculated
position is RA, Dec = 80.490, 47.523 deg which is
    RA(J2000)  =  05h 21m 57.7s
    Dec(J2000) = +47d 31' 23.8"
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 37%.

The mask-weighted light curve consists of about about ten major pulses
spread over ~100 sec.  T90 (15-350 keV) is 90.6 +- 1.5 sec (estimated
error including systematics).

The time-averaged spectrum from T-2.2 to T+117.5 sec is best fit by a
simple power-law model.  The power law index of the time-averaged
spectrum is 1.52 +- 0.04.  The fluence in the 15-150 keV band is
9.4 +- 0.2 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from
T+9.3 sec in the 15-150 keV band is 5.5 +- 0.3 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/307931/BA/

T. A. Fatkhullin, A. S. Moskvitin, V. V. Sokolov (SAO-RAS, Nizhnij Arkhyz), 
A. S. Pozanenko (IKI, Moscow), A. de Ugarte Postigo (ESO, Santiago), M. 
Jelínek, J. Gorosabel and A. J. Castro-Tirado (IAA-CSIC Granada), on 
behalf of a larger collaboration, report:

"Following the detection of GRB 080328 by Swift (Perri et al. GCNC 
7525), we have obtained BVRI imaging and spectroscopy (3800-7500 A) with 
the 6.0m BTA SAO-RAS telescope starting on Mar 28.76 UT  (i.e. 12.4 hr 
after the onset of the event). A faint optical source (with R about 
22.5) consistent with the UVOT position (Ward et al. GCNC 7530) is 
detected in all frames, thus implying an upper limit of about 2.5 for 
the GRB 080328 redshift. Its brightness is not consistent with the 
extrapolation of the early decay reported by Guidorzi et al. (GCNC 7526) 
indicating significant contribution of the reverse shock emission in the 
FTN data. Our BTA spectrum (2 x 900s) shows only a faint continuum and 
nothing conclusive can be reported (except the non-existence of strong 
emission lines arising from an underlying host galaxy)."

This message can be quoted.

[GCN OPS NOTE(29mar08): Per author's request, 3 typos were fixed
in the Fatkhullin, Moskvitin and Pozanenko names.]

S. Golenetskii, R.Aptekar, E. Mazets, V. Pal'shin, D. Frederiks,
and T. Cline on behalf of the Konus-Wind team report:

The long GRB 080328 (Swift-BAT trigger #307931: Perri et al., GCN
7525
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 , Krimm et al., GCN 7533
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 )
triggered Konus-Wind at T0=28982.306 s UT (08:03:02.306).

The burst light curve shows a multipeaked structure
with a total duration of ~90 s.

As observed by Konus-Wind the burst
had a fluence of 2.23(-0.22, +0.23)x10^-5 erg/cm2,
and a 256-ms peak flux measured from T0+10.512 s
of (2.51 +/- 0.41)x10^-6 erg/cm2/s
(both in the 20 keV - 1 MeV energy range).

The time-integrated spectrum of the burst
(from T0 to T0+90.368 s) is well fitted (in the 20 keV-1 MeV range)
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with alpha = -1.13(-0.20, +0.17),
and Ep = 289(-57, +93) keV (chi2 = 62.8/56 dof).

The spectrum of the most intense part (from T0+8.448 to T0+16.640 s)
is well fitted (in the same range)
by a power law with exponential cutoff model
with alpha =  -0.59(-0.19, +0.17)
and Ep = 338(-40, +51) keV (chi2 = 60.8/56 dof).
The fluence of this part is (8.79 +/- 0.68)x10^-6 erg/cm2.

All the quoted errors are at the 90% confidence level.

The Konus-Wind light curve of this GRB is available
at http://www.ioffe.rssi.ru/LEA/GRBs/GRB080328_T28982/

N. Kodaka, M. Tashiro, Y. Terada, Y. Urata, A. Endo,
K. Onda, M. Suzuki, K. Morigami (Saitama U.),
K. Yamaoka, Y. E. Nakagawa, S. Sugita (Aoyama Gakuin U.),
M. Ohno, T. Uehara, T. Takahashi, Y. Fukazawa,
C. Kira, Y. Hanabata (Hiroshima U.), T. Tamagawa (RIKEN),
T. Enoto, R. Miyawaki, K. Nakazawa, K. Makishima (Univ. of Tokyo),
E. Sonoda, M. Yamauchi, H. Tanaka, R. Hara (Univ. of Miyazaki),
M. Kokubun, M. Suzuki, T. Takahashi (ISAS/JAXA), S. Hong (Nihon U.),
on behalf of the Suzaku WAM team, report:

The long GRB 080328 (Swift/BAT trigger #307931 ; Perri et al.,
GCN 7525
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 ) was detected by the the Suzaku Wide-band  All-sky Monitor
(WAM) which covers an energy range of 50 keV - 5 MeV at 2008-03-28 
08:03:14 UT (=T0). The observed light curve shows a multi-peaked
structure starting at T0+0s, ending at T0+100 with a duration (T90)
of about 85 seconds. The fluence in 100 - 1000 keV was
1.61 (-0.40,+0.37) * 10^-5 erg/cm^2. The 1-s peak flux measured from
T0+0s was 6.4 (-0.39,+0.39) photons/cm^2/s in the same energy range.

Preliminary result shows that the time-averaged spectrum from T0-0s to
T0+100s is well fitted by a single power-law with a photon index
of 1.72 (-0.26, +0.38) (chi^2/d.o.f = 11.9/15).
All the quoted errors are at statistical 90% confidence level,
in which the systematic uncertainties are not included.

The light curves for this burst are available at:
http://www.astro.isas.jaxa.jp/suzaku/HXD-WAM/WAM-GRB/grb/trig/grb_table.html

H.Tanaka, K.Kono, R.Hara, N.Ohmori, H.hayasi, M.Yamauchi, E.Sonoda
(University of Miyazaki)

We have observed the field covering the error circle of
GRB080328 (GCN 7527
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 , A.P. Beardmore et al.) with
the unfiltered CCD camera on the 30-cm telescope at
University of Miyazaki.
The observation was started 11:09:32 UT; about 186 minutes
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.)
--------------------------------------------------------------
11:10:49 11:11:07 	1 		~15.74
11:10:59 12:58:24 	65 		~17.70
---------------------------------------------------------------

K. Kinugasa, O. Hashimoto, S. Honda, E. Nishihara, Y. Kozai (Gunma
Astronomical Observatory) and H. Karoji (NAOJ) report:

 The field of GRB 080328 (Perri et al. GCN 7525
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 ) was observed
with the 150 cm telescope of the Gunma Astronomical Observatory.
Starting at 09:49 UT (1.75 hours after the trigger), Rc frames
were acquired for 9 x 3-min exposures  under a poor seeing
(~4.5arcsec) condition.

 The UVOT position is close to a star, so that the field are affected
with the light from this star. We do not identify the optical counterpart
reported by UVOT to limiting magnitudes of Rc=20.7 relative to USNO-B1.0 R2
magnitudes at the meantime of 10:08 UT.

 Combining the results reported by Guidorzi et al. (GCN 7526
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 ), the decay
index is > 0.9, which is consistent with the intial index reported by
Guidorzi et al. (GCN 7526
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 ).