GRB 080408

Subject: GRB 080408: Gamma Ray Burst Localization by SuperAGILE

P. Soffitta, I. Donnarumma, E. Del Monte, M. Feroci, Y. Evangelista, 
E. Costa, I. Lapshov, F. Lazzarotto, L. Pacciani, M. Rapisarda
(INAF/IASF Rome), A. Giuliani, S. Vercellone, A. Chen, S. Mereghetti, A. 
Pellizzoni, F. Perotti, F. Fornari, M. Fiorini, P. Caraveo, 
A. Zambra (INAF/IASF Milan), A. Bulgarelli, F. Gianotti, 
M. Trifoglio, G. Di Cocco, C. Labanti, F. Fuschino, M. Marisaldi, 
M. Galli, (INAF/IASF Bologna), M. Tavani, G. Pucella, F. D'Ammando, V. 
Vittorini, A. Argan, A. Trois (INAF/IASF Rome), G. Barbiellini, 
F. Longo (INFN Trieste), P. Picozza, A. Morselli (INFN Roma-2),  
M. Prest, E. Vallazza (Universita` dell'Insubria), P. Lipari, 
D. Zanello (INFN Roma-1), and  P. Giommi, C. Pittori,  
(ASDC) and L. Salotti (ASI), on bhealf of the AGILE Team, report:

"SuperAGILE detected and localized a gamma ray burst 
on April 8th, at 18:12:48 UT. The event was approximately 
13 degrees off-axis. The observed duration in the 20-60 keV
energy range is about 20 seconds, with a single pulse structure.
The burst was triggered and localized onboard, although distributed
after verfication on ground.  
The burst position was reconstructed as (RA, Dec) (114.678 deg, 
33.305 deg), which is:

RA(J2000) = 07h 38m 42.68s
Dec(J2000) = 33d 18' 16.7"

with an uncertainty of 3' radius. The given uncertainty accounts 
for both the statistical and systematic errors. 

An analysis of the AGILE Gamma Ray Imager (GRID) data is in progress."

This message may be cited.

S. Mereghetti, S. Vercellone, A. Giuliani, A. Chen, A. Pellizzoni, F. 
Perotti, F. Fornari, M. Fiorini, P. Caraveo, A. Zambra (INAF/IASF Milan), 
P. Soffitta, I. Donnarumma, E. Del Monte, M. Feroci, Y. Evangelista, E. 
Costa, I. Lapshov, F. Lazzarotto, L. Pacciani, M. Rapisarda (INAF/IASF 
Rome), A. Bulgarelli, F. Gianotti, M. Trifoglio, G. Di Cocco, C. Labanti, 
F. Fuschino, M. Marisaldi, M. Galli, (INAF/IASF Bologna), M. Tavani, G. 
Pucella, F. D'Ammando, V. Vittorini, A. Argan, A. Trois (INAF/IASF Rome), 
G. Barbiellini, F. Longo (INFN Trieste), P. Picozza, A. Morselli (INFN 
Roma-2), M. Prest, E. Vallazza (Universita` dell'Insubria), P. Lipari, D. 
Zanello (INFN Roma-1), and P. Giommi, C. Pittori, (ASDC) and L. Salotti 
(ASI), on behalf of the AGILE Team, report:


A preliminary analysis of the AGILE GRID data (E>100 MeV) does not show 
any significant gamma ray emission at the time and coordinates of the 
burst GRB 080408 localized by SuperAGILE (GCN 7571
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 ).

This message may be cited.

K.L. Page (U. Leicester) reports on behalf of the Swift-XRT Team:

Swift performed a Target of Opportunity observation of the SuperAGILE GRB 
080408 (Soffitta et al., GCN Circ 7571
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 ), starting ~25 ks after the 
trigger. The intended observation was cut short by the BAT detection of 
GRB 080409 (Holland et al., GCN Circ. 7573
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 ), but a source is still 
detected during the 800 s of data obtained, at a position of RA, Dec = 
114.66547, +33.30341, which is equivalent to

RA(J2000):   07 38 39.71
Dec(J2000): +33 18 12.3

with an uncertainty of 8.6 arcsec (radius, 90% containment). This is 38.1 
arcsec from the SuperAGILE position, within their error circle.

The source has a count rate of 0.010 +/- 0.004 count s^-1, however, with 
the limited data, it is not possible to determine whether it is fading.

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

P. Schady (MSSL-UCL) reports on behalf of the Swift-UVOT team:

The Swift/UVOT performed a Target of Opportunity observation on the SuperAGILE 
GRB 080408 (Soffitta et al., GNCN Circ. 7571), starting ~7hrs after the 
trigger. Observations were made in the b, u and uvw1 filters. The optical 
afterglow is not detected in any of these filters at the XRT position (Page et 
al., GCN Circ 7576
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 ) down to the following 3 sigma upper limits:

Filter  Tstart  Exp   Mag UL (3sig)
         (hrs)   (s)
b       7.12    185   > 19.96
u       7.06    200   > 19.63
uvw1    6.95    399   > 19.97

The above magnitudes are not corrected for the Galactic extinction 
corresponding to a reddening of E(B-V)=0.04 mag (Schlegel et al., 1998, ApJS, 
500, 525). The photometry is on the UVOT flight system described in Poole et 
al. (2008, MNRAS, 383, 627).

T. Kruehler, J. Greiner, A. Kupcu Yoldas, C. Clemens, A. Yoldas (all MPE
Garching) and G. Szokoly (Eoetvoes Univ., Budapest and MPE Garching)
report on behalf of the GROND team:

We observed the field of GRB 080408 detected by SuperAGILE (Soffitta et
al., GCN #7571
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 ) simultaneously in g'r'i'z'JHK with GROND mounted at the
2.2m ESO/MPI telescope at La Silla Observatory (Chile).

Observations started at 23:22:39 UT on April 8th, 2008, 5h 10min, and 
continued on April, 9th at 23:21:34 UT, 29h 9min after the burst. Due to
visibility constraints, only about 1 hr of observations were obtained at
each epoch.

In the first epoch we detect a single point source in the XRT error 
circle (Page et al. GCN #7576
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 ) at

RA (J2000.0) = 07:38:39.59
DEC (J2000.0) = +33:18:14.9

with an uncertainty of 0.5".

The object is detected in all of the seven bands, implying a redshift
smaller than 3.5.

Preliminary photometry yields magnitudes of g' = 23.12, r' = 22.03, i' =
21.62, z' = 21.26, J = 20.60, H = 19.90 and K = 19.06, with typical 
errors of +/- 0.10 in g'r'i'z' and +/- 0.15 in JHK. Magnitudes are
calibrated against USNO and 2MASS field stars.

In the second night, the object had faded to a r' band magnitude of 23.2
+/- 0.2.

We therefore suggest this to be the afterglow of GRB 080408.

The given magnitudes are not corrected for the Galactic foreground
reddening of E(B-V)=0.04 mag (Schlegel et al., 1998).