GRB 060322

M. Perri (ASDC), S.D. Barthelmy (GSFC), N. Gehrels (NASA/GSFC),
J. A.  Kennea (PSU), C.B. Markwardt (GSFC/UMD), D. M. Palmer (LANL) and
L.  Vetere (ASDC) report on behalf of the Swift Team:

At 23:00:21 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 060322 (trigger=202442).  Swift did not slew to this burst
because the location is within the Moon observing constraint (8 deg).
The BAT on-board calculated location is RA,Dec 274.245, -36.697
{18h 16m 59s, -36d 41' 50"} (J2000) with an uncertainty of 
3 arcmin (radius, 90% containment, including systematic uncertainty).
The BAT light curve shows a double episode of multi-peak structures.
The first episode starts at T-10 sec and lasts to T+35 sec.
The second episode starts at T+155 sec and lasts to T+200.  The total
duration is about 210 sec.  We note that this location is near
the Galactic Bulge, but that the light curve is much more like
a GRB than any galactic x-ray bursting source.  The peak count rate
was ~1600 counts/sec (15-350 keV), at ~1 sec after the trigger in the first
episode and the same rate at T+180 sec in the second episode.

This location will come out of Moon constraint at 09:00 24 Mar 06.

D. Palmer (LANL), L. Barbier (GSFC), S. Barthelmy (GSFC),
J. Cummings (GSFC/NRC), E. Fenimore (LANL), N. Gehrels (GSFC),
D. Hullinger (BYU-Idaho), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), 
A. Parsons (GSFC), M. Perri (ASDC), T. Sakamoto (GSFC/NRC),
G. Sato (ISAS), J. Tueller (GSFC)
on behalf of the Swift-BAT team:

Using the data set from T-239 to T+963 sec from recent telemetry downlinks,
we report further analysis of BAT GRB 060322 (trigger #202442)
(Perri, et al., GCN 4903
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 ).  The BAT ground-calculated position is
RA,Dec = 274.235,-36.721 deg {18h 16m 56.4s, -36d 43' 14.7"} (J2000)
+- 1.0 arcmin, (radius, sys+stat, 90% containment).  The partial coding was 80%.
 
The mask-weighted lightcurve shows two well separated episodes of emission.
The first episode starts at T-22 sec and ends at T+40 sec with six main peaks
within that interval.  Then the emission drops below the BAT sensitivity
until the second episode.  The second episode starts at T+155 sec and
ends at T+204 sec with six main peaks within that second interval.
There is no further emission out to T+670 sec.  T90 (15-350 keV) is
213 +- 5 sec (estimated error including systematics).
 
The time-averaged spectrum from T-21.7 to T+232.3 is best fit by a power law
with an exponential cutoff.  This fit gives a photon index 1.04 +- 0.32, 
and Epeak of 94.4 +- 44.7 keV (chi squared 57.29 for 56 d.o.f.).  
For this model the total fluence in the 15-150 keV band is
5.1 +- 0.2 x 10^-06 erg/cm2 and the 1-sec peak flux measured from T+182.19 sec
in the 15-150 keV band is 2.1 +- 0.2 ph/cm2/sec.  A fit to a simple
power law gives a photon index of 1.58 +- 0.07 (chi squared 65.5
for 57 d.o.f.).  All the quoted errors are at the 90% confidence level.

Additionally, separate spectral analyses of the two episodes
in the light curve show that the second episode is spectrally softer
than the first.  The best fit to the first episode is a simple power law
with a photon index of 1.36 +- 0.09 (chi squared 30.3 for 56 d.o.f.).
The second episode is best fit by a power law with an exponential
cutoff.  This fit gives a photon index alpha = 0.89 +-0.31 and Epeak 
of 72.8 +- 12.6 keV (chi squared 51.6 for 55 d.o.f.).  Fitting a
simple power law to the second episode yields a power-law index
of 1.69 +- 0.07 (chi squared 70.5 for 56 d.o.f.)  All the quoted errors
are at the 90% confidence level.

M. Perri, L. Vetere (ASDC), D.N. Burrows (PSU) report on behalf of
the Swift XRT team:

The Swift XRT began observing the field of GRB 060322 (trigger #202442,
Perri et al., GCN 4903
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 ) at 2006-03-24 11:36:11 UT, approximately 37
hours (1.5 days) after the BAT trigger. In a first XRT exposure of ~9 ks
we detect a faint uncatalogued X-ray source at the following coordinates:

RA(J2000) = 18h 16m 56.4s
Dec(J2000) = -36d 42' 31"

with an estimated uncertainty of 5 arcseconds (90% containment).
This position lies 45 arcseconds from the BAT refined position reported
by Palmer et al. (GCN 4907
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 ).

Due to the small number of counts, we are unable to determine whether
the source is decaying at this time. Observations are continuing and
further analysis regarding the fading nature of this source will be
issued as the data becomes available.

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

M. Jelínek, S. Guziy (IAA-CSIC, Granada), J. M. González-Pérez
(IAC, La Laguna)  and A. J. Castro-Tirado (IAA-CSIC), on behalf
of a larger collaboration,

report:

Following the detection of the long GRB 060322 by SWIFT (Perri
et al. GCNC 4903), we have observed the field with the 0.8m
IAC80 telescope at Observatorio del Teide in Canary Islands.
Images were taken in the R- and I-bands starting on 23.265 UT
(i.e. 7.3 hr after the event), under not optimal observing
conditions (high airmass and 9 degrees away from the last quarter
moon). We do not detect any object within the 5" radius error
box of the possible X-ray afterglow (Perri et al. GCNC 4919).
The 5-sigma limiting magnitude for the co-added R-band frame
(3 x 300s) is 19.3 .

This message can be quoted.

M. Perri, L. Vetere (ASDC), D.N. Burrows (PSU) report on behalf of
the Swift XRT team:

The Swift XRT observed the field of GRB 060322 (GCN 4903
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 , Perri et al.)
for a second time on 2005-03-25 from 00:37:09 UT until 21:53:57 UT.
We confirm that the X-ray source identified by Perri et al. (GCN 4919
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 ,
RA(J2000) = 18h 16m 56.4s, Dec(J2000) = -36d 42' 31" )
has faded from view and is therefore the likely X-ray afterglow of
this burst.

Using an exposure of ~11 ks in Photon Counting mode we place a three
sigma upper limit on the 0.3-10 keV count rate of 2.0e-3 cts/s which
is significantly lower than the count rate observed with the first
exposure (3.0+/-0.7)e-3 cts/s, implying that the source has faded.

We conclude that the candidate reported in GCN 4919
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  is the X-ray
afterglow of GRB 060322.

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

A. Pereyra, T. Dominici, A. M. Magalh�es and Z. Abraham (IAG, Univ. of S�o Paulo) report:

We observed the field of GRB 060322 (Perri et al. GCN 4903
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 ) with the IAG-USP 60cm 
telescope at the Laborat�rio Nacional de Astrof�sica (LNA), Brazil. The observations 
were made on March 24.342 (UT middle of observation) and 1.381 days after the burst 
under non-optimal sky conditions. Comparison to the DSS2 (Red) did not reveal any object 
inside the error circle from Perri et al. (GCN 4919
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 ). Our sequence of co-added R-band 
images (8x300s + 5x50s) yielded a 3-sigma limit magnitude of 18.7 using USNO B1.0 field 
stars.

This message can be quoted.