GRB 010324

K. Hurley, on behalf of the Ulysses GRB team, and C. Guidorzi, E. Montanari,
and F. Frontera, on behalf of the BeppoSAX GRBM team, report:

Ulysses and the BeppoSAX GRBM observed GRB010324, reported in
the GCN/RXTE ASM BURST POSITION NOTICE.  The triangulation
annulus is 8' wide, and is almost parallel to the long side
of the RXTE ASM error box.  The error box is fully contained
within the annulus, though, so the annulus does not reduce its
area.  However, these two observations confirm that the event
observed by RXTE is indeed a GRB.  The annulus probably cannot
be refined substantially.

Optical Observations of GRB 010324

J. S. Bloom, D. W. Fox (CIT), J. M. Schombert (U. Oregon), S. G.
Djorgovski, A. Mahabal, D. E. Reichart, and P. A. Price (CIT) report on
behalf of the larger Caltech-NRAO-CARA GRB Collaboration:

"On 25.27 March 2001 UT, James Schombert observed the field of GRB 010324
(GCN/RXTE ASM; Hurley et al., GCN #1011
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 ) using COSMIC on the Palomar
200-inch atop Mt. Palomar.  The entire XTE error box was observed in
V-band in two pointings with a total of 1800 sec per pointing.  We found
no new candidate source when compared visually with the J, F, N-plates of
DPOSS-II. Further optical monitoring is encouraged."

Original DPOSS images of the field are available at:

  http://www.astro.caltech.edu/~jsb/GRB/grb010324/

We thank Rick Burruss at Palomar for his assistance.

This message may be cited.

K. Hurley, on behalf of the Ulysses GRB team, and C. Guidorzi,
E. Montanari, and F. Frontera, on behalf of the BeppoSAX GRBM
team, report:

This burst (RXTE/ASM and GCN 1011
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 ) had a duration of
approximately 15 seconds in 25-150 keV gamma-rays.  Its
Earth-crossing time was ~41558 s, and its 25-100 keV
fluence was ~1.8x10^-6 erg/cm^2; over 0.25 s, its peak
flux was ~4.3x10^-7 erg/cm^2 s.  The latter numbers are
uncertain by about a factor of 2 at present, but can
probably be refined with further processing.

A. Oksanen, H. Hyvonen (Nyrola Observatory);
A. Price, D. West, G. Lubcke, D. Kaiser, D. Hurdis (AAVSO);
M. O'Conner, D. Marcus, R. Pason, F. Chalupka,
D. Hohman, W. Aquino (Buffalo Astronomical Association)
report on behalf of the AAVSO International GRB network:

We have observed the error box for the RXTE ASM GRB010324
(Hurley et al., GCN 1011
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 ) with a variety of telescopes
and image scales.  Based on comparison with the POSS-II
red plate as digitized at USNO, we find no new object
within the error box.  A log of observations is given below.
For the Filter field, C=unfiltered, R=Cousins R,
I=Cousins I.  The Delay field is the time since
burst (010324.484 UTD).  Several of these composite images
are available at ftp://ftp.aavso.org/grb/

Observer/      UTD      Delay   Tel  Totexp Field Filt Limit
Observatory   (mid)     (hr)          (min) ('x')      (mag)
Nyrola      010324.938  10.9   0.40m    9   18x12  C    18.8
Price       010325.04   13.2   0.25m   10    9x12  R    18.2
West        010325.075  14.2   0.25m    5   48x32  C    17.5
Lubcke      010325.076  14.2   0.28m   12   13x13  R    18.2
Kaiser      010325.095  14.7   0.35m   60   18x18  R    18.5
Hurdis      010325.132  15.6   0.40m   10   19x12  I    17.0
BAA         010325.212  17.5   0.30m   30    7x11  R    19.4

C. Guidorzi, E. Montanari and F. Frontera, Physics Dept. University of
Ferrara; F. Calura, Dept of Physics University of Trieste; L. Amati,
Istituto TESRE, CNR, Bologna; and M. Feroci, Istituto
Astrofisica Spaziale, CNR, Roma; on behalf of the BeppoSAX/GRBM Team, 
and K. Hurley on behalf of the Ulysses GRB Team, report:

GRB010324 (GCN/RXTE ASM Burst Position Notice of Sat. 24 Mar 01 and GCN
1011
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 ) triggered the BeppoSAX/GRBM at 11h32m46s UT, 285.4 s before the ASM
trigger. From the GRBM 40-700 keV light curve, the actual onset time is
about 80 s before the GRBM trigger time. The event shows a multi-peak
behavior with an outstanding peak occurring 10 s after the GRBM trigger
time and a peak flux of 1100 cts/s, corresponding to ~1x10^-6 erg/cm^2 s. 
The trigger time of ASM occurs in correspondence of the tail of the last
peak of the burst, whose centroid is ~360 s after the onset time and
its peak flux is a factor 8 lower than that of the main peak. 

This message can be cited.

Further Optical Observations of GRB 010324

J. S. Bloom, P. A. Price, D. W. Fox, S. G. Djorgovski (CIT), and
J. M. Schombert (U. Oregon) report on behalf of the larger
Caltech-NRAO-CARA GRB Collaboration:

"On 26.27 March 2001, we obtained a second night of exposures of the
field of GRB 010324 (GCN/RXTE ASM; Hurley et al., GCN #1011
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 ) using
COSMIC on the Palomar 200-inch atop Mt. Palomar.  Using the same
pattern as in the first epoch of imaging (GCN #1012
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 ), the entire XTE
error box was observed in V-band in two pointings with a total of 1800
sec per pointing.

Both image differencing and differential aperture photometry between
the two epochs revealed no obviously varying source.  No absolute
photometry for the field is available at this time.  However, adopting
V = 19.1 mag for a USNO A2.0 star at RA: 07:11:26.301, DEC:
+19:58:30.32 (J2000) we estimate the absence of variation by more than
0.3 mag down to V = 22.3 mag.

Sources brighter than V~18.5 mag were saturated however all such sources
were previously observed in DPOSS (see GCN #1012
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 ); therefore any GRB
afterglow is now likely to be faint (V > 22.3 mag). One caveat to this
conclusion is that the GRB field has a high stellar density and so it is
possible to have missed a varying source near a bright star."

This message may be cited.

A. Henden (USRA/USNO) reports on behalf of the USNO GRB team:

We have acquired preliminary BVRcIc all-sky photometry for
an 11x11 arcmin field centered at the RXTE ASM localization
(GCN/RXTE ASM; Hurley et al., GCN #1011
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 ) for GRB010324
with the USNOFS 1.0-m telescope on one marginally photometric
night.  Stars brighter than V=15 are saturated and should be used
with care.
  We have placed the photometric data on our anonymous ftp site:
ftp://ftp.nofs.navy.mil/pub/outgoing/aah/grb/grb010324.dat
The astrometry in this file is based on linear plate solutions
with respect to USNO-A2.0.  The internal errors are less than 100mas.
  We have less confidence than usual in the quality of this
photometry.  The all-sky reduction of standards had an RMS
error of 1.4 percent, but a high-airmass standard observation
that immediately followed the GRB field observation deviated
from the mean by 4 percent.  We will attempt to reobserve
this field on the next photometric night.

A. Henden (USRA/USNO) reports on behalf of the USNO GRB team:

We have obtained a second night of photometry with the
NOFS 1.0m telescope for the field of GRB010324.  The
revised BVRcIc photometry file can be found at
ftp://ftp.nofs.navy.mil/pub/outgoing/aah/grb/grb010324.dat
The quality of this file is still below our normal
standards, but is good to about 0.03mag for all
magnitudes and colors.  No further revisions are
anticipated unless an optical transient is discovered
in this field.
  The USNO-A2.0 star mentioned in Bloom et al. (GCN1024
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 )
lies just to the south of this calibration field and
so is not included in the file.
Arne