GRB 020410

BeppoSAX ALERT: possible GRB020410

On Apr. 10, 10:41:20 UT a possible GRB  has been
detected in BeppoSAX WFC2. Unfortunately GRBM was switched off at that
time and the nature of the transient is still under examination.
A GRB or X-ray flash classification is however very probable.

Refined coordinates are:

R.A.(2000)= 331.768
DEC.(2000)= -83.821

The error radius  is 2'.

G. Gandolfi
on behalf of
BeppoSAX Mission Scientist

P. Kilmartin (p.kilmartin@phys.canterbury.ac.nz)
and A. Gilmore, Mount John Observatory, on behalf
of the AAVSO International GRB Network, report:

We have imaged the entire BeppoSAX error circle of the possible
GRB020410 (Gandolfi GCN1349
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 ), using the MJO 0.6m
telescope and ST-9E CCD.  Fifteen unfiltered 60-second
exposures, centered on UT 020410.691 (6hrs after the burst),
were taken and median combined.  Comparing against the
POSS-II red plate, we see nothing new down to approximately R=19.

The AAVSO would like to thank the Curry Foundation for supporting the
AAVSO International GRB Network.

GRB 020410, optical observations
--------------------------------

A. J. Castro-Tirado, J. Gorosabel,  (Instituto de Astrofísica de Andalucía,
IAA-CSIC,Granada),
J. M. Castro Céron (ROA, San Fernando),
B. Nelson, P. Tristram, P. Kilmartin, & A. Gilmore (Univ. of Canterbury) and
Ph. Yock (Univ. of Auckland),


report:

We have obtained several R-band exposures centred at the GRB
020410 error box (Giandolfi et al. GCN#1349
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 ) starting on 10 Apr 2002
at 16:58 UT, i.e. 6.28 hr after the trigger, with the 0.6 m MOA telescope
at the Mt. John University Observatory in New Zealand. A visual
inspection of the images does not reveal any transient objects down
to the DSS-2 limiting magnitude within the 2' BSAX error box.

This message is quotable.

[GCN OPS NOTE (11Apr02): P. Kilmartin & A. Gilmore were added to the 
author list.]
[GCN OPS NOTE (20jul02):  The affiliation for JMCC was changed
from "IAA-CSIC and ROA, San Fernando" to "ROA, San Fernando".]

GRB020410: BeppoSAX NFI observation

A BeppoSAX TOO observation of GB020410 has started about 20
hours after the GRB.
A preliminary analysis of MECS (1.6-10 keV) image of the first orbits
shows a bright unknown source in the WFC error circle.

The position is:

RA(2000) = 331.603
Delta(2000) = -83.82

The error radius is 1 arcminute.

G. Gandolfi
on behalf of BeppoSAX Mission Scientist

GRB020410: second BeppoSAX NFI observation

On Apr. 12 at 17:00 U.T. a second BeppoSAX NFI observation has been
started, 54.3 hours after the burst. The unknown source previously reported is
detected again and its flux is decreased about a factor 2. This fact makes
more probable the connection with the WFC transient of April the 10th
whose nature is however still to be understood. Further analysis are in
progress.

Giangiacomo Gandolfi
on behalf of BeppoSAX Mission Scientist

L. Nicastro, Istituto di Astrofisica Spaziale e Fisica Cosmica (IASF-CNR),
Palermo; L. Piro, G. Gandolfi, M. Feroci, (IASF-CNR), Rome;
M. Capalbi, M. Perri, ASI Science Data Center, Rome;
J. Heise, J. in't Zand, Space Research Organization Netherlands, Utrecht,
report:

"BeppoSAX performed two NFI observations of the candidate GRB 020410.
Start times were Apr. 11, 06:53 UT (20.2 hrs after the burst) and
Apr. 12 16:49 UT (54.3 hrs after the burst). We detect a single
unknown slowly fading source in both observations whose refined
coordinates (J2000) are:

 RA: 22 06 25.8, Dec: -83 49 27

This is 1.3 arcmin from the WFC derived position (GCN 1349
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 ) and 15 arcsec
from the quick-look analysis derived one (GCN 1366
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 ).
The error circle radius is 20 arcsec (90% confidence).
This is the smallest ever reported for a BSAX-NFI detected GRB.
For more information about NFI source coordinates accuracy see the
BeppoSAX-ASDC report at the URL:
  http://www.asdc.asi.it/bepposax/coord_correction.html

Images of the two observations and the decay behavior are posted at the URL:
  http://www.ifcai.pa.cnr.it/~nicastro/saxtoo-grb020410

We note that no gamma-ray detection was reported so far (the BSAX-GRBM
was not operative). This fact, the X-ray properties of the WFC (2-28 keV)
prompt event and the spectral/temporal behavior of the afterglow
strongly support the hypothesis of a XRF or anomalous GRB.

(Sub-)arcsec position accuracies obtainable with Chandra or XMM-Newton
would greatly facilitate deeper studies at other wavelengths."

This message may be cited.

D. A. Frail (Caltech/NRAO), M. H. Wieringa (ATNF), E. Berger
(Caltech), and R. Wark (ATNF) report on behalf of a larger
collaboration:

"Beginning on 2002 April 23 at 8:00 UT we observed a region centered
on the position of the fading X-ray source reported by Nicastro et al.
(GCN #1374
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 ) with the Australia Telescope Compact Array (ATCA) at 8.7
GHz. An image made of the entire error circle (20-arcsec radius) shows
no radio sources above a 4-sigma level of 200 microJy.

This message may be cited."

A.S. Fruchter, A.J. Levan, I. Burud (STScI), P.E. Nugent (LBNL) report
for the larger GOSH Collaboration:

We observed the field of GRB 020410 (GCN 1349
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 ) with HST using the STIS
CCD in open (50CCD) mode on the 8 May and 14 June 2002.   The 50" field
of STIS was centered on the refined NFI BeppoSax postion of Nicastro
et al. (GCN 1374
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 ), which has a 90% confidence error-circle radius of
20".

We find a variable source located at RA=22h 06m 31.87s, DEC=-83d 49m 28.3"
where the astrometry has been derived from the headers of the two HST
images (which agree to approximately 0."5).  This position is offset
from the center of the NFI error circle by approximately 6".

Using a zeropoint of V=26.3 for the wide-band STIS 50CCD image, we find
the source had a magnitude of V=25.35 on 8 May and 26.90 on 14 June,
where the uncertainty in the photometry is dominated by the color
correction (which one might expect to be of order 0.1 mags).  The source is
largely point-like, though it lies near a 25th magnitude galaxy, and
shows possible evidence of a faint underlying object.

The decline of ~1.55 magnitudes between the two observation dates is
equivalent to an effective power-law decay of -1.65.  While this value
is completely consistent with the late-time decay of the optical
afterglow of a GRB, we cannot rule out the possibility that a
supernova, unrelated to the GRB, occurred in our search region.  Given
the rates of discovery by HST of supernovae in deep images of random
fields (c.f. Gilliland, Nugent and Phillips 1999) we conservatively
estimate a ~5% chance that this could be such a chance superposition.
Further observations, which we expect will give us both a late-time
magnitude and color, should allow us to distinguish between these
possibilities.

Were the source to have faded consistently as a power law of exponent
-1.65 from early after the burst, then its magnitude would have been
~17 at 6 hours after burst when observations by Castro-Tirado et al.
(GCN 1355
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 ), which reached the DSS-2 limit, failed to detect a
counterpart.  BeppoSAX observations (GCN 1358
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 , 1366
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 ) taken 20 and 54
hours after burst indicated that the x-ray afterglow associated with
the GRB fell by only a factor of two, consistent with an effective
power law decline of -0.9.  Therefore a break may be the most likely
explanation for the non-detection of this transient in early optical
observations.

If, as expected, this is indeed the OT of GRB 020410, this would be the
first time that HST (or any orbiting observatory) has discovered the OT
of a GRB.

The HST images of the field of GRB 020410 can be found at
http://www.stsci.edu/~fruchter/GRB/020410.