GCN Circular 1348

J.J.M. in 't Zand, University of Utrecht and Space Research
Organization Netherlands (SRON); L. Kuiper and J. Heise, SRON; L. Piro
and G. Gandolfi, Istituto di Astrofisica Spaziale e Fisica Cosmica,
Rome, report:

"A refined analysis of the BeppoSAX Narrow Field Instruments data on
GRB 020321, collected between 8.1 and 10.6 hrs after the burst, has
resulted in a significance of only 3.0 for the tentative X-ray afterglow
detection reported in GCN 1285
Not found
 
 
. The source is also not confirmed by
the XMM-Newton observation that took place between 10.3 and 24.2 hrs
after the burst (see
http://xmm.vilspa.esa.es/external/xmm_news/items/grb020321). Therefore,
we regard this detection as marginal. We would like to point out
another source which is outside the error circle of the marginal NFI
source but inside the WFC error circle of the burst (GCN 1281
Not found
 
 
) and
which draws the attention through a comparison between the XMM-Newton
EPIC-pn image and the Chandra ACIS-S3 observation (a 5.5 hr exposure
starting 9.9 days after the burst; see Fox et al., GCN Circ. 1342
Not found
 
 
). It
concerns source No. 2 in the EPIC-pn image which is located at

R.A. = 16h 12m 43.7s, Decl. = -83d 43' 13.9"

(equinox 2000.0; error 4"). This source 1) is 0.9' from the WFC
centroid; 2) shows a declining, though not smoothly, trend in the
EPIC-pn photon count rate (see aforementioned Vilspa web page); 3) is
the only EPIC-pn source covered but not detected in the ACIS-S3
image. Therefore, we propose that this is likely the X-ray afterglow
and urge optical and radio observers to concentrate on this position
for this 'dark' GRB.

We thank P. Rodrigues, N. Schartel and M. Santos at the XMM-Newton
Science Operations Centre (ESA) in Vilspa for advice on the XMM-Newton
data."

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