Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: GRB 010921: Strong Limits on an Underlying Supernova from HST   GRB 010921 was the first HETE-2 GRB to be localized via its afterglow
emission. The low-redshift of the host galaxy, z=0.451, prompted us to
undertake intensive multi-color observations with the Hubble Space Telescope
with the goal of searching for an underlying supernova component. We do not
detect any coincident supernova to a limit 1.34 mag fainter than SN 1998bw at
99.7% confidence, making this one of the most sensitive searches for an
underlying SN. Analysis of the afterglow data allow us to infer that the GRB
was situated behind a net extinction (Milky Way and the host galaxy) of A_V ~
1.8 mag in the observer frame. Thus, had it not been for such heavy extinction
our data would have allowed us to probe for an underlying SN with brightness
approaching those of more typical Type Ib/c supernovae.

31
The categories of this paper are: ao-sci
29
The categories of this paper are: funct-an
1
The categories of this paper are: cs
14
The categories of this paper are: math-ph
15
The categories of this paper are: nucl-ex
17
The categories of this paper are: q-fin
30
The categories of this paper are: q-alg
5
The categories of this paper are: gr-qc
22
The categories of this paper are: chao-dyn
8
The categories of this paper are: hep-ex
3
The categories of this paper are: physics
16
The categories of this paper are: stat
11
The categories of this paper are: hep-lat
23
The categories of this paper are: solv-int
37
The categories of this paper are: supr-con
4
The categories of this paper are: cond-mat