Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Early Light Curve of the Optical Afterglow of GRB 021211   The Katzman Automatic Imaging Telescope (KAIT) at Lick Observatory observed
GRB 021211 starting 105 s after the burst, among the earliest observations of
an optical afterglow to date. Our well-sampled light curve, consisting of 18
points in the first 10 min and a total of 28 useful observations in the first
2.5 hr after the GRB, directly shows for the first time a break at $t \approx
10$ min. The light curve can be represented as a sum of two components with
power-law decay indices of $-1.82\pm0.02$ and $-0.82\pm0.11$. We hypothesize
that the data before the break were dominated by emission from the reverse
shock, as was previously suggested for GRB 990123. Our data suggest that either
GRB 021211 underwent a dramatic color change at early times, or there are
small-scale variations superimposed on the power-law decay of the reverse-shock
emission. The faintness of GRB 021211, coupled with the fast decline typical of
optical afterglows, suggests that some of the "dark bursts" were not detected
because optical observations commenced too late after the GRB.

16
The categories of this paper are: stat
36
The categories of this paper are: cmp-lg
37
The categories of this paper are: supr-con
20
The categories of this paper are: acc-phys
23
The categories of this paper are: solv-int
19
The categories of this paper are: eess
33
The categories of this paper are: plasm-ph
21
The categories of this paper are: adap-org
4
The categories of this paper are: cond-mat
18
The categories of this paper are: econ
26
The categories of this paper are: bayes-an
34
The categories of this paper are: chem-ph
12
The categories of this paper are: nucl-th
32
The categories of this paper are: atom-ph
28
The categories of this paper are: alg-geom
5
The categories of this paper are: gr-qc