Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The broad-line type Ic SN 2020bvc: signatures of an off-axis gamma-ray
  burst afterglow   Long-duration gamma-ray bursts (GRBs) are almost unequivocally associated
with very energetic, broad-lined supernovae (SNe) of Type Ic-BL. While the
gamma-ray emission is emitted in narrow jets, the SN emits radiation
isotropically. Therefore, some SN Ic-BL not associated with GRBs have been
hypothesized to arise from events with inner engines such as off-axis GRBs or
choked jets. Here we present observations of the nearby ($d = 120$ Mpc) SN
2020bvc (ASAS-SN 20bs) which support this scenario. \textit{Swift} UVOT
observations reveal an early decline (up to two days after explosion) while
optical spectra classify it as a SN Ic-BL with very high expansion velocities
($\approx$ 70,000 km/s), similar to that found for the jet-cocoon emission in
SN 2017iuk associated with GRB 171205A. Moreover, \textit{Swift} X-Ray
Telescope and \textit{CXO} X-ray Observatory detected X-ray emission only three
days after the SN and decaying onwards, which can be ascribed to an afterglow
component. Cocoon and X-ray emission are both signatures of jet-powered GRBs.
In the case of SN 2020bvc, we find that the jet is off axis (by $\approx$ 23
degrees), as also indicated by the lack of early ($\approx 1$ day) X-ray
emission which explains why no coincident GRB was detected promptly or in
archival data. These observations suggest that SN 2020bvc is the first orphan
GRB detected through its associated SN emission.

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The categories of this paper are: bayes-an
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The categories of this paper are: math-ph
33
The categories of this paper are: plasm-ph
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The categories of this paper are: eess
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The categories of this paper are: patt-sol
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The categories of this paper are: mtrl-th
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The categories of this paper are: chem-ph
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The categories of this paper are: q-fin
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The categories of this paper are: hep-ex
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The categories of this paper are: q-bio
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The categories of this paper are: chao-dyn
2
The categories of this paper are: math
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The categories of this paper are: acc-phys
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The categories of this paper are: cond-mat
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The categories of this paper are: dg-ga
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The categories of this paper are: nucl-th