Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Optical/Near-IR Colors of Broad Absorption Line Quasars, Including
  the Candidate Radio-Loud BAL Quasar 1556+3517   A candidate radio-loud broad absorption line quasar (RLBAL) has been reported
by Becker et al. (1997). We present JHK observations of this object and three
other radio-detected BALs taken with the new Michigan-Dartmouth-MIT/Ohio
State/Aladdin IR Camera (MOSAIC) on the KPNO 4-meter. The candidate RLBAL
1556+3517 has B-K=6.63, redder than all but one or two known z>1 quasars. This
strongly suggests the observed continuum of this quasar is reddened by dust.
Even when this extreme reddening is taken into account 1556+3517 is still
probably radio-loud, although near-IR spectroscopy to measure its Balmer
decrement will be needed to verify this. In addition, since it is a
flat-spectrum object, VLBI observations to determine the extent (if any) to
which beaming affects our estimate of its radio luminosity will be needed
before 1556+3517 can be unequivocally declared a radio-loud BAL. We also use
our data and data from the literature to show that optically selected BALs as a
class have B-K colors consistent with the observed distribution for optically
selected quasars as a whole. Thus there is currently no evidence that the
tendency of optically selected BALs to be preferentially radio-intermediate
(Hooper, Francis, & Impey 1993) is due to extinction artificially lowering
estimated BAL optical luminosities. However, as most quasar surveys, both radio
and optical, would be insensitive to a population of reddened radio-quiet BALs,
the existence of a large population of reddened BALs similar to 1556+3517
cannot yet be ruled out.

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The categories of this paper are: q-bio
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The categories of this paper are: bayes-an
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The categories of this paper are: nucl-ex
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The categories of this paper are: cs
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The categories of this paper are: cmp-lg
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The categories of this paper are: mtrl-th
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The categories of this paper are: quant-ph
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The categories of this paper are: dg-ga
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The categories of this paper are: hep-lat
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The categories of this paper are: solv-int
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The categories of this paper are: hep-th
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The categories of this paper are: plasm-ph
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The categories of this paper are: stat
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The categories of this paper are: hep-ex
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The categories of this paper are: nucl-th
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The categories of this paper are: atom-ph