Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: HD 77407 and GJ 577: two new young stellar binaries detected with the
  Calar Alto Adaptive Optics system ALFA   We present the first results from our search for close stellar and
sub-stellar companions to young nearby stars on the northern sky. Our infrared
imaging observations are obtained with the 3.5 m Calar Alto telescope and the
AO system ALFA. With two epoch observations which were separated by about one
year, we found two co-moving companion candidates, one close to HD 77407 and
one close to GJ 577. For the companion candidate near GJ 577, we obtained an
optical spectrum showing spectral type M4.5; this candidate is a bound low-mass
stellar companion confirmed by both proper motion and spectroscopy. We estimate
the masses for HD 77407 B and GJ 577 B to be ~0.3 to 0.5 Msun and ~0.16 to 0.2
Msun, respectively. Compared to Siess al.(2000) models, each of the two pairs
appears co-eval with HD 77407 A,B being 10 to 40 Myrs old and GJ 577 A,B being
older than 100 Myrs. We also took multi-epoch high-resolution spectra of HD
77407 to search for sub-stellar companions, but did not find any with 3 Mjup as
upper mass (msin(i)) limit (for up to 4 year orbits); however, we detected a
long-term radial velocity trend in HD 77407 A, consistent with a ~ 0.3 Msun
companion at ~ 50 AU separation, i.e. the one detected by the imaging. Hence,
HD 77407 B is confirmed to be a bound companion to HD 77407 A. We also present
limits for undetected, but detectable companions using a deep image of HD 77407
A and B, also observed with the Keck NIRC2 AO system; any brown dwarfs were
detectable outside of 0.5 arcsec (17 AU at HD 77407), giant planets with masses
from ~ 6.5 to 12 Mjup were detectable at > 1.5 arcsec.

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The categories of this paper are: chao-dyn
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The categories of this paper are: patt-sol
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The categories of this paper are: gr-qc
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The categories of this paper are: physics
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The categories of this paper are: comp-gas
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The categories of this paper are: funct-an
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The categories of this paper are: supr-con
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The categories of this paper are: plasm-ph
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The categories of this paper are: q-alg
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The categories of this paper are: adap-org
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The categories of this paper are: q-fin
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The categories of this paper are: cs
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The categories of this paper are: q-bio
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The categories of this paper are: cmp-lg
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The categories of this paper are: dg-ga
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The categories of this paper are: hep-ex