Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: New companions in the stellar systems of DI Cha, Sz 22, CHXR 32, and Cha
  Halpha 5 in the Cha I star-forming region   The star-forming regions in Chamaeleon (Cha) are among the nearest (distance
~165 pc) and youngest (age ~2 Myrs) conglomerates of recently formed stars and
among the ideal targets for studies of star formation. We search for new,
hitherto unknown binary or multiple-star components and investigate their
membership in Cha and their gravitationally bound nature. We used the NACO
instrument at the VLT UT 4/YEPUN of the Paranal Observatory, at 2 or 3
different epochs, in order to obtain relative and absolute astrometric
measurements, as well as differential photometry in the J, H, and Ks band. On
the basis of known proper motions and these observations, we analysed the
astrometric results in proper motion diagrams to eliminate possible
(non-moving) background stars and establish co-moving binaries and multiples.
DI Cha turns out to be a quadruple system with a hierachical structure,
consisting of two binaries: a G2/M6 pair and a co-moving pair of two M5.5
dwarfs. For both pairs we detected orbital motion (P~130 and ~65 years),
although in opposite directions. Sz 22 is a binary whose main component is
embedded in a circumstellar disc or reflection nebula, accompanied by a
co-moving M4.5 dwarf. CHXR 32 is a triple system, consisting of a single G5
star, weakened by an edge-on disc and a co-moving pair of M1/M3.5 dwarfs whose
components show significant variations in their angular separation. Finally,
Cha Halpha 5 is a binary consisting of two unresolved M6.5 dwarfs whose strong
variations in position angle at its projected separation of only 8 AU imply an
orbital period of ~46 years. DI Cha D and Cha Halpha 5 A&B are right at the
stellar mass limit and could possibly be brown dwarfs. In spite of various
previously published studies of the star-forming regions in Cha we found four
hitherto unknown components in young low-mass binaries and multiple systems.
(abridged)

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The categories of this paper are: q-alg
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The categories of this paper are: nucl-ex
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The categories of this paper are: hep-ph
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The categories of this paper are: econ
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The categories of this paper are: hep-lat
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The categories of this paper are: nlin
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The categories of this paper are: adap-org
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The categories of this paper are: eess
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The categories of this paper are: funct-an
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The categories of this paper are: solv-int
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The categories of this paper are: math
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The categories of this paper are: dg-ga
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The categories of this paper are: q-bio
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The categories of this paper are: alg-geom
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The categories of this paper are: q-fin
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The categories of this paper are: ao-sci