J/A+A/466/917 Brightest stars of sigma Orionis cluster (Caballero+, 2007)
The brightest stars of the sigma Orionis cluster.
Caballero J.A.
<Astron. Astrophys. 466, 917 (2007)>
=2007A&A...466..917C 2007A&A...466..917C
ADC_Keywords: Clusters, open ; Stars, bright ; Photometry, infrared ;
Proper motions
Keywords: open clusters and associations: individual: sigma Orionis -
stars: general - planetary systems: protoplanetary discs -
astronomical data bases: miscellaneous
Abstract:
The very young sigma Orionis cluster (about 3Ma) is a cornerstone for
the understanding of the formation of stars and substellar objects
down to planetary masses. However, its stellar population is far to be
completely known.
This study has the purpose of identifying and characterising the most
massive stars of sigma Orionis to complement current and future deep
searches for brown dwarfs and planetary-mass objects in the cluster.
I have cross-correlated the sources in the Tycho and 2MASS catalogues
in a region of 30arcmin radius with centre in the O-type star
sigma Ori A.
In the area, I have studied the membership in the Ori OB 1b
Association of the brightest stars in the optical using astrometric,
X-ray and infrared and optical photometric data from public catalogues
and spectroscopic data from the literature.
A list of 26 young stars, four candidate young stars and 16 probable
foreground stars has arised from the study. Seven young stars probably
harbour discs (four are new). There is no mass-dependence of the disc
frequency in the cluster. I have derived for the first time the mass
spectrum in sigma Orionis from 1.1 to 24M☉
(alpha=+2.0+0.2-0.1; roughly Salpeter-like). I have also provided
additional proofs on the existence of several spatially superimposed
stellar populations in the direction of sigma Orionis. Finally, the
cluster may be closer and older than previously considered.
Description:
Table A1 provides the photometric data for the 41 stars in the
Tycho-2/2MASS correlation and the five missing stars in the
Tycho-2/2MASS correlation, ordered by VT-band magnitude. It is given
the name of each star (if not available, then the Tycho identification
is provided), the BT- and VT-band magnitudes from the Tycho-2
catalogue and the J-, H- and Ks-band magnitudes from the 2MASS
catalogue.
Table A2 provides the astrometric data and the spectral types in the
same manner as in Table A1. It is given the name of each star, Tycho
identification, right ascension and declination from the Tycho-2
catalogue (FK5, Equinox=J2000.0, Epoch=J2000.000, proper motions taken
into account), proper motions in right ascension and in declination
from the Tycho-2 catalogue and spectral types from the literature.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 86 46 Optical and near-infrared photometry of all stars
table2.dat 103 46 Astrometry, spectral type and radial velocity
(when available) of all the stars
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See also:
I/239 : The Hipparcos and Tycho Catalogues (ESA 1997)
I/259 : The Tycho-2 Catalogue (Hog+ 2000)
II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)
I/297 : NOMAD Catalog (Zacharias+ 2005)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 20 A20 --- Name Name
21 A1 --- n_Name [a-e] Individual notes (1)
23- 28 F6.3 mag BTmag Tycho-2 BT magnitude
30- 34 F5.3 mag e_BTmag Error in Tycho-2 BT magnitude
36- 41 F6.3 mag VTmag Tycho-2 VT magnitude
43- 47 F5.3 mag e_VTmag Error in Tycho-2 VT magnitude
49- 54 F6.3 mag Jmag 2MASS J magnitude
56- 60 F5.3 mag e_Jmag Error in 2MASS J magnitude
62- 67 F6.3 mag Hmag 2MASS H magnitude
69- 73 F5.3 mag e_Hmag Error in 2MASS H magnitude
75- 80 F6.3 mag Ksmag 2MASS Ks magnitude
82- 86 F5.3 mag e_Ksmag Error in 2MASS Ks magnitude
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Note (1): Notes as follows:
a = Also BD-02 1323C
b = Also 2E 0537.1-0243
c = Name from Wolk (1996AJ....111.2066W 1996AJ....111.2066W). Also SO210457
d = Name from Caballero (2006, Ph.D. Thesis, Universidad de La Laguna)
e = Johnson B- and V-band photometry from
Greenstein & Wallerstein (1958ApJ...127..237G 1958ApJ...127..237G)
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 20 A20 --- Name Name
21 A1 --- r_Name [a-c] note on the origin of astrometry (1)
23- 33 A11 --- TYC Identification in Tycho-2 Catalogue (I/259)
35- 36 I2 h RAh Right ascension (J2000)
38- 39 I2 min RAm Right ascension (J2000)
41- 46 F6.3 s RAs Right ascension (J2000)
48 A1 --- DE- Declination sign
49- 50 I2 deg DEd Declination (J2000)
52- 53 I2 arcmin DEm Declination (J2000)
55- 59 F5.2 arcsec DEs Declination (J2000)
61- 66 F6.2 mas/yr pmRA Proper motion in right ascension
68- 71 F4.2 mas/yr e_pmRA Error in proper motion in right ascension
73- 78 F6.2 mas/yr pmDE Proper motion in declination
80- 83 F4.2 mas/yr e_pmDE Error in proper motion in declination
85- 93 A9 --- SpType MK spectral type
95- 99 F5.1 km/s HRV ? Heliocentric radial velocity
101-103 F3.1 km/s e_HRV ? Error in heliocentric radial velocity
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Note (1): Notes as follows:
a = Proper motions from Perryman et al. (1997, HIP, Cat. I/239).
The spectral types of the components of the triple system
are O9.5V, B0.5V and K:
b = Proper motions from Hog et al. (1998, Tycho, Cat. I/239).
c = Coordinates from the 2MASS catalogue (Cat. II/246) and proper
motion from the NOMAD1 catalogue (Cat. I/297).
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Acknowledgements:
Jose A. Caballero, caballero(at)mpia.de
(End) Patricia Vannier [CDS] 08-Jan-2007