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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
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:
FileName Lrecl Records Explanations
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
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
Bytes Format Units Label Explanations
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
Note (1): Notes as follows: a = Also BD-02 1323C b = Also 2E 0537.1-0243 c = Name from Wolk (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)
Byte-by-byte Description of file: table2.dat
Bytes Format Units Label Explanations
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
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).
Acknowledgements: Jose A. Caballero, caballero(at)
(End) Patricia Vannier [CDS] 08-Jan-2007
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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