J/ApJ/664/481 Optical/IR photometry of Collinder 69 (Barrado y Navascues+ 2007)
Spitzer: accretion in low-mass stars and brown dwarfs in the λ Orionis
cluster.
Barrado y Navascues D, Stauffer J.R., Morales-Calderon M., Bayo A.,
Fazzio G., Megeath T., Allen L., Hartmann L.W., Calvet N.
<Astrophys. J., 664, 481-500 (2007)>
=2007ApJ...664..481B 2007ApJ...664..481B
ADC_Keywords: Photometry ; Magnitudes ; Stars, pre-main sequence ; YSOs ;
Clusters, open
Keywords: open clusters and associations: individual (lambda Orionis) -
stars: low-mass, brown dwarfs - stars: pre-main sequence
Abstract:
We present multiwavelength optical and IR photometry of 170 previously
known low-mass stars and brown dwarfs of the 5Myr Collinder 69
cluster (λ Orionis). The new photometry supports cluster membership
for most of them, with less than 15% of the previous candidates
identified as probable nonmembers. The near-IR photometry allows us to
identify stars with IR excesses, and we find that the Class II
population is very large, around 25% for stars (in the spectral range
M0-M6.5) and 40% for brown dwarfs, down to 0.04M☉, despite the
fact that the Hα equivalent width is low for a significant fraction
of them. In addition, there are a number of substellar objects,
classified as Class III, that have optically thin disks. The Class II
members are distributed in an inhomogeneous way, lying preferentially
in a filament running toward the southeast. The IR excesses for the
Collinder 69 members range from pure Class II (flat or nearly flat
spectra longward of 1um), to transition disks with no near-IR excess
but excesses beginning within the IRAC wavelength range, to two stars
with excess only detected at 24um. Collinder 69 thus appears to be
at an age where it provides a natural laboratory for the study of
primordial disks and their dissipation.
Description:
The optical and the near-IR (NIR) data for the bright candidate
members come from Barrado y Navascues et al. (2004, Paper I, Cat.
J/ApJ/610/1064). The RI (Cousins system) data were collected with
the Canada-France-Hawaii Telescope (CFHT) in 1999, whereas the JHKs
data come from the Two Micron All Sky Survey (2MASS; Cutri et al.
2003, Cat. II/246). For the objects with large Error in 2MASS JHKs,
we have obtained additional measurements with the WHT (La Palma
Observatory, Spain) and INGRID (4.1'x4.1' FOV) in 2002 November and
2003 February and with the Calar Alto 3.5m telescope (Almeria, Spain)
and Omega2000 in 2005 October. Our Spitzer data were collected during
2004 March 15 (MIPS) and October 11 (IRAC).
Objects:
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RA (2000) DE Designation(s)
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05 35.2 +09 42 λ Ori cluster = Cl Collinder 69
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 48 61 *Additional Near-IR Photometry for the Candidate
Members of the λ Orionis Cluster
(WHT/INGRID, La Palma, 2002Nov and 2003Feb)
table3.dat 136 167 *Photometry for Candidate Members of the λ
Orionis Cluster (CAHA/Omega2000)
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Note on table1.dat and table3.dat: LOri 097 and LOri 145 are artifacts.
LOri 123 is a non-member and has uncertainties in its photometry.
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See also:
J/AJ/118/2409 : VRI photometry of λ Ori PMS stars (Dolan+, 1999)
J/AJ/121/2124 : λ Ori pre-main-sequence stars photometry (Dolan+, 2001)
J/AJ/123/387 : VRI phot. of λ Ori star-forming region (Dolan+, 2002)
J/ApJ/610/1064 : lambda Ori substellar population (Barrado y Navascues+, 2004)
J/A+A/488/167 : Low-mass stars in σ Ori and λ Ori (Sacco+, 2008)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- --- [LOri]
6- 8 I3 --- LOri Sequence number (lOri-CFHT NNN in Simbad)
10- 15 F6.3 mag Imag I band magnitude
17- 21 F5.2 mag Jmag WHT/INGRID J band magnitude
23- 26 F4.2 mag e_Jmag Error in J band magnitude
28- 32 F5.2 mag Hmag ?=- WHT/INGRID H band magnitude
34- 37 F4.2 mag e_Hmag ? Error in H band magnitude
39- 43 F5.2 mag Ksmag ?=- WHT/INGRID Ks band magnitude
45- 48 F4.2 mag e_Ksmag ? Error in Ks band magnitude
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- --- [LOri]
6- 8 I3 --- LOri Sequence number (lOri-CFHT NNN in Simbad)
10- 14 F5.2 mag Rcmag CFHT Cousins R band magnitude
16- 19 F4.2 mag e_Rcmag Error in Rc band magnitude
21- 25 F5.2 mag Icmag CFHT Cousins I band magnitude
27- 30 F4.2 mag e_Icmag Error in Ic band magnitude
32- 37 F6.3 mag Jmag ?=- 2MASS J band magnitude
39- 43 F5.3 mag e_Jmag ? Error in J band magnitude
45- 50 F6.3 mag Hmag ?=- 2MASS H band magnitude
52- 56 F5.3 mag e_Hmag ? Error on H band magnitude
58- 63 F6.3 mag Ksmag ?=- 2MASS Ks band magnitude
65- 69 F5.3 mag e_Ksmag ? Error on Ks band magnitude
71- 76 F6.3 mag 3.6mag ?=- Spitzer/IRAC 3.6micron band magnitude
78- 82 F5.3 mag e_3.6mag ? Error on 3.6micron band magnitude
84- 89 F6.3 mag 4.5mag ?=- Spitzer/IRAC 4.5micron band magnitude
91- 95 F5.3 mag e_4.5mag ? Error on 4.5micron band magnitude
97-102 F6.3 mag 5.8mag ?=- Spitzer/IRAC 5.8micron band magnitude
104-108 F5.3 mag e_5.8mag ? Error on 5.8micron band magnitude
110-115 F6.3 mag 8.0mag ?=- Spitzer/IRAC 8.0micron band magnitude
117-121 F5.3 mag e_8.0mag ? Error on 8.0micron band magnitude
123-127 F5.3 mag 24mag ?=- Spitzer/IRAC 24micron band magnitude
129-133 F5.3 mag e_24mag ? Error on 24micron band magnitude
135-136 A2 --- Mm [YN?] Final membership
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History:
From electronic version of the journal
(End) Emmanuelle Perret [CDS] 27-May-2009