J/ApJ/610/1064 Substellar population of lambda Ori (Barrado y Navascues+, 2004)
The substellar population of the young cluster λ Orionis.
Barrado Y Navascues D., Stauffer J.R., Bouvier J., Jayawardhana R.,
Cuillandre J.-C.
<Astrophys. J., 610, 1064-1078 (2004)>
=2004ApJ...610.1064B 2004ApJ...610.1064B
ADC_Keywords: Clusters, open ; Stars, pre-main sequence ; Photometry, Cousins ;
Photometry, infrared ; Spectroscopy
Keywords: open clusters and associations: individual (λ Orionis) -
stars: low-mass, brown dwarfs - stars: pre-main-sequence
Abstract:
By collecting optical and infrared photometry and low-resolution
spectroscopy, we have identified a large number of low-mass stars and
brown dwarf candidates belonging to the young cluster (∼5Myr)
associated with the binary star λ Orionis. The lowest mass
object found is an M8.5 with an estimated mass of 0.02M☉
(∼0.01M☉ for objects without spectroscopic confirmation). For
those objects with spectroscopy, the measured strength of the Hα
emission line follows a distribution similar to other clusters with
the same age range, with larger equivalent widths for cooler spectral
types.
Description:
On 1999 September 29 and 30, we conducted an optical photometric
survey around the star λ Orionis, using the
Canada-France-Hawaii Telescope (CFHT) 12k mosaic camera and the
Cousins R and I filters. We have collected low-resolution optical
spectroscopy in two different campaigns. The first one took place on
2002 November 35 at the Keck I telescope. For the second run, we used
the B&C spectrograph attached to the Magellan II telescope on 2003
March 9-11.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 69 170 Positions and optical photometric data for our
λ Orionis candidate members
table2.dat 90 146 Positions and IR photometry from 2MASS for our
λ Orionis candidate members
table3.dat 30 33 Spectroscopic data
--------------------------------------------------------------------------------
See also:
II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)
J/AJ/118/2409 : λ Ori PMS stars VRI photometry (Dolan+, 1999)
J/AJ/123/387 : λ Ori star-forming region VRI photometry (Dolan+, 2002)
J/AJ/121/2124 : λ Ori pre-main-sequence stars photometry (Dolan+, 2001)
J/A+A/357/1001 : λ-Orionis ring in CO (Lang+ 2000)
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 I3 --- LOri-CFHT λ Ori candidate number
5 I1 h RAh Hour of Right Ascension (J2000)
7- 8 I2 min RAm Minute of Right Ascension (J2000)
10- 14 F5.2 s RAs Second of Right Ascension (J2000)
15 A1 --- DE- Sign of Declination (J2000)
16- 17 I2 deg DEd Degree of Declination (J2000)
19- 20 I2 arcmin DEm Arcminute of Declination (J2000)
22- 26 F5.2 arcsec DEs Arcsecond of Declination (J2000)
28- 32 F5.2 mag IcmagS ? Shallow exposure Ic band magnitude
34- 37 F4.2 mag (Rc-Ic)S ? Shallow exposure Rc-Ic color index
39- 42 F4.2 mag e_RcmagS ? Shallow exposure Rc band error (1)
44- 47 F4.2 mag e_IcmagS ? Shallow exposure Ic band error (1)
49- 53 F5.2 mag IcmagD ? Deep exposure Ic band magnitude
55- 58 F4.2 mag (Rc-Ic)D ? Deep exposure Rc-Ic color index
60- 63 F4.2 mag e_RcmagD ? Deep exposure Rc magnitude error (1)
65- 68 F4.2 mag e_IcmagD ? Deep exposure Ic magnitude error (1)
--------------------------------------------------------------------------------
Note (1): Internal error as computed with IRAF. For other sources of
photometric errors, see the text.
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 I3 --- LOri-CFHT λ Ori candidate number
5- 9 F5.2 mag Icmag The Ic band magnitude
11- 14 F4.2 arcsec Dist Optical/IR source to 2MASS coordinate distance
16- 17 I2 h RAh 2MASS Hour of Right Ascension (J2000)
19- 20 I2 min RAm 2MASS Minute of Right Ascension (J2000)
22- 26 F5.2 s RAs 2MASS Second of Right Ascension (J2000)
28 A1 --- DE- 2MASS Sign of the Declination (J2000)
29- 30 I2 deg DEd 2MASS Degree of Declination (J2000)
32- 33 I2 arcmin DEm 2MASS Arcminute of Declination (J2000)
35- 38 F4.1 arcsec DEs 2MASS Arcsecond of Declination (J2000)
40- 45 F6.3 mag Jmag The J band magnitude
47- 51 F5.3 mag e_Jmag ? Uncertainty in Jmag
53- 58 F6.3 mag Hmag The H band magnitude
60- 64 F5.3 mag e_Hmag ? Uncertainty in Hmag
66- 71 F6.3 mag Kmag The K band magnitude
73- 77 F5.3 mag e_Kmag ? Uncertainty in Kmag
79 A1 --- M1 (K,J-K) membership selection criteria (1)
80 A1 --- M2 (Ic,I-K) membership selection criteria (1)
81 A1 --- M3 (Ic-J,H-K) membership selection criteria (1)
82 A1 --- M4 (Ic-J,I-K) membership selection criteria (1)
83 A1 --- M5 (J-H,H-K) membership selection criteria (1)
84 A1 --- M6 Spectral type membership selection criteria (1)
86- 89 A4 --- MCode Final membership assessment (G1)
--------------------------------------------------------------------------------
Note (1): The membership selection criteria is defined as:
Y = Yes;
N = No;
- = not available
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 I3 --- LOri-CFHT Source designation
6- 9 A4 --- SpType MK Spectral type
11 A1 --- f_SpType [a] Flag on SpType (1)
14- 18 F5.1 0.1nm W(Ha) ? Hα line width
21- 24 F4.1 0.1nm e_W(Ha) ? Uncertainty in W(Ha)
27- 30 A4 --- Mem Membership assessment (G1)
--------------------------------------------------------------------------------
Note (1): "a" indicates that, because of low S/N, the uncertainty in the
spectral type classification is one subclass, compared with half
for the rest of the sample.
--------------------------------------------------------------------------------
Global Notes:
Note (G1): The membership assessment is defined as follows:
Mem+ = Both spectral type and photometric data in agreement with cluster
sequence. Probable members.
NM? = The estimated spectral type does not agree with the photometry, but
all CMD and CCD indicate membership. We also have included here
LOri-CFHT-119, with photometry in disagreement with membership and
whose spectral type does not indicate clearly its status.
NM+ = Both spectral type and photometric data in disagreement with
cluster sequence. Probable non-members.
Mem = All CMD and CCD indicate membership. Probable members.
Mem? = One or two CMD or CCD in disagreement with the cluster sequence. In
few cases, the spectral type is in agreement with membership.
Possible members.
NM- = At least a CMD and another CMD or CCD in disagreement with the
membership. Possible non-member.
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Marianne Brouty [CDS] 08-Jun-2005