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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
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 R_c_ band error (1)
  44- 47  F4.2  mag     e_IcmagS   ? Shallow exposure I_c_ 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 R_c_ magnitude error (1)
  65- 68  F4.2  mag     e_IcmagD   ? Deep exposure I_c_ 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