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J/AJ/133/971  Wide companions of low-mass stars and brown dwarfs  (Allen+, 2007)
A new brown dwarf desert? A scarcity of wide ultracool binaries.
    Allen P.R., Koerner D.W., McElwain M.W., Cruz K.L., Reid I.N.
   <Astron. J., 133, 971-978 (2007)>
   =2007AJ....133..971A
ADC_Keywords: Stars, double and multiple ; Stars, dwarfs

Keywords: binaries: general - stars: low-mass, brown dwarfs


Abstract:
    We present the results of a deep-imaging search for wide companions to
    low-mass stars and brown dwarfs using NSFCam on the Infrared Telescope
    Facility. We searched a sample of 132 M7-L8 dwarfs to magnitude
    limits of J∼20.5 and K∼18.5, corresponding to secondary-to-primary
    mass ratios of ∼0.5. No companions were found with separations between
    2" and 31" (∼40 to ∼1000AU). This null result implies a wide
    companion frequency below 2.3% at the 95% confidence level within the
    sensitivity limits of the survey. Preliminary modeling efforts
    indicate that we could have detected 85% of companions more massive
    than 0.05M☉ and 50% above 0.03M☉.

Description:
    We observed all 132 targets using NSFCam on NASA's Infrared Telescope
    Facility (IRTF). The initial observations were obtained over four
    epochs, 2000 August, 2001 May, 2001 October, and 2002 February.

File Summary:

       FileName      Lrecl  Records   Explanations

ReadMe            80        .   This file
table1.dat        89      132   IRTF and WIYN Observations
table2.dat        72       36   Color-Selected Candidate Companions


See also:
  J/ApJ/476/311 : 2MASS M-dwarf discoveries (Kirkpatrick+ 1997)
  J/AJ/123/3409 : SDSS M, L, and T dwarfs (Hawley+, 2002)
  J/AJ/126/2421 : 2MASS-Selected sample of ultracool dwarfs (Cruz+, 2003)


Byte-by-byte Description of file: table1.dat

   Bytes Format Units   Label     Explanations

   1-  9  A9    ---     Name      Object name
  11- 15  F5.2  mag     Jmag      The IRTF J band magnitude
  17- 20  F4.2  mag     e_Jmag    Uncertainty in Jmag
  22- 26  F5.2  mag     Ksmag     The IRTF Ks band magnitude
  28- 31  F4.2  mag     e_Ksmag   Uncertainty in Kmag
  33- 36  A4    ---     SpType    Spectral type
  38- 41  F4.1  pc      Dist      Distance
      43  A1    ---     f_Dist    Flag on Dist (1)
  45- 49  F5.2  mag     Jlim      The J band limit
  51- 55  F5.2  mag     Klim      The K band limit
  57- 84  A28   ---     Obs       The IRTF observation date(s)
  86- 87  I2    ---     Ref       Reference(s) (2)
      89  A1    ---     Note      [*] Individual note (3)

Note (1): Derived from trigonometric parallaxes in Dahn et al.
          (2002AJ....124.1170D).
Note (2): References as follows:
      1 = Gizis et al. (2000AJ....120.1085G)
      2 = Kirkpatrick et al. (1999ApJ...519..802K)
      3 = Kirkpatrick et al. (2000AJ....120..447K)
      4 = Cruz et al. (2003, Cat. J/AJ/126/2421)
      5 = Kirkpatrick et al. (1997, Cat. J/ApJ/476/311)
      6 = Dahn et al. (2002AJ....124.1170D)
      7 = Delfosse et al. (1999A&AS..135...41D)
      8 = Martin et al. (1999AJ....118.2466M)
      9 = Fan et al. (2000AJ....119..928F)
     10 = Hawley et al. (2002, Cat. J/AJ/123/3409)
Note (3): For 2M2054+15, Ksmag=15.58 was corrected into Ksmag=14.82 as in
     Kirkpatrick et al., 2000AJ....120..447K


Byte-by-byte Description of file: table2.dat

   Bytes Format Units   Label     Explanations

   1-  9  A9    ---     Name      Object name
  12- 15  A4    ---     SpType    Primary spectral type
  17- 20  F4.1  mag     JMAG      Secondary absolute magnitude
  22- 25  F4.1  mag     J-K       Secondary J-K colour index
  27- 30  F4.1  pc      Dist      Distance
  32- 36  F5.1  arcsec  DRA       Offset in RA from the primary
  38- 42  F5.1  arcsec  DDE       Offset in DE from the primary
  44- 72  A29   ---     Notes     Notes (1)

Note (1): Notes as follows:
     SDSS = Object is in SDSS DR5 field.
    WIYNa = Field observed with WIYN in 2002 August.
    WIYNf = Field observed with WIYN in 2003 February.
            All objects detected in either SDSS or with WIYN imaging have
            colors that are too blue to be consistent with an ultracool dwarf.
        * = Candidates that still require follow-up observations to
            determine their nature.


History:
    From electronic version of the journal
(End)                  Greg Schwarz [AAS], Patricia Vannier [CDS]    09-Jan-2009