J/AJ/134/252         New nearby white dwarf systems          (Subasavage+, 2007)
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The solar neighborhood.
XIX. Discovery and characterization of 33 new nearby white dwarf systems.
    Subasavage J.P., Henry T.J., Bergeron P., Dufour P., Hambly N.C.,
    Beaulieu T.D.
   <Astron. J., 134, 252-261 (2007)>
   =2007AJ....134..252S
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ADC_Keywords: Stars, nearby ; Stars, white dwarf ; Photometry, infrared ;
              Effective temperatures
Keywords: solar neighborhood - stars: distances - stars: evolution -
          stars: statistics - white dwarfs

Abstract:
    We present spectra for 33 previously unclassified white dwarf systems
    brighter than V=17, primarily in the southern hemisphere. Of these
    new systems, 26 are DA, 4 are DC, 2 are DZ, and 1 is DQ. We suspect
    that three of these systems are unresolved double degenerates. We
    obtained VRI photometry for these 33 objects, as well as for 23 known
    white dwarf systems without trigonometric parallaxes, also primarily
    in the southern hemisphere. For the 56 objects, we converted the
    photometry values to fluxes and fit them to a spectral energy
    distribution using the spectroscopy to determine which model to use
    (i.e., pure hydrogen, pure helium, or metal-rich helium), resulting in
    estimates of Teff and distance.

Description:
    Spectroscopic observations were taken on five separate observing runs
    in 2003 October and December, 2004 March and September, and 2006 May
    at the Cerro Tololo Inter-American Observatory (CTIO) 1.5m telescope
    as part of the Small and Moderate Aperture Research Telescope System
    (SMARTS) Consortium.

File Summary:
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 FileName   Lrecl  Records   Explanations
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ReadMe         80        .   This file
table1.dat    106       57   Optical and infrared photometry and derived
                              parameters for new and known white dwarfs
table3.dat     86       57   Astrometry and alternate designations for new
                              and known white dwarfs
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See also:
 J/AJ/129/413  : New high proper motion stars (-90<DE<-47) (Subasavage+, 2005)
 J/AJ/130/1658 : New high proper motion stars (-47<DE<-00) (Subasavage+, 2005)
 J/AJ/133/2898 : New proper-motion stars (-90<DE<-47) (Finch+, 2007)

Byte-by-byte Description of file: table1.dat
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   Bytes Format Units   Label     Explanations
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       1  I1    ---   n_WD        [1/3] New or nearby WD (G1)
   3- 11  A9    ---     WD        WD Name  (HHMM+DDdA)
  14- 18  F5.2  mag     Vmag      Johnson V magnitude
  20- 24  F5.2  mag     Rcmag     Cousins R magnitude
  26- 30  F5.2  mag     Icmag     Cousins I magnitude
      32  I1    ---     Nobs      Number of observations
  34- 38  F5.2  mag     Jmag      J magnitude
  40- 43  F4.2  mag   e_Jmag      rms uncertainty on Jmag
  45- 49  F5.2  mag     Hmag      H magnitude
  51- 54  F4.2  mag   e_Hmag      ? rms uncertainty on Hmag
  56- 60  F5.2  mag     Ksmag     Ks magnitude
  62- 65  F4.2  mag   e_Ksmag     ? rms uncertainty on Ksmag
  67- 71  I5    K       Teff      ? Effective temperature
  73- 76  I4    K     e_Teff      ? rms uncertainty on Teff
  78- 85  A8    ---     Comp      Composition (main chemical elements)
  87- 90  F4.1  pc      Dist      ? Distance
  92- 95  F4.1  pc    e_Dist      ? rms uncertainty on Dist
  97-102  A6    ---     SpType    MK Spectral type
 105-106  I2    ---     Rem       [1/12]? Individual notes (1)
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Note (1): Individual notes as follows:
      1 = Distance via SED fit (not listed) is underestimated because the
          object is likely an unresolved double degenerate with one
          magnetic component (see Sect. 4.2). Instead, we adopt the
          trigonometric parallax distance of 17.7+/-0.7pc derived via CTIOPI.
      2 = Distance via SED fit (not listed) is underestimated because the
          object is likely a distant (well beyond 25pc) unresolved double
          degenerate (see Sect. 4.2).
      3 = Distance via SED fit (not listed) is underestimated because the
          object is likely a distant (well beyond 25pc) unresolved double
          degenerate with components of type DA and DB (see Sect. 4.2).
          Temperatures derived from the spectroscopic fit yield
          9640+/-303 and 14170+/-1228K for DA and DB, respectively.
      4 = Object is likely cooler than Teff~5000K, and the theoretical
          models do not provide an accurate treatment at these
          temperatures (see Sect. 4.2). Instead, we use the linear
          photometric distance relation of Salim et al.
          (2004ApJ...601.1075S) and obtain a distance estimate of
          19.3+/-3.9pc.
      5 = This object was observed as part of the EC survey and was
          classified as an sdB+ (Kilkenny et al. 1997, Cat. J/MNRAS/287/867).
      6 = Distance of 19.1+/-3.0pc is estimated using VRIJHKS for the
          common proper-motion companion M dwarf and the relations of
          Henry et al. (2004AJ....128.2460H). System is possibly within
          25pc (see Sect. 4.2).
      7 = Distance estimate is undetermined. Instead, we adopt the
          distance measured via trigonometric parallax of 17.1+/-0.4pc
          (see Sect. 4.2).
      8 = Not listed in McCook & Sion (1999ApJS..121....1M, III/210,
          III/235) but identified as a DC/DQ WD by Henry et al.
          (2002AJ....123.2002H). We obtained blue spectra that show Ca II
          H and K absorption and classify this object as DZ.
      9 = The SED fit to the photometry is marginal. This object displays
          deep swan-band absorption that significantly affects its
          measured magnitudes.
     10 = Not listed in McCook & Sion (1999ApJS..121....1M, III/210,
          III/235) but identified as a WD by Luyten (1949ApJ...109..528L).
          Spectral type is derived from our spectra.
     11 = As of mid-2004, object has moved onto a background source.
          Photometry is probably contaminated, which is consistent with
          the poor SED fit for this object.
     12 = Spectral type was determined using spectra published by Scholz
          et al. (2002ApJ...565..539S).
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Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
   Bytes Format Units    Label     Explanations
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       1  I1    ---    n_WD        [1/3] New or nearby WD (G1)
   3- 11  A9    ---      WD        WD Name (HHMM+DDdA)
  13- 14  I2    h        RAh       Right ascension (J2000)
  16- 17  I2    min      RAm       Right ascension (J2000)
  19- 23  F5.2  s        RAs       Right ascension (J2000)
      25  A1    ---      DE-       Declination sign (J2000)
  26- 27  I2    deg      DEd       Declination (J2000)
  29- 30  I2    arcmin   DEm       Declination (J2000)
  32- 35  F4.1  arcsec   DEs       Declination (J2000)
  37- 41  F5.3 arcsec/yr pm        Total proper motion
  43- 47  F5.1  deg      pmPA      Proper motion position angle
      49  I1    ---    r_pm        Reference for proper motion (2)
  51- 86  A36   ---      ONames    Alternative name(s)
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Note (2): References as follows:
      1 = Luyten 1979, LHS Catalogue (I/87), NLTT Catalogue (I/98)
      2 = Subasavage et al., 2005, Cat. J/AJ/129/413, J/AJ/130/1658, this work
      3 = Pokorny et al., 2004, Cat. J/A+A/421/763
      4 = Lepine et al., 2003AJ....126..921L, 2005ApJ...633L.121L
      5 = Oppenheimer et al., 2001, Cat. J/other/Sci/292/698
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Global notes:
Note (G1): Types as follows:
     1 = New spectroscopically confirmed WDs
     2 = Known WDs without a trigonometric parallax estimated to be within 25pc
     3 = Known WDs without a trigonometric parallax estimated to be beyond 25pc
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History:
    From electronic version of the journal

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(End)                                      Patricia Vannier [CDS]    25-Aug-2009