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J/A+A/324/1059     C-rich stars IR and UBVRI photometry   (Le Bertre 1997)
Optical and infrared observations of 23 carbon-rich stars.
Modelling of the circumstellar dust shells
     Le Bertre T.
    <Astron. Astrophys. 324, 1059 (1997)>
    =1997A&A...324.1059L      (SIMBAD/NED BibCode)
ADC_Keywords: Stars, carbon ; Photometry, UBVRI ; Photometry, infrared

Keywords: Radiative transfer - stars: carbon - (stars:) circumstellar matter -
          stars: mass loss - stars: AGB and post-AGB - Infrared: stars

Abstract:
    A study of circumstellar dust shells (CDS) around carbon stars is
    presented. This study is based on the analysis of the 1-100µm
    broad-band spectra of 23 objects which have been monitored in the
    1-20µm region over several years at ESO. The sources in the sample
    range from Irr/SR variables and optical Miras to Extreme Carbon Stars
    which have only been discovered recently in infrared surveys. A
    modelling accounting for the photometric variations with phase (with
    up to 9 spectra per object) has been developed. All the CDSs in the
    sample can be modelled successfully in spherical geometry with a dust
    opacity law ∝λ-1.3 and a dust formation temperature
    ∼950K. The modelling favors the case of an acceleration of dust, from
    the site of formation and on a distance of ∼1015cm, over the case of
    a uniform expansion. Mass loss rates in the range
    0.1-50x10-6M☉/yr are derived. The estimates based on this
    modelling are consistent with those derived from the CO emission line
    measurements. In view of the incoming near-infrared surveys
    (DENIS and 2MASS), an analysis of the location of carbon-rich sources
    in color diagrams is presented. It is shown that the near-infrared
    colors are well correlated with the mass loss rate. This property can
    be used to get an estimate, within a factor 3, of this rate for carbon
    stars without a priori on the distance.

File Summary:

       FileName      Lrecl  Records   Explanations

ReadMe            80        .   This file
table2            54       79   10-20 microns photometric data
table3            48       23   UBVRI photometric data
table4            94       86   Model parameters
tables.tex        76      320   LaTeX version of the tables


Byte-by-byte Description of file: table2

   Bytes Format Units   Label     Explanations

   1- 15  A15   ---     Name      Star name
  17- 23  I7    d       JD        Julian date
  25- 29  F5.2  mag     Nmag      ? N (10.36 microns) magnitude
  31- 35  F5.2  mag     N1mag     N1 (8.38 microns) magnitude
  37- 41  F5.2  mag     N2mag     N2 (9.69 microns) magnitude
  43- 47  F5.2  mag     N3mag     N3 (12.89 microns) magnitude
      48  A1    ---     u_N3mag   [)] Uncertainty flag on N3mag
  50- 54  F5.2  mag     Q0mag     ? Q0 (18.06 microns) magnitude


Byte-by-byte Description of file: table3

   Bytes Format Units   Label     Explanations

   1- 10  A10   ---     Name      Star name
  12- 18  I7    d       JD        Julian date
  20- 24  F5.2  mag     Umag      ? U magnitude
  26- 30  F5.2  mag     Bmag      ? B magnitude
  32- 36  F5.2  mag     Vmag      ? V magnitude
  38- 42  F5.2  mag     Rmag      ? R magnitude
  44- 48  F5.2  mag     Imag      ? I magnitude


Byte-by-byte Description of file: table4

   Bytes Format Units    Label     Explanations

   1- 15  A15   ---      Name      Usual name
  17- 23  I7    d        JD        Julian Date
  25- 28  F4.2  ---      Phase     ? [0-1[ Phase
  30- 34  F5.2  ---      Tau1um    Optical depth at 1 micron
  36- 40  F5.3  mpc      Rc        Inner radius of the dust shell
  42- 46  F5.2 100solLum L*        Bolometric luminosity
  48- 50  I3    K        Tc        Grain temperature at the inner radius
  52- 57  F6.4  mpc     Tau1um*Rc  Product of the optical depth with the
                                    inner radius


Acknowledgements: Thibaut Le Bertre 

(End)                                         Patricia Bauer [CDS]   26-Feb-1997