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 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:
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FileName Lrecl Records Explanations
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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
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Byte-by-byte Description of file: table2
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Bytes Format Units Label Explanations
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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
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Byte-by-byte Description of file: table3
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Bytes Format Units Label Explanations
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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
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Byte-by-byte Description of file: table4
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Bytes Format Units Label Explanations
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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
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Acknowledgements: Thibaut Le Bertre
(End) Patricia Bauer [CDS] 26-Feb-1997