Astronomy and Astrophysics – Astronomy
Scientific paper
Aug 2001
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2001arep...45..631s&link_type=abstract
Astronomy Reports, Volume 45, Issue 8, August 2001, pp.631-642
Astronomy and Astrophysics
Astronomy
3
Scientific paper
We have studied the structural evolution of the dust envelope of V4334 Sgr, starting with the onset of its condensation in 1997. A model with complete cloud cover, with the optical depth growing until the end of 1999, gives the best fit to the photometric data in the optical and IR. The inner radius of the dust layer remained virtually constant, whereas its thickness increased due to expansion. The deep minimum in the visual light curve of V4334 Sgr in October 1998 is attributed to the arrival at the dust-grain condensation zone of a density discontinuity in the circumstellar envelope. The discontinuity was probably formed early in 1997 due to an increase in the mass-loss rate by a factor of about four, possibly associated with an increase in the luminosity of V4334 Sgr during its transformation into a carbon star. After this luminosity increase, the mass-loss rate was . In the summer of 1999, the mass of the dust envelope was . In the complete-cloud-cover model, the envelope consists of graphite grains with a gr=0.05 µm, to ˜85% per cent in terms of the number of grains. The remaining ˜15 per cent of the grains have sizes a gr=0.1 and 0.25 µm. To reproduce the small hump in the spectral energy distribution of V4334 Sgr near 11 µm, some silicon carbide grains must be added to the graphite mixture. Their contribution to the V optical depth is ≤4%. The first deep minimum in the visual light curve could also be reproduced using a model in which the dust cloud has condensed along the line of sight, but a detailed analysis of the resulting characteristics of the cloud and envelope indicates that this model is improbable.
Shenavrin V. I.
Yudin Boris F.
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