2001A&A...379..925K


C.D.S. - SIMBAD4 rel 1.7 - 2020.10.24CEST00:35:54

2001A&A...379..925K - Astronomy and Astrophysics, volume 379, 925-935 (2001/12-1)

The warm circumstellar envelope and wind of the G9 IIb star HR 6902.

KIRSCH T., BAADE R. and REIMERS D.

Abstract (from CDS):

IUE observations of the eclipsing binary system HR 6902 obtained at various epochs spread over four years indicate the presence of warm circumstellar material enveloping the G9 IIb primary. The spectra show SiIV and CIV absorption up to a distance of 3.3 giant radii (Rg). Line ratio diagnostics yields an electron temperature of ∼78000K which appears to be constant over the observed height range. Applying a least square fit absorption line analysis we derive column densities as a function of height. We find that the inner envelope (<3Rg) of the bright giant is consistent with a hydrostatic density distribution. The derived line broadening velocity of ∼70km/s is sufficient to provide turbulent pressure support for the required scale height. However, an improved agreement with observations over the whole height regime including the emission line region is obtained with an outflow model. We demonstrate that the common β power-law as well as a P ∝ρ wind yield appropriate fit models. Adopting a continuous mass outflow we obtain a mass-loss rate of {dot}(M)=0.8-3.4x10–11M/yr depending on the particular wind model. The emission lines observed during total eclipse are attributed mostly to resonance scattering of B star photons in the extended envelope of the giant. By means of a multi-dimensional line formation study we show that the global envelope properties are consistent with the wind models derived from the absorption line analysis. We argue that future high resolution UV spectroscopy will resolve the large-scale velocity structure of the circumstellar shell. As an illustration we present theoretical SiIV and CIV emission profiles showing model-dependent line shifts and asymmetries.

Abstract Copyright:

Journal keyword(s): binaries: eclipsing - binaries: spectroscopic - mass loss - stars: individual: HR 6902 - ultraviolet: stars

Simbad objects: 7

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Number of rows : 7

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2020
#notes
1 * iot Aur V* 04 56 59.6210887 +33 09 57.958479 6.00 4.22 2.69 1.63 0.81 K3II-III 264 0
2 * alf TrA * 16 48 39.89508 -69 01 39.7626   3.36 1.92     K2III_Ba1 229 0
3 * tet Her V* 17 56 15.1805442 +37 15 01.934351 6.70 5.23 3.88 2.98 2.38 K1IIaCN2 207 0
4 HD 169689 Al* 18 25 38.7987210726 +08 01 55.231059632   6.545 5.665     G9II+B9V 99 0
5 * gam Aql * 19 46 15.5802908 +10 36 47.740788 5.93 4.23 2.72 1.65 0.87 K3II 420 0
6 * bet Aqr * 21 31 33.5317148 -05 34 16.232006 4.27 3.71 2.89 2.29 1.84 G0Ib 433 0
7 * alf Aqr * 22 05 47.0359315 -00 19 11.456766 4.65 3.90 2.94 2.27 1.76 G2Ib 423 0

    Equat.    Gal    SGal    Ecl

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2020.10.24-00:35:54

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