Query : 2011A&A...529A.115M

2011A&A...529A.115M - Astronomy and Astrophysics, volume 529A, 115-115 (2011/5-1)

AMBER observations of the AGB star RS Capricorni: extended atmosphere and comparison with stellar models.


Abstract (from CDS):

We report on K-band VLTI/AMBER observations at medium spectral resolution (∼1500) of RS Capricorni, an M6/M7III semi-regular AGB star. From the spectrally dispersed visibilities, we measure the star diameter as a function of observing wavelength from 2.13 to 2.47-microns. We derive a Rosseland angular diameter of 7.95±0.07mas, which corresponds to an effective temperature of 3160±160K. We detect size variations of around 10% in the CO band heads, which are indicative of strong opacity effects of CO in the stellar photosphere. We also detect a linear increase in the size as a function of wavelength, beginning at 2.29-microns. Models of the stellar atmosphere, based on the mass of the star estimated from stellar-evolution models, predict CO-size effects of about half the sizes observed, and cannot reproduce the linear size increase with wavelength, redward of 2.29-microns. We are able to model this linear size increase with the addition of an extended water-vapor envelope around the star. However, we are unable to fit the data in the CO bandheads. Either the mass of the star is overestimated by the stellar-evolution models and/or there is an additional extended CO envelope in the outer part of the atmosphere. In any case, neither the water-vapor envelope nor the CO envelope can be explained using the current models.

Abstract Copyright:

Journal keyword(s): techniques: interferometric - stars: atmospheres - stars: late-type - stars: invididual: RS Cap

Simbad objects: 4

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Number of rows : 4
N Identifier Otype ICRS (J2000)
ICRS (J2000)
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2024
1 V* S Ori Mi* 05 29 00.8923286472 -04 41 32.762469480   10.44 7.20     M6.5-7.5e 201 0
2 * 75 Leo PM* 11 17 17.4004699320 +02 00 38.001093758 8.54 6.70 5.18 3.91 2.97 M0III 112 0
3 * ome Cap V* 20 51 49.2905373888 -26 55 08.885443656 7.66 5.75 4.12 2.87 1.93 M0IIIBa0.5 100 0
4 V* RS Cap AB* 21 07 15.4311630672 -16 25 21.462156804   9.56 8.36     M6/7III 70 0

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