研究目的
Investigating the physical parameters of the outer atmosphere of a sample of eight evolved stars by spatially resolving the stars in the individual carbon monoxide (CO) first overtone lines.
研究成果
The study successfully determined the physical parameters of the outer atmosphere of a sample of eight evolved stars by spatially resolving the stars in the individual carbon monoxide (CO) first overtone lines. The results suggest the existence of some heating mechanism in the outer atmosphere of AGBs, RGBs and RSGs. The study advocates for a large survey of these stars, at different wavelengths and using a richer (u, v)-coverage, for different ranges of temperatures and luminosities to better understand the mass-loss mechanism of the large family of evolved stars.
研究不足
The technical and application constraints of the experiments include the sparse (u, v) coverage which limits the ability to determine the position or the number of spots on the MOLsphere. Potential areas for optimization include the use of a global optimizer, which is a hybrid between the MCMC method and a genetic algorithm, called the genetic evolution Markov chain (GEMC) method.
1：Experimental Design and Method Selection:
Used the Astronomical Multi-BEam combineR (AMBER) instrument at the Very Large Telescope Interferometer (VLTI), in high-resolution mode (λ/(cid:5)λ ≈ 12 000) between
2：28 and 31 μm in the K band. The maximal angular resolution is 10 mas, obtained using a triplet telescope configuration, with baselines from 7 to 48 m. Sample Selection and Data Sources:
A sample of eight evolved stars, including the red supergiant α Scorpii, the red giant branch stars α Bootis and γ Crucis, the K giant λ Velorum, the normal M giants BK Virginis and SW Virginis, and the Mira star W Hydrae (in two different luminosity phases).
3：List of Experimental Equipment and Materials:
VLTI/AMBER instrument, Auxiliary Telescopes (ATs) triplets B2-C1-D0 (16-32-48m) for 2009 April 16, B2-C1-D0 (10-20-30m) for 2014 February 11 and A1-B2-C1 (7-10-15m) for 2014 April
4：Experimental Procedures and Operational Workflow:
Observations carried out using the high spectral resolution mode of AMBER (λ/(cid:5)λ ≈ 12 000) in the K band (HR K) between
5：28 and 31 μm. The measurements have been performed with a detector integration time (DIT) of 12 s and 500 exposures. Data Analysis Methods:
Used a numerical model of a molecular atmosphere in a spherical shells (MOLsphere), called PAMPERO, to add multiple extended CO layers above the photospheric MARCS model at an adequate spatial resolution. The differential visibilities and the spectrum were used to estimate the size (R) of the CO MOLsphere, its column density (NCO) and temperature (Tmol) distributions along the stellar radius.
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