A Grid of MARCS Model Atmospheres for S Stars

• S-type stars are late-type giants whose atmospheres are enriched in carbon and s-process elements because of either extrinsic pollution by a binary companion or intrinsic nucleosynthesis and dredge-up on the thermally-pulsing AGB. A large grid of S-star model atmospheres has been computed covering the range 2700 \le T$_eff$(K) \le 4000 with 0.5 \le C/O \le 0.99. ZrO and TiO band strength indices as well as VJHKL photometry are needed to disentangle T$_eff$, C/O and [s/Fe]. A \ldquobest-model finding tool\rdquo has been developed using a set of well-chosen indices and checked against photometry as well as low- and high-resolution spectroscopy. It is found that applying M-star model atmospheres (i.e., with a solar C/O ratio) to S stars can lead to errors in T$_eff$ up to 400 K. We constrain the parameter space occupied by the S stars of the vast Henize sample in terms of T$_eff$, [C/O] and [s/Fe].

Ämnesord

NATURVETENSKAP  -- Fysik -- Astronomi, astrofysik och kosmologi (hsv//swe)

NATURAL SCIENCES  -- Physical Sciences -- Astronomy, Astrophysics and Cosmology (hsv//eng)

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