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Title: Helium-abundance and other composition effects on the properties of stellar surface convection in solar-like main-sequence stars

We investigate the effect of helium abundance and α-element enhancement on the properties of convection in envelopes of solar-like main-sequence stars using a grid of three-dimensional radiation hydrodynamic simulations. Helium abundance increases the mean molecular weight of the gas and alters opacity by displacing hydrogen. Since the scale of the effect of helium may depend on the metallicity, the grid consists of simulations with three helium abundances (Y = 0.1, 0.2, 0.3), each with two metallicities (Z = 0.001, 0.020). We find that changing the helium mass fraction generally affects structure and convective dynamics in a way opposite to that of metallicity. Furthermore, the effect is considerably smaller than that of metallicity. The signature of helium differs from that of metallicity in the manner in which the photospheric velocity distribution is affected. We also find that helium abundance and surface gravity behave largely in similar ways, but differ in the way they affect the mean molecular weight. A simple model for spectral line formation suggests that the bisectors and absolute Doppler shifts of spectral lines depend on the helium abundance. We look at the effect of α-element enhancement and find that it has a considerably smaller effect on the convectivemore » dynamics in the superadiabatic layer compared to that of helium abundance.« less
Authors:
; ;  [1]
  1. Department of Astronomy, Yale University, P.O. Box 208101, New Haven, CT 06520-8101 (United States)
Publication Date:
OSTI Identifier:
22341956
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 778; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABUNDANCE; COMPARATIVE EVALUATIONS; COMPUTERIZED SIMULATION; CONVECTION; DISTRIBUTION; DOPPLER EFFECT; GRAVITATION; HELIUM; HYDRODYNAMICS; HYDROGEN; MAIN SEQUENCE STARS; METALLICITY; MOLECULAR WEIGHT; OPACITY; SURFACES; THREE-DIMENSIONAL CALCULATIONS