TY - JOUR
T1 - The asteroseismic surface effect from a grid of 3D convection simulations - I. Frequency shifts from convective expansion of stellar atmospheres
AU - Trampedach, Regner
AU - Aarslev, Magnus J.
AU - Houdek, Günter
AU - Collet, Remo
AU - Christensen-Dalsgaard, Jørgen
AU - Stein, Robert F.
AU - Asplund, Martin
N1 - Publisher Copyright:
© 2016 The Authors.
PY - 2017/3/21
Y1 - 2017/3/21
N2 - We analyse the effect on adiabatic stellar oscillation frequencies of replacing the near-surface layers in 1D stellar structure models with averaged 3D stellar surface convection simulations. The main difference is an expansion of the atmosphere by 3D convection, expected to explain a major part of the asteroseismic surface effect, a systematic overestimation of p-mode frequencies due to inadequate surface physics.We employ pairs of 1D stellar envelope models and 3D simulations from a previous calibration of the mixing-length parameter, α. That calibration constitutes the hitherto most consistent matching of 1D models to 3D simulations, ensuring that their differences are not spurious, but entirely due to the 3D nature of convection. The resulting frequency shift is identified as the structural part of the surface effect. The important, typically non-adiabatic, modal components of the surface effect are not included in this analysis, but relegated to future papers. Evaluating the structural surface effect at the frequency of maximum mode amplitude, υmax, we find shifts from δυ = -0.8 μHz for giants at log g = 2.2 to -35 μHz for a (Teff = 6901 K, log g = 4.29) dwarf. The fractional effect δυ(υmax )/υmax, ranges from -0.1 per cent for a cool dwarf (4185 K, 4.74) to -6 per cent for a warm giant (4962 K, 2.20).
AB - We analyse the effect on adiabatic stellar oscillation frequencies of replacing the near-surface layers in 1D stellar structure models with averaged 3D stellar surface convection simulations. The main difference is an expansion of the atmosphere by 3D convection, expected to explain a major part of the asteroseismic surface effect, a systematic overestimation of p-mode frequencies due to inadequate surface physics.We employ pairs of 1D stellar envelope models and 3D simulations from a previous calibration of the mixing-length parameter, α. That calibration constitutes the hitherto most consistent matching of 1D models to 3D simulations, ensuring that their differences are not spurious, but entirely due to the 3D nature of convection. The resulting frequency shift is identified as the structural part of the surface effect. The important, typically non-adiabatic, modal components of the surface effect are not included in this analysis, but relegated to future papers. Evaluating the structural surface effect at the frequency of maximum mode amplitude, υmax, we find shifts from δυ = -0.8 μHz for giants at log g = 2.2 to -35 μHz for a (Teff = 6901 K, log g = 4.29) dwarf. The fractional effect δυ(υmax )/υmax, ranges from -0.1 per cent for a cool dwarf (4185 K, 4.74) to -6 per cent for a warm giant (4962 K, 2.20).
KW - Asteroseismology
KW - Convection
KW - Stars: atmospheres
KW - Stars: evolution
KW - Stars: latetype
UR - http://www.scopus.com/inward/record.url?scp=85016317829&partnerID=8YFLogxK
U2 - 10.1093/mnrasl/slw230
DO - 10.1093/mnrasl/slw230
M3 - Article
SN - 1745-3925
VL - 466
SP - L43-L47
JO - Monthly Notices of the Royal Astronomical Society: Letters
JF - Monthly Notices of the Royal Astronomical Society: Letters
IS - 1
ER -