Abstract
Stellar surface magnetoconvection (granulation) creates asymmetries in
the observed stellar absorption lines that can subsequently manifest
themselves as spurious radial velocities (RVs) shifts. In turn, this can
then mask the Doppler reflex motion induced by orbiting planets on their
host stars and represents a particular challenge for determining the
masses of low-mass, long-period planets. Herein, we study this impact by
creating Sun-as-a-star observations that encapsulate the granulation
variability expected from 3D magnetohydrodynamic simulations. These
Sun-as-a-star model observations are in good agreement with empirical
observations of the Sun but may underestimate the total variability
relative to the quiet Sun due to the increased magnetic field strength
in our models. We find numerous line profile characteristics that
linearly correlate with the disk-integrated convection-induced
velocities. Removing the various correlations with the line bisector,
equivalent width, and the V asy indicator may reduce
∼50%–60% of the granulation noise in the measured velocities.
We also find that simultaneous photometry may be a key diagnostic, as
our proxy for photometric brightness also allowed us to remove ∼50%
of the granulation-induced RV noise. These correlations and
granulation-noise mitigations break down in the presence of low
instrumental resolution and/or increased stellar rotation, as both act
to smooth the observed line profile asymmetries.
Original language | English |
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Pages (from-to) | 55 |
Journal | The Astrophysical Journal |
Volume | 879 |
Issue number | 1 |
DOIs | |
Publication status | Published - 03 Jul 2019 |
Keywords
- line: profiles
- planets and satellites: detection
- stars: activity
- stars: low-mass
- Sun: granulation
- techniques: radial velocities