TY - JOUR
T1 - Modeling Stellar Surface Features on a Subgiant Star with an M-dwarf Companion
AU - Schutte, Maria C.
AU - Hebb, Leslie
AU - Lowry, Simon
AU - Wisniewski, John
AU - Hawley, Suzanne L.
AU - Mahadevan, Suvrath
AU - Morris, Brett M.
AU - Robertson, Paul
AU - Rohn, Graeme
AU - Stefansson, Gudmundur
N1 - Funding Information:
We thank our referee for providing us very constructive feedback that helped us to improve the clarity and content of this paper. We acknowledge support from NSF grant AST-1907622. This research has made use of the NASA Exoplanet Archive, which is operated by the California Institute of Technology, under contract with the National Aeronautics and Space Administration under the Exoplanet Exploration Program. This paper includes data collected by the Kepler mission and obtained from the MAST data archive at the Space Telescope Science Institute (STScI). Funding for the Kepler mission is provided by the NASA Science Mission Directorate. STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 526555.
Publisher Copyright:
© 2022. The Author(s). Published by the American Astronomical Society.
PY - 2022/7/1
Y1 - 2022/7/1
N2 - Understanding magnetic activity on the surface of stars other than the Sun is important for exoplanet analyses to properly characterize an exoplanet's atmosphere and to further characterize stellar activity on a wide range of stars. Modeling stellar surface features of a variety of spectral types and rotation rates is key to understanding the magnetic activity of these stars. Using data from Kepler, we use the starspot modeling program STarSPot (STSP) to measure the position and size of spots for KOI-340, which is an eclipsing binary consisting of a subgiant star (T eff = 5593 ± 27 K, R ∗ = 1.98 ± 0.05 R ⊙) with an M-dwarf companion (M ∗ = 0.214 ± 0.006 M ⊙). STSP uses a novel technique to measure the spot positions and radii by using the transiting secondary to study and model individual active regions on the stellar surface using high-precision photometry. We find that the average size of spot features on KOI-340's primary is ∼10% the radius of the star, i.e., two times larger than the mean size of solar-maximum sunspots. The spots on KOI-340 are present at every longitude and show possible signs of differential rotation. The minimum fractional spotted area of KOI-340's primary is 2-2+12%, while the spotted area of the Sun is at most 0.2%. One transit of KOI-340 shows a signal in the transit consistent with a plage; this plage occurs right before a dark spot, indicating that the plage and spot might be colocated on the surface of the star.
AB - Understanding magnetic activity on the surface of stars other than the Sun is important for exoplanet analyses to properly characterize an exoplanet's atmosphere and to further characterize stellar activity on a wide range of stars. Modeling stellar surface features of a variety of spectral types and rotation rates is key to understanding the magnetic activity of these stars. Using data from Kepler, we use the starspot modeling program STarSPot (STSP) to measure the position and size of spots for KOI-340, which is an eclipsing binary consisting of a subgiant star (T eff = 5593 ± 27 K, R ∗ = 1.98 ± 0.05 R ⊙) with an M-dwarf companion (M ∗ = 0.214 ± 0.006 M ⊙). STSP uses a novel technique to measure the spot positions and radii by using the transiting secondary to study and model individual active regions on the stellar surface using high-precision photometry. We find that the average size of spot features on KOI-340's primary is ∼10% the radius of the star, i.e., two times larger than the mean size of solar-maximum sunspots. The spots on KOI-340 are present at every longitude and show possible signs of differential rotation. The minimum fractional spotted area of KOI-340's primary is 2-2+12%, while the spotted area of the Sun is at most 0.2%. One transit of KOI-340 shows a signal in the transit consistent with a plage; this plage occurs right before a dark spot, indicating that the plage and spot might be colocated on the surface of the star.
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U2 - 10.3847/1538-3881/ac70ca
DO - 10.3847/1538-3881/ac70ca
M3 - Article
AN - SCOPUS:85133542254
SN - 0004-6256
VL - 164
JO - Astronomical Journal
JF - Astronomical Journal
IS - 1
M1 - 14
ER -