Characterization of starspots on a young M-dwarf K2-25: multi-band observations of stellar photometric variability and planetary transits
Monthly Notices of the Royal Astronomical Society(2024)
摘要
Detailed atmospheric characterization of exoplanets by transmission
spectroscopy requires careful consideration of stellar surface inhomogeneities
induced by starspots. This effect is particularly problematic for planetary
systems around M-dwarfs, and their spot properties are not fully understood. We
investigated the stellar activity of the young M-dwarf K2-25 and its effect on
transit observations of the sub-Neptune K2-25b. From multi-band monitoring
observations of stellar brightness variability using ground-based telescopes
and TESS, we found that the temperature difference between the spots and
photosphere is <190 K and the spot covering fraction is <61
also investigated the effect of starspot activity using multi-epoch, multi-band
transit observations. We rule out cases with extremely low spot temperatures
and large spot covering fractions. The results suggest that spots could distort
the transmission spectrum of K2-25b by as much as ∼100 ppm amplitude,
corresponding to the precision of JWST/NIRSPEC of the target. Our study
demonstrates that simultaneous multi-band observations with current instruments
can constrain the spot properties of M-dwarfs with good enough precision to
support atmospheric studies of young M-dwarf planets via transmission
spectroscopy.
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