Simulations of starspot anomalies within TESS exoplanetary transit light curves. II. Forecasting the frequency of starspot anomalies appearing in TESS exoplanetary transit light curves
Abstract
Aims: We determine the starspot detection rate in exoplanetary transit light curves for M and K dwarf stars observed by the Transiting Exoplanet Survey Satellite (TESS) using various starspot filling factors and starspot distributions.
Methods: We used 3.6 × 10^{9} simulations of planetary transits around spotted stars using the transitstarspot model PRISM. The simulations cover a range of starspot filling factors using one of three distributions: uniform, polarbiased, and midlatitude. After construction of the stellar disc and starspots, we checked the transit cord for starspots and examined the change in flux of each starspot to determine whether or not a starspot anomaly would be detected. The results were then compared to predicted planetary detections for TESS.
Results: The results show that for the case of a uniform starspot distribution, 64 ± 9 M dwarf and 23 ± 4 K dwarf transit light curves observed by TESS will contain a starspot anomaly. This reduces to 37 ± 6 M dwarf and 12 ± 2 K dwarf light curves for a polarbiased distribution and 47 ± 7 M dwarf and 21 ± 4 K dwarf light curves for a midlatitude distribution.
Conclusions: Currently there are only 17 M dwarf and 10 K dwarf confirmed planetary systems from TESS, none of which are confirmed as showing starspot anomalies. All three starspot distributions can explain the current trend. However, with such a small sample, a firm conclusion cannot be made at present. In the coming years when more TESS M and K dwarf exoplanetary systems have been detected and characterised, it will be possible to determine the dominant starspot distribution.
 Publication:

Astronomy and Astrophysics
 Pub Date:
 May 2021
 DOI:
 10.1051/00046361/202038261
 arXiv:
 arXiv:2103.16539
 Bibcode:
 2021A&A...649A.130T
 Keywords:

 stars: latetype;
 stars: activity;
 starspots;
 planets and satellites: general;
 methods: numerical;
 techniques: photometric;
 Astrophysics  Earth and Planetary Astrophysics;
 Astrophysics  Solar and Stellar Astrophysics
 EPrint:
 11 pages, 6 figures, and 7 tables. Accepted for publication in A&