Simulations of starspot anomalies within TESS exoplanetary transit light curves. II. Forecasting the frequency of starspot anomalies appearing in TESS exoplanetary transit light curves
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 × 109 simulations of planetary transits around spotted stars using the transit-starspot model PRISM. The simulations cover a range of starspot filling factors using one of three distributions: uniform, polar-biased, and mid-latitude. 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 polar-biased distribution and 47 ± 7 M dwarf and 21 ± 4 K dwarf light curves for a mid-latitude 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.
Astronomy and Astrophysics
- Pub Date:
- May 2021
- stars: late-type;
- stars: activity;
- planets and satellites: general;
- methods: numerical;
- techniques: photometric;
- Astrophysics - Earth and Planetary Astrophysics;
- Astrophysics - Solar and Stellar Astrophysics
- 11 pages, 6 figures, and 7 tables. Accepted for publication in A&