Benchmarks for stellar magnetic activity – ISSI 2022

ISSI Workshop on “Solar and stellar dynamos”, Bern, Switzerland

Transcript

1. New and old benchmarks for stellar magnetic activity Brett Morris Universität Bern, Switzerland
2. “Stars know how to do it.” S. L. Hawley
3. What’s a benchmark? Singular reference object(s) that we use to anchor our understanding for a broader class.
4. Which stars are benchmarks? Sun (G2V) HAT-P-11 (K4V) TRAPPIST-1 (M8V) GJ 1243 (M4V)
5. Key stats: • Active latitudes near 15° • 11 year activity cycle ◦ Expressed in spot number, chromospheric emission • Log-normal spot radius distribution The oldest: direct observations Christoph Scheiner (1630)
6. Key stats: • Active latitudes near 15° • 11 year activity cycle ◦ Expressed in spot number, chromospheric emission • Log-normal spot radius distribution The oldest: direct observations Morris et al. (2019)
7. Key stats: • Active latitudes near 15° • 11 year activity cycle ◦ Expressed in spot number, chromospheric emission • Log-normal spot radius distribution The oldest: direct observations Hall et al. (2008) 𝜆 4300 CH G CaII H
8. Key stats: • Active latitudes near 15° • 11 year activity cycle ◦ Expressed in spot number, chromospheric emission • Log-normal spot radius distribution The oldest: direct observations Egeland et al. (2017)
9. Morris et al. (in prep) Elder benchmarks: classical stellar spectroscopy Chromospheric emission reveals disk-integrated magnetic activity
10. Elder benchmarks: classical stellar spectroscopy Baliunas et al. (1995) Chromospheric emission reveals activity cycle behavior in Sun-like stars S-index
11. Elder benchmarks: classical stellar spectroscopy Chromospheric emission reveals activity cycle behavior in Sun-like stars Morris et al. (2022, in prep) S-index
12. Which stars are benchmarks? Sun (G2V) HAT-P-11 (K4V) TRAPPIST-1 (M8V) GJ 1243 (M4V)
13. Kepler benchmark: HAT-P-11 Morris et al. (2017a) Transiting planets can constrain starspot sizes, positions
14. Kepler benchmark: HAT-P-11 Morris et al. (2017a) Transiting planets can map starspot sizes, positions
15. Kepler benchmark: HAT-P-11 Morris et al. (2017a) Transiting planets can map starspot sizes, positions
16. Kepler benchmark: HAT-P-11 Morris et al. (2017b) Ground-based spectroscopy finds an activity cycle
17. Which stars are benchmarks? Sun (G2V) HAT-P-11 (K4V) TRAPPIST-1 (M8V) GJ 1243 (M4V)
18. Kepler benchmark: GJ 1243 (M4V) Davenport et al. (2015) Starspots on late-type stars are stable over years
19. Kepler/TESS benchmark: GJ 1243 (M4V) Davenport et al. (2020) Starspots on late-type stars are stable over years decades
20. Which stars are benchmarks? Sun (G2V) HAT-P-11 (K4V) TRAPPIST-1 (M8V) GJ 1243 (M4V)
21. K2/Spitzer benchmark: TRAPPIST-1 Morris et al. (2018) Dark spots would cause small variability in Spitzer
22. K2/Spitzer benchmark: TRAPPIST-1 Morris et al. (2018) Bright spots would cause ~no variability in Spitzer
23. K2 benchmark: TRAPPIST-1 Morris et al. (2018) Flare-flux correlation?
24. Active region occultations Summary F G K M Spectroscopic activity cycles Observations Active Region Characteristics “sunspot-like” Scaled-up sunspots Here be dragons! (long lived, bright?) Rotational Modulation