CfA Exoplanet Lunch Talk

Virtual Talk -- October 19, 2021

Transcript

1. The Obstacles and Opportunities Presented by Young Planetary Systems Adina Feinstein NSF Graduate Research Fellow, University of Chicago ! 1 October 19, 2021 CfA Exoplanet Lunch
2. Know thy star, know thy planet. ! 2
3. The “problems” with young stars: ! 3 • Starspot/active region coverage • Stellar flares
4. The “problems” with young stars: ! 4 • Starspot/active region coverage • Stellar flares
5. A large percentage of their surfaces are covered in star spots and inhomogeneities. ! 5 Normalized Flux Time [BJD - 2457000] (Feinstein+2020ab)
6. The amplitude of variability can be produced by many different spot configurations. ! 6 Created using starry (Feinstein+2020ab)
7. The amplitude of variability can be produced by many different spot configurations. ! 6 Created using starry (Feinstein+2020ab)
8. The amplitude of variability can be produced by many different spot configurations. ! 6 Created using starry (Feinstein+2020ab)
9. Variations in line depth come from different surface inhomogeneities and planets occulting these regions. ! 7 (Guilluy+2020)
10. Variations in line depth come from different surface inhomogeneities and planets occulting these regions. ! 7 (Guilluy+2020)
11. While studying planets for the planets’ sake is interesting, we can leverage follow-up observations to learn more about the stars themselves. ! 8
12. Newly discovered young exoplanets occupy a sparse region of period-radius space. ! 9
13. Newly discovered young exoplanets occupy a sparse region of period-radius space. ! 9
14. Newly discovered young exoplanets occupy a sparse region of period-radius space. ! 9 (David+2019ab)
15. V1298 Tau is a 23 Myr K star with 4 transiting planets, all with periods < 60 days. ! 10 (David+2019ab)
16. Spoilers: TESS is observing V1298 Tau as we speak and we think we’ve caught a transit of planet e. ! 11 (Feinstein+ in prep.)
17. What is the spin-orbit alignment for V1298 Tau c in this young multi-planet system? !12
18. ! 13 Young planets also key us in to migratory paths, where an aligned system suggests a smooth disk migration. !13 DS Tuc Ab — Montet, Feinstein+2020 Zhou+2020 AU Mic b — Addison+2020 Hirano+2020
19. Doppler tomography measures the deviations in given lines when an object passes along our line of sight. !14
20. Doppler tomography measures the deviations in given lines when an object passes along our line of sight. !14
21. We measure an obliquity λ = 5° , indicating V1298 Tau c is well aligned. !15 +13° -8° (Feinstein+2021; Johnson et al. in prep)
22. ! 16 Young planets also key us in to migratory paths, where an aligned system suggests a smooth disk migration. DS Tuc Ab — Montet, Feinstein+2020 Zhou+2020 AU Mic b — Addison+2020 Hirano+2020 !16
23. The tomographic signal is driven by deviations in the core of the Ca ɪɪ IRT. !17 (Feinstein+2021)
24. Variations in Ca ɪɪ H&K and Ca ɪɪ IRT have previously been attributed to star-planet interactions. !18 Shkolnik+2008; Lanza+2012; Cauley+2018
25. The Hɑ is seen to be varying smoothly during during the transit of V1298 Tau c. !19 (Feinstein+2021)
26. Based on the current x-ray luminosity of the star, V1298 Tau c could evolve to 1 - 5.5 R⊕ . !20 (Poppenhaeger+2021)
27. But unlike in the Ca ɪɪ, the Hɑ shows no Doppler tomographic signal… !21 (Feinstein+2021)
28. Where is the Hɑ coming from? !22
29. If you assume an underlying trend from stellar activity, the Hɑ could look transit-y. !23
30. If you assume an underlying trend from stellar activity, the Hɑ could look transit-y. !23 1.85% depth from line fit
31. This Hɑ trend is not unique, but perhaps it’s coincidental. ! 24 (Schlawin, Ilyin, Feinstein+2021)
32. The Hɑ can be recreated strictly from star spots and faculae. !25 Created using starry (Feinstein+2021)
33. The Hɑ can be recreated strictly from star spots and faculae. !25 Created using starry (Feinstein+2021)
34. We can leverage transits to map surfaces of young stars to better understand starspot contamination. ! 26 (Morris+2017) (PI Feinstein, 2 nights on Magellan)
35. The “problems” with young stars: ! 27 • Starspot/active region coverage • Stellar flares
36. We’ve seen that young stars have higher flare rates than main sequence stars. ! 28 (Feinstein+2020ab) (Feinstein+PRL, under review)
37. We’ve seen that young stars have higher flare rates than main sequence stars. ! 28 (Feinstein+2020ab) (Feinstein+PRL, under review)
38. We’ve covered problems with starspots, now onto flares! ! 29 (Plavchan+2020)
39. TESS light curves of AU Mic show 1-5 flares per day, significantly higher than most young stars. ! 30 (Gilbert+2021) (flare identification with stella)
40. It should maybe not be surprising, then, that our Hubble observations are riddled with flares. ! 31 (Feinstein+ in prep.) (PI: P. Wilson Cauley)
41. We can now learn more about flares by tracing the flare energy with the formation temperature of ionized species. ! 32 (Feinstein+ in prep.)
42. Final Takeaways ! 33 • Young stellar activity poses significant issues when trying to learn about transiting planets. • But, with new high-resolution high-cadence observations of these systems, we can start learning about the host stars themselves. • We can map stellar inhomogeneities via transits of young planets to understand fractional spot coverage along the transit chord on young stars. • With time-series spectroscopy, we can learn about flare properties on other stars and start comparing where flares form on other stars to properties of solar flares. October 19, 2021 CfA Exoplanet Lunch