Dartmouth Events

Abstract: Understanding stellar magnetic activity is crucial for exoplanet research: activity can mask signatures from exoplanet detection and characterization, and impact planetary habitability. This is particularly important for M dwarf stars, which are highly magnetically active, displaying spectroscopic and photometric signatures of flares and rotational variability. In this talk, I will present two complementary perspectives on M dwarf magnetic activity. First, I will discuss a study of short-term variability. I made new ground-based observations of 77 M dwarfs and tested the connection between chromospheric emission and photometric variability. I find a weak positive correlation between Hα luminosity (tracing magnetic heating) and photometric amplitude (tracing starspots), a relation that becomes increasingly dispersed for higher-order Balmer lines. This finding is consistent with increased intrinsic variability. Moreover, I found that this connection is complicated by sporadic and nonflaring variability in Balmer lines on timescales much shorter than the stellar rotation period. I also observed discrepant signatures in the Balmer decrement during flares and evidence for dark spots on one young M dwarf. Second, I scale this up to a population-level analysis. The stellar activity just discussed can introduce a serious selection bias in planet searches. Mazeh et al. (2015) has used Kepler photometric amplitudes to derive stellar obliquities, providing statistical insight into planetary system architectures. I first update those results using Santos et al. (2019, 2021) and extend the study with TESS to M dwarfs. I find that M dwarf stellar variability introduces a detection bias in transit surveys and quantifies the implications for missing planets around active M dwarfs with TESS. My work shows that not only can stellar variability be unpredictable, but it also directly affects our ability to find transiting exoplanets.

Graduate Advisor: Elisabeth Newton

Zoom Link: https://dartmouth.zoom.us/j/94565863318

Email Rowan Kowalsky for password.