Author ORCID Identifier
Date of Award
Winter 4-10-2026
Document Type
Thesis (Ph.D.)
Department or Program
Physics and Astronomy
First Advisor
Elisabeth R. Newton
Second Advisor
Burçin Mutlu-Pakdil
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 thesis, 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 H$\alpha$ 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.
Original Citation
García Soto, A., Duvvuri, G.~M., Newton, E.~R., et al. 2025, Astrophysical Journal, 982, 2, 98. doi:10.3847/1538-4357/adb615
García Soto, A., Newton, E. R., Douglas, S. T., et al. 2023, Astronomical Journal, 165, 5, 192. doi:10.3847/1538-3881/acc2ba
Recommended Citation
Garcia Soto, Aylin, "Variability on M-dwarf Stars And Its Effect on Exoplanet Detection" (2026). Dartmouth College Ph.D Dissertations. 456.
https://digitalcommons.dartmouth.edu/dissertations/456
