Stellar Coronal Mass Ejections and their Impact on Exoplanet Habitability

[摘要] Exoplanet habitability depends on many factors and most are still poorly understood.One such factor is space weather due to stellar coronal mass ejections (CMEs).Stellar CMEs remain experimentally unconstrained leading to a heavy reliance on solar scaling relationships to estimate their impacts. I propose a methodology for interpreting radio (and multi-wavelength) observations to constrain CME properties and test it on fully constrained solar observations.I then report on 15 hours of radio observation taken at the Low Frequency Array (LOFAR) focusing on the nearby M dwarf YZ CMi, 20 hours of simultaneously observed in radio at the Jansky Very Large Array (JVLA) and optical observation taken at the Apache Point Observatory and 44 of radio only observations of the nearby M dwarf binary EQ Peg.This provides the longest campaign for the search of low frequency radio signals and also the longest campaign for a single active M dwarf (EQ Peg). Analysis of the solar observations yields the result that CME velocity can be constrained to within a factor of 2 and CME mass to within a factor of ~10 using dish-integrated solar flare light curves and low-frequency radio dynamic spectrum. No radio transients were observed during the 15 hours of LOFAR observations or the 20 hours of the multi-wavelength observations.I constrain the emission parameter space due to the non-detections and sensitive limits. I use solar scaling relationships of the observed flares in the multi-wavelength observations to constrain potential CME properties. Two radio transients were observed during the final 44 hours of observations. Both bursts lasted on the order of 20 min, have a median polarization of ~30 %, have a frequency drift rate of ~10 kHz/s, and are likely not associated to CMEs.The lack of detections implies a CME rate of less than 1 event per 79 hours for all observations and less than 1 event per 64 hours for the EQ Peg binary system.The absence of events suggests a breakdown of solar scaling relations on CMEs.The impacts of space weather, and its potential deleterious effects, would be partially, if not completely, mitigated relative to current expectations.

[发布机构] Johns Hopkins University

[效力级别] M Dwarf

[关键词] Type II Burst;M Dwarf;EQ Peg;Coronal Mass Ejection;Physics