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Out of Sync: Redefining the Neupert Effect in M Dwarfs through Multi-Wavelength Timing Analysis of AU Mic’s Flares

Presentation #550.02 in the session “Variable Stars”.

Published onJan 11, 2021
Out of Sync: Redefining the Neupert Effect in M Dwarfs through Multi-Wavelength Timing Analysis of AU Mic’s Flares

M dwarfs are considered one of the most likely places to find extraterrestrial life in part due to their large numbers in the nearby solar neighborhood. However, they have much more intense flaring events than stars like our Sun, which could negatively impact the habitability of close-in exoplanets. Our current understanding of the multi-wavelength connections of M dwarf flaring events is surprisingly far from complete, both in wavelength coverage and temporal resolution. To rectify this, our team collected multi-wavelength data of the dM1e flare star AU Mic over 7-days with the Neil Gehrels Swift Observatory, XMM-Newton, the Las Cumbres Observatory Global Telescope (LCOGT) network, the Small and Moderate Aperture Telescope Research System (SMARTS) 0.9m and 1.5m telescopes at the Cerro Tololo Inter-American Observatory, the ARC 3.5m at APO, the ATCA, and the Jansky Very Large Array. Here we discuss the Neupert effect among the X-ray, UV, and optical response in a sample of high-energy flares. We present high time-resolution light curves, flare correlations across the spectrum, and cumulative flare frequency distribution (CFFD) statistics. We find that AU Mic’s U-band CFFD is consistent with other M dwarfs in the literature, that the Neupert effect (i.e. the X-ray derivative peak and NUV peak timings overlap) is not present in all characterized flares, and that while timing differences between the U and UVW2 flare peaks are small (<2 min.), their decay timings are not always similar. We propose a new Neupert classification system that includes Quasi-Neupert (response in X-ray and NUV, but the timings do not match) and Non-Neupert (missing a response from either X-ray or NUV). Future work on this project includes adding existing AU Mic radio and Hα observations to our analysis and using our RADYN flare modeling program to determine the electron beam heating, proton beam heating, and magnetic mirroring needed to reproduce the full range of multi-wavelength responses we see in observations.

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