Stellar Cartography

Preparing For The Early eVolution Explorer

By Keith Cowing

Status Report

astro-ph.EP

November 18, 2024

Filed under astro-ph.EP, atmosphere, Early eVolution Explorer (EVE), exoplanet, M Dwarfs, Photochemistry, radiation, space weather, Stellar Cartography, Swift, TESS, Ultraviolet flare

Preparing For The Early eVolution Explorer — Although flare rates and energies are measured in the optical for most stars, the FUV and NUV energies determine the photochemical radiation environment of orbiting planets during these events. Simultaneous observations at UV and optical wavelengths are needed to derive the energy budget as flares with similar emission levels at optical wavelengths can produce NUV fluxes that differ by 2–20× depending on the T_eff of the flare, correlating with order-of-magnitude discrepancies at FUV wavelengths. Spectra of ϵ Eri during the two flares are obtained by superimposing the flare blackbody onto the semi-empirical base spectrum from Behr et al. (2023). — astro-ph.EP

Ultraviolet flare emission can drive photochemistry in exoplanet atmospheres and even serve as the primary source of uncertainty in atmospheric retrievals. Additionally, flare energy budgets are not well-understood due to a paucity of simultaneous observations.

We present new near-UV (NUV) and optical observations of flares from three M dwarfs obtained at 20 s cadence with Swift and TESS, along with a re-analysis of flares from two M dwarfs in order to explore the energy budget and timing of flares at NUV–optical wavelengths. We find a 9000 K blackbody underestimates the NUV flux by ≥2× for 54±14% of flares and 14.8× for one flare.

We report time lags between the bands of 0.5–6.6 min and develop a method to predict the qualitative flare shape and time lag to 36±30% accuracy. The scatter present in optical-NUV relations is reduced by a factor of 2.0±0.6 when comparing the total NUV energy with the TESS energy during the FWHM duration due to the exclusion of the Teff≈5000 K tail.

We show the NUV light curve can be used to remove flares from the optical light curve and consistently detect planets with 20% smaller transits than is possible without flare detrending. Finally, we demonstrate a 10× increase in the literature number of multi-wavelength flares with the Early eVolution Explorer (EVE), an astrophysics Small Explorer concept to observe young clusters with simultaneous NUV and optical bands in order to detect young planets, assess their photochemical radiation environments, and observe accretion.

Preparing for the Early eVolution Explorer: Characterizing the photochemical inputs and transit detection efficiencies of young planets using multiwavelength flare observations by TESS and Swift

Ward S. Howard, Meredith A. MacGregor, Adina D. Feinstein, Laura D. Vega, Ann Marie Cody, Neal J. Turner, Valerie J. Scott, Jennifer A. Burt, Laura Venuti

Comments: 27 pages, 13 figures, 4 tables, accepted to The Astronomical Journal
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)
Cite as: arXiv:2411.08092 [astro-ph.EP] (or arXiv:2411.08092v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2411.08092
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Submission history
From: Ward Howard
[v1] Tue, 12 Nov 2024 19:00:00 UTC (3,408 KB)
https://arxiv.org/abs/2411.08092

Astrobiology

Keith Cowing

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻

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