Space Weather & Heliophysics

Multi-wavelength Campaign Observations of a Young Solar-type Star, EK Draconis I. Discovery of Prominence Eruptions Associated with Superflares

By Keith Cowing

Status Report

astro-ph.SR

November 15, 2023

Filed under astro-ph.SR, CME, coronal mass ejections, EK Draconis, exoplanet, M-dwarfs, NICER, Seimei telescope, solar-type star, space weather, Superflare, TESS

Multi-wavelength Campaign Observations of a Young Solar-type Star, EK Draconis I. Discovery of Prominence Eruptions Associated with Superflares — Relations between Hα, X-ray, and white-light energies for solar and stellar flares. (left) The relation between Hα and Bolometric X-ray energies (0.1–100 keV = 0.124–124 ˚A). Data of superflares on the G-dwarf EK Dra detected in this study are represented by red squares. Other solar and stellar data are taken from Kawai et al. (2022). The function fitted to the observational data with a power-law is shown by the cyan line. (right) The relation between bolometric white-light and Hα energies. Data of superflares on the G-dwarf EK Dra, which are associated with filament/prominence eruptions, are represented by filled red squares, whereas those without eruptions are represented by open red squares (this study, Namekata et al. 2022d, Namekata et al. 2022c). For E1, the total energy including the blueshift component is plotted as the upper limit, with the radiative energy of the central component from the two-component fit being plotted as the lower limit. Data of M-dwarf flares are taken from Maehara et al. (2021), Namizaki et al. (2023), and (Notsu et al. 2023). Solar flare data are taken from Namekata et al. (2022a). The function fitted to the observational data, excluding flare E1, with a power-law is shown by the cyan line. — astro-ph.SR

Young solar-type stars frequently produce superflares, serving as a unique window into the young Sun-Earth environments. Large solar flares are closely linked to coronal mass ejections (CMEs) associated with filament/prominence eruptions, but its observational evidence for stellar superflares remains scarce.

Here, we present a 12-day multi-wavelength campaign observation of young solar-type star EK Draconis (G1.5V, 50-120 Myr age) utilizing TESS, NICER, and Seimei telescope. The star has previously exhibited blueshifted Hα absorptions as evidence for a filament eruption associated with a superflare. Our simultaneous optical and X-ray observations identified three superflares of 1.5×1033 — 1.2×1034 erg.

We report the first discovery of two prominence eruptions on a solar-type star, observed as blueshifted Hα emissions at speed of 690 and 430 km s−1 and masses of 1.1×1019 and 3.2×1017 g, respectively. The faster, massive event shows a candidate of post-flare X-ray dimming with the amplitude of up to ∼10 \%. Several observational aspects consistently point to the occurrence of a fast CME associated with this event.

The comparative analysis of the estimated length scales of flare loops, prominences, possible dimming region, and starspots provides the overall picture of the eruptive phenomena.

Furthermore, the energy partition of the observed superflares in the optical and X-ray bands is consistent with flares from the Sun, M-dwarfs, and close binaries, yielding the unified empirical relations. These discoveries provide profound implications of impact of these eruptive events on the early Venus, Earth and Mars and young exoplanets.

Kosuke Namekata, Vladimir S. Airapetian, Pascal Petit, Hiroyuki Maehara, Kai Ikuta, Shun Inoue, Yuta Notsu, Rishi R. Paudel, Zaven Arzoumanian, Antoaneta A. Avramova-Boncheva, Keith Gendreau, Sandra V. Jeffers, Stephen Marsden, Julien Morin, Coralie Neiner, Aline A. Vidotto, Kazunari Shibata

Comments: 48 pages, 29 figures, 11 tables. Accepted for publication in The Astrophysical Journal
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2311.07380 [astro-ph.SR] (or arXiv:2311.07380v1 [astro-ph.SR] for this version)
Submission history
From: Kosuke Namekata
[v1] Mon, 13 Nov 2023 15:06:41 UTC (5,858 KB)
https://arxiv.org/abs/2311.07380
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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