V1355 Orionis (also known as HD 291095) is an RS CVn-type binary star system located 400 light-years away in the constellation of Orion.
An artist’s impression of the superflare from the main member of the V1355 Orionis binary system. Image credit: NAOJ.
“Solar flares are explosive phenomena wherein magnetic energy stored around sunspots is suddenly released through magnetic reconnection. Generally, a solar flare releases about 1026-1032 erg,” said Kyoto University astronomer Shun Inoue and colleagues.
“Emission in a wide range of wavelengths from radio waves to X-rays occurs during a flare.”
“Generally, prominence eruptions on the Sun, which are associated with flares, are observed as Hα (hydrogen alpha) emission and absorption when they erupt outside a limb and on a disk, respectively.”
“Prominence or filament eruptions can lead to coronal mass ejections (CMEs) when the prominence velocity is sufficiently large.”
“Flares are widely observed both on the Sun and stars,” the astronomers added.
“In the case of stars, superflares, which release 10 times larger energies than the largest solar flares, have been confirmed.”
Dr. Inoue and co-authors used the 3.8-m Seimei Telescope in Japan and NASA’s Transiting Exoplanet Survey Satellite (TESS) to monitor the binary star system V1355 Orionis, which is known to frequently release large-scale superflares.
“We succeeded in capturing a superflare with continuous, high temporal resolution observations,” they said.
“Our data analysis shows that the superflare originated with a phenomenon known as a prominence eruption.”
“Calculating the velocity of the eruption requires making some assumptions about aspects that aren’t directly observably, but even the most conservative estimates far exceed the escape velocity of the star (347 km/s), indicating that the prominence eruption was capable of breaking free of the star’s gravity and developing into CMEs.”
“The prominence eruption was also one of the most massive ever observed, carrying trillions of tons of material.”
The findings were published in the Astrophysical Journal.
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Shun Inoue et al. 2023. Detection of a High-velocity Prominence Eruption Leading to a CME Associated with a Superflare on the RS CVn-type Star V1355 Orionis. ApJ 948, 9; doi: 10.3847/1538-4357/acb7e8
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