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[Fizinfo] Szemináriumi meghívó / Invitation to a seminar

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  • From: vidakris AT
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  • Subject: [Fizinfo] Szemináriumi meghívó / Invitation to a seminar
  • Date: Fri, 18 Nov 2022 08:40:18 +0100
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Szemináriumi meghívó / Invitation to a seminar


Date: Nov 24, 2022 (Thursday) 14:00

Hiroyuki Maehara
(National Astronomical Observatory of Japan)
Hunting for mass ejections associated with superflares on solar-type stars

Solar flares are energetic explosions in the solar atmosphere (corona) caused
by the rapid release of magnetic energy through magnetic reconnection. Solar
flares are sometimes accompanied by mass ejections such as
prominence/filament eruptions and coronal mass ejections (CMEs). In the case
of other stars, including ordinary solar-type stars, much larger flares
called 'superflares' with the energy of 10^33-10^38 erg have been observed.
However, it is still an open question whether stellar superflares can produce
super-CMEs. By analogy with prominence/filament eruptions associated with
solar flares, mass ejections due to stellar flares could be observed as the
blue-shifted emission/absorption component in chromospheric lines (e.g.,
H-alpha line). We performed time-resolved optical spectroscopy of active
solar-type stars simultaneously with TESS and detected several superflares on
young solar-type stars EK Dra and V889 Her. Among them, a 10^33 erg
superflare on the solar-type star EK Dr
a exhibited a blue-shifted absorption component with a velocity of ~500 km/s
in the H-alpha line (Namekata et al. 2022, Nature Astronomy). The temporal
evolution of the H-alpha line during this superflare is similar to that of
the Sun-as-a-star spectrum during the solar flare accompanying a filament
eruption. This similarity suggests that the blue-shifted absorption component
is caused by the prominence eruption associated with a superflare on EK Dra.

The seminar will be held live in the Detre hall with audience, but also
streamed online via Zoom. If you are unable to attend the presentation in
person, The seminar will be held online via Zoom. you can join us via this
or the meeting ID: 828 0691 1982 and passcode: 206265

Everyone is welcome!

Krisztián Vida, Ramon Brasser

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