ELFT HÍRADÓ

[vidakris AT konkoly.hu]

Szemináriumi meghívó / Invitation to a seminar
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CSFK CSI SZEMINÁRIUM / KONKOLY OBSERVATORY 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 
link 
https://us06web.zoom.us/j/82806911982?pwd=SVZpT0syQ1J6dHBvSkF4N2dXNEQ0dz09
or the meeting ID: 828 0691 1982 and passcode: 206265




Everyone is welcome!

Krisztián Vida, Ramon Brasser
organizers
https://konkoly.hu/szeminar/szeminarium.shtml