[Astronomy seminar] SU astronomy departmental seminar Friday January 27th - Mingjie Jian

[Astronomy seminar announcements]

Dear all,

The next SU astronomy departmental seminar will take place on Friday January 27th at 10:30 in room FC 61 (AlbaNova building, 6th floor) and on zoom.

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Speaker: Mingjie Jian (SU)
Title: The behavior of the chromospheric lines of helium at 10830Å in late-type stars
<https://www.albanova.se/event/early-kilonova-from-neutron-star-merger/>https://www.albanova.se/event/astronomy-departmental-seminar-mingjie-jian-su/

Abstract:
The  stellar helium abundance is an essential parameter which is expected to  provide important clues on the chemical evolution of our Milky Way. It is believed to be enhanced in the second (and later) generation(s) in globular clusters and one of the double red clump, though the latter is still under intense debate. However, it is hard to determine the helium  abundance of late-typed star spectroscopically. Previous studies have shown that the chromospheric helium line at 10830 Å (He 10830) has the potential to be used as a helium abundance indicator, but observations of this line have been insufficient. We collected a large sample of medium- and high-resolution spectra covering the wavelength range of He  10830 for over 700 stars. We found systemic trends between line strength and other parameters, and that the photoionization-recombination formation mechanism dominates in the dwarfs and warm giants. Thus He 10830 is difficult to use as a helium abundance tracer for these stars. The cool giants, on the other hand, are expected to have weak or no corona, thus still having the possibility to trace their helium abundance using He 10830.

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We look forward to seeing many of you there. Thanks!

Eliot and Kris



Upcoming Events:

2023-02-03 Kelley Hess (IAA - Granada, Spain)
2023-02-10 No seminar - OKC day
2023-02-17 Diane Feuillet (Lund Obs.)
2023-02-24 Martin Rey (Oxford)

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Topic: Astronomy Department Seminar Mingjie Jian
Time: Jan 27th, 2023 10:30 AM Stockholm

Join Zoom Meeting:
https://stockholmuniversity.zoom.us/s/61002076352
Meeting ID: 610 0207 6352

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