Habitable Zones & Global Climate

Ultraviolet And Chromospheric Activity And Habitability Of M Stars

By Keith Cowing
Status Report
April 4, 2024
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Ultraviolet And Chromospheric Activity And Habitability Of M Stars
Galactic distribution of the sample stars. The color bar means the extinction value. — astro-ph.SR

M-type stars are crucial for stellar activity studies since they cover two types of magnetic dynamos and particularly intriguing for habitability studies due to their abundance and long lifespans during the main-sequence stage.

In this paper, we used the LAMOST DR9 catalog and the GALEX UV archive data to investigate the chromospheric and UV activities of M-type stars. All the chromospheric and UV activity indices clearly show the saturated and unsaturated regimes and the well-known activityrotation relation, consistent with previous studies. Both the FUV and NUV activity indices exhibit a single-peaked distribution, while the Hα and Ca II H&K indices show a distinct double-peaked distribution.

The gap between these peaks suggests a rapid transition from a saturated population to an unsaturated one. The smoothly varying distributions of different subtypes suggest a rotationdependent dynamo for both early-type (partly convective) to late-type (fully convective) M stars. We identified a group of stars with high UV activity above the saturation regime (logR’NUV<.sub> > −2.5) but low chromospheric activity, and the underlying reason is unknown.

By calculating the continuously habitable zone and the UV habitable zone for each star, we found about 70% stars in the total sample and 40% stars within 100 pc are located in the overlapping region of these two habitable zones, indicating a number of M stars are potentially habitable. Finally, we examined the possibility of UV activity studies of M stars using the China Space Station Telescope.

Hertzsprung–Russell diagram of all sample. Blue points means all sample, red points means the sample with period. The grey points are the stars from Gaia eDR3 with distances d < 200 pc, Gmag between 4–18 mag, and Galactic latitude —b— > 10. No extinction was corrected for these stars. — astro-ph.SR

Xue Li, Song Wang, Henggeng Han, Huiqin Yang, Chuanjie Zheng, Yang Huang, Jifeng Liu

Comments: 27 pages, 32 figures, accepted by ApJ
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2402.17384 [astro-ph.SR] (or arXiv:2402.17384v2 [astro-ph.SR] for this version)
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Submission history
From: Xue Li
[v1] Tue, 27 Feb 2024 10:24:41 UTC (1,698 KB)
[v2] Wed, 27 Mar 2024 06:53:41 UTC (1,697 KB)

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) 🖖🏻