High-velocity blue-shifted Fe XXV He$α$ line during a superflare of the RS CVn-type star IM Peg
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| Formato: | Preprint |
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2024
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| author | Inoue, Shun Iwakiri, Wataru Buz Enoto, Teruaki Uchida, Hiroyuki Kurihara, Miki Tsujimoto, Masahiro Notsu, Yuta Hamaguchi, Kenji Gendreau, Keith Arzoumanian, Zaven Tsuru, Takeshi Go |
| author_facet | Inoue, Shun Iwakiri, Wataru Buz Enoto, Teruaki Uchida, Hiroyuki Kurihara, Miki Tsujimoto, Masahiro Notsu, Yuta Hamaguchi, Kenji Gendreau, Keith Arzoumanian, Zaven Tsuru, Takeshi Go |
| contents | Monitor of All-sky X-ray Image (MAXI) detected a superflare, releasing $5\times 10^{37}$ erg in 2$-$10 keV, of the RS CVn-type star IM Peg at 10:41 UT on 2023 July 23 with its Gas Slit Camera (GSC; 2$-$30 keV). We conducted X-ray follow-up observations of the superflare with Neutron Star Interior Composition ExploreR (NICER; 0.2$-$12 keV) starting at 16:52 UT on July 23 until 06:00 UT on August 2. NICER X-ray spectra clearly showed emission lines of the Fe XXV He$α$ and Fe XXVI Ly$α$ for $\sim 1.5$ days since the MAXI detection. The Fe XXV He$α$ line was blue-shifted with its maximum Doppler velocity reaching $-2200 \pm 600$ $\mathrm{km \: s^{-1}}$, suggesting an upward-moving plasma during the flare, such as a coronal mass ejection (CME) and/or chromospheric evaporation. This is the first case that the Fe XXV He$α$ line is blue-shifted during a stellar flare and its velocity overwhelmingly exceeds the escape velocity of the star ($-230$ $\mathrm{km \: s^{-1}}$). One hour before the most pronounced blueshift detection, a signature of reheating the flare plasma was observed. We discuss the origin of the blueshift, a CME or high-velocity chromospheric evaporation. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2406_06940 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | High-velocity blue-shifted Fe XXV He$α$ line during a superflare of the RS CVn-type star IM Peg Inoue, Shun Iwakiri, Wataru Buz Enoto, Teruaki Uchida, Hiroyuki Kurihara, Miki Tsujimoto, Masahiro Notsu, Yuta Hamaguchi, Kenji Gendreau, Keith Arzoumanian, Zaven Tsuru, Takeshi Go Solar and Stellar Astrophysics High Energy Astrophysical Phenomena Monitor of All-sky X-ray Image (MAXI) detected a superflare, releasing $5\times 10^{37}$ erg in 2$-$10 keV, of the RS CVn-type star IM Peg at 10:41 UT on 2023 July 23 with its Gas Slit Camera (GSC; 2$-$30 keV). We conducted X-ray follow-up observations of the superflare with Neutron Star Interior Composition ExploreR (NICER; 0.2$-$12 keV) starting at 16:52 UT on July 23 until 06:00 UT on August 2. NICER X-ray spectra clearly showed emission lines of the Fe XXV He$α$ and Fe XXVI Ly$α$ for $\sim 1.5$ days since the MAXI detection. The Fe XXV He$α$ line was blue-shifted with its maximum Doppler velocity reaching $-2200 \pm 600$ $\mathrm{km \: s^{-1}}$, suggesting an upward-moving plasma during the flare, such as a coronal mass ejection (CME) and/or chromospheric evaporation. This is the first case that the Fe XXV He$α$ line is blue-shifted during a stellar flare and its velocity overwhelmingly exceeds the escape velocity of the star ($-230$ $\mathrm{km \: s^{-1}}$). One hour before the most pronounced blueshift detection, a signature of reheating the flare plasma was observed. We discuss the origin of the blueshift, a CME or high-velocity chromospheric evaporation. |
| title | High-velocity blue-shifted Fe XXV He$α$ line during a superflare of the RS CVn-type star IM Peg |
| topic | Solar and Stellar Astrophysics High Energy Astrophysical Phenomena |
| url | https://arxiv.org/abs/2406.06940 |