[P-EM19] 太陽物理学の最前線

[PEM19-P05] Stellar flare of a close binary system monitored by the Hisaki satellite during the NICER-Hisaki Observing Campaign 2018-2019

*木村 智樹¹、岩切 渉²、山崎 敦³、村上 豪³、土屋 史紀⁴、吉岡 和夫⁵、鳥海 森⁶、北 元³、桑原 正輝³ (1.東北大学学際科学フロンティア研究所、2.中央大学理工学部、3.JAXA宇宙科学研究所、4.東北大学惑星プラズマ大気研究センター、5.東京大学新領域創成科学研究科、6.国立天文台)

キーワード：恒星フレア、ひさき

Dynamics of stellar flare is still not well understood compared to that of the sun because of lack of continuous monitoring of distant stars in multiple wavelengths. Here we present a flare event at a close binary system, UX Arietis, monitored with the planetary extreme ultraviolet (EUV) space telescope Hisaki during the coordinated observing campaign with the NICER X-ray Telescope from late 2018 to early 2019. Time variability in the EUV spectrum of the binary was successfully monitored from the begging to the end of flare. Emission power at the EUV wavelengths peaked at ~6x10^24 W, which is comparable with that measured in the previous X-ray observations by e.g., the Advanced Satellite for Cosmology and Astrophysics (ASCA) (Gudel et al., 1999). The EUV spectrum showed emission lines of carbon, nitrogen, oxygen, and silicon ions. Electron temperature and density, emission measure, and ion balance were reduced from the emission lines by EUV spectral diagnostics. Dynamics of the stellar flare will be discussed based on comparison of the reduced plasma parameters with the X-ray spectrum measured with NICER.