New Results on Stellar Flares Monitored with MAXI/GSC Yohko Tsuboi, Kyohei Yamazaki, Akiko Uzawa, Takanori Matsumura (Chuo Univ.), Satoshi Nakahira (Aoyama Gakuin Univ.), Motoki Nakajima (Nihon Univ.), and the MAXI team

Stars detected with MAXI/GSC Flare theta Ori C Eta Carinae RS CVn stars T Tauri star Massive stellar binary : 2 Low-mass star : 8 Single T Tauri star : 1 RS CVn binary : 7

T Tauri star TWA-7 fast rotator deep convection zone TWA-7 V=19.2 km s -1 (cf. V sun =0.6 km s -1 )

X-ray variability of TWA-7 Phase 0Phase 1 Phase 2 t d < 8 [ks]

Spectrum of TWA-7 flare log EM [cm -3 ] = Lx [erg s -1 ] = 1.2 ×10 33 (2-20keV, The error fixes kT. ) log EM [cm -3 ] = Lx [erg s -1 ] = 1.2 ×10 33 (2-20keV, The error fixes kT. ) log EM [cm -3 ] = Lx [erg s -1 ] = 1.2 ×10 33 (2-20keV, The error fixes kT. ) log EM [cm -3 ] = Lx [erg s -1 ] = 1.2 ×10 33 (2-20keV, The error fixes kT. ) log EM [cm -3 ] = Lx [erg s -1 ] = 1.2 ×10 33 (2-20keV, The error fixes kT. ) log EM [cm -3 ] = Lx [erg s -1 ] = 1.2 ×10 33 (2-20keV, The error fixes kT. ) Lx = ×10 33 [erg s -1 ] cf. Lx _sun =10 27 [erg s -1 ] +0.3 – One of the brightest flare in those on T Tauri stars

RS CVn type stars close detached binaries tidally locked fast rotators deep convection zone

Flares from RS CVn stars 14 flares from 7 RS CVn binaries 2 biggest flares in all the stellar flares Lx = 5 +4 ×10 33 erg s Lx = ×10 33 erg s -1 - II Peg GT Mus

Flare frequency Flares come from specific stars Then which component is special? Interaction between each component is special? Poisson distribution (the expectation value is the same as that of the data)

Spin velocity [km s -1 ] Spin velocity vs flares MAXI detected MAXI non detected Probability that two datasets differ significantly 69% (not weighted) 97% (flare freq. weighted) 21% 44%

Radius [solar radius] MAXI detected MAXI non detected Radius vs flares 96% (not weighted) 99.8% (flare freq. weighted) 10% 74% Probability that two datasets differ significantly

Orbital period [day] Separation [solar radius] MAXI detected MAXI non detected Binary parameters vs flares 51% (not weighted) 86% (flare freq. weighted) 11% 73% Probability that two datasets differ significantly

Summary Lx = 5 +4 erg s We increased the big flare samples (14 flares from 7 RS Cvns, 1 flare from 1 T Tauri star) 2 biggest flares : II Peg : GT Mus: Lx = 4+-1 erg s -1 Hint for “Main big flare maker is subgiantcomponent”  2, 3 years are needed to conclude

TWA-7 RS CVn stars V=19.2 km s -1 V cool = km s -1

Only spin velocity and the depth of the convection zone are keys to originate big flares?