Download O-17 - maxi

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
Eta Carinae
Flare
T Tauri star
theta Ori C
Massive stellar
binary
:2
Low-mass star : 8
Single T Tauri star : 1
RS CVn binary : 7
RS CVn
stars
T Tauri star TWA-7
• fast rotator
V=19.2 km s-1
(cf. Vsun=0.6 km s-1)
• deep convection zone
TWA-7
X-ray variability of TWA-7
Phase 0
Phase 1
Phase 2
td < 8 [ks]
Spectrum of TWA-7 flare
Lx
= 1.2+0.3 ×1033
-0.4
[erg s-1]
cf. Lx_sun
=1027[erg s-1]
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
33
-1
Lx = 5+4
-2 ×10 erg s
II Peg
Lx = 4+1 ×1033 erg s-1
-
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 vs flares
MAXI detected
MAXI non
detected
Spin velocity [km s-1]
Probability that
two datasets
differ significantly
21%
44%
Spin velocity [km s-1]
69% (not weighted)
97% (flare freq. weighted)
Radius vs flares
MAXI detected
MAXI non
detected
Radius [solar radius]
Probability that
two datasets
differ significantly
10%
74%
Radius [solar radius]
96% (not weighted)
99.8% (flare freq. weighted)
Binary parameters vs flares
MAXI detected
MAXI non
detected
Orbital period [day]
11%
Probability that
73%
two datasets
differ significantly
Separation [solar radius]
51% (not weighted)
86% (flare freq. weighted)
Summary
• We increased the big
flare samples
(14 flares from 7 RS Cvns, 1
flare from 1 T Tauri star)
• 2 biggest flares :
-1
II Peg : Lx = 5+4
-2 erg s
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
V=19.2 km s-1
RS CVn stars
Vcool=10-100 km s-1
Only spin velocity and the depth of
the convection zone are keys to
originate big flares?