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Young active star research with SONG and mini-SONG
Huijuan Wang
National Astronomical ObservatoriesChinese Academy of Sciences
@ Charleston
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Contents
Young active star
With SONG
With mini-SONG
When SONG + mini-SONG
Why young active star
The past of our Sun
The evolution history of Milky Way
Good targets for extrasolar planets search
Distinguish between variation in frequency
caused by oscillation and activities
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PTTS
CTTS
WTTS
ZAMS
Early evolution of solar-like stars
( Neuhäuser 1997 )
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M < 2.5M ⊙ ( Late spectral type )
Early phase of evolution(t<10Myr/100Myr)
Obvious absorption line of Li 6708 Å
Weak emission line of Hα ( EWHα≤10Å )
No circle-stellar disk (mostly)
Strong soft X-ray emission
Characters of WTTS & PTTS
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Young active star
Background Identification of a sample of young solar-
type star candidates Identification of an active spectroscopic
binary: HD146875 Research of two young solar-type stars
within 20pc summary
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Background introduction
ROSAT soft X-ray survey Observational research of WTTS -> central area of
Taurus-Auriga (Neuheauser et al 1995; Wichmann et al 2000 )
Observational research of our group Xinglong group: Li & Hu 1998 ROSAT bright source catalog & Tycho catalog = > sample of young solar type stars
criterion: logC + 0.4V (Lx > 1030 erg s-1)
Monitoring observation on 60 cm telescope at Xinglong observation station
WTTS candidates most distributed in the outside region of Taurus—Auriga
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Why high resolution?
Identify these YSS candidates Study the relationship between them and the
nearby young groups Research the relationship between the EW
of Li and the rotation period
High resolution observations are necessary.
( Wichmann 1996; Martin 1998 )
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Research method
Sample V< 9.5 mag,63 stars
Observation 2.16m tel & Coude echelle spectrograph(R = 4000
0 ) Data reduction & analysis
IRAF software (Echelle, Daophot)
Expect results Equivalent width (EW) of Li Radial velocity (RV) Projected rotation velocity Spectroscopic binary etc.
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stars year 23 -- 2000 & 2001 37 -- 2004 & 2005 18 -- 2006 22 -- 2007 31 -- 2008
==>Sample : 63 stars ( 167spectra)
Spectroscopic observation log
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Histogram of EW (Li)
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WTTW+PTTS
21 stars 33%
ZAMS20stars
32%
MS22 stars
35%About 2/3 are young stars
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Young active star
Background Identification of a sample of young solar-
type star candidates Identification of an active spectroscopic
binary: HD146875 Research of two young solar-type stars
within 20pc summary
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Young low-mass binary
Opportunity to derive precise measurements of the fundamental stellar parameters of their constituent stars ( stellar mass & radius)
Derive calibrations of young-star evolutionary models Determine the unbiased mass-ratio and orbital-period
distribution The sample of well-studied young low-mass binaries
remains small High resolution spectroscopic observation (powerful technique)
Identify binary Obtain accurate parameters (mass & mass ratio)
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HD146875 Bright X-ray source (Schwope 2000)
V = 8.81 mag
None hight resolution spectroscopic observations before then
2005.04.25 : show double lines
2006.02.17 & 06.09 : show shift between lines
till 2008.03.25 : totally 45 spectra
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Radial velocity curve
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Spectral Disentangling
KOREL code (Hadrava 1995)
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Photometic varibility
2008.02.15-04.14
Amplitude:0.057mag
Cased by spots on the primary, but not ellipsoidal distortion
a synchronous system (spots face us / pri -)
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Age - method 1
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Age - method 2
Age ~ 100 - 150Myr
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-
=
Subtracted profile
Chromospheric activity
Observed spectrum
ModelG9 + K0 Strong chromospheric activity on the primary
Emission originates in plage-like regions
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Young active star
Background Identification of a sample of young solar-
type star candidates Identification of an active spectroscopic
binary: HD146875 Research of two young solar-type stars
within 20pc summary
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TW Hya Association(TWA) TW Hya 20Myr , 56.4PC
The nearest star formation region. ( Zuckerman b. et al 2001 , 2004)
Nearby young groups
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11 stars in our sample: EW(Li) > 100 mÅ D < 50 PC
So close & so young early evolution of the sun understand the structure and the evolution
history of the Milky Way perfect sample for exoplanet survey
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2 stars D<20PC
( Wang & Wei, 2009, RAA, 9, 315 )
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HIP 544 46843
Age (Myr) 100-800 30-100
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Young active star
Background Identification of a sample of young solar-
type star candidates Identification of an active spectroscopic
binary: HD146875 Research of two young solar-type stars
within 20pc summary
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Summary
Finish the identification of a sample comprising 63 stars, and 2/3 of them are young solar-type stars (YSS)
Identify a ZAMS active double lined spectroscopic binary : HD 146875
Spectroscopic study of two YSS (HIP 544 & HIP 46843 ) within 20 pc of the sun
Shortage of these observations
Single site, single telescope
Time gap is big
We need network & continuous observations
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SONG
With SONG -spectroscopy
Stellar Observations Network Group(SONG)
Eight telescopes (3/8 in progress)
Filling the time gap ( avoid aliasing frequencies)
Astroseismic research of pulsating stars
Astroseismic research of Other objects
including young active stars
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Astroseismology, C. Aerts,J. Christensen Dalsgaard, D.W. Kurtz
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With mini-SONG
Photometry Multicolor Simultaneous
Distinguish variation caused by planets and stellar activities
Low frequency oscillation of stars Primary parameters of stars
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When SONG + mini-SONG
Precise spectroscopy + multicolor photometry Simultaneous!
Distinguish between variation in frequency caused by oscillation and activities
Oscillation evolution of solar like stars along the evolution track
…
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What can we do?
For our SONG & mini-SONG
Cooperate shoulder to shoulder Research, site …
Let’s enjoy it !
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