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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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