Young active star research with SONG and mini-SONG

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Young active star research with SONG and mini-SONG
4th Workshop for SONG

• Huijuan Wang
• National Astronomical Observatories
• Chinese Academy of Sciences
• _at_ Charleston

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Contents

• Young active star
• With SONG
• With mini-SONG
• When SONG mini-SONG

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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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Early evolution of solar-like stars
CTTS
WTTS
PTTS
ZAMS
(Neuhäuser 1997)
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Characters of WTTS PTTS

• Mlt2.5M? ( Late spectral type )
• Early phase of evolution(tlt10Myr/100Myr)
• Obvious absorption line of Li 6708 Å
• Weak emission line of Ha(EWHa10Å)
• No circle-stellar disk (mostly)
• Strong soft X-ray emission

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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 -gt central area of
  Taurus-Auriga
• (Neuheauser et al
  1995 Wichmann et al 2000 )

• Observational research of our group
• Xinglong groupLi Hu 1998
• ROSAT bright source catalog Tycho catalog gt
  sample of young solar type stars
• criterionlogC 0.4V (Lx gt 1030 erg s-1)
• Monitoring observation on 60 cm telescope at
  Xinglong observation station
• WTTS candidates most distributed in the outside
  region of TaurusAuriga

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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.

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Research method

• Sample
• Vlt 9.5 mag,63 stars
• Observation
• 2.16m tel Coude echelle spectrograph(R40000)
• 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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Spectroscopic observation log

• stars year
• 23 -- 2000 2001
• 37 -- 2004 2005
• 18 -- 2006
• 22 -- 2007
• 31 -- 2008
• gtSample63 stars(167spectra)

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Histogram of EW (Li)
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About 2/3 are young stars
WTTWPTTS 21 stars 33
MS 22 stars 35
ZAMS 20stars 32
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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)
• V8.81 mag
• None hight resolution spectroscopic observations
  before then
• 2005.04.25show double lines
• 2006.02.17 06.09show shift between lines
• till 2008.03.25totally 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
• Amplitude0.057mag
• 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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Chromospheric activity

• 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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Nearby young groups

• TW Hya Association(TWA)
• TW Hya 20Myr,56.4PC
• The nearest star formation region.
• (Zuckerman b. et al 2001,2004)

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• 11 stars in our sample
• EW(Li) gt 100 mÅ
• D lt 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 Dlt20PC
(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
  binaryHD 146875
• Spectroscopic study of two YSS (HIP 544 HIP
  46843 ) within 20 pc of the sun

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Shortage of these observations

• Single site, single telescope
• Time gap is big
• We need network continuous observations

SONG
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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?

• Cooperate shoulder to shoulder
• Research, site

• For our SONG mini-SONG

Lets enjoy it !
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Thanks!