Young active star research with SONG and mini-SONG

1. 4th Workshop for SONG Young active star research with SONG and mini-SONG Huijuan Wang National Astronomical Observatories Chinese Academy of Sciences @ Charleston

2. Contents • Young active star • With SONG • With mini-SONG • When SONG + mini-SONG

3. 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

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

5. Characters of WTTS & PTTS • 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

6. 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

7. 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

8. Why high resolution? （Wichmann 1996; Martin 1998） • 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.

9. Research method • Sample • V< 9.5 mag,63 stars • Observation • 2.16m tel & Coude echelle spectrograph(R＝40000） • Data reduction & analysis • IRAF software (Echelle, Daophot) • Expect results • Equivalent width (EW) of Li • Radial velocity (RV) • Projected rotation velocity • Spectroscopic binary etc.

10. Spectroscopic observation log stars year • 23 －－ 2000 & 2001 • 37 －－ 2004 & 2005 • 18 －－ 2006 • 22 －－ 2007 • 31 －－ 2008 ==>Sample：63 stars（167spectra）

12. Histogram of EW (Li)

14. About 2/3 are young stars

15. 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

16. 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)

17. 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

19. Radial velocity curve

21. Spectral Disentangling • KOREL code (Hadrava 1995)

23. 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 -)

24. Age － method 1

25. Age － method 2 • Age ~ 100 －150Myr

26. Observed spectrum － ModelG9＋K0 ＝ Subtracted profile Chromospheric activity • Strong chromospheric activity on the primary Emission originates in plage-like regions

27. 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

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

29. 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

30. 2 stars D<20PC （Wang & Wei, 2009, RAA, 9, 315）

32. 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

33. 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 20pc of the sun

34. Shortage of these observations • Single site, single telescope • Time gap is big • We need network & continuous observations SONG

35. 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

36. Astroseismology, C. Aerts,J. Christensen Dalsgaard, D.W. Kurtz

37. With mini-SONG • Photometry • Multicolor • Simultaneous • Distinguish variation caused by planets and stellar activities • Low frequency oscillation of stars • Primary parameters of stars

38. 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 • …

39. What can we do? • Cooperate shoulder to shoulder • Research, site … • For our SONG & mini-SONG Let’s enjoy it !

40. Thanks!