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Near IR Spectroscopy of Symbiotic Stars and Young Planetary Nebulae

Near IR Spectroscopy of Symbiotic Stars and Young Planetary Nebulae. Hee -Won Lee ARCSEC and Dept. of Astronomy Sejong University 2010 August 26. Contents. Introduction to symbiotic s tars ans youn g PNs Mass Transfer and Mass Loss in Symbiotics Mass Loss and IR Observations of PNs

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Near IR Spectroscopy of Symbiotic Stars and Young Planetary Nebulae

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  1. Near IR Spectroscopy of Symbiotic Stars and Young Planetary Nebulae Hee-Won Lee ARCSEC and Dept. of Astronomy SejongUniversity 2010 August 26

  2. Contents • Introduction to symbiotic stars ans young PNs • Mass Transfer and Mass Loss in Symbiotics • Mass Loss and IR Observations of PNs • Conclusion

  3. Introduction to Young PNs • AGB to Planetary Nebulae • Short-lived stage  Shortage of target objects • Heavily obscured by dust  Difficulty in opitcal observations • Often brightest sources in IR sky • Young PNs are hot enough to produce strong UV and harbor molecular material indicative of mass loss  coexistence of ionized, neutral and molecular components!

  4. Introduction to Symbiotic Stars • Wide binary systems of a hot white dwarf and a giant star. • Prominent emission lines and TiO absorption bands • D(usty) type symbiotics are characterized by IR excess indicative of a warm dust component, which is absent in S(tellar) type symbiotics. • Unlike cataclysmic variables, the giant does not fill the Roche lobe. • Mass loss through slow stellar wind and accretion process by gravitational capture. • Highly uncertain are the mass loss rate, mass transfer rate and orbital parameters.

  5. Problems? • How can you make bipolar nebulae? Planetary nebulae exhibit a variety of morphology from spherical, elliptical to bipolar and multipolar. • Binarity? Magnetic Field? Massive Progenitors? • What are IR spectroscopic characteristics of bipolar nebulae? • Accretion processes and mass loss in symbiotic stars. • Bipolar morphology in symbiotics • Molecules in Symbiotics • Quite uncertain orbital parameters.

  6. He II, OVI Emission Region H I Scattering Region Mass Loss and Mass Transfer in Symbiotics • The giant component loses mass in the form of a slow stellar wind. • Some fraction of stellar wind may be captured by a white dwarf resulting in bipolar outflows and strong UV radiation. • Coexistence of hot UV source and cool HI region leads to an interesting radiative transfer process.

  7. Raman Scattering by HI in PNe and Symbiotic Stars • Half of symbiotic stars exhibit 6830 and 7088 emission features that are formed from Raman scattering of OVI 1032, 1038 by atomic hydrogen identified by Schmid (1989). • A number of young planetary nebulae exhibit Raman scattering feature of He II. • O VI Raman scattering requires a thick H I region with column density N(HI) =1023cm-2 that is illuminated by a strong UV source.

  8. Atomic Raman Spectroscopy in Symbiotics 1. Raman O VI features are well-fit by a Keplerian accreting flow with an additional absorbing or an emission component. 2. Needs to know the physical dimensions of the emission region and scattering region in order to obtain accurate mass transfer rate and mass loss rate. 3. Notoriously difficult to find the distance and the orbital parameters BOES Data of V1016 Cyg

  9. Molecular Components of Symbiotics? • Quite uncertain orbital elements of D-type symbiotics. • Binary separation is essential in order to model the mass transfer processes. • Molecular emission and/or absorption provides the reference for the giant with respect to which strong UV emission region may be located. • High resolution IR spectroscopy will be best used to locate the mass losing giant component in velocity space.

  10. IR spectroscopy of Symbiotics 1. In RR Tel (the prototypical D-type symbiotic) and He 2-38, CO and H2O absorption at 2 micron are seen. 2. CO absorption bands are also found in HM Sge and V1016 Cyg, all of which exhibit prominent Raman scattered O VI. 3. Periodic IR flux variation expected from a Mira varibale. 4. Neutral atomic lines such as Fe, Sc, Ti may trace the stellar atmosphere of the cool giant. S. Gemini IR spectroscopy of several IR spectroscopy by Fekel et al.

  11. FUSE Spectroscopy of Mira B • Ly alpha fluoresced H2 emission • Wood & Karovska (2003)

  12. IR images of PNe NGC 7293 (Helix) 3.2, 4.5, and 8.0 microns blue, green, and red NGC 6543 Spitzer image 3.6 microns : blue, 5.8 microns green, 8.0 microns : red

  13. 2MASS Images

  14. Egg Nebula (RAFGL 2688) Strikingly different shapes in optical and infrared. H2 molecules are mainly found in the equatorial plane. Different spatial distribution and kinematics. The molecular component is important in bipolar morphology.

  15. Molecular Hydrogen in Planetary Nebulae H2 was detected first in NGC7027. Molecular hydrogen was detected in six planetary nebulae (Isaacman, 1984, UKIRT). H2 spectra were interpreted by shock excitation. 4 . T=1000-2000 K, N=104-105 cm-3 5. H2 emission in M2-9, NGC 7027 is interpreted by UV fluorescence (Hora & Latter 1994, Graham et al. 1993)

  16. Molecular Hydrogen in PNs H2 and Optical Composite • First detected in NGC 7027 in 1976 by Treffers et al. • Thermal emission from shocked molecular region. • Existence of possibly two highly collimated bipolar jets. • Ionized region delineated by an ellipsoid H2 image

  17. Composite image of Helix H-alpha (green) and O III (blue) gases from the Hubble Space Telescope. Molecular hydrogen (red) from Spitzer observations at 4.5 and 8.0 microns.

  18. Optical Raman Spectroscopy of Young PNs • Clear detection of Raman scattered He II 6545 in NGC 6790, NGC 7027, NGC 6302 and IC 5117. • The flux ratio of He II 6560 and Raman scattered He II6545 gives a good estimate of the mass loss rate.

  19. Line Profile Analysis • The central star is surrounded by neutral hydrogen in the form of a cylinder. • The H I region is expanding with v_exp.

  20. Monte Carlo Profile Analysis Raman He II Monte Carlo profiles for various expanding velocities of the cylinder with fixed N HI and opening angles. The Raman feature shows the shift of line center sensitively. Stronger profiles are obtained for higher expansion velocity due to proximity to the resonance of the Raman scattering cross section. Determination of HI expansion velocity region is possible from a Monte Carlo line profile analysis.

  21. Molecular Componentin Young Planetary Nebulae • May reside outside the HI region moving away. • May play an important role in shaping a bipolar nebula. • Excitation of H2 by shock and/or strong UV radiation • AJ, 2005, Smith, Balick and Gehrz • CSHELL, NASA’s IRTF • R=43,000

  22. Conclusion • High resolution IR spectroscopy will provide a powerful tool to trace molecular components in PNs and symbiotic stars • The mass loss/transfer processes in planetary nebulae and symbiotic stars will be studied in greater detail using IGRINS.

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