Hee-Won LeeARCSEC and Dept. of Astronomy

Sejong University2010 August 26

Near IR Spectroscopy of Symbiotic Stars and Young Planetary Nebulae

Introduction to symbiotic stars ans young PNs

Mass Transfer and Mass Loss in Sym-biotics

Mass Loss and IR Observations of PNs

Conclusion

Contents

Introduction to Young PNs

AGB to Planetary Nebulae-Short-lived stage Shortage of tar-get objects-Heavily obscured by dust Difficulty in opitcal observations-Often brightest sources in IR sky

Young PNs are hot enough to pro-duce strong UV and harbor molecu-lar material indicative of mass loss coexistence of ionized, neutral and molecular components!

Wide binary systems of a hot white dwarf and a giant star.

Prominent emission lines and TiO absorp-tion 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 cap-ture.

Highly uncertain are the mass loss rate, mass transfer rate and orbital parameters.

Introduction to Symbiotic Stars

How can you make bipolar nebulae?Planetary nebulae exhibit a variety of mor-

phology from spherical, elliptical to bipolar and multipolar.

Binarity? Magnetic Field? Massive Progeni-tors?

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.

Problems?

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 result-ing in bipolar outflows and strong UV radiation.

Coexistence of hot UV source and cool HI re-gion leads to an interest-ing radiative transfer process.

Mass Loss and Mass Transfer in Symbiotics

He II, OVIEmission Region

H I ScatteringRegion

Half of symbiotic stars exhibit 6830 and 7088 emission fea-tures that are formed from Raman scattering of OVI 1032, 1038 by atomic hydro-gen identified by Schmid (1989).

A number of young planetary nebulae exhibit Raman scat-tering feature of He II.

O VI Raman scattering re-quires a thick H I region with column density N(HI) =1023 cm-2 that is illuminated by a strong UV source.

Raman Scattering by HI in PNe and Symbiotic Stars

Atomic Raman Spectroscopy in Symbi-otics

1. Raman O VI features are well-fit by a Keplerian accret-ing flow with an additional absorbing or an emission com-ponent.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

Quite uncertain orbital ele-ments of D-type symbiotics.

Binary separation is essential in order to model the mass trans-fer processes.

Molecular emission and/or ab-sorption provides the reference for the giant with respect to which strong UV emission re-gion may be located.

High resolution IR spectroscopy will be best used to locate the mass losing giant component in velocity space.

Molecular Components of Sym-biotics?

IR spectroscopy of Symbiotics

S. Gemini IR spectroscopy of several IR spectroscopy by Fekel et al.

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 ex-hibit prominent Raman scat-tered 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.

Ly alpha fluoresced H2 emission

Wood & Karovska (2003)

FUSE Spectroscopy of Mira B

IR images of PNe

NGC 6543 Spitzer image3.6 microns : blue, 5.8 microns green, 8.0 microns : red

NGC 7293 (Helix)3.2, 4.5, and 8.0 microns blue, green, and red

2MASS Images

Egg Nebula (RAFGL 2688)

1. Strikingly different shapes in optical and infrared.

2. H2 molecules are mainly found in the equatorial plane.

3. Different spatial distri-bution and kinematics.

4. The molecular compo-nent is important in bipolar morphology.

Molecular Hydrogen in Planetary Nebulae

1. H2 was detected first in NGC7027.

2. Molecular hydrogen was de-tected in six planetary neb-ulae (Isaacman, 1984, UKIRT).

3. H2 spectra were interpreted by shock excitation.

4 . T=1000-2000 K,N=104-105 cm-35. H2 emission in M2-9, NGC 7027 is interpreted by UV fluo-rescence (Hora & Latter 1994, Graham et al. 1993)

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

Molecular Hydro-gen in PNs

H2 image

H2 and Optical Composite

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.

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 Ra-man scattered He II6545 gives a good estimate of the mass loss rate.

Optical Raman Spectroscopy of Young PNs

The central star is surrounded by neutral hydrogen in the form of a cylinder.

The H I region is expanding with v_exp.

Line Profile Analysis

Monte Carlo Profile AnalysisRaman 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 prox-imity to the resonance of the Raman scattering cross section.

Determination of HI expansion veloc-ity region is possible from a Monte Carlo line profile analysis.

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

Molecular Component in Young Planetary Nebulae

• AJ, 2005, Smith, Bal-ick and Gehrz• CSHELL, NASA’s IRTF• R=43,000

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.

Conclusion