A BIPOLAR PLANETARY NEBULA NGC 6537: PHOTOIONIZATION OR SHOCK HEATING?

  • HYUNG SIEK (Bohyunsan Optical Astronomy Observatory)
  • Published : 1999.04.01

Abstract

NGC 6537 is an extremely high excitation bipolar planetary nebula. It exhibits a huge range of excitation from lines of [N I] to [Si VI]or [Fe VII], i.e. from neutral atoms to atoms requiring an ionization potential of $\~$167eV. Its kinematical structures are of special interest. We are here primarily concerned with its high resolution spectrum as revealed by the Hamilton Echelle Spectrograph at Lick Observatory (resolution $\~0.2{\AA}$) and supplemented by UV and near-UV data. Photoionization model reproduces the observed global spectrum of NGC 6537, the absolute H$\beta$ flux, and the observed visual or blue magnitude fairly well. The nebulosity of NGC 6537 is likely to be the result of photo-ionization by a very hot star of $T_{eff} \~ 180,000 K$, although the global nebular morphology and kinematics suggest an effect by strong stellar winds and resulting shock heating. NGC 6537 can be classified as a Peimbert Type I planetary nebula. It is extremely young and it may have originated from a star of about 5 $M_{\bigodot}$.

Keywords

References

  1. Strasbourg - ESO Catalogue of Galactic Planetary Nebulae Acker, A.;Ochsenbein, F.;Stenholm, B.;Tylenda, R.;Marcout, J.;Schohn, C.
  2. A&AS v.33 Acker, A.
  3. Physics of Thermal Gaseous Nebulae Aller, L. H.
  4. Proc. Natl. Acad. Sci. Aller, L. H.;Hyung, S.;Feibelman, W. A.
  5. ApJ v.308 Barker, T.
  6. A&A v.297 Bassgen, M.;Diesch, D.;Grewing, M.
  7. A&A v.240 Blocker, T.;Schonberner, D.
  8. MNRAS v.229 Clegg, R. E. S.
  9. A&A v.304 Cuesta, L.;Philips, J. P.;Mampaso, A.
  10. Proc. Natl. Acad. Sci. v.82 Feibelman, W. A.;Aller, L. H.;Keyes, C. D.;Czyzak, S. J.
  11. A&A v.157 Gathier, R.;Pottasch, S. R.;Goss, W. A.
  12. Origin and Evolution of the Elements Grevesse, N.;Noels, A.;N. Prantzos(ed.);E. VangioniFlam(ed.);M. Casse(ed.)
  13. Computer Phys. Comm. v.52 Hubeny, I.
  14. ApJS v.90 Hyung, S.
  15. ApJ v.491 Hyung, S.;Aller, L. H.
  16. MNRAS v.278 Hyung, S.;Aller, L. H.
  17. MNRAS v.272 Hyung, S.;Keyes, C. D.;Aller, L. H.
  18. MNRAS v.257 Kingsburgh, R. L.;Barlow, M. J.
  19. A&A v.122 Koppen, J.
  20. ApJ v.367 Lame, N. J.;Ferland, G. J.
  21. MNRAS v.244 Middlemass, D.
  22. IAU Symp. 76, Planetary Nebulae Peimbert, M.;Y. Terzian(ed.)
  23. A&A v.332 Perinotto, M.;Corradi, R. L. M.