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L U N D UN I V E R S I T YFluorescence and resonant ionization in Eta Carinae           - an astrophysical laboratory     ...
L U N D UN I V E R S I T YLaboratory Astrophysics @ Lund University                             -   Stellar high resolutio...
L U N D UN I V E R S I T YCollaborators  Lund/Malmö: H.Nilsson, H.Lundberg, L.Engström, S.Huldt, T.Lennartsson,  T.Brage, ...
L U N D UN I V E R S I T YOutline  -    Introduction, Eta Carinae  -    Fluorescence  -    Selective ionization (RETPI – R...
L U N D UN I V E R S I T Y   Eta Carinae                 Homunculus                 Central stars                         ...
L U N D UN I V E R S I T Y 5.54 year periodicity observed in X-rayRXTE-obsverations, courtesy of M.Corcoran.              ...
L U N D UN I V E R S I T YEta CarinaeMaximum state– the radiation from the centralstar is driving thephotoprocesses in the...
L U N D UN I V E R S I T YThe Bowen mechanism (fluorescence)                                     8
L U N D UN I V E R S I T YFluorescence lines in HST spectra of WB                                          9
L U N D UN I V E R S I T YTemporal variations of HI and FeII lines                             The temporal variations dur...
L U N D UN I V E R S I T YVariations of SiIII] 1892 Å linemaximum                            Spatial scaleminimum         ...
L U N D UN I V E R S I T YVariations of SiIII] 1892 Å line                                   12
L U N D UN I V E R S I T YRETPI of Si+, enhancing the 1892Å SiIII] line                             The 2-photon process i...
L U N D UN I V E R S I T YEstimation of the RETPI rate in the Weigelt blobs The 2-photon process involving HLyα and HLyγ d...
L U N D UN I V E R S I T YIonization balance in the Weigelt blobs                                          15
L U N D UN I V E R S I T YPossibilities for RETPI producing [FeIII]                             The double H Lyα energy co...
L U N D UN I V E R S I T Y    Conclusion and outlook•    In the Weigelt blobs of Eta Carinae (as in many other astrophysic...
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Fluorescence and resonant ionization in astrophysical plasmas, with emphasis on and examples from the star Eta Carinae

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Talk given by Henrik Hartman at 3d CDAMOP, 14-16 December 2011, Delhi University, Delhi, India.

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Fluorescence and resonant ionization in astrophysical plasmas, with emphasis on and examples from the star Eta Carinae

  1. 1. L U N D UN I V E R S I T YFluorescence and resonant ionization in Eta Carinae - an astrophysical laboratory Henrik Hartman, Lund University, Sweden Current Development in Atomic, Molecular and Optical Physics, Delhi 2011 1
  2. 2. L U N D UN I V E R S I T YLaboratory Astrophysics @ Lund University - Stellar high resolution spectroscopy (VLT; HST) - High-resolution FTS measurements of dishcarges (Edlén lab) - Lifetime measurements: LIF on laser produced plasmas (LLC) 2
  3. 3. L U N D UN I V E R S I T YCollaborators Lund/Malmö: H.Nilsson, H.Lundberg, L.Engström, S.Huldt, T.Lennartsson, T.Brage, P.Jönsson, N.Ryde, (S.Johansson & V.Letokhov) Eta Carinae: T.Gull (NASA), M.Bautista, V.Fivet (U Mich), J.Groh(MPIfI) Lifetimes: E.Biemont group (th, Liege), S.Mannervik group (exp, Stockholm) Thanks to: CDAMOP2011 organizers Swedish Science Council (VR), Swedish National Space Board (SNSB) Johansson & Letokhov (deceased 2009) 3
  4. 4. L U N D UN I V E R S I T YOutline - Introduction, Eta Carinae - Fluorescence - Selective ionization (RETPI – Resonance Enhanced Two-Photon Ionization) for SiIII and FeIII - Outlook 4
  5. 5. L U N D UN I V E R S I T Y Eta Carinae Homunculus Central stars Strontium filamentWeigelt blobs 10” 1” HST / WFPC2 image 5
  6. 6. L U N D UN I V E R S I T Y 5.54 year periodicity observed in X-rayRXTE-obsverations, courtesy of M.Corcoran. K. Nielsen 6
  7. 7. L U N D UN I V E R S I T YEta CarinaeMaximum state– the radiation from the centralstar is driving thephotoprocesses in the Weigeltcondensation.Minimum state– the radiation from the centralstar is blocked for severalmonths. The transition into theminimum is referred to as thespectroscopic event. 7
  8. 8. L U N D UN I V E R S I T YThe Bowen mechanism (fluorescence) 8
  9. 9. L U N D UN I V E R S I T YFluorescence lines in HST spectra of WB 9
  10. 10. L U N D UN I V E R S I T YTemporal variations of HI and FeII lines The temporal variations during the spectroscopic event is different for different kinds of lines. Hydrogen lines and fluroescent lines vary quicker, whereas the (most) forbidden lines excited by collisions have a much slower response set by the recombination time scale, i.e. removal of electrons. 10
  11. 11. L U N D UN I V E R S I T YVariations of SiIII] 1892 Å linemaximum Spatial scaleminimum 11
  12. 12. L U N D UN I V E R S I T YVariations of SiIII] 1892 Å line 12
  13. 13. L U N D UN I V E R S I T YRETPI of Si+, enhancing the 1892Å SiIII] line The 2-photon process involving HLyα and HLyγ leaves the atom doubly ionized and in an excited state, producing the 1892 Å radiation as it decays. Johansson & Letokhov, Science (2001) Johansson, Hartman, Letokhov A&A (2006) 13
  14. 14. L U N D UN I V E R S I T YEstimation of the RETPI rate in the Weigelt blobs The 2-photon process involving HLyα and HLyγ depends on the difference between the real level and the virtual level, and in the intensity of the H Lyman lines. With estimates of the conditions in the WB, the observed intensity of the 1892 Å feature, 7x10-12 erg cm-2 s-1 Å-1, can be explained buy the RETPI process. 14
  15. 15. L U N D UN I V E R S I T YIonization balance in the Weigelt blobs 15
  16. 16. L U N D UN I V E R S I T YPossibilities for RETPI producing [FeIII] The double H Lyα energy corresponds to the difference between the 3d5(6S) 4s 5S in FeIII and 3d6(5D) 4s 4D in FeII, with the 5p levels in between. 16
  17. 17. L U N D UN I V E R S I T Y Conclusion and outlook• In the Weigelt blobs of Eta Carinae (as in many other astrophysical plasmas), fluorescence is an important process for line formation. The temporal variations in the incident radiation from the central star allow us to study these processes separate from the collisional excitation and ionization.• The same HST spectra indicate that RETPI (Resonance Enhanced Two-Photon Ionization) can be responsible for the formation of strongly varying lines. During the high state (maximum), the RETPI process can control the ionization equilibrium for many ions.• RETPI often leaves the ions in an excited state. With the RETPI producing strong forbidden lines, e.g. Si III] and [FeIII], care must be taken when using simple line rations for determination of physical conditions.• Forbidden lines are often strong and used for diagnostics in emission line objects like stellar winds, AGNs and Quasars. Eta Carinae is an ideal and rare object to study these processes, but the importance of these processes are probably much wider. 17

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