By Sun Kwok (auth.), Ryszard Szczerba, Sławomir K. Górny (eds.)
The time period proto-planetary nebulae (PPNe) within the context of the overdue phases of stellar evolution used to be created purely a little greater than twenty years in the past to precise the assumption that during the close to destiny those items becomes planetary nebulae (PNe). the 1st proto-planetary nebulae (called additionally post-Asymptotic tremendous department, or almost immediately post-AGB gadgets) AFGL 2688 and AFGL 618 have been chanced on in mid seventies in process the Air strength Sky Survey. research of this part of stellar evolution built very quickly in 1980's after the IRAS challenge whilst it grew to become transparent that proto-planetary nebulae emit an important a part of their strength within the mid-and far-infrared. hundreds and hundreds of latest applicants were proposed however the reputation of the true proto-planetary nebulae isn't an easy activity and wishes a considerable attempt to exclude instances that signify diverse evolutionary phases. excessive answer spectroscopy of stellar atmospheres is of a lot significance during this recognize. strangely, just a small workforce of important stars, the so known as 21 11m emitters, express chemical signatures of the three rd dredge up approach. Very lately, a extra distinct reviews of mid-infrared spectra from the Infrared house Observatory (ISO) let for a greater figuring out of chemical composition and evolution of circumstellar fabric round those stars. a brand new impetus within the box of proto-planetary nebulae study used to be began within the 1990's with excessive spatial solution imaging in mid-infrared and optical wavelength ranges.
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Additional info for Post-AGB Objects as a Phase of Stellar Evolution: Proceedings of the Toruń Workshop held July 5–7, 2000
The H2 emission line may be excited either by fluorescence, through the absorption of UV photons from the central star in the photodissociation region or by shocks. t molecular hydrogen and a study of H2 to Br-y flux ratios in hot post-AGB stars would enable us to understand the origin offast stellar winds in the hot post-AGB phase and their role in the shaping and formation of planetary nebulae. 6. CONCLUSIONS From an analysis ofIRAS data several hot post-AGB candidates were identified. Their low gravities and extended atmospheres appear to imitate Population I supergiants.
Based on these observations, the central star of Hen1475 was presumed to be at the origin of a 15"long structure containing symetrically opposing bright knots. The knots were found to have radial velocities of ± 500 km s-l. The bright central component seen in the NTT images was resolved by the HST into a highly asymmetric structure a few arcseconds across. A multi wavelength study of Hen 1475 by Riera et al. (1995) established the object as a massive post-AGB star in the transition phase between the end of the AGB and the formation of a new PN.
And Heber U. R. , Garda-Lario P. et al. 1993, A&A, 267, L19 Parthasarathy M. 1993a, ApJ 414, L109 Parthasarathy M. ) Luminous High Latitude Stars, ASP Conf. 173 Parthasarathy M. R, Clavel J. 1993d, In: J. ) The MK Process at 50 years, ASP Conf. , de Martino D. S. , Sivarani T. et al. , et al. R, Parthasarathy M. c. , Zijlstra A. , et al. , Kwok S. B. B. 1972, A&A 18,390 PROPERTIES OF POST-AGB STARS WITH IRAS COLORS TYPICAL OF PLANETARY NEBULAE Griet C. M. van Hoof C1TA, University of Toronto, 60 St.
Post-AGB Objects as a Phase of Stellar Evolution: Proceedings of the Toruń Workshop held July 5–7, 2000 by Sun Kwok (auth.), Ryszard Szczerba, Sławomir K. Górny (eds.)