Monthly Archives: July 2012

Improved He I Emissivities in the Case B Approximation

R.L. Porter (1), G.J. Ferland (2), P.J. Storey (3), M.J. Detisch (2) ((1)Department of Physics and Astronomy and Center for Simulational Physics, University of Georgia, Athens, GA 30602, USA;(2)Dept. of Physics & Astronomy, University of Kentucky, Lexington, KY 40506, USA; … Continue reading

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Resolving the electron temperature discrepancies in H II regions and planetary nebulae: kappa-distributed electrons

David Nicholls (Australian National University, Australia) The measurement of electron temperatures and metallicities in H II regions and Planetary Nebulae has, for several decades, presented a problem: results obtained using different techniques disagree. There have been numerous attempts to explain … Continue reading

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Oxygen abundances from optical O I and O II recombination lines in planetary nebulae with [WC] central stars

Jorge García-Rojas (Instituto de Astrofísica de Canarias, Spain) I will present the analysis of very deep echelle spectra of a dozen planetary nebulae with [WC] or weak emission lines (wels) central stars. Physical conditions (electron density and temperature) are derived … Continue reading

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Temperature fluctuations in ionized nebulae and their effect on the oxygen abundance determination

Antonio Peimbert (Instituto de Astronomia–UNAM, Mexico) The two most common ways of determining chemical abundances on ionized regions are: 1.- the one that comes from assuming homogeneous temperature and using the observed collisionally excited line ratios (the direct method) and … Continue reading

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Oxygen abundances in ionized nebulae from photoionization model fitting

Christophe Morisset (Instituto de Astronomia-­UNAM, Mexico) In this talk I will present a review on the determination of oxygen abundance from photoionization models of nebulae. I will first describe the way models are performed using photoionization codes, explaining the necessary … Continue reading

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Very deep spectroscopy of planetary nebula NGC 7009 – The rich optical recombination spectrum and new effective recombination coefficients

Xuan Fang  (Department of Astronomy, School of Physics, Peking University, China) New ab-initio calculations of the effective recombination coefficients for the N II and O II recombination spectrum were carried out in the intermediate coupling scheme by Fang, Storey & … Continue reading

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The reliability of atomic data used for oxygen abundance determinations

Claudio Mendoza (IVIC, Caracas,  and CeCalCULA, CPTM, Mérida, Venezuela) The reliability of the atomic data required in astrophysical applications, in particular in abundance determinations, has been a perennial concern to the few research groups that cater for this well-established data demand. In … Continue reading

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