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Stars are the major source of information about the Universe. Understanding their properties and applying our knowledge is the aim of research about stellar structure and evolution at MPA.

The theory of stellar structure and evolution has a long history at MPA, starting with the pioneering work by Kippenhahn, Meyer-Hofmeister and Weigert.

Their stellar evolution code has continuously been updated, reshaped and extended until the present day, still being among the top codes available. It is used for the calculation of solar models as well as the evolution of single stars of all masses.

Current research focuses on solar models, low and intermediate mass stars, convection theory, and the application to stellar populations and questions related to cosmology and basic physics.

Members:
Achim Weiss
Aldo Serenelli
Paula Jofre Pfeil
Monique Alves-Cruz
Victor Silva
Zazralt Magic

Collaborators visiting frequently:
Maurizio Salaris (John Moores Univ., Liverpool)
Leo Girardi (Univ. of Padova)
Paola Marigo (Univ. of Padova)
Corinne Charbonnel (Geneva Observatory)
Santi Cassisi (Osservatorio Collurania, Teramo)
Cesare Chiosi (Univ. of Padova)
Jason Ferguson (Wichita Univ.)
Brian Chaboyer (Dartmouth College)

Former Members:
Helmut Schlattl
Martin Flaskamp
Xu Kong
Lorenzo Piovan
Agis Kitsikis
Friedrich Kupka
Jerome Ballot

Current projects:

(always subject to updates....)

Origin and nature of the most metal-poor stars in the Galaxy: Pop III or Pop II.5? A. Weiss, H. Schlattl, S. Cassisi, and M. Salaris At the extreme end of the metallicity distribution of galactic halo stars we find objects being factors of 10,000 or more depleted in heavy elements as compared to the Sun. What is the nature of these stars? Are they "First Stars" (Population III), which were born from primordial, metal-free material, and which acquired the few heavy elements during their long life, or are they stars made in  the immediate neighbourhood of Pop.III Supernovae, carrying the chemical imprint of only a few or even single "parent star"? The anomalous carbon and nitrogen abundances found in many of these ultra-metal poor stars might be the clue to uncover their origin. We are investigating several scenarios to explain the CNO-abundances with stellar evolution calculations of metal-free, polluted or very metal-poor stars. Currently, we are favouring the "Pop II.5" scenario.
Theoretical modelling of the Planetary Nebulae Luminosity Function P. Marigo, L. Girardi, A. Weiss, M. Groenewegen, and C. Chiosi The luminosity function of Planetary Nebulae (PN) in external galaxies empirically has been found to be an excellent distance indicator out to as much as 20 Mpc. In particular the cut-off brightness at the bright end appears to be a universal quantity, if observed in the 5007 A band of the [OIII] ion. Theoretically, however, such a universality is difficult to understand, because PNe are the end product of the complicated Asymptotic Giant Branch evolution plus the expansion of the shed envelope. We developed the most complete self-consistent model for a synthetic PN population and find that for your populations we indeed can reproduce the observed PNLF. However, for populations with no recent star formation, as in elliptical galaxies, the bright end is much fainter than observed. This requires further investigation.

Stellar Model Challenge

to the Stellar Model Challenge pages

Useful links to stellar evolution data:

The Padua stellar evolution library

BaSTI - A bag of Stellar Tracks and Isochrone

Comments to: Achim Weiss (aweiss at this domain)