Postdoc Opening

"Extreme Mass Loss from Super-Eddington Stars"

Stan Owocki
Bartol Research Institute
Department of Physics & Astronomy
University of Delaware

HST image of Eta Carinae  HST image of Eta Carinae (credit: NASA)

Basic Information:

I am looking for a post-doc (or "research scientist") to work with me on developing models of instabilities and mass loss for  massive stars near and above the Eddington limit, and/or to test such models against observations of Luminous Blue Variable (LBV) stars.  The position is supported by a NSF and  grant, and could last for up to 3 years. The full AAS job listing below gives some futher details.

Inquiries and even electronic applications (names of 3 references, PDFs of vita and research statement,  no later than Jan. 31, 2006) can be sent by email to:

Stan Owocki

Full AAS Job Listing:

Postdoctoral Research on "Extreme Mass Loss from Super-Eddington Stars"

Bartol Research Instititute of the University of Delaware

The Bartol Research Institute in the Department of Physics and Astronomy at the University of Delaware seeks  postdoctoral applicants to carry out research on episodic mass loss from extremely luminous, massive stars that approach, and apparently sometimes exceed, the Eddington limit.  As manifest in giant eruption events of eta Carinae and other "Luminous Blue Variable" (LBV) stars, the extreme mass loss during super-Eddington episodes may play a key role in setting the final states of massive stars, including progenitors of Gamma Ray Burst (GRBs), and even a first  generation of massive stars thought to have reionized the universe. Research in this position would involve collaboration in the group led by Prof. Stan Owocki. The central focus would nominally be theoretical, namely to develop fundamental radiation hydrodynamical models of instabilities that lead to eruption events. But observational candidates with a strong background in using observations (particularly of LBVs) to test and constrain theoretical models are also welcome. The start date is as soon as possible, but no later than September 2006.   Initial appointment will be for one year,  with nominal renewal for a second and even a third year, subject to both satisfactory progress and continued availability of funds.   Applicants should send a curriculum vita, a brief outline of relevant  interests and experience, and the names and addresses (including email) of  three references, no later than January 31, 2006 to ensure full  consideration.  Prof. Owocki will be available at the Jan. 2006 AAS meeting to meet with interested candidates.  Women and minorities are particularly encouraged to apply.  AAE/EOE.

Colloquium on overall research project:

Over the past year or so I've given several talks and colloquia on research related to this project. The latest was on Dec. 14, 2005 at ESO in Santiago, Chile, and was titled "Breaching the Eddington Limit in the Most Massive, Most Luminous Stars", for which the full talk slides are available in both PPT and PDF formats.

Here a paste of the ESO announcement and abstract:

On Wednesday, December 14 at 16:30 hr at ESO/Vitacura

Prof. Stanley OWOCKI
University of Delaware, USA & ESO Visiting Scientist

will give an ESO colloquium on:

Breaching the Eddington Limit in the Most Massive, Most Luminous Stars

One of the most fundamental tenets in astronomy is the Eddington limit, at which the radiative force from electron scattering equals the binding force of gravity. Luminous Blue Variable (LBV) stars observed near this limit often show evidence of unstable episodes of extensive mass loss, with the most extreme example being the 1840-60 giant eruption of eta Carinae, which resulted in ejection of ca. 10 solar masses in a bipolar outflow seen today as the Homunculus nebula. This talk will discuss how a super-Eddington luminosity can lead to such extreme mass loss, through continuum driving moderated by the "porosity" associated with structure arising from instabilities in the star's envelope and atmosphere. I will conclude with a brief discussion of the broad implications of such episodes of super-Eddington mass loss for massive star evolution, including progenitors of gamma-ray bursts, and even the first stars in the universe.

Further information on project funding:

Support for this post-doc position will come through project funded by NSF.  Here is some information from the original  proposal:

Proposal title: Radiation Hydrodynamics of Porsosity-Mediated Mass Loss from Super-Eddington Stars

P.I.:      Prof. Stanley P. Owocki,  University of Delaware, Newark, DE  USA
co-I.:      Dr. Nir Shaviv,  Hebrew University,  Jerusalem, Israel


We propose to develop radiation hydrodynamical models of the strong mass loss expected from stars that approach or exceed the Eddington limit. A general motivation is to understand  the nature, origin, and consequences of the extreme stellar wind and episodic mass loss seen in  Luminous Blue Variable (LBV) stars like η Carinae. In this regard, two key issues are: (1) the role of a continuum-radiation-driven, "super-Eddington" outflow in giant eruption events like the historical (1840-60) ejection of the ca. 10 solar masses that became the Homunculus nebula,  and (2) the role of rapid, near-critical stellar rotation in shaping a bipolar form to the wind and  nebula. Our analyses will build upon recent dynamical studies for how the spatial structure, or "porosity", of a super-Eddington medium can moderate continuum driving, leading to strong mass loss. Unlike standard stellar wind models based on radiation scattering in metal lines, this mass loss is independent of metalicity. The central theoretical effort will be to develop self-consistent, dynamical models of spatial structure arising from various instabilities near and  above the Eddington limit, and to apply these to simulations of porosity-mediated, continuum-driven mass loss. The general goal is to understand the role of rotation and super-Eddington mass loss in massive star evolution, with an eye to implications for the first generation of zero-metalicity, massive stars, as well as for the rotating-core-collapse model of Gamma Ray Bursts.

(Qualified applicants can be provided access to the full proposal to review.)

Links to relevant scientific publications:

Here is a link to a key background paper, as taken from NASA ADS.

1  2004ApJ...616..525O
1.000 11/2004 A      E  F      X                      R  C      S              U  H  

Owocki, Stanley P.; Gayley, Kenneth G.; Shaviv, Nir J.
A Porosity-Length Formalism for Photon-Tiring-limited Mass Loss from Stars above the Eddington Limit

Others can be found by browsing Prof. Owocki's publication list.

General background information on institute and department:

The Bartol Research Institute is a research center within the Department of Physics and Astronomy at the University of Delaware .

Prof. Owocki's  web page can be found here.

Further information on UDel Massive-Star Research Group

Prof. Owocki leads an active group carrying out research on hot, massive stars at the University of Delaware.This currently consists of two "research scientists",  Dr. Rich Townsend, and Dr. Asif ud-Doula. We are also currently supervising two Ph. D. thesis students (Tom Madura and Mary Oksala) and an undergraduate senior thesis student (Dan Cutright). UDel Prof. Jim MacDonald is also participating in this super-Eddington project.

Prof. Owocki also has active collaborations with many other researchers around the world, including Prof. Nir Shaviv of Hebrew University in Jerusalem, Israel. Prof. Shaviv was a co-investigor on the NSF proposal that funds this super-Eddington project.

Further information of the research activities of our group is available on request.

Questions? Send them to

Page last updated: Feb. 8, 2006