This page contains papers, posters, talks, and internal technical reports authored by the Eta Carinae team at the University of Minnesota.

HST Treasury Program Proposal (2001)

For a variety of reasons, HST can provide a very special and unique data set when Eta Car experiences its next spectroscopic event in mid-2003. Explaining the phenomenon is only part of the motivation. This star and its ejecta have unique characteristics that make them important for several branches of astrophysics; and when a spectroscopic event occurs, it's like varying the parameters in an experiment (or rather, set of experiments). The 2003 event will be the last chance in the forseeable future to obtain such a data set.

Eta Carinae has extreme parameters; it is mysterious in surprisingly basic ways; and HST/STIS can gather useful data on it at a terrific rate. As we explain below, the proposed data set will be valuable in several independent ways: It will help solve a specific set of current problems, it will constitute a large and unique archival data base for both stellar and nebular astrophysics, and it will be well-suited for educational uses.

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Published papers

The Chrysalis Opens? Photometry from the Eta Carinae HST Treasury Project, 2002--2006

J. C. Martin, K. Davidson, M. Koppelman

Observed with 0.1-arcsec spatial resolution, the star has continued to brighten at an unprecedented rate. This probably represents either a reduced dust formation rate, or destruction of dust, or both; but indirectly some physical change of the wind is implicated. We suspect that the mass-loss rate may be decreasing on a timescale of only a few years. (The complex relation between the star's apparent brightness, and the brightness of the entire Homunculus observed from the ground, is not entirely understood.)

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Variable Unidentified Emission Near 6307 AA in Eta Carinae

J. C. Martin, K. Davidson, F. Hamann, O. Stahl, K. Weis

The paper will appear in the May 2006 PASP. We discovered a conspicuous unidentfied emission feature near 6307AA in the spectrum of the central star. It is significant for two reasons: such prominent unidentified lines are now rare in this object, and this feature varies strongly and systematically. This line may be tied to both the spectroscopic cycle and the long-term brightening trend.

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The 2005 HST Calibration Workshop

The following papers where presented by members of the Minnesota Treasury Project Team at the 2005 HST Calibration Workshop in Baltimore, MD.

On The He II Emission in Eta Carinae and the Origin of Its Spectroscopic Events

J.C. Martin, K. Davidson, R.M. Humphreys (University of Minnesota), D.J. Hillier (University of Pittsburg), & K. Ishibashi (MIT)

Published in the 2006 March 20 Astrophysical Journal. High excitation He II emission, anomalous in some respects, appeared during the 2003.5 spectroscopic event. Several of its characteristics strongly support an ejection or wind-disturbance model for the event and not an eclipse model. This is important because it probably indicates a surface instability, which if true, is a valuable clue to the star's structure.

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A Change in the Physical State of Eta Carinae?

K. Davidson, J.C. Martin, R. M. Humphreys (University of Minnesota), K. Ishibashi (MIT), T. R. Gull (NASA/Goddard), O. Stahl, K. Weis (Ruhr-Universitat Bochum), D. J. Hillier (University of Pittsburg), A. Damineli (IAG - University of Sao Paulo), M. Corcoran (NASA/Goddard), F. Hamann (Univeristy of Florida)

A paper published in the February 2005 Astronomical Journal which describes the evolution of the Balmer emission line profiles in the central star over the last six years as observed by the HST STIS. We conclude from the observed changes that the central star of Eta Carinae may be entering a new phase of recovery from the 1850 Great Eruption.

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Fate of the Most Massive Stars (Conference)

The following are papers presented by members of the University of Minnesota Eta Carinae Treasury Project Team at The Fate of the Most Massive Stars Conference held in Jackson Hole, WY in May 2004.

Eta Carinae: Early Results & STIS Techniques

Kris Davidson, University of Minnesota

The brief article mentions some of the improvements that we are making with regards to STIS processing techniques. These are potentially useful for observations of other objects.

Link to STScI site

“Eta Carinae's Brightness Variations Since 1998: HST Observations of the Central Star”

J.C. Martin, M.D. Koppelman (Univ. Minn), & The HST Treasury Program on Eta Carinae

A paper published in the April 2004 Astronomical Journal which details the brightness changes in the central star over the 1998-2003.5 spectroscopic cycle. We show that the central star has continued to brighten by some unknown mechanism at an acellerated pace.

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“The Hubble Treasury Program on Eta Carinae”

Kris Davidson, University of Minnesota

This article was prepared for the Spring 2002 issue of the STScI Newsletter, which contained brief descriptions of the three original HST Treasury Programs.

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Three Essential pre-2004 Theoretical Overviews

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“Brightness Variations of η Carinae Since 1998”

J.C. Martin, M.D. Koppelman (Univ. Minn), & The HST Treasury Program on Eta Carinae

“The HST Treasury Project on η Carinae: Data technique development and early results”

K. Davidson (University of Minnesota) and the project team*

“A Complex Two-Dimensional Spectroscopic Database: The HST Treasury Archive for Eta Carinae”

R.M. Humphreys, K. Davidson, M. Gray, M.D. Koppelman, An Qian, J.C. Martin (Univ. Minn.), and K. Ishibashi (MIT) for the Eta Car HST Treasury Team

“The Historical Spectra of η Carinae”

R.M. Humphreys, M.D. Koppelman

“An Unexpected Development in the Spectrum of η Carinae”

K. Davidson (Univ. of Minnesota), J. Martin, R.M. Humphreys, K. Ishibashi, O. Stahl, K. Weis, T.R. Gull, D.J. Hillier, A. Damineli, M.F. Corcoran, F. Hamann, M. Bautista, S. Johansson, & H. Hartman

“Mysterious Transient Emission Features in Eta Carinae”

John C. Martin, Kris Davidson, Roberta Humphreys (Univ Minn), K. Ishabashi & The HST Treasury Program on Eta Carinae

“Update on the HST Treasury Project for Eta Carinae”

Kris Davidson, John C. Martin (Univ Minn), & The HST Treasury Program on Eta Carinae

“Extended Nebular Emission Around Eta Carinae”

John C. Martin & Kris Davidson (Univ Minn)

“Explaining the He II Emission in Eta Carinae”

Kris Davidson, J.C. Martin, R.M. Humphreys (Univ Minn), & K. Ishibashi

FUV Detection of Eta Carinae A

Kris Davidson (Univ Minn) & N. Smith (Univ Colorado)

Proper Motions and Radial Velocities of Ejecta Around Eta Carinae from STIS 2-D Spectroscopy

M.D. Koppelman, J.C. Martin and K. Davidson, University of Minnesota

Spatially Resolved Spectroscopy of Eta Car's NW Homunculus Cap

J.C. Martin, K. Davidson, & R.M. Humphreys, University of Minnesota

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Technical Memos (Separate Page)

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