NOAO >   Observing Info >   Approved Programs >   2009B-0274

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Proposal Information for 2009B-0274


PI: Nathan Smith, University of California Berkeley, nathans@astro.berkeley.edu
Address: Astronomy Department, 601 Campbell Hall, Berkeley, CA 94720, USA

Title: IR Variability of Eta Carinae: The 2009 Event

Abstract: Every 5.5 years, \eta Carinae experiences a dramatic ``spectroscopic event'' when high-excitation lines in its UV, optical, and IR spectrum disappear, and its hard X-ray and radio continuum flux crash. This periodicity has been attributed to an eccentric binary system with a shell ejection occurring at periastron, and the next periastron event will occur in January 2009. The last event in June/July 2003 was poorly observed because the star was very low in the sky, but this next event is perfectly suited for an intense ground-based monitoring campaign. Mid-IR images and spectra with T-ReCS provide a direct measure of changes in the current bolometric luminosity and a direct measure of the mass in dust formation episodes that may occur at periastron in the colliding wind shock. Near-IR emission lines trace related changes in the post-event wind and ionization changes in the circumstellar environment needed to test specific models for the cause of \eta Car's variability as it recovers from its recent ``event''. Because the nebular geometry is known very well from previous observations in this program, monitoring the changes in nebular ionization will yield a 3-D map of the changing asymmetric UV radiation field geometry in the binary system, and the first estimate of the orientation of its orbit. \bf Note: This proposal was originally granted long term status in Band 1 in 2008B, but the program was not carried over to 2009B. Here I am requesting only the final two epochs in 2009B to complete the program.


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