Doug Welch McMaster University Citizen Sky Workshop August 2009

Image credit: Kerry Ann Lecky-Hepburn Stars are not created equal in the information they provide to observers Stars are not created equal in the information they provide to observers eps Aur is a rare combination of extra observables eps Aur is a rare combination of extra observables This eclipse is at a tipping point in our ability to understand it. This eclipse is at a tipping point in our ability to understand it.

Image credit: Hans Hillewaert (Lycaon) Lycaon Rare massive star Rare supergiant Rare long-period Rare orbital alignment Rare opportunity =? Good observational constraint Clearer understanding

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2.035 day pulsation period day orbital period D. Lepischak M.Sc. Thesis and papers

18 nights on the Mt Stromlo nights on the Mt Stromlo 74 Complete phase coverage in BVI Complete phase coverage in BVI

Several pulsational cycles within single eclipse.CepheidCompanionRadius ± ± Radial Ampl ± [mags] [mags] 17.2 ± ± ± ± ± ± ± ± ± ± 0.1 Results: Results: χ ν 2 = 1.4 χ ν 2 = 1.4 Relative to orbital separation

Companion – large, cool, dim Inconsistent with isolated single-star evolution? Observed Cepheid Companion De-reddened

What is the companion? M–type. Mass loss?

Image credit: Sky & Telescope Watching the Detections …

The Force has a strong effect on weak minds – Obiwan Kenobi OR (translated) Most of the previous interpretations are wrong in one (or more!) important ways Look at the actual observational data with fresh eyes Separate findings from suspicions Keep track of the dominant signals

Monoliths could reproduce the eclipse lightcurve, too! Monoliths could reproduce the eclipse lightcurve, too!

1. eps Aur has a timescale, not a period 2. Nobody has factored in the effects of radial pulsation of the supergiant during the eclipse 3. We have been blind to more common analogues. Predictions 1. There wont be a central peak this eclipse 2. The peaks in eclipse are due to the primary, not details of the secondary

This eclipse and observing campaign will likely be definitive. Outcome 1: The scales will fall from our eyes and we will extract new, important understanding from this system. OR Outcome 2: It will become clear that this system is too much of a mess to provide improvements in our understanding of evolutionary issues. Part of the scientific process is knowing your efforts are providing diminishing returns!