Astronomy Tea Talk

Speaker 1: Dennis Lee (postdoc at JPL)

Title: Searching for the Shortest-wavelength Aromatic Infrared Bands

Abstract: Polycyclic aromatic hydrocarbons (PAHs) are responsible for a variety of near- and mid-infrared spectral features in Galactic and extragalactic sources. A feature at 1.05 μm arising from electronic transitions in PAH cations is predicted by laboratory experiments but has never been observationally confirmed. We conduct a dedicated search for this feature in absorption on a highly-extinguished sight line toward BD+40 4223, a blue supergiant in Cyg OB2, using the TripleSpec spectrograph at Palomar Observatory. Our results place a strong upper limit on the feature strength ruling out theoretical estimates with > 10σ significance. As dust on the sight line toward BD+40 4223 appears typical of the diffuse interstellar medium, this non- detection challenges existing models of PAH material properties and/or charge distribution.

Speaker 2: Matthias Fabry (postdoc at Villanova University)

Title: Contact binaries: Tightest buddies in space

Abstract: Binarity is the rule rather than the exception among massive-star populations. Furthermore, very short period binaries dominate the initial-period distribution, making that over 40% of massive stars engage in a so-called contact phase. Very often, these contact binaries end their life as a stellar merger, which create peculiar stars such as blue stragglers. In this talk, I will present the physical processes that occur to make a contact binary, and discuss their evolution and end products. Special consideration will be given on how to represent the 3D structure in 1D evolution models, and I will suggest several shortcomings that might cause discrepancies between theory and observations of a sample of massive contact systems.