Nine Years of Observing Novae with SMARTS: New Insights into the Phenomenon?

Tuesday, 22 January 2013 8:30 a.m. — 9:30 a.m. MST

AURA Lecture Hall

NOIRLab South Colloquia
FREDERICK M. WALTER (Dept. of Physics and Astronomy, Stony Brook University & NOAO South Visiting Astronomer)

Novae, the manifestations of thermonuclear explosions in a degenerate hydrogen layer on the surfaces of white dwarf stars, are highly dynamic phenomena. Novae may brighten by up 20 magnitudes; gas may be expelled with velocities of over 5000 km/s in extreme cases. Their rapid onsets and decay timescales of months to years are difficult to fit into a classical observing program, but are well-suited for service/queue observations on dedicated facilities.  Nearly a decade ago we initiated a project to generate a more-or-less uniform set of spectroscopy and photometry of novae accessible to the SMARTS facilities at the Cerro Tololo InterAmerican Observatory. The atlas now contains observations of over 70 novae, some observed for as long as 9 years past their eruption.

As is to be expected, high cadence observations of a large sample of novae for extended periods have revealed new and exciting phenomena.

Following a general description of the nova phenomenon, I shall turn to two topics that I am currently engaged in. The first is an attempt to explain the peculiar line profiles of the He-N (or recurrent) novae. These do not resemble the optically thick shells of the Fe II (or classical) novae, but can be modeled as optically-thin accretion disks. If so, this will require a change in our understanding of the inner environs of the novae.  The second is an examination of the N III Bowen fluorescence lines, and their relation the He II 4686 line. This mechanism is understood in the static case, but the novae are highly dynamic. The light curves of the N III and He II lines and the supersoft X-ray flux suggest an interpretation as a temperature gauge.