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Mass Loss, Dust Formation, and the Astrophysics of the Galactic Novae

Event Details

Event Dates: 

Friday, November 11, 2016 - 12:00pm

Seminar Location: 

  • JILA 10th Floor - Foothills Room

Speaker Name(s): 

Frederick M. Walter

Speaker Affiliation(s): 

Stony Brook University/NSO
Seminar Type/Subject

Scientific Seminar Type: 

  • Astrophysics Lunch Seminar

Event Details & Abstract: 

Galactic novae, the third largest class of explosions in our universe, are thermonuclear runaways (i.e., hydrogen bombs) on the surfaces of white dwarf stars accreting matter from a close binary companion. Novae are astrophysically important because they are a common end-point of low mass
stellar evolution, and because the nuclear-processed matter they eject enriches the galactic abundances of low-z atoms to a greater extent than do the supernovae.

In 2003 we started monitoring galactic novae using the small telescopes  of the SMARTS facility atop Cerro Tololo, Chile. The Stony Brook/SMARTS Atlas of (mostly) Southern Novae (http://www.astro.sunysb.edu/fwalter/SMARTS/NovaAtlas/) now contains data on over 80 novae. Unique features
of the atlas are 7-band optical through near-IR photometry and high-resolution (R=78,000), high-cadence (~daily) synoptic spectroscopy. These data permit the most detailed observational investigations of the mass loss and dust formation to date in galactic novae.

Following an overview of the galactic novae and some of the challenges they offer the spectroscopist, I will focus on two bright recent novae for which we have exquisite data, V1369 Cen (N Cen 2013) and V5668 Sgr (N Sgr 2015b). Both novae formed dust, but V5668 Sgr features a deep dust dip indicative of dust formation on the line of sight. Spectroscopy shows that the mass loss is not steady, and may be episodic on scales of weeks. The absorption velocities tend to accelerate outwards from a few hundred km/s to over 4000 km/s on timescales of weeks. Time-resolved spectra show evidence for interactions between discrete ejection events, and perhaps for forward and reverse shocks.