0.8 - 2.5 micron Spectroscopy of Novae Aquilae 1999, Nova Sagittarii 1999, Nova Sagittarii 1998 and Nova Cassiopeiae 1995
We present and discuss recent spectra of the above mentioned novae, and compare the results to those of other novae. The most striking thing about many novae spectra - especially during the early phases (10-100 days after outburst) - is the large differences in the strengths of the metal lines, especially C, N and O. In some cases the lines are so strong that significant overabundance of the parent element is certain; in other cases the lines are entirely absent. Large variations in the widths of the emission lines are seen from object to object. Occasionally the HI and HeI lines will display both broad and narrow components. Frequently the HI Paschen and Brackett lines show large departures from case B cases during the early stages. All of these observational features are clearly the result of widely varying physical conditions in the novae ejecta. These, in turn, require that there be large variations in the thermonuclear runaway strengths, in the geometries, and in the surface structures and abundances of the white dwarfs. Two of the most useful features in the spectra are the Lyman beta fluoresced OI lines at 0.8446 and 1.1287 microns. These are strong in the early phases and can be used to estimate the reddening when the hydrogen line ratios differ from their case B values and forbidden lines are not yet present. Because the novae frequently lie in the Galactic plane, the reddening is essential in establishing the distance and the absolute luminosity.
American Astronomical Society Meeting Abstracts
- Pub Date:
- December 1999