Previous
abstract 
Next
abstract
We observed Nova Cir 1995 and Nova Aql 1995 with the Hopkins Ultraviolet Telescope during the Astro-2 shuttle mission in 1995 March. The spectra provide coverage from 840 \AA\ to 1860 \AA\ with a spectral resolution of about 3 \AA, extending, for the first time, the ultraviolet wavelength coverage of novae to the region between Ly\thinspace$\alpha$ and the Lyman limit. These far-ultraviolet observations show strong, broad, nebular emission lines from carbon, nitrogen, and oxygen, as well as a weak continuum. The Nova Cir observation shows strong C~{\small IV}~$\lambda1549$ emission, with a total flux of about $10^{-10}$~ergs~cm$^{-2}$~s$^{-1}$~\AA$^{-1}$, as well as N~{\small IV}]~$\lambda1486$, N~{\small III}]~$\lambda1750$, C~{\small II}~$\lambda1335$, N~{\small V}~$\lambda1240$, O~{\small IV}]~$\lambda1403$, O~{\small III}]~$\lambda1665$, He~{\small II}~$\lambda1640$, He~{\small II}~$\lambda1085$, C~{\small III}~$\lambda1176$, and C~{\small III}~$\lambda977$. The observed continuum is below $5\times 10^{-13}$ ergs~cm$^{-2}$ s$^{-1}$ \AA$^{-1}$. Nova Aql, which Sun constraints have prevented IUE from observing, was observed three times during the mission. The strongest line in the observations is N~{\small III}]~$\lambda1750$, with a flux of about $10^{-11}$~ergs~cm$^{-2}$~s$^{-1}$~\AA$^{-1}$. Also present are C~{\small IV}~$\lambda1549$, N~{\small IV}]~$\lambda1486$, N~{\small V}~$\lambda1240$, O~{\small IV}]~$\lambda1403$, O~{\small III}]~$\lambda1665$, C~{\small II}~$\lambda1335$, and He~{\small II}~$\lambda1640$. The continuum is below $10^{-14}$~ergs~cm$^{-2}$~s$^{-1}$~\AA$^{-1}$. The flux in many of the lines, especially the higher ionization states of carbon, nitrogen, and oxygen, increases over the ten days spanned by the three observations. The He~{\small II}~$\lambda1640$ to He~{\small II}~$\lambda1085$ flux ratios indicate a significant amount of extinction at the shorter wavelengths, possibly an indication of dust formation in the shells of both novae. The extinction is more severe for Nova Aql. The observed emission will allow us to place constraints on the abundances of carbon, nitrogen, and oxygen in the nova shells, as well as estimate their expansion velocities.
This work was supported by NASA contract NAS 5-27000 to the Johns Hopkins University.
