Engineering topics

Cassatella, Angelo

Publications and source records attributed to Cassatella, Angelo.

2 records

NASA NTRS1990

Nova LMC 1990 no. 2: The first extragalactic recurrent nova

International Ultraviolet Explorer (IUE) observations of Nova LMC (Large Magellanic Cloud) 1990 number 2 are presented. It is the first recurrent nova to be observed outside the Galaxy. Earlier optical outburst of the nova was observed in 1968, when it reached a maximum of about V = 10.2. The first observations caught the nova at UV maximum, and IUE spectra were obtained between 16 Feb. and 26 Mar. 1990, with 8 hour resolution during the first day of observations. No P Cyg profiles developed on the resonance lines, suggesting that very little mass was ejected and that the outburst was not spherical. The integrated UV luminosity was then 3.4 x 10(exp 38) erg/s which is above the Eddington limit for a one solar mass white dwarf (assuming E (B - V) = 0.15 and a distance of 55 kpc to the LMC). This is the first time that the luminosity of a recurrent nova has been directly obtained.

Shore, Steven N.↗

NASA NTRS1990

Narrow circumstellar emission lines in SN 1987A

Low and high dispersion short wavelength prime (SWP) spectra of SN 1987A show that the supernova's progenitor was in a post red giant branch stage of evolution at the time of its demise in February 1987. The development of narrow high temperature emission lines of N 5, N 4, N 3, C 3, He 2 and O 3 were followed since May 1987. Observations through April 1990 are presented. The lines are interpreted as arising in a low density gas surrounding the supernova which was photoionized by the extreme UV pulse at shock breakout. In this picture, their temporal evolution is determined primarily by light travel time effects and recombination. Comparison of models of circumstellar environment with the International Ultraviolet Explorer (IUE) observations are discussed.

Sonneborn, George↗