Engineering topics

Mazzali, Paolo A.

Publications and source records attributed to Mazzali, Paolo A..

3 records

NASA NTRS2004

An Off-Axis Model for GRB 031203

The low luminosity radio emission of the unusually faint GRB 031203 has been argued to support the idea of a class of intrinsically sub-energetic gamma-ray bursts (GRBs), currently comprising two members. While low energy GRBs probably exist, we show that the collective prompt and multiwavelength observations of the afterglow of GRB 031203, do not necessarily require a sub-energetic nature for that event. In fact, the data are more consistent with a typical, powerful GRB seen at an angle of about twice the opening angle of the central jet. The (redshift corrected) peak energy, E(sub p), of GRB 031203 then becomes approximately 2 MeV, similar to many other GRBs.

Ramirez-Ruiz, Enrico↗

NASA NTRS1987

The ultraviolet spectrum of Beta Lyrae

The high-resolution UV spectrum of Beta Lyrae observed with the IUE satellite between 1980 and 1986 is analyzed. A complete list of line identifications for the entire spectral range of the IUE (1225-3125 A) is presented. The main spectral features are P Cygni profiles of resonance lines of high ionization states typical of stellar winds, some of which are combined with a broad emission feature due probably to an accretion disk; P Cygni profiles due to moderately ionized atoms in the iron group (mostly Fe III and Ni III); and absorption lines of elements in lower ionization stages, such as S II, Si II (higher multiplets), Ni II, and a large number of Fe II lines.

Mazzali, Paolo A.↗

NASA NTRS1986

A study of the P-Cygni lines in the ultraviolet spectrum of Beta Lyrae

The properties of the mass loss from the nondegenerate interacting binary system of beta Lyrae are investigated by analyzing the P-Cygni line profiles in the UV spectrum and considering these to be emitted in the wind outflow from the B8II primary component. Observed UV lines obtained by IUE are compared with theoretical models obtained using Sobolev's approximation. The models give satisfactory fittings. Simultaneous fitting of the resonance lines of Al II (1670 A) and Al III (1863 A) show that if the lines are emitted in the same region of the outflowing shell, as the line widths indicate, the electron temperature in the region is 23,500 K, and the mass loss is 2 times 10 to the minus 7th power solar masses/yr.

Mazzali, Paolo A.↗