Other
Scientific paper
Jul 1994
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994apj...429..300w&link_type=abstract
The Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 429, no. 1, p. 300-318
Other
136
Binary Stars, Gamma Ray Observatory, Stellar Evolution, Supernovae, Ubv Spectra, Astronomical Models, Metallic Stars, Neutron Stars, Roche Limit, Stellar Spectrophotometry
Scientific paper
The evolution of the bright Type II supernova discovered last year in M81, SN 1993J, is consistent with that expected for the explosion of a star which on the main sequence had a mass of 13-16 Solar Mass but which, owing to mass exchange with a binary companion (a intially approximately 3-5 AU, depending upon the actual presupernova radius and the masses of the two stars) lost almost all of its hydrogen-rich envelope during late helium burning. At the time of explosion, the helium core mass was 4.0 +/- 0.5 Solar Mass and the hydrogen envelope, 0.20 +/- 0.05 Solar Mass. The envelope was helium and nitrogen-rich (carbon-deficient) and the radius of the star, 4 +/- 1 x 1013 cm. The luminosity of the presupernova star was 3 + 1 x 1038 ergs/s, with the companion star contributing an additional approximately 1038 ergs/s. The star may have been a pulsating variable at the time of the explosion. For an explosion energy near 1051 ergs (KE at infinity) and an assumed distance of 3.3 Mpc, a mass of Ni-56 in the range 0.07 +/- 0.01 Solar Mass was produced and ejected. This prescription gives a light curve which compares favorably with the bolomatric observations. Color photometry is more restrictive and requires a model in which the hydrogen-envelope mass is low and the mixing of hydrogen inward has been small, but in which appreciable Ni-56 has been mixed outward into the helium and heavy-element core. It is possible to obtain good agreement with B and V light curves during the first 50 days, but later photometry, especially in bands other than B and V, will require a non-local thermo-dynamic equilibrium (LTE) spectral calculation for comparison. Based upon our model, we predict a flux of approximately 10-5(3.3 Mpc/D)2 photons/sq cm/s in the 847 keV line of CO-56 at peak during 1993 August. It may be easier to detect the Computonized continuum which peaks at a few times 10-4 photons /s/sq cm/MeV at 40 keV a few months after the explosion (though neither of these signals were, or should have been, detected by the Compton Gamma-Ray observatory (CGRO). The presupernova star was filing its Roche lobe at the time of the explosion and thus its envelope was highly deformed (about 3:2). The companion star is presently embedded in the supernova, but should become visable at age 3 yr (perhaps earlier in the ultraviolet) when the supernova has faded below 1038 ergs/s. Indeed, if 'kicks' have not played an important role, it is still bound to the neutron star.
Eastman Ronald G.
Pinto Philip A.
Weaver Thomas A.
Woosley Stan E.
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