Accretion onto and radiation from the compact object formed in SN 1987A

Details Accretion onto and radiation from the compact object formed in SN 1987A Accretion onto and radiation from the compact object formed in SN 1987A

Dec 1994

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994apj...436..843b&link_type=abstract

Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 436, no. 2, p. 843-847

Astronomy and Astrophysics

Astronomy

38

Accretion Disks, Black Holes (Astronomy), Neutron Stars, Stellar Mass Accretion, Supernova 1987A, Photons, Radioactive Decay, Stellar Luminosity, Trapped Particles

Scientific paper

We follow the work of Chevalier, Houck, Blondin, and Park on hypercritical spherical accretion onto compact objects, applying their work to the case of the compact object and remnant formed in SN 1987A. We begin by motivating the Bondi spherical accretion theory, obtaining an expression for the mass accretion rate. We take SN 1987A parameters from Woosley and Bethe to evaluate the expression for this particular case and find hypercritical accretion on the order of 104 times the Eddington rate. The Eddington rate can be (greatly) exceeded because neutrinos carry off the energy. In this situation photons within a certain distance from the compact object are trapped; we derive an expression for this trapping radius, which decreases in time. For the case that the compact object is a neutron star, even though photons are trapped, neutrinos can still escape and carry off accretion energy, allowing for self-consistent solutions for hypercritical accretion. We use the work of Dicus on neutrino cooling to derive an expression for the shock radius, that is, the distance of the accretion shock front from the neutron star. The shock radius increase with time, so that at some critical time the shock radius equals the trapping radius. We find this critical time to be about 0.6 yr. After this time the luminosity in photons should increase to the Eddington limit, 3.8 x 1038 ergs/s. For the case that the compact object is a black hole, only the internal energy produced by the pdV work on the infalling matter outside of the trapping radius can be radiated. This would result in a luminosity approximately 1034-1035 ergs/s. The observed light curve of SN 1987A is explained by radioactive decays with a current luminosity of a few times 1036 ergs/s. The expected contribution from spherical accretion onto a neutron star is clearly not present, while the expected contribution for a black hole would be too small to detect. Our considerations thus support the hypothesis that the compact object formed in SN 1987A is a black hole rather than a neutron star.

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