UK Physics & Astronomy Physics & Astronomy
Colloquium


Colloquium



3:30 PM, Friday, April 19, 2002


Room 155, Chem-Phys Building







Dr. Gerry Brown


Physics Department
SUNY, Stoney Brook





Black-hole Mass-Period Correlation in Soft-X-ray Transients and its Implication for Gamma Ray Bursters





In usual binary evolution of compact objects, the hydrogen envelope of the more massive star is transferred to the companion star in Roche Lobe Overflow. However, if this takes place before helium core burning is finished in the more massive star, its helium core will blow away, and not go into a black hole. Therefore, the hydrogen envelope must be taken off by the companion star only later.

In taking the hydrogen envelope off, the companion star brings the helium core of the massive star into corotation with it. The center of the helium core burns to a neutron star, which later accretes more matter and drops into a black hole. Because the black hole must preserve the angular momentum of the neutron star which was rotating with the Keplerian velocity of the inner disk around it, and the black hole is much smaller than the neutron star its surface rotates at nearly the velocity of light.

A black hole rotating in the strong equipartition magnetic field acts like a generator of electricity, supplying sufficient power to run a gamma ray burster. The rapidly rotating black hole also couples through closed field lines with the accretion disk, the remainder of the helium star, and in trying to torque it up, drives a hypernova explosion.

Reading: A Theory of Gamma-Ray Bursts, G.E. Brown, C.-H. Lee, R.A.M.J. Wijers, H.K. Lee, G. Israelian, and H.A. Bethe, New Astronomy 5 (2000) 191.



*** Refreshments served at 3:15 PM ***


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Moshe Elitzur
moshe@pa.uky.edu



File translated from TEX by TTH, version 3.01.
On 3 Jan 2002, 14:42.