CENTER FOR APPLIED MATHEMATICS AND THEORETICAL PHYSICS
UNIVERZA V MARIBORU UNIVERSITY OF MARIBOR
KREKOVA 2 SI-2000 MARIBOR SLOVENIA
Phone +(386) (2) 2355 350 and 2355 351 $\bullet$ Fax +(386) (2) 2355 360
Robnik@uni-mb.si $\bullet$ www.camtp.uni-mb.si
PROF.DR. MARKO ROBNIK, DIRECTOR

Seminarsko predavanje
Centra za uporabno matematiko in teoreticno fiziko

THE GAMMA-RAY BURSTS - TOPICAL AS EVER

Profesor Dr. Wolfgang Kundt
Institut für Astrophysik, Universität Bonn
Bonn, Germany

Abstract: Earth is hit daily by some three bursts of gamma-rays, isotropically from all directions, with energy fluxes $S = 10^{-5 \pm 3} erg/cm^2 s$, energies $\int S dt = 10^{-5 \pm 2.5} erg/cm^2$, durations $\Delta t$ between $10^{-3} s$ and $10^3 s$, temporal fine structure $\Delta t \ge 10^{3.7 s}$, power-law spectra like superpositions of cooling sparks with peak fluxes straddling $1 MeV$, and with composite lightcurves which differ vastly from burst to burst whereby hardness drops during subbursts. A small subclass, $\le 2\%$, come from midatmospheric lightning discharges; all the others have $\Delta t \ge 10^{-1.7} s$. Among them, there is the subclass of ($\ge 5$) repeaters, SGRs, which emit somewhat softer bursts many times per year, yet occasionally also hard bursts, like all the others. They have been identified as Galactic neutron stars, of spin periods between $5s$ and $8s$ (with one controversial candidate). All the others are presently thought to come from cosmic distances, because of their isotropic arrivals, and because their afterglow spectra show large absorption redshifts. In my opinion, all the extraterrestrial bursts come from nearby Galactic neutron stars, $50pc \le d \le 300pc$, via spasmodic accretion.

Seminarsko predavanje bo v torek 27. marca 2001 ob 15:15 uri v seminarski sobi CAMTP, Krekova 2, pritlicje. Vljudno vabljeni vsi zainteresirani, tudi študentje.

Prof.Dr. Marko Robnik
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