All-Moscow Seminar of Astrophysicists
(ASA)
annotation of talk
Wolfgang Kundt (Bonn University)
The Gamma-ray Bursts -- Topical as Ever
Earth is hit daily by some three bursts of gamma-rays, isotropically from all
directions, with energy fluxes S = 10-5 +/- 3 erg/cm2s, energies integral
S dt = 10-5 +/- 2.5erg/cm2,
durations dt between 10-3s and 103s,
temporal fine structure dt >= 10-3.7s, 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, <=2%, come from midatmospheric lightning
discharges; all the others have dt >= 10-1.7s. Among them, there is the
subclass of (>=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 1
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 <= d <= 300pc, via spasmodic accretion. The afterglows and
their absorption redshifts stem from self-generated transient hadronic winds
es-caping at relativistic speeds, reminiscent of SS 433.