Newsgroup: it.scienza.astronomia
Titolo: Il GRB piu' luminoso mai ripreso

Il lavoro congiunto del satellite Swift  e del sistema "Pi of the Sky"
(Osservatorio Las Campanas) hanno permesso di riprendere quasi
simultaneamente in ottico e gamma un lampo GRB.
Si ritiene che questo tipo di GRB abbia origine dal collasso di stelle
giganti, in buco nero. Ma la questione non e' ancora ben definita.
http://grb.fuw.edu.pl/pi/ot/grb080319b/normal.html
See press release: The smallest telescope detects the largest cosmic
explosion
"Pi of the Sky" observation of GRB080319B
the brightest ever gamma ray burst
During night 2008.03.18/19 the "Pi of the Sky" apparatus located at Las
Campanas Observatory was observing the Swift satellite field of view
with 10s exposures from 5:49 UT. At 6:12 UT we observed exceptionally
bright optical flash reaching 5.8 magnitudo. It was automatically
detected by the flash recognition algorithm.
The first image with the flash visible started 2 s before the Swift
trigger GRB 080319B. The flash was registered near the border of the
frame. After taking 3 images the alert from the Swift satellite was
received and the apparatus moved to position the GRB in the center of
the frame. Consequent images show the decay of the source down to 11
magnitudo in 4 minutes. We have published the results as GCN 7439 and 7445.
The "Pi of the Sky" observation combined with the Swift gamma-ray data
for the first time confirmed that optical and gamma-ray emission start
simultaneously with 10s precision.
Preliminary lightcurve:
This observation was the proof of the novel concept of the "Pi of the
Sky" project. Usually, optical emission from GRB is observed by
telescopes listening to alerts from satellite gamma ray detectors.
Signal distribution and turning the telescope take some time and the
very first minute of the outburst cannot be observed. The principle of
the "Pi of the Sky" project is different. The apparatus monitors
continuously large fraction of the sky taking 10s exposures and detects
optical flashes independently, while the satellite information confirms
the origin of the flash.
Observing the optical emission during the gamma ray burst which usually
last less than 2 minutes is crucial to understand the mechanism
releasing enormous amount of energy. It is commonly believed that in the
case of GRB longer than 2 s the phenomenon is caused by a collape of a
massive star ending with a formation of a black hole. The details of the
process however, still remains uncertain.
The most important results of this "Pi of the Sky" observation are
- measurement of the maximum brightness of GRB 080318B equal to 5.8
magnitudo
- determination of the length of the rising edge of the light curve to
be between 5 and 20 s
- observing that the begining of the optical emission coincide with the
gamma emission within 10 s
The peak of the GRB 080319B was observed also by TORTORA wide-field
optical camera having lower limiting magnitude and superior time
resolution. The first exposure with visible source started at T0+16s
(S.Karpov et al, GCN 7452).
Also RAPTOR observed the field before and during the GRB 080319B. The
first image with the visible source started at T0+2s. (P.Wozniak et al.
GCN 7464).
Swift UVOT telescope started the observation at T0+51s (S.T.Holland et al.)


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credevo che fosse oramai certo...
cosa manca ? 

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Di certo è l'ipotesi più probabile, però è difficile da dimostrare, perchè il
buco nero che si dovrebbe essere formato è un oggetto estremamente elusivo.
Potrebbe essere rivelato da un effetto di lente gravitazionale, ma dovrebbe
passare un oggetto esattamente dietro per essere rivelato, e le probabilità non
sono molto alte.
Un altro modo di rivelarlo potrebbe essere tramite la presenza di un disco di
accrescimento che emette raggi X e relativi getti, ma è un fenomeno che può
avvenire solo successivamente, in tempi decisamente lunghi, almeno rispetto alla
vita umana.
--
ciao
  Stefano