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Study and Modelling of 021004 and 050408. Antonio de Ugarte Postigo IAA-CSIC (Granada, Spain). Santorini, 1st Sept. 2005. GRB 021004 Modelled by multiple energy injections. Discovery I. Detected by HETE-II on 4th October 2002 at 12:06:13.57 UT. Duration of ~100 s.
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Study and Modelling of 021004 and 050408 Antonio de Ugarte Postigo IAA-CSIC (Granada, Spain) Santorini, 1st Sept. 2005
Discovery I • Detected by HETE-II on 4th October 2002 at 12:06:13.57 UT. • Duration of ~100 s. • Position transmited to Earth 49 s after the begining of the burst. • First observations began 3 min after t0. http://space.mit.edu/HETE/Bursts/GRB021004/
Discovery II • Detected at R~15.3. • Position reported 3 hours after the begining of the event (Fox et al. 2002). • High redshift event still at R~17 at t0 + 4h. • Photometry, spectroscopy, polarimetry.
Spectroscopy • Fast detection allowed to take high resolution spectra few hours after the event. • Z=2.3293 • Luminosity distance 18.2 Gpc • Lookback time 10.4 Gyr (79.5 % of the present Universe age) Castro Tirado et al. 2005
Host Galaxy Starburst Galaxy ~15 Myr MB=-22.0±0.3 AV=0.06±0.08
Energy Injection Model • Developed by G. Björnsson, G. Jóhannesson and E.H. Gudmundsson and based on the standard Fireball model by Sari et al. (1998) modified by adding multiple energy injections. • Several shells are released simultaneously with different Lorentz factors. • The fastest shell drives the initial afterglow and decelerates. • The slower shells finally catch up with the decelerated shock front adding up to it and producing an energy injection.
Conclusions • 7 energy injection episodes. • Total burst energy of 7.8·1051 ergs. • Collimated jet with 1º.8 half opening angle. • Host galaxy is a MB=-22.0±0.3 with low extinction AV=0.06±0.08.
GRB 050408 t0 + 5.4 hr
GRB050408: Discovery • Detected by HETE-II. • Afterglow discovered at R~20.9 with images obtained in the 1m and 6m telescopes at SAO (Russia) ~2h after the burst. • Spectra shows a redshift of z=1.2356 (Berger et al. 2005).