Observational constraints

• Beacons inside galaxy
• Z=1-3
• Detected through any obscuration
• Long (>2s) Gamma Ray Bursts:
• Collapse of massive stars - SN
• Accretion disk, torus, jet
• Jet produce γ-ray
• Detected at z=0-10
• Detected through any obscuration
• X-ray, Opt, … Radio afterglow