 The GRB literature has been convolved with my brain 

Geometric Structure of Blast Wave Outflow: Why we care  Explain Features of Afterglow Light Curves / Spectra Outside the Standard Spherical Model  Keys to Central Engine Dynamics: Collimation & Energetics  Constrain “True” GRB Rates  Improve Afterglow Models  Constrain Microphysical Parameters

All Fluid Properties Uniform with Solid Angle  Spherically Symmetric Hydro Always Valid (B/M or T/S) Simplest Model: Isotropic Expansion (No Jet)

Problems with Isotropic Expansion  GRBs Are Not Supernovae  Supernovae are explosions; GRBs are irregular winds.  Supernovae are relative standard candles; Isotropic GRB models show a wide E iso distribution  Observational Evidence to the Contrary  Central Engine Models Favor Collimation  Its hard to maintain “clean” isotropic expansion.  BH accretion disk / Magnetar angular momentum has a preferred direction.  Special Relativity is Tricky, Secretive, and Deceitful  GRB and afterglow observers are causally-disconnected from the majority of the emission for the majority of the time.  Ultra-relativistic motion “freezes” angular profile at acceleration region. Frail et al. (2001) ALSO…

Just as “Simple”: Jets Are Common As Well

Balloons, Jets, or Pancakes? How to Identify Collimated Outflow

Idea (1): Resolve Angular Emission Structure Problems  GRB / Early Afterglow Not Resolveable  Only in Causal Contact with Small Fraction of Outflow  Can’t Distinguish Emission of Uniform Sphere from Uniform Jet Viewed Head-ON!

Idea (2): Orphan Afterglow Surveys (Rhoads 1997) If Isotropic Expansion  N RADIO = N OPTICAL = N X-RAY = N GRB (every direction sees a GRB and each kind of afterglow) If Collimated Expansion  N RADIO > N OPTICAL > N X-RAY > N GRB (only ~ % of GRBs are observable) USE DISTRIBUTION OF OBSERVED AFTERGLOWS TO CONSTRAIN COLLIMATION Problems  Orphan transients difficult to detect  Lots of biases to remove (e.g., afterglow samples are flux-limited)  In some cases various afterglows missing anyways (e.g., “Dark” bursts)  A significant fraction of GRBs may ‘fail’ due to baryon contamination but still produce afterglows (Huang, Dai, Lu 2002)  Depends on Jet Models

Idea (3): “Wait Until Structure Becomes Visible” As the WHY was UNOBVIOUS to me, lets first take a “Refresher” on Relativistic Emission…. In Afterglow Calculations Thus Far We Haven’t Cared About The Causality Cone WHY? FOR FAST COOLING (SARI, PIRAN, and NARAYAN 1998) (Even though microscopic quantities are correct relativistically there is no mention of an integration over some restricted solid angle)

Emission From a Homogeneous Blob: The Non- Relativistic Limit V<< c R0R0 D HOW MUCH TOTAL ENERGY PER DETECTOR AREA IS MEASURED? And Aliens At Different Viewing Angles Would Concur In the Blob Frame

Emission From a Homogeneous Sphere: The Ultra-Relativistic Limit D HOW MUCH TOTAL ENERGY PER DETECTOR AREA IS MEASURED? R0R0 SAME

Before A Spherical Solution is Fully Accurate Because Different Solid Angles Are Not In Causal Contact with one Another

Observation Signature of a Jet  Will Depend on Model of Jet we Assume

1 st Beaming Model: TOP HAT Our Strategy is to

Early Support For Jets Problem with jetting – smoothness of jet break by panitescu and meszaros 1998 Argument against extreme beaming => lack of orphan afterglows

AFTERGLOW POLARIZATION: Constraining the Jet Structure?