Poonam Chandra Jansky Fellow, NRAO, Charlottesville & University of Virginia

Collaborators: Dale Frail (NRAO) Brad Cenko (Caltech) Roger Chevalier (Univ. Virginia) Shri Kulkarni (Caltech) Douglas Bock (CARMA) Jean-Pierre Macquart (ATNF).. And Caltech-Carnegie Mellon collaboration

Jet break due to beaming

Jet break: geometrical effect

Is it really true? Observation wavebands: X-ray: not possible…only Chandra and XMM… Radio: scintillation effects, large errorbars Optical: only possibility. Acromaticity in V, B, R, I’ etc. bands

Many jet breaks were seen in optical GRB GRB

Swift was launched in 2004

Well sampled curve in X-rays by Swift XRT Well sampled curve in optical by various optical telescopes Well sampled curve in X-rays by Swift XRT Well sampled curve in optical by various optical telescopes Opportunity to see achromatic jet break in really different bands

Possible Theories Chromaticity of jet breaks: Do not arise from structured outflows from jets. Missing jet breaks in XRT light curves: do not arise from the passage of a spectral break Microphysical parameters evolve with time. Optical and X-ray emissions arise from different outflows. Upscattered forward shock emission And many more………………. Panaitescu et al 2006, Panaitescu 2008, Burrows et al. 2008, Racusin et al etc.

MULTIWAVEBAND MODELING OF BRIGHTEST RADIO GRB IN SWIFT ERA

 X-ray band: Swift and ChandraXO (For 40 days)  Optical Band: Palomer 60 inch and others (For 27 days)  Submm Bands: IRAM in 250 GHz (For 20 days) CARMA in 95 GHz (For 24 days)  Radio Bands: VLA in 22.5, 15.0, 8.5, 4.8 and 1.4 GHz (For 1 year)  X-ray band: Swift and ChandraXO (For 40 days)  Optical Band: Palomer 60 inch and others (For 27 days)  Submm Bands: IRAM in 250 GHz (For 20 days) CARMA in 95 GHz (For 24 days)  Radio Bands: VLA in 22.5, 15.0, 8.5, 4.8 and 1.4 GHz (For 1 year)

XRAY :JET BREAK Thanks to Swift-XRT team

Optical i’ band Optical R band JET BREAK

Jet breaks in optical and X-rays

Standard GRB afterglow model Fits multiwaveband data Emission due to synchrotron mechanism Incorporates scintillation errors in radio data Comprehensive analysis Assumes achromatic jet break Fixed Jet break to day 3.7, same as optical jet break time Fits multiwaveband data Emission due to synchrotron mechanism Incorporates scintillation errors in radio data Comprehensive analysis Assumes achromatic jet break Fixed Jet break to day 3.7, same as optical jet break time (Yost et al. 2003, 2004)

Model (Yost et al. 2003, 2004)

Derive Inverse Compton Scattering Light curves, using synchrotron model parameters  IC affects only X-ray bands. Not low frequency optical or radio bands.  IC starts to become important from day 2.8 onwards IC Light Curve: Chandra et al. 2008, accepted for publication in ApJ, astro-ph/

Conclusions Inverse Compton scattering is responsible for the delay in jet break in GRB IC scattering may be responsible for chromatic jet break/ missing jet breaks. IC scattering will be depending on physical conditions. IC scattering will dominate in high density systems. Radio data is very crucial since it determines the density of the medium. Inverse Compton scattering is responsible for the delay in jet break in GRB IC scattering may be responsible for chromatic jet break/ missing jet breaks. IC scattering will be depending on physical conditions. IC scattering will dominate in high density systems. Radio data is very crucial since it determines the density of the medium. Chandra et al. 2008, accepted for publication in ApJ, astro-ph/

Best fit parameters Isotropic Kinetic Energy: 2.98 x ergs Jet beaming angle : 0.23 radians Electron index: 2.27 Circumburst density: 16 cm -3 Electron energy fraction: 0.28 Magnetic energy fraction: 0.28 Cooling transition time: 8 days Jet break time: 3.7 days Isotropic Kinetic Energy: 2.98 x ergs Jet beaming angle : 0.23 radians Electron index: 2.27 Circumburst density: 16 cm -3 Electron energy fraction: 0.28 Magnetic energy fraction: 0.28 Cooling transition time: 8 days Jet break time: 3.7 days

Inverse Compton (IC) scattering delayes the jet break in X-ray light curves and either push it beyond the last Swift observation or result in Chromatic jet break. IC does not affect optical or radio light curves. To deduce this crucial to have very well sampled multiwaveband data including in radio and sub-mm bands.