The Structure and Dynamics of Relativistic Jets

Image credit: AURA / Lynette Cook

Tanmoy Laskar Jansky Fellow

NRAO / UC Berkeley

Relativistic jets in Astrophysics

NASA and The Hubble Heritage Team (STScI/AURA)

Relativistic jets in Astrophysics

AGN Mergers GRBs TDFs

Relativistic Jets in Gamma-ray bursts

Gamma-ray Bursts: two classes

LongShort

Long-duration Gamma-ray Bursts

• Located in star forming regions of galaxies

• Associated with supernovae • Most energetic explosions in the

universe: Eγ,iso ~ 1054 ergVisible to high redshifts (z ~ 9, and beyond!)

• Short durations (minutes) → Relativistic expansion

• Powered by compact central engine

Catastrophic death of a massive star

The Fireball model

GRBs: The Radiation Mechanism

Sari, Piran & Narayan (1998)

Energy, EK Density, n Shock physics (𝜺e, 𝜺B)

Flux

den

sity

Frequency

The Structure & Dynamics of Relativistic Jets

• What is the central engine (NS? BH?)

• What is the energy extraction mechanism?

• What is the jet launching mechanism?

• How are the jets collimated?

Measure fundamental quantities: Lorentz factor, energy, magnetization, collimation

The Reverse Shock

The Reverse Shock

Then Reverse ShockIf baryonic ejecta,

GRBs: Relativistic Transients

Radi

o

Opt

ical

X-ra

ys

Mill

imet

er

Multi-wavelength follow-up

The GRB Afterglow Multi-wavelength Modeling Application

Multi-wavelength modelling

• Full broadband spectral evolution • RS + FS • Jet breaks (radio to X-rays) • Non-relativistic transition (radio) • Inverse Compton cooling (X-rays) • Effects of dust (optical) • IGM absorption (optical) • Interstellar scintillation (radio)

GAMMA

+ Robust statistical framework

Intri

nsic

Extri

nsic

The hunt for reverse shocks

⌫m,RS =⌫m,FS

�2

⌫c,RS = ⌫c,FS

F⌫,m,RS = �F⌫,m,FS

The Reverse shock

Optical

Radio

GRB 990123

Radi

owav

e

Opt

ical

X-ra

ys

Mill

imet

erw

ave

980703

980329

Chandra & Frail (2012)

Radio Observations of GRBs

A Reverse shock in GRB 130427A

Radi

o

Opt

ical

X-ra

ys

Mill

imet

er

TL+13, ApJ, 776, 119

RS FSFS

RS

X-ray

Optical

Radio

RS FSInfra-red

A Reverse shock in GRB 130427A

RS and FS parameters independently derived, yet consistent: imply Γ~ 130

⌫m,RS =⌫m,FS

�2

⌫c,RS = ⌫c,FS

F⌫,m,RS = �F⌫,m,FS

A Reverse shock in GRB 160509AΔt = 1.1d

Radi

o

Opt

ical

X-ra

ys

Mill

imet

er

A Reverse Shock in

GRB 160509A

TL+16, ApJ, 833, 88

A Reverse shock in GRB 160509A

• Γ~ 330

• Ejecta kinetic energy, EK ~ 4 x 1050 erg

• Low circumburst density, n ~ 10-3 cm-3

⌫m,RS =⌫m,FS

�2

⌫c,RS = ⌫c,FS

F⌫,m,RS = �F⌫,m,FS

TL+16, ApJ, 833, 88

A Reverse Shock in GRB 161219B The First ALMA GRB Light Curve!

X-ra

yU

VO

ptic

alin

frare

dRa

dio

TL+18, submitted

Reverse Shocks require low circumburst density

The Structure and Dynamics of Relativistic Jets