World Cup of VHE Gamma Rays

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World Cup of VHE Gamma Rays

• J-Dog, for the SNR/PWN Pack

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SNR Types/Evolution

• Type Ia result from accretion in a binary
  explosion typically into uniform medium.
• Type II core collapse of a 8-15 M? star
  explosion into slow (10 km/s) wind neutron star
  left behind.
• Type Ib core collapse of a gt15 M? star
  explosion into fast (1000 km/s) wind black hole
  left behind.
• All yield 0.5 2.0 1051 erg initial ejecta
  kinetic energy.
• Rate of 3/century ? need 16 energy converted
  to CRs to maintain galactic CR flux.
• Sedov phase begins mass of swept-up material
  ejecta energy.
• Usually takes few 100 few 1000 years to reach.
• SN energy now split roughly evenly between bulk
  kinetic, thermal, and relativistic particles.
• Beginning of Sedov phase is when gamma-ray
  emission from CR-proton interactions (pion decay)
  is expected to peak.
• SNR expands adiabatically for 100 kyr until gas
  cools enough to radiate efficiently, starting a
  phase of rapid cooling.

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PWN Overview

• Evolution of a PWN
• Expansion Phase
• nebula expands into cold gas medium
• Interaction with reverse shock
• compression and transition to hot gas medium
• possible distortion of nebula by asymmetric
  reverse shock arrival
• Sedov Phase
• pulsar exits the original relic nebula and
  generates a new smaller nebula.
• At 2/3 distance to the forward shock becomes
  supersonic and generates a bow shock
• Interstellar Gas Phase the pulsar has left the
  building

Gaensler Slane, 2006
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SNR/PWN Science Morphology

• Resolve locations of maximum particle
  acceleration in nearby remnants
• in SNR shells (RXJ 1713, Vela Jr)
• to distinguish nebula emission from shell (e.g.
  G0.9-0.1)
• to resolve jets in jet-dominated PWN (MSH 15-52)
• PWN evolution indicators
• pulsar/X-ray/TeV nebula offsets ? inhomogeneous
  interaction with reverse shock (Vela X,
  G18.0-0.9, Kookaburra, Rabbit)
• TeV vs X-ray size ? differing synchrotron
  lifetimes (G18.0-0.9)

RXJ 1713.7-3946
G0.9-0.1 (contours VLA)
MSH 15-52
Vela X
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Utility of MWL Information
(from Aharonian, etal., arXivastro-ph/0606311)
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Key Project Justification I

• Science Motivation
• Understand the role of SNRs in cosmic-ray
  acceleration.
• Study particle acceleration (ion and electron)
  mechanisms.
• Maximum energy achievable in shock acceleration.
• Resolution of jet structure, pulsar and X-ray
  nebula offsets, Doppler boosting.
• Use the spectral shape, morphology, and MWL
  information to discriminate between acceleration
  models.
• Even upper limits can place important constraints
  on models.
• What are the conditions that lead to efficient
  cosmic-ray acceleration?
• Extending spectrum to GeV with GLAST, study
  modification of shock dynamics by cosmic rays.
• Study shell/nebula structure and evolution.
• Constrain shell, nebula magnetic fields.
• Reverse shock compression/asymmetries in
  surrounding medium.
• Measure synch. cooling break, particularly in
  combination with GLAST.
• TeV provides integrated history of injected
  electron population while X-ray indicates recent
  history.
• Expansion rate and age of nebula.
• Probe interstellar medium.
• Indirect measure of local photon densities.

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Key Project Justification II

• Discovery Potential
• The largest class of objects that HESS has
  detected is SNRs/PWNe.
• Most of the HESS sources are in a region of the
  galactic plane at a distance of 4-10 kpc,
  whereas the region of the plane visible to
  VERITAS (30o lt l lt 220o) contains spiral arms
  at 2-4 kpc.
• SNRs and PWNe are steady sources and have fairly
  hard spectra (index 2.0-2.5), making them more
  readily detectable with a new instrument.
• Why VERITAS?
• Cas A, Tycho, 3C 58, and J2021 are unobservable
  by HESS/CANGAROO.
• VERITAS has better sensitivity than MAGIC for
  extended sources and at higher energies.
• Why a Key Project?
• These objects form a set of the best known
  candidates of different classes of SNRs/PWNe
  synergy between them maximizes their science
  reach.

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Proposal I

• Year I Observe a number of SNRs/PWNe with
  sensitivity to detect or set limits at few
  Crab level.
• Year II We anticipate a request of 100-150
  hours.
• Follow up of sources detected in the first year.
• Follow up of Sky Survey and GLAST detections.

Month Primary Targets Primary Targets Secondary
Oct J2021 Cas A 3C 58
Nov Cas A Tycho J2021
Dec Cas A Tycho 3C 58
Jan IC 443 Monoceros
Feb IC 443 Monoceros
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Proposal II
Object J2021 Cas A Tycho 3C 58 IC 443 Mono
Shell ? ? ? ?
PWN ? ? ?
Progenitor Type CC CC Ia CC CC ?
Cloud Interaction ? ?
Months Oct-Nov Oct-Dec Nov-Dec Oct-Dec Jan-Feb Jan-Feb
Hours 10 25 25 25 25 25
CC Core collapse
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SNR/PWN Observability ( gt 55 deg)
Hours per Year (Jul, Aug, Sept excluded)
IC443
Midi
Mono
Crab
DA530
3C58
Tycho
CTB80
J1930
J2229
gCygni
J2021
CTB87
R5
W44
W49B
Cas A
Cygnus Loop
Sky survey region
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Summary

• Is that the end?

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Additional Info
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3C 58 (G1303.1)

• Powered by 3rd most energetic pulsar in the
  galaxy, J02056449 (after Crab and G21.5-0.9).
• Relatively nearby at 3.2 kpc.
• Possible association with SN 1181 but
  observations imply an older object.
• age important for X-ray constraints on neutron
  star cooling.
• Crab-like morphology (jet/torus).
• Low magnetic field ? e- producing TeV emit
  synchrotron in the UV band.
• TeV probes otherwise unobservable section of e-
  spectrum.
• Similar nebula of PSR B1509-58 detected in TeV.

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IC 443
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J20213651