Bronek Rudak (CAMK)

Jarek Dyks (CAMK) Michał Frąckowiak

Gottfried Kanbach (MPE)

Aga Słowikowska (U. of Crete)

Pulsar studies in the high energy domain

, X-ray binaries, accretion disks and compact objects” Oct 7 - 13, 2007

„

- What do we know about high energy radiation from pulsars?

- How do the observations constrain pulsar models?

- Why we need GLAST, H.E.S.S.II and … POGOLite ?

For the purpose of this talk:

high energy = optical, UV, X-rays, gamma rays

with emphasis on gamma rays

The ATNF Pulsar Database:

~1770 objects

Why do pulsars radiate in high energy?

1) Pulsars are rotating, strongly magnetized neutron stars; they can act as unipolar inductors

2) The maximum potential drop can reach

Vmax 7 1012 B12 P-2 Volts,

i.e. for young pulsars Vmax can exceed 1016 Volts.

3) This potential drop can accelerate charged particles to ultrarelativistic energies emitting high energy photons.

Important: The size and shape of the accelerators (the gaps) is model dependent.

Pulsars across electromagnetic spectrum:light curves and spectra

D.J. Thompson 2003

Vela pulsar

Harding et al., 2001

D.J. Thompson 2003

H.E.S.S. results (F. Schmidt et al., 2005)

Venter & de Jager 2004

Radiative processes in strong magnetic field

1. Curvature radiation

2. Inverse Compton Scattering (resonant + non-resonant)

3. Magnetic pair creation ( 1γ e± )

4. Photon-photon pair creation ( 2γ e± )

5. Synchrotron radiation

6. Photon splitting ( 1γ 2γ )

Examples of modelsof

phase-averagedenergy spectrum of

B0833-45(Vela)

Fig. by A.K. Harding

Two-pole caustic – slot gap model

outward emission along last open field lines

inward emission along last open field lines

Dyks & R. 2003

Two-pole caustic model and outer gap model

vs.

Vela

Vela

DC 2% of MP p 33%, 119º

Polarimetry of the Crab pulsar - Słowikowska et al. 2006 (OPTIMA)

Position Angle Polarization Degree

Light curves and polarisation characteristics within the framework of three high energy magnetospheric emission models of pulsars

Dyks et al. 2004

T. Kamae et al.2007

The Polarised Gamma-ray Observer –-Lightweight Version

POGOLite

a baloon-borne polarimeter

Energy range: 25 – 80 keV

First flight in 2009

Kamae et al. 2007

Main pulse of the Crab pulsarby three models

with 6 hour of simulatedobservations by POGOLite

What about pulsars which don’t have slot gaps?

Harding, Muslimov & Zhang 2002

Taken from S. Ritz (2007)

H.E.S.S. II

A single, 28m diameter dish

Lowers threshold to ~ 20 GeVin standalone mode

Improves overall array sensitivity in coincidence

Key science questions:

AGN population & the EBL; microquasar & XRB models; hadrons vs. leptons in SNR; pulsar detection; EGRET UiD sources; gamma ray bursts; dark matter.

W. Hofmann (2007)

W. Hofmann (2007)

Rotation leads to non-axisymmetric

magnetic absorption

P = 0.1s

For GLAST

Peak-to-peak separation changes w. energyin presence of

magnetic absorption For GLAST

VELA - polar cap model #1: super-exponential cutoff in the spectrum

For GLAST

VELA - polar cap model #2: BUT exponential cutoff in the spectrum !

For GLAST

HE spectra of millisecond pulsars

Kuiper & Hermsen 2003

PSR J0218+4232 – the first millisecond pulsar in gamma-rays

BeppoSAX points - Mineo et al.. 2000EGRET points - Kuiper et al.. 2000

P = 2.32 ms

Bpc = 0.001 TG

d = 5.85 kpc

Example:

P = 2.3 msB = 0.001 TGinclination: α = 60°

Simple polar gap model for

gamma rays inmillisecond pulsars

Two models of J0437-4715: photon maps and light curves above 100 MeV

= 35, = 40

= 20, = 16

For GLAST

A model of B1821-24 P = 3.1 ms, B = 0.002 TG, d = 5.1 kpc

photon flux above 100 MeV = 50o = 45o

photon flux above 100 GeV

For GLAST

For H.E.S.S. II

Model of J0218+4232

w. mini-caustics (slot gaps), = 25, = 47

GLAST

H.E.S.S.