Bronek Rudak (CAMK) Jarek Dyks (CAMK) Michał Frąckowiak
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Transcript of Bronek Rudak (CAMK) Jarek Dyks (CAMK) Michał Frąckowiak
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.