1. Observation of Pulsars and Plerions with MAGIC
The Crab Nebula in X-rays
(Chandra)
Nepomuk Otte
for
the MAGIC collaboration

2. Outline the pulsar wind complex pulsar pulsar wind nebula
the MAGIC telescope
Observations: Crab / PSR B
Conclusions
Max-Planck-Institut für Physik /
Humboldt Universität Berlin

3. The Pulsar Wind Nebula Complex
magnetized, spinning neutron star
powerful source of energy
particle acceleration in:
magnetosphere
shock front
pulsar powerful source of energy
VHE gamma-rays expected from various sites
up to now only the nebula detected in VHE gamma rays (at least that is what people believe)
one ofter the other
relativistic particles
emit VHE-γ-rays
γ-rays are messengers
of non-thermal processes
Max-Planck-Institut für Physik /
Humboldt Universität Berlin

4. Gamma-Ray Emission from the Pulsar
Crab pulsar in optical
three different sites favored for particle acceleration
emission appears pulsed
lighthouse model
Max-Planck-Institut für Physik /
Humboldt Universität Berlin

5. Pulsar: Broadband Emission
MAGIC
spectroscopy >10GeV needed
strong cutoff exponential or even stronger
Thompson et al. 1999
HE-emission processes
synchrotron radiation
curvature radiation
inverse Compton scattering
no pulsar detected above ~100GeV
Max-Planck-Institut für Physik /
Humboldt Universität Berlin

6. The Pulsar Wind Nebula Complex
shock front
acceleration up to 1016 eV
synchrotron emission
inverse Compton scattering
SSC model
electrons stream out in uniform flow from the pulsar
accelerated at standig reverse shock, randomized in pitch angle
cooled by synchrotron radiation
VHE-gamma rays due to IC scattering of thermal photons or synchrotron photons.
Max-Planck-Institut für Physik /
Humboldt Universität Berlin

7. PWN: Broadband Emission
MAGIC
Synchrotron Spectrum well described in MHD model calculations
Above 1GeV inverse Compton scattering dominates
observational gap between 10GeV and ~400GeV
Aharonian & Atoyan (1998)
Max-Planck-Institut für Physik /
Humboldt Universität Berlin

8. Crab and PSR B1951+32 Pulsar Crab PSR B1951+32 Age ~103 yrs ~105 yrs
Energy loss rate
1038 erg sec-1
4x1036 erg sec-1
Maximum detected energy
~10 GeV
~20 GeV
Spectral shape
~2.2
~1.8
Indication of cutoff
yes no
pulsar space velocity
140±8 km sec-1
240±40 km sec-1
PWN in Gamma rays
detected
not detected
Pulsar
young vs. middle aged
similar gamma ray luminosities at 10GeV
no cutoff in prs1951  prime candidate for observation
pwn should be detectable with MAGIC according to predictions
but first for the pulsar case
Max-Planck-Institut für Physik /
Humboldt Universität Berlin

9. The MAGIC Telescope largest Air Cherenkov Telescope
lowest energy threshold
~50GeV
highest sensitivity >200GeV
~2% Crab in 50 hours
γ-PSF ~ 0.1°
energy resolution:
~30% at 100 GeV
~20% > 300 GeV
Max-Planck-Institut für Physik /
Humboldt Universität Berlin

10. Crab Pulsar preliminary ~65 GeV no pulsed emission detected
cutoff <30 GeV
Max-Planck-Institut für Physik /
Humboldt Universität Berlin

11. PSR B1951+32 Pulsar no pulsed emission detected
strong constrain on the cutoff energy <30GeV
constrain predicted IC at TeV
previous observations compare
note for experts; polar cap more favorable than outer gap
predicted IC flux higher than in Crab
not detectedunfavorable magnetic field configuration at the light cylinder
überleitung auf nebel
Max-Planck-Institut für Physik /
Humboldt Universität Berlin

12. The Crab Nebula preliminary
gamma-ray emission detected over two decades of energy
60 GeV – 9 TeV
preliminary
power-law behavior disfavored
Max-Planck-Institut für Physik /
Humboldt Universität Berlin

13. Crab Nebula: Broad Band Emisision
good agreement with other experiments >400GeV
data well described in SSC framework
just above the expected IC-peak
preliminary
Spectral energy density
Max-Planck-Institut für Physik /
Humboldt Universität Berlin

14. Crab Nebula: Change of Photon Index
clear change of photon index with energy
nicely reproduced by model calculations
preliminary
Max-Planck-Institut für Physik /
Humboldt Universität Berlin

15. Crab Nebula: Variability
no variability detected
on several time scales:
minutes
days
months
preliminary
preliminary
10 minute binning
flux steady within experimental resolution
Max-Planck-Institut für Physik /
Humboldt Universität Berlin

16. CTB80 / PSR B1951+32 no detection of gamma-ray emission
Max-Planck-Institut für Physik /
Humboldt Universität Berlin

17. CTB80 / PSR B
model calculation do not take pulsar motion into account
emission smeared over a larger volume?
magnetic field larger than assumed
 wind not particle dominated?
emission smeared  reduced sensitivity propto 1/sqrt(area)
Max-Planck-Institut für Physik /
Humboldt Universität Berlin

18. Conclusions
no pulsed gamma-ray emission from Crab and PSR B (a prime candidate to search for pulsed emission)
need to lower the threshold below 50 GeV
 MAGIC II / CTA, better photon detectors (see e.g. T 604.4)
no steady emission from CTB80/PSR B (< few %Crab)
motion of pulsar has to be taken into account in models
pulsar wind particle dominated (σ>1)?
Crab nebula emission
detected down to 60 GeV
good agreement with SSC model
no variability detected
consistent with a point source
Max-Planck-Institut für Physik /
Humboldt Universität Berlin

19. 80 GeV to 100 GeV (estimated energy)
Max-Planck-Institut für Physik /
Humboldt Universität Berlin

20. Crab Nebula: Morphology
gamma-ray source is pointlike for MAGIC down to 100 GeV
expect increasing source size with decreasing energy
preliminary
~250 GeV emission:
center of gravity
upper limit on the emission region <2.3’
Max-Planck-Institut für Physik /
Humboldt Universität Berlin