Understanding the fundamental parameters of millisecond pulsars ...

Understanding the
fundamental
parameters of
millisecond pulsars
through high energy
observations and
modelling of the
X-ray lightcurve
Benoit Pancrazi
CESR–Toulouse
benoit.pancrazi@cesr.fr
Barcelona, April 12, 2010

Generalities of millisecond pulsars . . .
◮ Acceleration during accretion
phase.
◮ NS is spun up to ms periods
⇒ ”recycled”.
◮ Old pulsars (τ c ∼ 10 9 yrs).
◮ Low surface magnetic fields
(B s ∼ 10 7 − 10 9 G).
◮ Emission from radio to γ-rays.
Fundamental questions
◮ Location of the emission regions.
◮ Radiation mechanisms at the origin of the HE emission.
◮ Equation of state of the NS matter.
Benoit Pancrazi (CESR) Barcelona, April 12, 2010 2 / 12

High energy models
Open field line region
◮ E ⃗ · ⃗B ≠ 0
◮ ρ ≠ ρ GJ
⇒ ACCELERATION
3 Models
Corotating magnetosphere
◮ E ⃗ · ⃗B = 0
◮ ρ = ρ GJ
◮ Polar Cap : (unscreened
?) E ‖ , ICS, synchrotron.
◮ Slot Gap : extended,
along last open field line,
off-pulse emission.
◮ Outer Gap : high altitude,
CR, Vela/Crab type, no
off-pulse.
Benoit Pancrazi (CESR) Barcelona, April 12, 2010 3 / 12

X-ray and radio emission
X-ray emission
(Zhang & Cheng 2003)
◮
◮
Thermal : heating of PC.
Non-thermal : synchrotron at high altitude.
Radio : unknown mechanism
⇒ empirical model.
◮
◮
Core beam centred on the PC.
Surrounding cone beams.
Benoit Pancrazi (CESR) Barcelona, April 12, 2010 4 / 12

Multiwavelength observations
γ-rays : Fermi LAT.
X-rays : XMM-Newton.
◮ 100 MeV - 300 GeV
◮ 200 eV - 15 keV
◮ Timing resolution < 1 µs
◮ Timing resolution ∼ 30 µs
Radio : Nançay & Parkes.
◮
◮
Radio pulse profile.
Ephemerides
⇒ ABSOLUTE PULSE PROFILES (TEMPO2)
⇓
COMPARISON OF PHASE SHIFTS
Benoit Pancrazi (CESR) Barcelona, April 12, 2010 5 / 12

PSR J0613-0200 / timing analysis
> 5.5 σ
2.2 σ
γ-ray pulse profile
◮
◮
Modelling ⇒ SG/OG
(Venter at al. 2009).
Small precursor with
extended dataset ⇒ SG ?
X-rays & radio
◮
◮
No significant
pulsation in X-rays.
X-ray fluctuation &
radio peak aligned
& of similar widths.
Benoit Pancrazi (CESR) Barcelona, April 12, 2010 6 / 12

PSR J0613-0200 / spectral analysis
Thermal component
◮ Heated PC ?
Non-thermal
component
◮
◮
Use of γ-ray fitting
parameters :
Γ = 1.4 ± 0.3,
E c = 2.6 +1.0
−0.6 GeV.
Synchrotron at high
altitude ?
Benoit Pancrazi (CESR) Barcelona, April 12, 2010 7 / 12

PSR J1911-1114
2.5 σ
Evidence of thermal emission ?
◮ No significant pulsation in X-rays.
◮ X-ray fluctuation & radio peak aligned & of similar widths.
◮ Possible thermal component in the spectrum.
◮ Thermal emission coming from heated PC ?
Benoit Pancrazi (CESR) Barcelona, April 12, 2010 8 / 12

PSR J2129-5721
2.3 σ
Evidence of thermal emission ?
◮ No significant pulsation in X-rays.
◮ X-ray fluctuation & radio peak aligned & of similar widths.
◮ Possible thermal component in the spectrum (contaminating source).
◮ Thermal emission coming from heated PC ?
Benoit Pancrazi (CESR) Barcelona, April 12, 2010 9 / 12

PSR J1853+1303 & PSR J1600-3053
1.6 σ
1.8 σ
No source visible in the MOS data
◮ No significant pulsation in X-rays.
◮ Possible alignment for PSR J853+1303.
◮ Possible misalignment for PSR J1600-3053.
Benoit Pancrazi (CESR) Barcelona, April 12, 2010 10 / 12

Modelling of thermal X-rays from MSPs
Thermal emission coming from a heated PC on a weakly magnetised NS
covered by a H atmosphere (Bogdanov et al. 2007).
◮
Relativistic effects (light bending, aberration, Doppler boosting, time delays).
◮ Many parameters : M, R, freq, i, θ . . .
⇒ Reduce the number of free parameters (Venter et al. 2009).
⇒ Account for the oblateness of the NS (Morsink et al. 2007).
⇒
Tighter constraints on M/R.
Benoit Pancrazi (CESR) Barcelona, April 12, 2010 11 / 12

Summary & Prospects
5 multiwavelength observations of MSPs
(Pancrazi et al. 2010, submitted).
◮ No significant X-ray detection of pulsations
◮ (4 MSPs show an X-ray fluctuation aligned with
the radio peak).
Work in progress :
◮ Modelling of the X-ray lightcurve → EoS.
◮ Improvements + combination of X-rays & γ-rays
→ tighter constraints.
◮ Search for MSPs emitting in X-rays (thermal) &
in γ-rays.
Benoit Pancrazi (CESR) Barcelona, April 12, 2010 12 / 12