Upload
geoff
View
31
Download
0
Embed Size (px)
DESCRIPTION
Magnetic Field Decay and Core Temperature of Magnetars, Normal and MS pulsars. Shuang-Nan Zhang 张双南 1 Yi Xie 谢祎 2 1. Institute of High Energy Physics 2. National Astronomical Observatories of China. Evolutionary study of pulsars on p-pdot diagram. B decay required?. Han, J.L, 1997, A&A. - PowerPoint PPT Presentation
Citation preview
Magnetic Field Decay and Core Temperature of Magnetars, Normal and MS pulsars
Shuang-Nan Zhang 张双南 1
Yi Xie 谢祎 2
1. Institute of High Energy Physics
2. National Astronomical Observatories of China
2/16
Evolutionary study of pulsars on p-pdot diagram
Han, J.L, 1997, A&A
B decay required?
3/16
Indirect Evidence for B decay?
Han, J.L. (1997): power-law decay with “gene”: t0~B0 dependence
4/16
Direct Evidence for B Decay
Best fits
magnetars
Normal pulsars
ms pulsars
Magnetars do not cross death line: normal radio pulsar mechanism works here? Consistent with recent detection of radio magnetars (talks by Manchester and Yuan in this meeting).
5/16
P-Pdot or B-Age?
Direct observables: But all tracks calculated using B-dipole radiation model, and indirect comparison with B-decay model.
Derived quantities using B-dipole radiation model (OK if not overwhelmed by pulsar wind loss), but direct comparison with B-decay model.
P
Pdo
t
6/16
Inclination angle decay?
Magnetic-Dipole radiation model:
0 d obs NS dIf sin sin exp( ), then exp( )t t B B t t
• Then the observed B-decay may be in fact an illusion of inclination angle decay (Faucher-Giguère & Kaspi 2006; Weltevrede & Johnston 2008).
• However, B-decay by 100 times for each kind of pulsars is difficult for inclination angle decay alone.– A better and more physical model required.
3 32 2 0 2
2 6 2 6
3 3sin , assume 90 , then
8 8
c I c IB PP B PP
r r
7/16
B Decay Model: Heyl & Kulkarni, 1998, ApJL
The dominant term
8/16
~ Constant Core Temperatures of NSs
magnetars
normal pulsarsms pulsars
9/16
Best fits of real pulsars
All observed P and Pdot paired randomly
All observed P
All observed Pdot
General trend of the observed distributions!
10/16
Each class of observed P and Pdot paired randomly
Very similar to the observed distributions!
Model for real pulsars
11/16
Completely simulated data: Gaussian distributions
Still very similar to the observed distributions!
Model for real pulsars
logPP (s)
M σ M σ
8 2 -11 0.5
0.8 0.8 -16 0.2
0.002 0.001 -20 0.5
Input parameters
12/16
Completely simulated data: Not a surprise!logPP (s)
M σ M σ
8 0.2 -11 0.5
0.8 0.1 -16 0.2
0.002 0.0001 -20 0.5
Model for real pulsars
Simulated data follow model precisely!
& = 2B PP P P -1 2B P
-1 2B P=const
B-Dipole radiation:
For each type of pulsars
2 3 1 2B T B B T Ambipolar B-Decay model (T=const):
13/16
Why is the Pdot so small for all pulsars?
• B-dipole radiation
– But why the observed Pdot is so small?
• Ambipolar diffusion B-decay with constant core
temperature P~constant Pdot must be very small!
• This is a natural prediction of the above ambipolar
diffusion B-decay model.
2 3 1 2 1 2B T B B T B
1 2 & = 2B PP P P B P
14/16
Evidence for Hot Magnetars
15/16
Evidence for Equilibrium between Heating & Cooling?
?
16/16
Summary and Open Questions• No magnetar cross the pulsar’s death line
– Normal pulsar radiation mechanism?• All NSs show clear evidence for B-deday
– Agrees with ~constant Tcore ambipolar diffusion B-decay model well• Heating by B-decay energy and NS cooling by
neutrino and emission in ~equilibrium for all pulsars?• The model naturally predicts very small Pdot as observed
– Core temperature: Magnetars 2x108 K, Normal pulsars 2x107 K, ms pulsars 1x105 K• Different populations at birth?