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Transcript
A brief review of
double-pulsar system,
PSR J0737-3039
Burgay et al. (2005) ApJ 624, L113
Kaspi et al. (2004) ApJ 613, L137
Lyne et al. (2004) Science 303, 1153
McLaughlin et al. (2004) ApJ 616, L131
Double-pulsar system J0737-3039
Double neutron star binaries are rare (7 confirmed).
Table: Observed double neutron star binaries
PSR
eccen. a(Ro) Porb(days) period(ms)
J0737-3039 0.088 0.610 0.102
22.7, 2773
J1518+4904 0.249 8.634 8.634
40.9 The only
B1534+12
0.274 1.606 0.421
37.9 binary
J1756-2251 0.181 1.187 0.320
28.4 pulsar
J1811-1736 0.828 14.982 18.779
104.1
J1829+2456 0.139 3.117 1.176
41.0
B1913+16
0.617 1.009 0.323
59.0
Catherine et al. (2006) ApJ 652, 540
Double-pulsar system J0737-3039
Doppler variations of P from J0737-3039
→ double pulsar system
The double pulsar system J0737-3039 is
extremely compact (Porb=2.45 h),
mildly eccentric (e =0.088),
highly inclined (a =87.8o-89.6o).
Burgay et al. 2003, Nature 426, 531
Lyne et al. 2004, Science 303, 1153
The radio lightcurves show eclipse (by edge-on geom.).
Kaspi et al. 2004, ApJ 613, L137
Laboratory for magneto-ionic properties of a pulsar
magnetosphere.
Evolution of the double-pulsar system
Consider a binary evolution scenario of two massive MS stars.
After a first mass transfer stage, the primary (more massive star)
form a NS in a core-collapse supernova (Type II) explosion.
Under favorable conditions (small kick), the NS remains bound.
As the secondary evolves to a red giant, mass accretion takes
place in an HMXB phase.
The accretion spins up the NS into millisecond period in 106-107
years, dramatically reducing its magnetic field (to <1010G).
In a close binary, the secondary’s envelop enlarges to meet the
NS to spirals in. The common envelop material expelled from the
system, carrying most of the angular momentum, thereby
significantly reducing the binary separation.
The very compact binary consists of a NS and a He star.
A sufficiently massive He star undergoes a core-collapse
supernova explosion, leaving a young secondary NS.
Evolution of the double-pulsar system
Comparison of the two NSs:
Primary NS
Secondary NS
comment
recycled
young
rotation period
~ 30 ms
~ 1000 ms
period derivative, Pdot ~ 10-18 s s-1
~ 10-15 s s-1
characteristic age
P/(2*Pdot)
~ 500 M years
~ 20 M years
surface B field
1019.5(P Pdot)0.5G
<1010G
~1012G
Because of this large lifetime difference, double pulsar binaries
are rare.
Double-pulsar system J0737-3039
J0737-3039 is the most extreme relativistic binary system ever
discovered (Porb=2.45 h), with a remarkably high value of the
periastron advance (dw/dt = 16.9o/yr).
pulsar
Observational summary
PSR J0737-3039A
PSR J0737-3039B
period
22.7 ms
2773 ms
period derivative
1.75*10-18 s s-1
8.81*10-16 s s-1
eccentricity/dist.
0.0877 / 600 pc
characteristic age
210 M years
50 M years
surface B
6.3*109 G
1.2*1012 G
spin-down lumino. 6*1033 ergs s-1
2*1030 ergs s-1
stellar mass (Mo)
1.250(5)
1.337(5)
Probing pulsar magnetosphere
Because of the edge-on viewing angle (a ~88o), pulsar A experiences
a short eclipse by B’s magnetosphere due to synchrtrotron
absorption.
Eclipse ingress takes
3.5 times longer than
egress, independent
of radio frequency.
Fig: Pulsar A eclipse
light curves. The
vertical solid line
denotes conjunction.
Kaspi et al. (2004)
ApJ 613, L137
27s (FWHM)
Probing pulsar magnetosphere
When pulsar B is at longitude 270o
(at superior conjunction),
A’s beam pass within
0.07 lt-s of pulsar B,
which is much smaller
than B’s light cylinder
radius, 0.45 lt-s.
obs.
longitude=0o
Relative transverse
velocity ~ 680 km s-1
Eclipse duration ~ 60s
→ size~18,000 km
(0.060 lt-s)
~ impact parameter
(0.07 lt-s)
top view
B’s unperturbed
magnetosphere
(not to scale)
1~3o
Lyne et al. (2004) Science 303, 1153
side view
Probing pulsar magnetosphere
A’s transmitted pulsed flux modulates by the rotation of pulsar B.
1st eclipse
barycentric
arrival time
of B’s pulses
(calculated)
2nd eclipse
3rd eclipse
rotational period of B
sum
(offset
corrected)
2.8s
McLaughlin et al. (2006)
ApJ 616, L131
Probing pulsar magnetosphere
Dividing each 2.8 s
window of B’s rotational
phase into four equal
regions, they calculated
averaged light curves for
each region (bottom fig.).
→ smooth light curves
Symmetric when B axis of
B phases us or A.
Asymmetric when it is at
right angles to the l. o. s.
McLaughlin et al. (2006)
ApJ 616, L131
Synchrotron absorption model
Since A’s luminosity is about 3000 times greater than B,
A’s pulsar wind likely blow away B’s magnetosphere.
The bow shock compress
magnetosheath
wind plasma, leading to
magnetopause
a sharp jump in plasma
density and temperature.
→ synchrotron absorption.
A
B
wind of A
to Earth
Eclipse is symmetric when B’s
B axis is along the line of sight.
McLaughlin et al. (2004) bow shock
ApJ 616, L131
One more issue …
Pulsar B shows pulsed intensity variations
Pulsed radio flux from B increases systematically by
almost two orders of magnitude during two short portions
of its orbit.
Lyne et al. (2004) Science 303, 1153
bright peak 1
bright peak 2
one orbital revolution
Secular change of B’s pulse shape
bright peak 1
bright peak 2
18 months
The pulse shape
of B secularly
evolves.
Secular change of B’s pulse shape
The centroid of bp2 and the beginning of bp1 advance in orbital
longitude at 3o/yr, while the centroid of bp1 does not move.
Secular change of B’s pulse shape
Is the advance of bp2’s centroid and bp1’s beginning (3o/yr)
due to the geodesic precession (5.1o/yr) of B’s rotation axis
with respect to the orbital angular momentum axis?
If so, B’s spin axis should be misaligned to the orbital angular
momentum axis.
Periastron advance (17o/yr) appears to be unrelated…
Since pulsar A does not show evolution in its pulse shape or
radio flux, A’s spin axis may be aligned to the orbital angular
momentum axis.
Jump-start model for B’s pulsed emission
It is still difficult to interpret the secular evolution of B’s pulse
shape; however, excitation of B’s pulsed emission could be
understood by a toy model.
Lorimer (2004) Nature 428, 900
Summary
Still lots of things to do on this exciting double pulsar system.
What is known:
binary separation, eccentricity, viewing angle
periastron advance (→ test of GR)
gravitational readshift
NS masses (1.33, 1.25 times solar masses)
A’s spin axis (parallel to orbital ang. mom.)
What is unknown:
B’s spin axis (not parallel to orbital ang. m.)
B’s jump-start mechanism (stimulated PC?)
A’s eclipse (bow shock? hot closed zone?)