A brief review ofdouble-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

The onlybinarypulsar

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, 2773J1518+4904 0.249 8.634 8.634 40.9B1534+12 0.274 1.606 0.421 37.9J1756-2251 0.181 1.187 0.320 28.4J1811-1736 0.828 14.982 18.779 104.1J1829+2456 0.139 3.117 1.176 41.0B1913+16 0.617 1.009 0.323 59.0

Double-pulsar system J0737-3039

Catherine et al. (2006) ApJ 652, 540

Double-pulsar system J0737-3039Doppler 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 (=87.8o-89.6o).

Burgay et al. 2003, Nature 426, 531Lyne 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.

Because of this large lifetime difference, double pulsar binaries are rare.

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 ~ 500 M years ~ 20 M years P/(2*Pdot)

surface B field <1010G ~1012G 1019.5(P Pdot)0.5G

Evolution of the double-pulsar system

Double-pulsar system J0737-3039J0737-3039 is the most extreme relativistic binary system ever discovered (Porb=2.45 h), with a remarkably high value of the periastron advance (d/dt = 16.9o/yr).

Observational summary pulsar 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) 1.337(5) 1.250(5)

Probing pulsar magnetosphereBecause of the edge-on viewing angle ( ~88o), pulsar A experiences a short eclipse by B’s magnetosphere due to synchrtrotron absorption.

Eclipse ingress takes3.5 times longer thanegress, independentof radio frequency.

Fig: Pulsar A eclipselight curves. The vertical solid line denotes conjunction.Kaspi et al. (2004) ApJ 613, L137

27s (FWHM)

Probing pulsar magnetosphereWhen pulsar B is at longitude 270o (at superior conjunction), A’s beam pass within0.07 lt-s of pulsar B,which is much smallerthan B’s light cylinderradius, 0.45 lt-s.

Relative transverse velocity ~ 680 km s-1Eclipse duration ~ 60s→ size~18,000 km (0.060 lt-s) ~ impact parameter (0.07 lt-s)

Lyne et al. (2004) Science 303, 1153

top view

side view

1~3o

obs.

obs.

longitude=90o

long

itude

=18

0olo

ngitu

de=

0o

B’s unperturbed magnetosphere(not to scale)

Probing pulsar magnetosphereA’s transmitted pulsed flux modulates by the rotation of pulsar B.

McLaughlin et al. (2006)ApJ 616, L131

rotational period of B

2.8s

1st eclipse

2nd eclipse

3rd eclipse

sum(offset corrected)

barycentric arrival timeof B’s pulses(calculated)

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

Probing pulsar magnetosphere

Synchrotron absorption modelSince A’s luminosity is about 3000 times greater than B, A’s pulsar wind likely blow away B’s magnetosphere.

McLaughlin et al. (2004)ApJ 616, L131

wind of A

The bow shock compress wind plasma, leading toa sharp jump in plasmadensity and temperature. → synchrotron absorption.

bow shock

magnetopausemagnetosheath

to EarthA B

Eclipse is symmetric when B’s B axis is along the line of sight.

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 m

onth

s

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.

Bp2 centroid

Bp1 beginnig

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 angleperiastron advance (→ test of GR)gravitational readshiftNS 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?)