Presentation on theme: "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."— Presentation transcript:
A brief review of double-pulsar system, PSR J 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 only binary pulsar Double neutron star binaries are rare (7 confirmed). Table: Observed double neutron star binaries PSReccen. a(R o ) P orb (days)period(ms) J , 2773 J B J J J B Double-pulsar system J Catherine et al. (2006) ApJ 652, 540
Double-pulsar system J Doppler variations of P from J → double pulsar system The double pulsar system J is extremely compact ( P orb =2.45 h), mildly eccentric ( e =0.088 ), highly inclined ( =87.8 o o ). 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 years, dramatically reducing its magnetic field (to <10 10 G). 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 NSSecondary NS commentrecycledyoung rotation period ~ 30 ms~ 1000 ms period derivative, P dot ~ s s -1 ~ s s -1 characteristic age~ 500 M years ~ 20 M years P/(2*P dot ) surface B field<10 10 G~10 12 G (P P dot ) 0.5 G Evolution of the double-pulsar system
Double-pulsar system J J is the most extreme relativistic binary system ever discovered (P orb =2.45 h), with a remarkably high value of the periastron advance (d /dt = 16.9 o /yr). Observational summary pulsarPSR J APSR J B period 22.7 ms2773 ms period derivative1.75* s s * s s -1 eccentricity/dist / 600 pc characteristic age210 M years50 M years surface B 6.3*10 9 G1.2*10 12 G spin-down lumino.6*10 33 ergs s -1 2*10 30 ergs s -1 stellar mass (Mo)1.337(5)1.250(5)
Probing pulsar magnetosphere Because of the edge-on viewing angle ( ~88 o ), 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 270 o (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. Relative transverse velocity ~ 680 km s -1 Eclipse 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 1~3 o obs. longitude=90 o longitude=180 o longitude=0 o B’s unperturbed magnetosphere (not to scale)
Probing pulsar magnetosphere A’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 time of 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 model Since 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 to a sharp jump in plasma density and temperature. → synchrotron absorption. bow shock magnetopause magnetosheath 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 1bright peak 2 one orbital revolution
Secular change of B’s pulse shape bright peak 1bright 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 3 o /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 (3 o /yr) due to the geodesic precession (5.1 o /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 (17 o /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?)