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The Gamma Ray Pulsar Population

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					The Double Pulsar Binary System




         Maura McLaughlin
        West Virginia University
             July 16 2008
A double pulsar system?!
The Double Pulsar System: Outline

   •   Pulsar search history
   •   Double neutron star systems
   •   Discovery of the double pulsar
   •   Interactions - probing magnetospheres and winds
   •   Testing general relativity
   •   The ultimate fate!!
   •   Future prospects
The Double Pulsar System: Pulsars           - History




           Currently about 1800 pulsars known
The Double Pulsar System: Pulsars           - History




           Currently about 1800 pulsars known
The Double Pulsar System: Pulsars           - History




           Currently about 1800 pulsars known
The Double Pulsar System: Pulsars            - History




          First NS-NS binary!




            Currently about 1800 pulsars known
The Double Pulsar System: Pulsars           - History




           Currently about 1800 pulsars known
The Double Pulsar System: Pulsars           - History




           Currently about 1800 pulsars known
The Double Pulsar System: Pulsars   - Population
The Double Pulsar System: DNS            - How are they formed?




                Courtesy John Rowe animation
The Double Pulsar System: Pulsars   - Population




                               DNS binaries live here

                             8 double neutron star
                             systems known!
The Double Pulsar System: Pulsars                     - Population


Up until Oct 2003, three more pulsar “Holy Grails”:


     • pulsar in orbit with a black hole
             to probe spacetime near black hole

     • pulsar with spin period faster than 1.5 ms
             to probe NS equations of state

     • pulsar in orbit with other pulsar
              to test general relativity
The Double Pulsar System: Discovery                 - of A
                                               Parkes Multibeam Receiver
 • PSR J0737-3039 (with spin period of 22 ms
   and 2.4-hr eccentric orbit) discovered in
   April 2003 in the Parkes Multibeam
   High Latitude Survey
   (Burgay et al. 2003, Nature, 426, 531).

 • Timing indicated that the companion must
   be another neutron star.
                                                   Pulse profile of A
The Double Pulsar System: Discovery                   - of B

 • In October 2003, analysis of data taken for studies of PSR J0737-
   3039 (now “A”) shows presence of 2.7-s pulsations.
 • Identical dispersion measure to A and period variations as expected
   for A’s measured orbit show that this is indeed A’s companion.
 • In agreement with simple evolutionary models in which
                      A is first-born, recycled neutron star
                                        (short period, low B)
                      B is younger, normal neutron star
                                        (long period, high B)
The Double Pulsar System: Summary
                      Pulsar                      A                  B
 Pulsar period (ms)                              22.7              2774
 Stellar mass (solar masses)                     1.34              1.25
 Projected semi-major axis (lt-s)                 1.4               1.5
 Characteristic age (Myr)                        210                50
 Surface magnetic field strength (Gauss)        6 x 109           2 x 1012
 Energy loss rate due to spin-down (ergs/s)   5800 x 1030         2 x 1030

 Distance (pc)                                            500
 Orbital inclination (degrees)                             90
 Orbital period (hours)                                   2.45

 Eccentricity                                             0.088

 First double pulsar system ever, and most extreme and relativistic
 pulsar binary system ever! (Lyne et al. 2004, Science, 303, 1153)
The Double Pulsar System: Interactions   - Geometry




                                     RLC = cP/2π

                                  B’s light cylinder is
                                  100 times that of A.



                                    .         .
                                    E ~ I P-3 P

                                  A’s energy loss due to
                                  spindown is 3000
                                  times that of B.
The Double Pulsar System: Interactions                         - Geometry

• A large portion of a pulsar’s energy is in the form of a relativistic wind of
ionized particles. A’s wind will distort B’s magnetosphere into a cometary
shape much like the Sun does the Earth’s.




                             www-istp.gsfc.nasa.gov
The Double Pulsar System: Interactions                            - Geometry

• A large portion of a pulsar’s energy is in the form of a relativistic wind of
ionized particles. A’s wind will distort B’s magnetosphere into a cometary
shape much like the Sun does the Earth’s.




      Graham-Smith & McLaughlin, 2004, Astronomy & Geophysics, February 2005
The Double Pulsar System: Interactions   - A on B
                                   Parkes data



 • B clearly visible at 2
   orbital phases and very
   weak otherwise.
 • Profile changes from strong
   main pulse and weak
   precursor to strong single
   pulse to roughly-equal
   double pulse.
 • These patterns are stable
   across observing frequency.
The Double Pulsar System: Interactions   - A on B




                                   Jenet & Ransom 2004,
                                   Nature, 428, 919
The Double Pulsar System: Interactions    - A on B




                      A



                                         Pulse profile of A




       B
                                     Hollow cone model
The Double Pulsar System: Interactions   - A on B


                                   A is “jumpstarting”
                                   pulsar B.
The Double Pulsar System: Interactions     - A on B




                                We think A is
                                actually “wiggling” B’s
                                emission beam into
                                and out of our line of
                                sight….




            Lyutikov 2005
The Double Pulsar System: Interactions                - A on B



    and from A!


  Single pulses from B


  Green Bank Telescope




                         McLaughlin et al. 2004, ApJ, 613, L57
The Double Pulsar System: Interactions                   - A on B

 • A appears to be a
  “normal” MSP.
 • However, we see a
  strange “drifting”
  behavior in B’s pulses.

   Green Bank Telescope




                            McLaughlin et al. 2004, ApJ, 613, L57
The Double Pulsar System: Interactions                     - A on B

  Predicted arrival times of A pulses at B




                    McLaughlin et al. 2004,ApJ, 613, L57

   Direct evidence for modulation of B’s emission by A’s radiation!!
The Double Pulsar System: Interactions                 - A on B


• Drifting only seen at
 some orbital phases.




                          McLaughlin et al. 2004, ApJ, 613, L57
The Double Pulsar System: Interactions   - A on B


• Drifting only seen at
 some orbital phases.

• These are the phases where
we see the cometary B
magnetosphere from the side.

• Further studies will allow us
to probe the cometary B
magnetosphere further and to
learn about A’s wind (i.e.
density,γ, σ).

• Also may help us to learn
how “normal” pulsar emission is
produced.
The Double Pulsar System: Interactions          - B on A
                                   GBT data – 820 MHz

• A is eclipsed for ~ 30 s
  once per orbit.

• This corresponds to an
  occulting region of size
  0.05 lt-s (15,000 km), or
  10% of the light-cylinder
  radius of B.

• A has “blown away” much of B’s
  magnetosphere.
The Double Pulsar System: Interactions                     - B on A
                                           GBT data – 820 MHz

• Eclipse duration is slightly
frequency dependent, lasting
longer at lower frequencies.

• Eclipse shape is asymmetric.

• Consistent with synchrotron
absorption of A’s radio emission
in B’s magnetosheath/sphere
(Arons et al 2004).




                                   Kaspi et al. 2004, ApJ, 613, 137
The Double Pulsar System: Interactions                       - B on A
                                              GBT data – 820 MHz

• There is significant modulation
of A’s intensity during eclipse.




                                    McLaughlin et al. 2004, ApJ, 613, L57
The Double Pulsar System: Interactions                                                                     - B on A

                                                                                       GBT data – 820 MHz
• There is significant modulation
of A’s intensity during eclipse.

• This modulation is at




                                     Pulsed flux density (arbitrary units)
exactly 0.5PB, with longer eclipse
at phases when beam
of B is pointing towards/away
from us.




  Arrival times of
  B’s pulses!                                                                          Orbital phase (degrees)
                                                                             McLaughlin et al. 2004, ApJ, 613, L57
The Double Pulsar System: Interactions                 - B on A




                        QuickTime™ an d a
                       H.264 de compressor
                  are need ed to see this p icture .
The Double Pulsar System: Interactions                   - B on A




As expected if caused by synchrotron absorption in B’s magnetosphere.
The Double Pulsar System: Interactions                  - B on A




    We see significant changes of the eclipse shape with time!
The Double Pulsar System: Testing GR     - Method


  Was Einstein Right???



  “Everything should be made as simple
  as possible, but not simpler.”
The Double Pulsar System: Testing GR                     - Method


  Was Einstein Right???
 Radio timing yields 5 Keplerian parameters
         PB – binary period
         a sin i – semi-major axis
         e – eccentricity
         ω – longitude of periastron
         T0 – epoch of periastron



 We have five measurable relativistic (Post-Keplerian) parameters
 and only 3 unknowns (MA, MB, i).


                 Can measure MA, MB, i AND test GR.
The Double Pulsar System: Testing GR   - MA vs MB
The Double Pulsar System: Testing GR   - MA vs MB




                                Mass function of A
The Double Pulsar System: Testing GR   - MA vs MB




 Mass function of B
The Double Pulsar System: Testing GR   - MA vs MB




                                     Mass ratio,
                                  theory independent
The Double Pulsar System: Testing GR       - MA vs MB




                                             Mercury PA

        Periastron
         advance




                         42 arcseconds/century for Mercury
                         17 degrees per year for 0737!
The Double Pulsar System: Testing GR   - MA vs MB




      Gravitational
        redshift
The Double Pulsar System: Testing GR    - MA vs MB




                                Shapiro delay
The Double Pulsar System: Testing GR   - MA vs MB




   MA ~ 1.335 Msun

    MB ~ 1.252 Msun
                                       i = 88 degrees
The Double Pulsar System: Testing GR                     - MA vs MB

  So far, Einstein is right!!




 • Most overconstrained system.
 • Most precise determination of neutron star masses ever.
 • “B” is the least massive neutron star known.


 • Continuing timing observations:
    – 2PPN corrections to PK parameters
    – Contributions of spin-orbit coupling (geodetic precession)
       First measurement of neutron star moment of inertia!
The Double Pulsar System: Testing GR                  - Precession




 • Geodetic precession should be measurable on short timescales
   (precession period ~ 70 yrs)
The Double Pulsar System: Testing GR       - Precession




  • It IS measurable…..and agrees with
    Einstein’s prediction to within 13%!
The Double Pulsar System: Testing GR   - Precession




Geodetic precession also means…

Pulsar B’s pulse profile is
changing and pulsar B is slowing
disappearing!!!

Eclipses will soon be the only
signature of B in the system!




                                   … and for B?
The Double Pulsar System: Testing GR




                                  orbital decay due
                                   to gravitational
                                       radiation
The Double Pulsar System: Testing GR                    - GW detection




                                                  orbital decay due
 • Stars will coalesce in 85 Myr.                  to gravitational
                                                       radiation




                                    • 40 – 660 per year detectable
                                    by advanced LIGO
                                    (Kalogera et al. 2004, 614, 137)
The Double Pulsar System: Testing GR   - GW detection
The Double Pulsar System: Future
 • ISS measurements allow velocity measurements, better determination
   of i and characterization of ISM properties
   (Coles, McLaughlin et al. 2004, ApJ, 623, 392).
 • X-ray/radio continuum studies allow study of shock interaction
   between A’s relativistic wind and B’s magnetosphere
   (McLaughlin et al. 2004, 605, 41).
 • Future radio observations will yield vital insights into physics of pulsar
   winds and magnetospheres – may aid understanding of Earth/Sun
   magnetospheric physics.
 • VLBI observations will yield precise distance and velocities, making
   GR tests even more stringent.
 • Future radio timing will enable most precise test of GR and most
   precise measurement of neutron star masses ever – will yield first
   ever measurement of NS moment of inertia.
 • Future searches with the GBT (!!!!!), ALFA (Arecibo Lband Feed Array)
   and the SKA (Square Kilometer Array) will yield more of these
   objects and, possibly, a pulsar/black hole binary!

				
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