1. The Transient Universe: AY 250 Spring 2007 Existing Transient Surveys: Radio I: Pulsars Geoff Bower

2. The Transient Universe: AY 250 Spring 2007 Pulsar Discovery “a bit of scruff” -J Bell

3. The Transient Universe: AY 250 Spring 2007 PSR Discovery Timescale July 1967: MRAO in operation Aug 1967: First PSR signals detected Nov 1967: Systematic observations of PSR 1919+22 Dec 1967: Three more PSRs known Feb 1968: Nature paper summarizing discovery (Hewish & Bell etal 1968)

4. The Transient Universe: AY 250 Spring 2007 MRAO Array of 2048 dipoles operating at 81.5 MHz with 1 MHz bandwidth Built for interplanetary scintillation of quasar signals –Required high time resolution (0.1 second) Hewish designed and Bell with other students build telescope over a couple of years

5. The Transient Universe: AY 250 Spring 2007 Alternatives to Pulsars Man-made interference Radar reflection off the Moon Television Reflections off nearby buildings LGM-1

6. The Transient Universe: AY 250 Spring 2007 Higher Time Resolution & Frequency Resolution Regular pulses Frequency dispersed pulses Interstellar scintillation Doppler variations and frequency stability

7. The Transient Universe: AY 250 Spring 2007 Progress of Understanding Immediate association with compact objects –Frequency sweep 5 MHz/s –Instantaneous bandwidth 80 kHz –  t<0.016 s  r<5000 km –White dwarfs or neutron stars Pulsation? (Hewish model) –Normal modes 8 s for WD 1 s for NS density

8. The Transient Universe: AY 250 Spring 2007 Pulsar in the Crab Nebula Staelin & Reifenstein 1968 Remnant of SN 1054

9. The Transient Universe: AY 250 Spring 2007 Optical Pulses from the Crab Cocke et al 1969

10. The Transient Universe: AY 250 Spring 2007

11. Very Rapid Theoretical Progress Basic model converged on within months Dozens of pulsars discovered Papers on –Interstellar scintillation –High energy emission –Cosmic rays –Synchrotron radiation –Electrodynamics –Optical and X-ray pulsars –Polarization

12. The Transient Universe: AY 250 Spring 2007 Discovery of the Millisecond Pulsar Backer, Kulkarni, Heiles, Davis, Goss 1982 1.5 msec period Search driven by IPS & steep spectrum Missed by earlier searches with less time resolution Computational requirements grow as P_min^-2

13. The Transient Universe: AY 250 Spring 2007 Significance of the MSP Rotation frequency ~642 Hz close to breakup for 1 M_sun neutron star –At 2000 Hz and 10 km radius, centrifugal and gravitational forces in equilibrium Extreme accuracy in timing possible –10^-15 s/s

14. The Transient Universe: AY 250 Spring 2007 The Pulsar Population Spin down –E_dot ~ B^2 P^-4 –E ~ P^-2 –  B^2 ~ P*P_dot Pulsars in SNR Normal pulsars Death line Spin up of MSP pulsars Diversity of B-field

15. The Transient Universe: AY 250 Spring 2007 Music of the Spheres MSP: 1937+21 PSR 0329+54 PSR 08-33

16. The Transient Universe: AY 250 Spring 2007 Binary Pulsars PSR 1913+16 Pulsar – NS binary Precision timing gives –Orbital elements –Constraints on masses NS masses ~1.4 M_sun as predicted by equation of state –GR induced shift in period ~10^-12 s/s due to gravitational radiation Taylor & Weisberg 1982

17. The Transient Universe: AY 250 Spring 2007 Pulsar Searching Search in phase space of period, and dispersion measure –DM ~ n_e * L –Pulse phase ~ DM * lambda^2

18. The Transient Universe: AY 250 Spring 2007 But Binaries are the Most Interesting and Short Period Binaries are the Most Interesting of Those For pulsar searching, pulse period changes within a fraction of an orbit Solution 1: Add period derivative search (or acceleration) –This is sensitive to P_orb >> P_observe –So, sensitivity is limited to detect short orbital periods: can be < 10 minutes

19. The Transient Universe: AY 250 Spring 2007 Solution 2: Sideband Search Ransom et al 2003 P_obs > P_orb

20. The Transient Universe: AY 250 Spring 2007 Implementation of Sideband Search 47 Tuc J Simulated MSP

21. The Transient Universe: AY 250 Spring 2007 Improvement in Sensitivity From Sideband Search

22. The Transient Universe: AY 250 Spring 2007 The Payoff for a New Technique 21 MSPs in Globular Cluster Ter 5 25% increase over total number in GCs from previous 35 years 13 binaries including two eclipsing and two highly eccentric systems –NS masses in range 1.7 – 1.96 M_sun –Due to collisions in the GC Probe of interactions, mass segregation Ransom et al 2005

23. The Transient Universe: AY 250 Spring 2007 Parkes Multi-Beam Survey

24. The Transient Universe: AY 250 Spring 2007 Parkes MBS The most successful PSR survey ever 742 PSRs discovered –Doubling previous number known A number of exotic objects found –RRATs –Numerous binaries –Double pulsar system

25. The Transient Universe: AY 250 Spring 2007 Pulsar Galactic Population Total number of galactic pulsars: –30,000 detectable (~5% currently detected) –155,000 +/- 6000 total –1.4 +/- 0.2 per century Smooth modelClumpy model

26. The Transient Universe: AY 250 Spring 2007 Innovation and Pulsar Science Instrumental –Low frequency instrumentation –High time resolution IPS telescope –Msec time resolution backend –Parkes Multibeam for large scale survey Technical –Search techniques –New binary search technique More to do –Higher frequencies, complete surveys, greater sensitivity, giant pulses, exotic objects