1. PULSARS & TRANSIENT SOURCES Pushing the Envelope with SKA Jim Cordes, Cornell 28 Feb 2000  Frontiers of Neutron Star Science  Complete census of transient sources  Implications for SKA

2. APPROACH WHAT CAN SKAs DO: In physics space (processes, conditions)? In observation space? POSSIBLE ANSWERS: Based on known objects. Extrapolate from rate of previous discoveries to new parameter space.

3. NEUTRON STARS PHYSICS SPACE Census of stellar evolution pathways - spin-driven pulsars, magnetars, strange stars…) - companion objects (WD, NS, BH, planets …) Tests of strong gravity (pulse timing) Extreme magnetic fields (>> 10 12 Gauss) Processes in core-collapse supernovae (~ 1 sec) - mass, photon, neutrino rockets

4. GUITAR NEBULA PULSAR

5. NEUTRON STARS PHYSICS SPACE (continued): Intervening Media: Interstellar Medium (ISM) - phase structure, turbulence - sculpting by supernovae - galactic structure: (spiral arms, molecular ring, bar) Intergalactic Medium (IGM)

6. NEUTRON STARS PHYSICS SPACE (continued): Full Galactic Census: NS birthrate in Galaxy (BR) Relation to supernova rate BR(t), BR(X) (starbursts in Galaxy) Comparison with BR in nearby galaxies Intergalactic Medium (IGM)

7. NEUTRON STARS PHYSICS SPACE (continued) ENDGAMES: Coalescence (NS-NS, NS-BH, NS-WD binaries) Escape from the Galaxy Relationship to GRBs

8. GUITAR NEBULA PULSAR

9. NEUTRON STARS OBSERVATION SPACE large G/T  search volume  (G/T) 3/2 (modulo propagation effects) high-resolution sampling in f-t plane (searching, scintillations) teraflops post processing multiple simultaneous beams for (a) searching (b) timing of pulsars

10. INTERSTELLAR DISPERSION

11. INTERSTELLAR SCATTERING

12. NEUTRON STARS OBSERVATION SPACE (continued) High angular resolution for astrometry VLBI resolution needed SKA == VLB array SKA == station in VLB array Currently ionosphere limited (  SKA at high frequencies: parallaxes to greater D (can go to > 5 kpc)

13. PERIODICITY SEARCHES ADVANTAGES OF SKA: large G/T large FOV Galactic Pulsars: D max   (G/T) 1/2 N h 1/4 -  /2 V max  D max 3 local D max 2 disk Go to high frequencies: less flux but less scattering  net increase in search volume

16. SKA GALACTIC PULSAR CENSUS > 1.4 GHz: detect all pulsars beamed toward us  100,000 x 0.2 = 20,000 pulsars Can detect many pulsars in short period binaries (large G/T  short integration times) Presumably will find exotic objects as counterparts to high energy objects (magnetars, SGRs, etc.) Can detect significant numbers of pulsars in the Galactic center star cluster (10 GHz)

17. TRANSIENT SOURCES PHYSICS SPACE OBJECTS: Neutron star magnetospheres Accretion disk transients (NS, blackholes) Gamma-ray burst sources Planetary magnetospheres & atmospheres Maser spikes ETI

18. TRANSIENT SOURCES PHYSICS SPACE PROCESSES: Scintillation induced vs. intrinsic Doppler boosting vs. inverse-Compton violations Coherent vs. incoherent sources PERHAPS THE MOST PROMISING: FISHING EXPEDITION: NEW FISH

19. TRANSIENT SOURCES OBSERVATION SPACE G/T (of course) Large instantaneous FOV dedispersion of time series (real time, multiple trial DMs) event testing for wide range of signal complexity best case: hemispheric coverage

21. GUITAR NEBULA PULSAR

22. CRAB GIANT PULSES > 10 5 Jy peak, < 50 micro sec wide @ 1/hr, 400 MHz A young pulsar phenomenon? Millisecond pulsars too? D max  1.5 Mpc (Arecibo) 5 Mpc (SKA)

24. OBSERVABLE DISTANCES OF CRAB PULSAR

25. Giant Pulses from Nearby Galaxies Wide field sampling of f-t plane Target individual supernova remnants (on/off) Expect > 10 Crabs / galaxy 10s - 100s of galaxies < 5 Mpc Dedisperse with trial DMs Threshold test (after matched filter) Reality checks: multiple hits @ same DM more hits on source

26. Giant Pulses from Nearby Galaxies SCIENTIFIC RETURN Many objects  map out IGM as well as ISMs of galaxies IGM: electron density and magnetic field NS birth rates in other galaxies Constraints on IMF Census of young pulsars, clues about magnetars?

27. Narrow pulses: Tb limits W = pulse width S pk = peak flux density = 0.29 microJy T 12 -2 W 2 / D kpc 2

29. SUMMARY SKA can dramatically alter our knowledge of galactic compact objects. Currently population models are highly leveraged from small samples. A full census of galactic pulsars will allow thorough mapping of NS birth sites, electron density, and B. SKA will discover significant numbers of extragalactic pulsars, allowing studies of the IGM, stellar evolution, occurrence of high-B magnetospheres, runaway pulsars, constraints on core-collapse processes. The preferred SKA configuration will fit into the current specifications for some but not all science goals (esp. transient surveys). Search algorithms require proportionate funding of real-time and offline processing capability.