PULSARS & TRANSIENT SOURCES

1. PULSARS & TRANSIENT SOURCES • Neutron Star Science & Pulsar Surveys • Transient sources • SKA = prolific, specific modes needed Pushing the Envelope with SKA Jim Cordes, Cornell 10 July 2001

2. Why more pulsars? • Extreme Pulsars: • P < 1 ms P > 5 sec • Porb < hours B > 1013 G • V > 1000 km s-1 • Population & Stellar Evolution Issues (NS-BH binary) • Physics payoff (core-collapse processes, EOS, QED processes, GR, LIGO, GRBs…) • Serendipity (strange stars, transient sources) • New instruments (AO, GBT, SKA) can dramatically increase the volume searched (galactic & extragalactic)

3. 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)

4. INTERSTELLAR DISPERSION DM = 0D ds ne(s)   DM -3

5. Pulse broadening (recent AO results, R. Bhat et al)  ~ D2/2c  -4 Pulse broadening

6. Dmax vs. Flux Density Threshold Scattering limited Dispersion limited Luminosity limited

7. Parkes MB Feeds

8. Surveys with Parkes, Arecibo & GBT. Simulated & actual Yield ~ 2000 pulsars. www.astro.cornell.edu/~cordes

9. SKA pulsar survey 600 s per beam ~104 psr’s

10. Pulsar Yield Up to 104 pulsars (~105 in MW, 20% beaming) NS-NS binaries (~ 100, merger rate) NS-BH binaries (?) Planets, magnetars etc. Pulsars as probes of entire Galaxy: • spiral arms • pulsar locations vs. age • electron density map (all large HII regions sampled) • magnetic field map from Faraday rotation • turbulence map for WIM (warm ionized medium)

11. TRANSIENT SOURCES Sky Surveys: The X-and--ray sky has been monitored highly successfully with wide FOV detectors (e.g. RXTE/ASM, CGRO/BATSE). The transient radio sky (e.g. t < 1 month) is largely unexplored. New objects/phenomena are likely to be discovered as well as the predictable classes of objects.

12. TRANSIENT SOURCES (2) • TARGET OBJECTS: • Neutron star magnetospheres • Accretion disk transients (NS, blackholes) • Supernovae • Gamma-ray burst sources • Brown dwarf flares (astro-ph/0102301) • Planetary magnetospheres & atmospheres • Maser spikes • ETI

13. TRANSIENT SOURCES (3) • TARGET PROCESSES: • Intrinsic: incoherent ( brightness limit) coherent (virtually no limit) continuum: low frequencies favored line: masers • Extrinsic: scintillation maser-maser amplification gravitational lensing absorption events

14. TRANSIENT SOURCES (4) • Certain detections: • Analogs to giant pulses from the Crab pulsar out to ~5 Mpc • Flares from brown dwarfs out to at least 100 pc. • GRB afterglows to 1 µJy in 10 hours at 10 . • Possibilities: • -ray quiet bursts and afterglows? • Intermittent ETI signals? • Planetary flares?

17. Crab Pulsar

18. OBSERVABLE DISTANCES OF CRAB PULSAR’S GIANT PULSES

19. MSP B1937+21

20. J1907+0918 226 ms DM = 358

21. J1909+0909 223 ms DM = 421

22. 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?

23. M33 Beam 2

24. Methods with the SKA I. Target individual SNRs in galaxies to 5-10 Mpc II. Blind Surveys: trade FOV against gain by multiplexing SKA into subarrays. III. Exploit coincidence tests to ferret out RFI, use multiple beams.

25. Summary • Prolific pulsar/transient science for the SKA • Pulsar surveys: need high G/T and solid angle coverage (with some trade off) • Transients: Want as large FOV as possible (e.g. hemispheric). Full G/T of SKA not necessarily needed. Exploit coincidence tests from spatially separated stations • Timing: need many narrow beams • Astrometry: SKA with long baselines (parallaxes across the Galaxy)

26. Full Radio Census of Spin-Driven Pulsars • 1200 known radio pulsars • 105 active in Galaxy (20% beamed to us) • detect 10 to 20,000  mapping of ionized gas (“DM tomography”)  identification of rare binaries  10-20 yr project (Arecibo, GBT, FAST,SKA)

27. How Far Can We Look? Dmax = D (S / Smin1 )1/2 Nh1/4 Smin1 = single harmonic threshold = m Ssys /(Dn T)1/2 m = no. of sigma ~ 10 Nh = no. of harmonics that maximize harmonic sum Nh  0 for heavily broadened pulses Regimes: Luminosity limited Dmax  Smin1 -1/2 DM/SM limited Dmax  Smin1 -x , x<1/2

28. I. Arecibo Galactic-Plane Survey • |b| < 5 deg, 32 deg < l < 80 deg • 1.35 GHz total bandwidth = 300 MHz • digital correlator backend (1024 channels) (1st quadrant available = WAPP) • multibeam system (7 feeds) • 300 s integrations, 3000 hours total • Can see 2.5 to 5 times further than Parkes (period dependent) • Expect at least 1000 new pulsars

29. 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.

30. NEUTRON STARSPHYSICS 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 (>> 1012 Gauss) • Processes in core-collapse supernovae (~ 1 sec) • - mass, photon, neutrino rockets

31. GUITAR NEBULA PULSAR

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

33. NEUTRON STARSPHYSICS 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)

34. NEUTRON STARSPHYSICS SPACE (continued) • ENDGAMES: • Coalescence (NS-NS, NS-BH, NS-WD binaries) • Escape from the Galaxy • Relationship to GRBs

35. GUITAR NEBULA PULSAR

36. NEUTRON STARSOBSERVATION 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

37. INTERSTELLAR DISPERSION

38. INTERSTELLAR SCATTERING

39. NEUTRON STARSOBSERVATION SPACE (continued) • High angular resolution for astrometry • VLBI resolution needed • SKA == VLB array • SKA == station in VLB array • Currently ionosphere limited (df ~ l) • SKA at high frequencies: parallaxes to greater D • (can go to > 5 kpc)

40. PERIODICITY SEARCHES • ADVANTAGES OF SKA: • large G/T • large FOV • Galactic Pulsars: • Dmax   (G/T)1/2 Nh1/4  - /2 • Vmax  Dmax3 local • Dmax2 disk • Go to high frequencies: • less flux but less scattering •  net increase in search volume

43. 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)

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

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

46. TRANSIENT SOURCESOBSERVATION 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

48. GUITAR NEBULA PULSAR

49. CRAB GIANT PULSES • > 105 Jy peak, < 50 micro sec wide @ 1/hr, 400 MHz • A young pulsar phenomenon? • Millisecond pulsars too? • Dmax  1.5 Mpc (Arecibo) • 5 Mpc (SKA)