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

Why more pulsars? Extreme Pulsars: P 5 sec P orb 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)

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)

INTERSTELLAR DISPERSION DM =  0 D ds n e (s)   DM -3

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

D max vs. Flux Density Threshold Luminosity limited Dispersion limited Scattering limited

Parkes MB Feeds

Surveys with Parkes, Arecibo & GBT. Simulated & actual Yield ~ 2000 pulsars.

SKA pulsar survey 600 s per beam ~10 4 psr’s

Pulsar Yield Up to 10 4 pulsars (~10 5 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)

TRANSIENT SOURCES Sky Surveys: The X-and-  -ray sky has been monitored highly successfully with wide FOV detectors 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.

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

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 absorptionevents

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?  -ray quiet bursts and afterglows? Intermittent ETI signals? Intermittent ETI signals? Planetary flares? Planetary flares?

Crab Pulsar

OBSERVABLE DISTANCES OF CRAB PULSAR’S GIANT PULSES

MSP B

J ms DM = 358

J ms DM = 421

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

M33 Beam 2

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.

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)

Full Radio Census of Spin- Driven Pulsars 1200 known radio pulsars 10 5 active in Galaxy (20% beamed to us) detect 10 to 20,000  mapping of ionized gas (“DM tomography”)  identification of rare binaries  yr project (Arecibo, GBT, FAST,SKA)

How Far Can We Look? D max = D (S / S min1 ) 1/2 N h 1/4 S min1 = single harmonic threshold = m S sys /(  T) 1/2 m = no. of sigma ~ 10 N h = no. of harmonics that maximize harmonic sum N h  0 for heavily broadened pulses Regimes: Luminosity limited D max  S min1 -1/2 DM/SM limited D max  S min1 -x, x<1/2

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

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.

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 (>> Gauss) Processes in core-collapse supernovae (~ 1 sec) - mass, photon, neutrino rockets

GUITAR NEBULA PULSAR

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)

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)

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

GUITAR NEBULA PULSAR

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

INTERSTELLAR DISPERSION

INTERSTELLAR SCATTERING

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)

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

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)

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

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

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

GUITAR NEBULA PULSAR

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

OBSERVABLE DISTANCES OF CRAB PULSAR

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 same DM more hits on source

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?

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

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.

Milky Way Census Targets: Targets:Molecular cloud regions YSOs, jets Main sequence stars (thermal!) Evolving & evolved stars Full Galactic Census Full Galactic Census: microquasars radio pulsars (P-DM searches, SKA-VLBI astrometry) SNR-NS connections (SGRs, magnetars, etc.)