Pulsars transient sources
Download
1 / 58

PULSARS & TRANSIENT SOURCES - PowerPoint PPT Presentation


  • 126 Views
  • Uploaded on

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. Why more pulsars?. Extreme Pulsars: P < 1 ms P > 5 sec P orb < hours B > 10 13 G

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about ' PULSARS & TRANSIENT SOURCES' - aphrodite-charles


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
Pulsars transient sources

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


Why more pulsars
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)


Ska galactic pulsar census
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 = 0D ds ne(s)

  DM -3


Pulse broadening (recent AO results, R. Bhat et al)

 ~ D2/2c  -4

Pulse broadening


D max vs flux density threshold
Dmax vs. Flux Density Threshold

Scattering limited

Dispersion limited

Luminosity limited



Surveys with Parkes, Arecibo & GBT.

Simulated & actual

Yield ~ 2000 pulsars.

www.astro.cornell.edu/~cordes


SKA pulsar survey

600 s per beam

~104 psr’s


Pulsar yield
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)


Transient sources
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.


Transient sources 2
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


Transient sources 3
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


Transient sources 4
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?





J1907+0918

226 ms

DM = 358


J1909+0909

223 ms

DM = 421


Giant pulses from nearby galaxies
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?


M33

Beam 2


Methods with the ska
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
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
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)


How far can we look
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


I arecibo galactic plane survey
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
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
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



Neutron stars physics space continued
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)


Neutron stars physics space continued1
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)


Neutron stars physics space continued2
NEUTRON STARSPHYSICS SPACE (continued)

  • ENDGAMES:

  • Coalescence (NS-NS, NS-BH, NS-WD binaries)

  • Escape from the Galaxy

  • Relationship to GRBs



Neutron stars observation space
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




Neutron stars observation space continued
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)


Periodicity searches
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


Ska galactic pulsar census1
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
TRANSIENT SOURCESPHYSICS SPACE

  • OBJECTS:

  • Neutron star magnetospheres

  • Accretion disk transients (NS, blackholes)

  • Gamma-ray burst sources

  • Planetary magnetospheres & atmospheres

  • Maser spikes

  • ETI


Transient sources physics space1
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


Transient sources observation space
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



Crab giant pulses
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)



Giant pulses from nearby galaxies1
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


Giant pulses from nearby galaxies2
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
Narrow pulses: Tb limits

  • W = pulse width

  • Spk = peak flux density

  • = 0.29 microJy T12-2 W2 / Dkpc2


Summary1
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
Milky Way Census

Targets: Molecular cloud regions

YSOs, jets

Main sequence stars (thermal!)

Evolving & evolved stars

Full Galactic Census:

microquasars

radio pulsars (P-DM searches, SKA-VLBI astrometry)

SNR-NS connections (SGRs, magnetars, etc.)


ad