joeri van leeuwen (uc berkeley) ben stappers...

finding pulsars with lofarvan leeuwen

introtelescopessimulationgalacticglobular clustersextragalacticconclusions

finding pulsars with lofar

joeri van leeuwen (uc berkeley)

ben stappers (astron)

http://astro.berkeley.edu/~joeri/



telescope evolution

flat, single beam nearby bright slow pulsars


introtelescopessimulationgalactic globular clustersextragalacticconclusions

telescope evolution

dish, multiple beams fast / binary pulsars



telescope evolution

lofar: many simple receivers + supercomputer all nearby pulsars



simulation

life, evolution and death of 107 neutron stars detection by all previous pulsar searches detection for different lofar configurations



simulation

Survey Simulated Detected MolongloII 230 224 UMass-NRAO 60 50 ParkesMB 800 980 Cambridge 80MHz 93-94 25 20 SKA 15-20k



simulation

lofar compact core setup 2km wide, 32 x ~60-meter stations each containing 96 high-frequency antennae effective area towards zenith of >25m2 / antenna combined in/coherently to 8 (later 24) beams

0 30 60 90Zenith angle (degrees)

Effe

ctiv

e ar

ea p

er ti

le (m

2 )

10

0

20

30

Com

pact

cor

e ga

in (K

/Jy)

10

0

20

30120MHz

160MHz

240MHz

200MHz



galactic pulsar searches

coherent addition beamsize = 0.0044 deg2 incoherent addition beamsize = 1.8 deg2

in 'sparse' telescopes, incoherent addition is usually better for all-sky surveys




fast, sensitive pulsar surveys possiblydoubling the known pulsar population

0 32168 64 128Pointings (minutes)

60 days with 8 beams

Num

ber o

f det

ecte

d pu

lsar

s

0

2500

2000

1500

1000

500




optimum frequency (pulsar brightness, background, scattering) determined by dipoles

120 160 200 240Observing frequency (MHz)

Num

ber o

f det

ecte

d pu

lsar

s

0

2500

2000

1500

1000

500



at 140 MHz radio-wave scattering is limiting;lofar detects the full local population

Lofar detectionParkesMB detectionGalactic centerSun

-20

-10

-20

y p

osi

tio

n (

kpc)

010

20

-10 0x position (kpc)

10 20



at 140 MHz radio-wave scattering is limiting;lofar detects the full local population


-20

-10

-20hei

gh

t ab

ove

th

e g

alac

tic

pla

ne

(kp

c)0

1020


10 20



neutron star birth velocities from z-distribution supernova kicks, binary disruption


-20

-10

-20hei

gh

t ab

ove

th

e g

alac

tic

pla

ne

(kp

c)0

1020


10 20



finds all pulsars within 1kpc the first count of the weak, previously invisible pulsars near the sun reliable birthrates which stars form pulsars

can find sub-millisecond pulsars within 1kpc if they exist



globular cluster pulsar searches

high stellar densities and interaction rate many interesting binaries limited regions on the sky: coherent addition



doubles the number in M15 with a single beam




extragalactic searches

for normal periodicities or for 'giant pulses' detect the 10 brightest pulsars in M33 detect Crab-like giant pulses from M81



conclusions

lofar can double the known pulsar population finds all local pulsars probes nearby globular clusters very deeply can find extragalactic pulsars

joeri van leeuwen (uc berkeley) ben stappers...

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