Pulsar Observations with LOFAR - astro.uni-bonn.detauris/NS2012/Hessels_LOFAR.pdf · NS Workshop -...

NS Workshop - MPIfR/Bonn - Feb. 27th, 2012

Pulsar Observations with LOFARJason Hessels (ASTRON / UvA)with the LOFAR Pulsar Working Group

B. Stappers (PI, U. Manchester)J. Hessels (BF co-lead, ASTRON)

A. Alexov (BF co-lead, UvA)T. Coenen (UvA)

J.-M. Griessmeier (U. Orleans)T. Hassall (U. Manchester)

A. Karastergiou (Oxford)E. Keane (MPIfR)

V. Kondratiev (ASTRON)

M. Kramer (MPIfR)J. van Leeuwen (ASTRON)

A. Noutsos (MPIfR)M. Pilia (ASTRON)

M. Serylak (U. Orleans)C. Sobey (MPIfR)

J. Verbiest (MPIfR)P. Weltevrede (U. Manchester)

with special thanks to Jan David Mol and John Romein

LOFAR Pulsar Working Group


Pulsars discovered in 1967at radio frequency of 82MHz

2012Super-

computer


Pulsars with LOFAR

1) (Near) full coverage of the 10-240MHz range.

- Emission physics

- Interstellar medium

2) Multi-beaming and wide field-of-view.

- High-cadence monitoring

- Long dwell-time surveys


Pulsars with LOFAR

1) (Near) full coverage of the 10-240MHz range.

- Emission physics

- Interstellar medium


PSR B0809+74 detected all the way down to 16MHz!

15 -

63 M

Hz

Obs

ervi

ng F

requ

ency

20m


Superterp stations in sync to ~1ns (single clock for the entire core is on the way)Credit: Kondratiev

PSR B0809+74 single pulses down to 16MHz!

Preliminary Preliminary


Credit: Kondratiev

Magnetosphere

Magnetosphere

Rotation axis

Magnetic axis

Pulsar

Rad

io F

requ

ency


Not to scale!

Aligning Profiles

•Cold-dispersion law good to 1/100,000.

• Radio emission from within <110km of the neutron star surface.

• All radio frequencies come from a region <59km in altitude (0.1% of the light cylinder).


Hassall et al., submitted

T. E. Hassall et al.: Wide-band Simultaneous Observations of Pulsars

Fig. 13. Linear polarisation profiles of PSR B0809+74 between 925and 328 MHz (Gould & Lyne 1998; Edwards & Stappers 2003b), andLOFAR polarisation profile at 136 MHz (black lines) plotted along withthe Stokes I profiles at each frequency (grey lines). The polarised com-ponent moves from the position of the leading component of the profiletowards later pulse longitudes, tracing the broad component of the pulseprofile.

The width of the conal components as a function of fre-quency has been a subject of interest in the past. Mitra & Rankin(2002) found that the component widths remain constant be-tween 40 and 3000 MHz. We also see evidence of this in ourmodel above 80 MHz, although the component widths beginto broaden below this value. Mitra & Rankin (2002) also no-ticed this broadening, and attributed it to dispersive smearingacross a frequency channel or scattering from the ISM. In ourobservations, the dispersive smearing at 48 MHz (across a sin-gle 12 kHz channel) is ∼ 1.5o, which is enough to explain theobserved broadening in the profile10. However, even disregard-ing this low frequency broadening Mitra & Rankin (2002) foundthat the spacing between the components between 100 MHz and10 GHz changes too rapidly to be caused by a dipolar magneticfield.

PSR B1133+16 is the pulsar which is most consistent withradius-to-frequency mapping of all the pulsars in our sample.However, in Section 6 we showed that its emission is confinedto a very narrow region in the magnetosphere (<59 km) whichis incompatible with the standard radius-to-frequency model.Radius-to-frequency mapping assumes that the emission at agiven emission height traces the last open field line in the pulsarmagnetosphere. From geometrical arguments (see for exampleLorimer & Kramer 2005) it is possible to write the opening an-

10 The half power width of component 1 increases from 1.9o at72 MHz to 3.6o at 48 MHz, and component 2 increases from 2.1o at72 MHz to 3.4o at 48 MHz. Fig. 14. PSR B1133+16 is modelled as three Gaussian components: two

conal components and one which is attributed to bridge emission.

16

LOFA

R b

ands

Pulsars with LOFAR

2) Multi-beaming and wide field-of-view.

- High-candence monitoring

- Surveys


Multiple, widely separated FoVs@ 24MHz


Credit: Hassall & Hessels

Millisecond Pulsars


Credit: Hessels & Kondratiev

See Mol & Romein 2011 for multi-beam tied-array benchmarking results


Credit: Hessels, Stappers & Scaife

LOFAR 127-beam Tied-Array


Credit: Hessels & Alexov

Andromeda


LOFAR Pulsar Pilot Survey


Thijs Coenen and P.W.G.: The LOFAR Pilot Pulsar Survey

23-02-12 17:28

Pagina 1 van 1file:///Users/thijscoenen/SEARCHBRIGHT_XML/00000006/diagnostic.xml

Data file (without suffix, DM=0) NONE_L2010_21756_RSP0_DM0.00Right Ascension 02:45:33.5494Declination 63:23:53.3904Epoch (MJD) 55534.916666700002679NextPrevious

0 500 1000 1500 2000 2500 3000

Time (s)

02

46

810

12

DM

0 500 1000 1500 2000 2500 3000

5 10 15 20 25 30

SNR

5 10 15 20 25 30

max 30.48

0 20 40 60 80

N

02

46

810

12

DM

0 20 40 60 80

Fig. 3. A detection plot of J0240+62 as produced by our single pulse post processing scripts. During this observation the pulsar

emits one very bright pulse of a signal-to-noise ratio of about 30.

6

Credit: Coenen

GBNCC ~150s S/N ~30

Thanks for listening!


Pulsar Observations with LOFAR - astro.uni-bonn.detauris/NS2012/Hessels_LOFAR.pdf · NS Workshop -...

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