Pulsars with LOFAR The Low-Frequency Array

Transcription

1 Pulsars with LOFAR The Low-Frequency Array Ben Stappers ASTRON, Dwingeloo With assistance from Jason Hessels,, Michael Kramer, Joeri van Leeuwen and Dan Stinebring.

2 Next generation radio telescope Telescope the size of the Netherlands plus parts of Germany Frequencies: MHz 10% Square Kilometer Array (SKA) prototype at low-frequencies Interferometer baselines: 100 km European Expansion to 1000 km Aperture array: Replace big dishes by many cheap dipoles 77 stations of 96 dipole antennas + extra sensors (geo+meteo) No moving parts: electronic beam steering supercomputer synthesizes giant dish Two orders of magnitude improvement in resolution and sensitivity LOFAR - phased array telescope construction:

3 IBM Blue Gene/L Stella the heart of LOFAR 27,4 Tflop Dutch minister of science ~ PCs Occupying 6 m KW power consumption Blue Gene 0,5 Tbit/s input Now operational Large (100 s processors) auxiliary clusters

4 LOFAR Stations Low Band Antennas 96 Low Band Antenna s Distributed over ~60 m Optimized for MHz 96 High Band Tiles 4x4 antenna s Distributed over ~50m Optimized ~ MHz High Band Antennas

5 LOFAR Configuration Virtual Core Phase I Layout Land acquisition: 350 out of 400 ha secured Network: Exloo Groningen link is in place

6 LOFAR Basic Parameters Frequency Range Low Band: MHz / High Band: MHz Number of Antennas Low Band: 7700 / High Band: 7700 (4x4) Polarization Configuration Full Stokes Virtual Core: 3200 antennas, 32 stations baselines 100 m - 2 km Outside Core: 4500 antennas, 45 stations baselines up to 100 km Digitized Bandwidth 100 MHz (10-90, and MHz) 80 MHz ( MHz) Processing Capacity Full Array Imaging: 32 MHz - 12 bit Core Station Beams: up to 32 MHz, 20 beams, 4-bit4 Can trade bandwidth for station beams. Possible to almost fully sample antenna beam (ASM) with 4 MHz beams.

7 LOFAR Basic Properties /10 /10 /10 /10 For pulsar observations with 32 MHz BW and 10% duty cycle

8 Currently 4, may be expanded in future. Epoch of Reionisation. Key Science Projects LOFAR 1.4 MHz 14 MHz 140 MHz 1.4 GHz Cosmological Redshift - Hydrogen line is seen at: Surveys. When & how did galaxies form? When & how did the first BHs form? When did the large scale structure form? What is the relative timescale of them all? LOFAR will have 1000 times higher resolution, 100 times higher sensitivity, and 10 5 times more integration time.

9 Currently 4, may be expanded in future. Cosmic Rays. Key Science Projects Transients. RSM - Detect all radio transients X-ray binaries, AGN, GRBs Pulsars Planets - solar and extra-solar Flare stars & Serendipity

10 RS Overall Development Plan CS-1 Phased roll-out Core Full System Procurement & land acquisition Rollout Core Remote Stations S/S CDRs CDR IOC UOC

11 European Expansion Current discussions: Germany ~12 stations UK ~3 stations Italy ~2 stations France ~1 station? Poland ~1 station?

12 LOFAR for Pulsars Wide Pulsar Surveys: Sparse array VC incoherent station beam 35 TA beams &pulsar b/ends ~20 VC station beams in MHz BW possible Narrow Pulsar Surveys & known sources: Use tied-array mode As many stations as possible Multiple TA beams possible 32 MHz BW anywhere in ~100 MHz range

13 Pulsars: All Sky Survey One hour pointings 150 MHz optimum frequency 20 beams simultaneously van Leeuwen & Stappers new pulsars: A full local census of radio emitting NSs limited in gl. plane by scattering weak nearby MSPs Possibly exotic systems

14 A Full Census of Radio Emitting NSs Sensitive to: Geminga like & AXPs/SGRs Steep spectrum (>-3,B0943) MSPs (unbroken spectra) RRATs (long pointings, low-dm) Mostly off sources (on 10%) MSP spectra don t turnover, Kuzmin & Losovsky 2001 RRATS, McLaughlin et al MHz, Shitov et al. 2000

15 Extragalactic Pulsars LOFAR will be sensitive to normal and giant pulse emission from nearby galaxies. van Leeuwen & Stappers 2006 In M33, 10 hour obsn can detect pulsars with L> 57 Jy kpc 2, 10 pulsars known Brightest could be obs d out to 1.2 Mpc Depending on SI can detect GPs out to Mpc Crab Giant Pulse observed with the WSRT LFFEs at 141 MHz. LOFAR will have at Least 30 times sensitivity, 12 times BW

16 Pulsar Emission: Spectra, Avg. Profiles & Single Pulses. Pulsar Spectra from Deshpande & Radhakrishnan 1992 (34.5 MHz data) Spectra over full LOFAR range simult. Important physics in break/non-break Large sample, check stats, e.g. α & β MSP spectra, really less show turnover PSRs B and showing Std. RFM and non-std RFM. Izvekova etal 1993 PSR B observed with the WSRT LFFEs at 141 MHz. LOFAR will have at Least 30 times sensitivity, 12 times BW Sensitive! 1/3 PSRs HB, 1/4 PSRs LB Plasma dynamics: μ-struct, drifting Polarisation, simult with HFs. MSPs! Nulling/Moding/Drifting Checks of RFM, aberration, retardation? Simultaneous wide frequency obs, DMs Polarisation Profile evolution (incl. high freqs.) PSR B τ scatt ~ s Single pulses SNR~20

17 Plasma and ISM Dispersion & Rotation Measure in the magnetosphere Refraction effects Study local ISM via DS & SS Can monitor these variations Excellent probe of local electron density via large number of PSRs Unique studies of scattering RMs will be measurable -- B gal. Can also be used to study these properties of the e-gal pulsars. A dynamic and secondary spectra for PSR B showing the influence of ~1 AU size structures in the ISM with electron densities of ~200. Hill et al. 2005

18 Other possibilities Exceptional sensitivity combined with the multi-beam capabilities make LOFAR useful for monitoring programs. Regular timing to catch Glitches Regular timing to provide solutions for gravitational wave observatories and GLAST Catch transitions of more off than on pulsars The radio-sky monitor will find new transient pulsar sources but will also allow rapid follow-up and via the TBB a look back in time at the event itself. TBB can store 100 MHz BW for 1.3s or 200 khz BW for 650s or anything in between. Transient Magnetars!!!

19 LOFAR will provide unprecedented sensitivity in the frequency range where pulsars are brightest and where they show significant changes. This will enable: Finding 1500 new pulsars A full census of local NS population Extragalactic pulsars Emission studies incl. Polarisation ISM & IGM studies Monitoring (Timing/Transients)