Vlad Kondratiev (ASTRON) Science at Low Frequencies III Caltech, Pasadena, CA Dec 9, 2016

Transcription

1 Pulsars at low radio frequencies Vlad Kondratiev (ASTRON) Science at Low Frequencies III Caltech, Pasadena, CA Dec 9, 2016

2 Renaissance of low radio frequencies DE601 IPS array LOFAR Ooty RT SKA Low LWA DKR1000 UTR-2 NenuFAR MWA VLA GURT ugmrt URAN-3 BSA

3 Renaissance of low radio frequencies Before: Now: mostly transit instruments limited BW and/or Pol full tracking (rise set) large BW huge Δf/f dual pols

4 Pulsar science at low freqs pulsar population studies emission mechanism intervening medium (ISM, IPM, ionosphere)

5 Pulsar science at low freqs pulsar population studies Surveys Complete PSR samples stellar evolution studies Compact systems GR tests Many more MSPs GW detection Many other interesting and exotic systems formation/evolution studies emission mechanism intervening medium (ISM, IPM, ionosphere)

6 Low frequency pulsar surveys Pros: large FoV faster good for steep spectra sources easy localization of the promising candidates with multiple TABs in single follow up observation precursors for SKA Low pulsar survey(s) Cons: dispersion and scattering are more pronounced low freq Tsys is higher, but can do larger dwell times FRBs, RRATs much larger data volume much more processing (more DM trials) more RFI?

7 Low frequency pulsar surveys Pros: large FoV faster good for steep spectra sources easy localization of the promising candidates with multiple TABs in single follow up observation precursors for SKA Low pulsar survey(s) Cons: dispersion and scattering are more pronounced low freq Tsys is higher, but can do larger dwell times FRBs, RRATs much larger data volume much more processing (more DM trials) more RFI? LOTAAS (survey for pulsars and fast transients with LOFAR) LNCC (LWA Northern Celestial Cap, irregular observations) MWA (planned in the near future)

8 LOTAAS vs. others GBNCC frequency (MHz) LOTAAS (coherent beams) SKA1 Low ~ number of beams dwell time (min) sensitivity (x GBNCC): instantaneous cumulative data rate (x GBNCC) field of view (sq. deg.) 200

9 LOFAR Tied Array All sky Survey (LOTAAS) LOFAR ''Superterp'' (12 innermost HBA sub stations) Currently for DEC > 0 deg Find MSPs out to DM ~50 pc/cc Smin ~ MHz The SKA Low precursor survey LOTAAS team: Jason Hessels, Ben Stappers, Vlad Kondratiev, Sotiris Sanidas, Sally Cooper, Daniele Michilli, Chia Min Tan, Cees Bassa, Ziggy Pleunis, Joeri van Leeuwen +LOFAR PWG

10 LOTAAS 1 SAP 1 survey pointing in red 4 survey pointings are shown in total 3 sub array pointings (SAPs, incoherent beams), ~ 30 sq. deg. total per pointing + 4 rings (61 tied array beams, TABs) for each SAP, ~9 sq. deg. total per pointing + 12 additional TABs pointed towards known pulsars => total of 222 TABs MHz BW = 32 MHz frequency channel =12 khz dt = 492 μs dwell time = 1 hour TABs (4 rings)

11 LOTAAS 1 pass (sparse) to cover Northern hemisphere with incoherent beams (651 pointings needed) 3 passes to cover Northern hemisphere with TABs

12 LOTAAS: Observing/Processing status 1045 pointings observed so far (as of Nov 11, 2016; Pass A complete; Pass B 61%) 977 processed (searched) Processing on Cartesius: 3 hrs/beam on 24 core node 2+ PB of data collected and archived Periodicity & single pulse searches (20M+ cands, 50M+ SP cands) Machine learning classifier 200 cands/pointing (periodicity classifier, Lyon cands/pointing (SP classifier) 100+ known pulsars redetections Cartesius Dutch national supercomputer 55M core hours allocated

13 LOTAAS: Observing/Processing status 1045 pointings observed so far (as of Nov 11, 2016; Pass A complete; Pass B 61%) 977 processed (searched) Processing on Cartesius: 3 hrs/beam on 24 core node 2+ PB of data collected and archived Periodicity & single pulse searches (20M+ cands, 50M+ SP cands) Machine learning classifier 200 cands/pointing (periodicity classifier, Lyon cands/pointing (SP classifier) 100+ known pulsars redetections Cartesius Dutch national supercomputer 55M hours allocated

14 LOTAAS: Discovery status

15 LOTAAS: Discovery status 53 pulsars discovered so far! (as of Dec 7, 2016) 1 confirmed MSP! (2 more not yet confirmed) 5 RRATs Currently 1 new pulsar per 20 hrs of observing Pass B Currently at ~1 discovery per 150 sq. deg. at the moment somewhat lower than predicted Timing with LOFAR and Lovell telescope at 1.4 GHz

16 First LOFAR millisecond pulsar J Fermi Unid targeted searches First MSP discovered at < 300 MHz Steep spectrum as Pleunis many other MSPs (α < 2.6)

17 Low lum nearby source J Cooper DM = 6.5 pc/cc d = 0.5 kpc

18 RRAT Michilli J

19 Pulsar science at low freqs pulsar population studies emission mechanism Spectra (turnover, GHz peaked spectra) Polarization Profile evolution Moding, drifting subpulses, giant pulses, etc. (see also posters by Bradley Meyers & Franz Kirsten) intervening medium (ISM, IPM, ionosphere)

20 Pulsar science at low freqs Hassall et al pulsar population studies emission mechanism Spectra (turnover, GHz peaked spectra) Polarization Profile evolution Moding, drifting subpulses, giant pulses, etc. (see also posters by Bradley Meyers & Franz Kirsten)? IPM, ionosphere) Also next talks in this session Carousel model (Rankin et al. 2006) Log (Flux density) intervening medium (ISM, ~ να Log (frequency)

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22 normal PSRs LOFAR Censuses Bilous et al Northern sources, δ > 8 outside Galactic plane, b > 3 not in Globular clusters good coordinates, position errors < 130 Observations LC1_003 Feb May 2014 Full core HBA, MHz 400 subs split in chan IQUV Δt = μs 1.31 ms 20 min, or at least 1000 periods (1 observation) MSPs Kondratiev et al Exploratory observations and preparation for pulsar timing Cycle 0 (most), Cycle 1 2 (some) Full Core HBA, MHz LBA, MHz 400 subs Complex voltage data Δt = 5.12 μs Typically 20 min (LBA 1 hour) Spectra work Not a single observation, but many more data (!): total number of HBA obs = 1508; (LBA obs = 18) Mainly timing data (Cycles 0 6)

23 Census' profiles of slow pulsars Bilous et al. 2016

24 MSP profiles (best single observation) Kondratiev et al. 2016

25 Census' spectra of slow pulsars Bilous et al. 2016

26 Preliminary MSP Spectra Kondratiev et al., in prep.

27 Average profile polarization 20 bright pulsars combining HBA polarization data with higher frequencies magnetospheric birefringence cannot be a sole explanation of observed evolution of polarized fraction with frequency scattering can mimic Faraday rotation leading to phasedependent RMs (but much smaller variation than at 1400 MHz) Noutsos et al. 2015

28 The «chameleon» pulsar B B mode X rays weak and unpulsed Radio pulses bright and orderly Hermsen et al. 2013, Science

29 The «chameleon» pulsar B Q mode X rays bright and pulsed Radio pulses weak and disorderly Hermsen et al. 2013, Science

30 The «chameleon» pulsar B with LBAs Bilous et al Discovery of a systematic B mode profile delay

31 The «chameleon» pulsar B Mereghetti et al LOFAR+Arecibo+LWA

32 Pulsar science at low freqs pulsar population studies emission mechanism intervening medium (ISM, IPM, ionosphere) DM / RM / scattering (see also poster by Veronica Dike) Scintillation studies Solar wind, CMEs (talk by Greg Taylor) Space weather input to high freq timing (DM chromaticity?)

33 Howard et al LWA Verbiest et al., in prep. Geyer et al., to be submitted Sobey et al., in prep.

34 Summary: Renaissance of low-frequency pulsar astronomy Low-frequency pulsar surveys are challenging but ideal to search for steep- spectrum sources and transients. Will pave the road for the SKA-Low Low frequencies are excellent to study pulsars and provide a complementary view to study pulsar emission mechanism and ISM Synergy/complementation with high-freq observations, space weather monitoring