Pulsars at low radio frequencies Vlad Kondratiev (ASTRON) Science - PowerPoint PPT Presentation

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

Renaissance of low radio frequencies DE601 IPS array LOFAR SKA Low NenuFAR Ooty RT LWA DKR- MWA UTR-2 1000 VLA GURT uGMRT URAN-3 BSA

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

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

Pulsar science at low freqs → Surveys ● pulsar population studies → ➤ 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)

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?

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)

LOTAAS vs. others GBNCC LOTAAS SKA1-Low (coherent beams) frequency (MHz) 350 135 200 data rate (x GBNCC) 1 25 ~50 – 100 field of view (sq. deg.) 0.25 10 1 number of beams 1 219 500 dwell time (min) 2 60 10 sensitivity (x GBNCC): instantaneous 1 0.4 9 cumulative 1 2 20

LOFAR Tied-Array All-sky Survey (LOTAAS) http://www.astron.nl/lotaas/ ● LOFAR ''Superterp'' (12 innermost HBA sub-stations) ● Currently for DEC > 0 deg ● Find MSPs out to DM ~50 pc/cc ● Smin ~ 3 mJy @ 135 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

1 survey pointing in red LOTAAS 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 1 SAP • + 12 additional TABs pointed towards known pulsars • => total of 222 TABs • 119 – 151 MHz • BW = 32 MHz • frequency channel =12 kHz • dt = 492 µs • dwell time = 1 hour TABs (4 rings)

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

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+15 ‣ 50 cands/pointing (SP classifier) • 100+ known pulsars redetections Cartesius – Dutch national supercomputer 55M core-hours allocated

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+15 ‣ 50 cands/pointing (SP classifier) • 100+ known pulsars redetections Cartesius – Dutch national supercomputer 55M hours allocated

LOTAAS: Discovery status http://www.astron.nl/lotaas/

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 http://www.astron.nl/lotaas/ moment somewhat lower than predicted • Timing with LOFAR and Lovell telescope at 1.4 GHz

First LOFAR millisecond pulsar J1552+5436 ▸ Fermi Unid targeted searche s ▸ First MSP discovered at < 300 MHz ▸ Steep spectrum as many other MSPs α ( < –2.6) Pleunis

Low-lum nearby source J1529+40 DM = 6.5 pc/cc d = 0.5 kpc Cooper

RRAT J0139+33 Michilli

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)

Pulsar science at low freqs Hassall et al. 2012 ● 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) Log (Flux density) ~ ν α Also next talks in this session Carousel model Log (frequency) (Rankin et al. 2006)

LOFAR Censuses MSPs normal PSRs Bilous et al. 2016 Kondratiev et al. 2016 → 194 Northern sources, δ > 8˚ → Exploratory observations and → outside Galactic plane, |b| > 3˚ preparation for pulsar timing → Cycle 0 (most), Cycle 1-2 (some) → not in Globular clusters → Full Core → good coordinates, → HBA, 110−188 MHz position errors < 130˝ LBA, 15−93 MHz → 400 subs → Complex-voltage data Observations → Δ t = 5.12 µs → Typically 20 min (LBA − 1 hour) • LC1_003 • Feb-May 2014 • Full core Spectra work • HBA, 110−188 MHz • 400 subs → • Not a single observation, but split in 32 −256 chan • IQUV many more data (!): • Δ t = 163.84 µs −1.31 ms → total number of HBA obs = 1508; • 20 min, or at least 1000 periods (LBA obs = 18) • Mainly timing data (Cycles 0−6) (1 observation)

Census' profiles of slow pulsars Bilous et al. 2016

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

Census' spectra of slow pulsars Bilous et al. 2016

MSP Spectra Kondratiev et al., Preliminary in prep.

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 phase- dependent RMs (but much smaller variation than at 1400 MHz) Noutsos et al. 2015

The «chameleon» pulsar B0943+10 B-mode X-rays weak and unpulsed Radio pulses bright and orderly Hermsen et al. 2013, Science

The «chameleon» pulsar B0943+10 Q-mode X-rays bright and pulsed Radio pulses weak and disorderly Hermsen et al. 2013, Science

The «chameleon» pulsar B0943+10 with LBAs Bilous et al. 2014 Discovery of a systematic B-mode profile delay

The «chameleon» pulsar B0943+10 Mereghetti et al. 2016 LOFAR+Arecibo+LWA

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?)

Howard et al. 2016 LWA Verbiest et al., in prep. Geyer et al., to be submitted Sobey et al., in prep.

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