LOFAR LBA Single Pulse Study of the PSR B0809+74

Vlad Kondratiev

Transcript

1. LOFAR LBA single­pulse study of the PSR B0809+74 Vlad Kondratiev (ASTRON) Jason Hessels, Ben Stappers, Tom Hassall, Aris Karastergiou, Anya Bilous, Michael Kramer, Patrick Weltevrede, and the LOFAR Pulsar Working Group, and the LOFAR TKP
2. Observations Variety of pulsar radio emission Drifting subpulses, nulling, mode changing Giant pulses and micropulses Spiky emission (Weltevrede et al. 2006) high frequencies Dec 4, 2012 TKP, Amsterdam
3. Observations Variety of pulsar radio emission Drifting subpulses, nulling, mode changing Giant pulses and micropulses Spiky emission (Weltevrede et al. 2006) ? ? high frequencies Strong pulses @ 111 MHz, BSA (Kuzmin & Ershov) Strong pulses @ 110-180 MHz WSRT (Karuppusamy et al. 2011) low frequencies Dec 4, 2012 TKP, Amsterdam
4. Observations Variety of pulsar radio emission Drifting subpulses, nulling, mode changing Giant pulses and micropulses Spiky emission (Weltevrede et al. 2006) Anomalously Intensive Pulses @ 18-30 MHz, UTR-2 (Ulyanov et al. 2006) ? ? high frequencies Strong pulses @ 111 MHz, BSA (Kuzmin & Ershov) Strong pulses @ 110-180 MHz WSRT (Karuppusamy et al. 2011) low frequencies ? Dec 4, 2012 TKP, Amsterdam
5. 62 MHz 15 MHz B0809+74 By studying pulsar emission at the lowest accessible frequencies, can we learn something new and fundamental? LOFAR provides full coverage of the 10–90 MHz window. Dec 4, 2012 TKP, Amsterdam
6. Dec 4, 2012 TKP, Amsterdam Observations • LBA Superterp • 15–62 MHz • 1 hour • ∆f ≈ 6 kHz • ∆t = 491.52 μs • Stokes I
7. Bright narrow­band pulses Kondratiev et al. (in prep) B1133+16 B0809+74 Dec 4, 2012 TKP, Amsterdam
8. Bright narrow­band pulses Kondratiev et al. (in prep) B1133+16 B0809+74 Dec 4, 2012 TKP, Amsterdam
9. Pulse energy distribution Kondratiev et al. (in prep) B0809+74 • Energies < 10 ‹E› • Can't diffirentiate between Log­Norm and PL • In general, Log­Norm fits better • PL works better for high­energy tail Dec 4, 2012 TKP, Amsterdam
10. Kondratiev et al. (in prep) B0809+74 Peak flux densities Dec 4, 2012 TKP, Amsterdam
11. Pulse spectra Kondratiev et al. (in prep) B0809+74 • ∆f ~ 1 – 16 MHz peaking at 3 MHz • For B1133+16 emission is much broader Dec 4, 2012 TKP, Amsterdam
12. ≤ 30 MHz vs. >30 MHz Kondratiev et al. (in prep) B0809+74 Energies Peak flux densities Dec 4, 2012 TKP, Amsterdam
13. Pulse ''super­sequence'' B0809+74 Kondratiev et al. (in prep) Dec 4, 2012 TKP, Amsterdam
14. ''super­sequence'' (afterglow) Kondratiev et al. (in prep) Dec 4, 2012 TKP, Amsterdam B0809+74
15. Pulse ''super­sequence'' Kondratiev et al. (in prep) Dec 4, 2012 TKP, Amsterdam B0809+74
16. Pulse ''super­sequence'' Dec 4, 2012 TKP, Amsterdam B0809+74 • downward motion of plasma enhancement along the magnetic field line (+radius-to-frequncy mapping, +geometry) • connection to frequency-dependent drifting subband (see Tom's talk), frequency drift rates are harmonically related?? • ...
17. ISM scintillations are averaged out (frequency resolution of 400 kHz) ∆ν d ~ 7 kHz @60 MHz ∆ν d ~ 2 kHz @40 MHz In agreement with BSA and DKR­1000 observations (Smirnova & Shishov 2008) Narrow­band origin? ISM? Kondratiev et al. (in prep) Dec 4, 2012 TKP, Amsterdam B0809+74
18. ISM scintillations are averaged out (frequency resolution of 400 kHz) ∆ν d ~ 7 kHz @60 MHz ∆ν d ~ 2 kHz @40 MHz In agreement with BSA and DKR­1000 observations (Smirnova & Shishov 2008) Narrow­band origin? ISM? Kondratiev et al. (in prep) Dec 4, 2012 TKP, Amsterdam B0809+74 Must be intrinsic to the pulsar ?..
19. Kondratiev et al. (in prep) Strong plasma turbulence? • ∆f/f c ~ 0.15 • Strong plasma turbulence model (SPT, Weatherall 1998) predicts ∆f/f ~ 0.1–0.2 • SPT plasma flow in → the radio emission region is likely to be unsteady Dec 4, 2012 TKP, Amsterdam B0809+74
20. • We observe occasional bright narrow­band pulses from the PSR B0809+74 at frequencies 15–62 MHz. Their spectra can be as narrow as 1 MHz and tend to have a width of 3 MHz. • We identified pulse sequences from the PSR B0809+74 where narrow patch of emission is drifting up in frequency from pulse to pulse. We see evidence for similar frequency drift for at least one other pulsar, B1919+21. • The origin of these narrow­band pulses is likely to be pulsar­intrinsic rather than due to propagation effects in ISM or ionosphere. • At the moment observed pulse properties of the PSR B0809+74 do not allow us to relate low­frequency bright narrow­band pulses to ``spiky emission'', or to giant pulses or regular emission. • Spectral width of strong emission patches scales with increasing frequency as f/f ∆ c ~0.15 for the PSR B0809+74 and qualitatively agrees with the prediction of the SPT model. This supports the relation between bright narrow­band pulses at low frequencies and giant pulses. Summary Dec 4, 2012 TKP, Amsterdam
21. Dec 4, 2012 TKP, Amsterdam LBA, 19 CS 1 h 8 bit 15–93 MHz Δt = 655 µs Δf ≈ 3 kHz
22. Dec 4, 2012 TKP, Amsterdam LBA, 19 CS 1 h 8 bit 15–93 MHz Δt = 655 µs Δf ≈ 3 kHz
24. Dec 4, 2012 TKP, Amsterdam