Some long-baseline aspects of transients

Olaf Wucknitz
LOFAR TKP Meeting, Amsterdam, June 2011

Transcript

1. Some long-baseline aspects of transients Olaf Wucknitz wucknitz@astro.uni-bonn.de LOFAR Transients KSP Meeting, Amsterdam, 28th June 2011
2. Long-baseline aspects of transients • gravitational lenses • Crab observations nebula polarisation of pulsar • RFI aircraft lightning • pulsar scattering studies titlepage introduction summary back forward previous next fullscreen 1
3. 0957+561 with LOFAR: VERY preliminary maps VLA [ Harvanek et al. 1997 ] titlepage introduction summary back forward previous next fullscreen 2
4. Long-baseline observations of the Crab (TauA/M1/3C144) • 12 h on 13/14 Feb 2011 L2011 23410 • 115–160 MHz • international stations: DE601, DE603, FR606 • NL stations: CS032, RS106,205,208,306,307,406,503 • problems DE601 failed 50 % of subbands bad in blocks of 30/31 significant ionospheric delays, differential Faraday rotation titlepage introduction summary back forward previous next fullscreen 3
5. Image of the pulsar BOTH: 0534+220 IPOL 123.828 MHZ 23410.ICL001.1 PLot file version 1 created 26-JUN-2011 20:14:37 Grey scale flux range= -0.018 8.566 JY/BEAM Cont peak flux = 8.5657E+00 JY/BEAM Levs = 8.566E-03 * (-2, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024) 0 2 4 6 8 DECLINATION (J2000) RIGHT ASCENSION (J2000) 05 34 32.4 32.3 32.2 32.1 32.0 31.9 31.8 31.7 31.6 22 00 55 54 53 52 51 50 49 titlepage introduction summary back forward previous next fullscreen 4
6. Imaging the nebula (flare?) titlepage introduction summary back forward previous next fullscreen 5
7. The nebula with the VLA at 5 GHz [ Bietenholz (2004) ] titlepage introduction summary back forward previous next fullscreen 6
8. Faraday dispersion function from Q and U (30 subbands) titlepage introduction summary back forward previous next fullscreen 7
9. After subtraction of leakage peak (one CLEAN iteration) titlepage introduction summary back forward previous next fullscreen 8
10. RFI spikes • strong spikes (< 1 sec) left after initial flagging • had consistent phases and someti- mes small delays • seen on all Dutch baselines • wide: < 115 MHz – ∼ 141 MHz • beyond airband • detectable for about 30 min titlepage introduction summary back forward previous next fullscreen 9
11. Mapping the signal • can measure delays on Dutch baselines • 3 baselines sufficient to determine position (in 3d) • add all baselines incoherently, scan in 2d or 3d • 2d scan at 10 km height find clear moving peak, scans with 8–60 subbands titlepage introduction summary back forward previous next fullscreen 10
12. Altitude and nearby trajectory (3d scans) titlepage introduction summary back forward previous next fullscreen 11
13. Full trajectory focused at 10200 m (2d scans) titlepage introduction summary back forward previous next fullscreen 12
14. Trajectory http://www.astro.uni-bonn.de/~wucknitz/lofar/lgm_large.html titlepage introduction summary back forward previous next fullscreen 13
15. Identification AFL 231 Moscow to Brussels aircraft VP-BUO titlepage introduction summary back forward previous next fullscreen 14
16. Lightning in 0957+561 observations titlepage introduction summary back forward previous next fullscreen 15
17. Trying to localise lightning . . . titlepage introduction summary back forward previous next fullscreen 16
18. KNMI lightning detections 5 June 2011 18047 discharges titlepage introduction summary back forward previous next fullscreen 17
19. Pulsar scattering: geometry DS observer θ scattering screen pulsar D τ = 1 2 θ2D D = DDs D−Ds ≈ D titlepage introduction summary back forward previous next fullscreen 18
20. Pulsar scattering: one/three screens 0 0.2 0.4 0.6 0.8 1 τ temporal profile -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 θ spatial profile -1 -0.5 0 0.5 1 0 0.1 0.2 0.3 0.4 0.5 0.6 θ τ -6 -4 -2 0 2 4 6 0 0.1 0.2 0.3 0.4 0.5 0.6 baseline length τ 0 0.2 0.4 0.6 0.8 1 τ temporal profile -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 θ spatial profile -1 -0.5 0 0.5 1 0 0.1 0.2 0.3 0.4 0.5 0.6 θ τ -6 -4 -2 0 2 4 6 0 0.1 0.2 0.3 0.4 0.5 0.6 baseline length τ titlepage introduction summary back forward previous next fullscreen 19
21. Pulsar scattering: continuous medium 0 0.2 0.4 0.6 0.8 1 τ temporal profile -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 θ spatial profile -1 -0.5 0 0.5 1 0 0.1 0.2 0.3 0.4 0.5 0.6 θ τ -6 -4 -2 0 2 4 6 0 0.1 0.2 0.3 0.4 0.5 0.6 baseline length τ titlepage introduction summary back forward previous next fullscreen 20
22. Summary • extended variability to find lenses • pulsars with long baselines • Crab polarisation • RFI from aircraft and lightning • new approach to pulsar scattering titlepage introduction summary back forward previous next fullscreen 21