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Imaging pulsar echoes at low frequencies
Olaf Wucknitz
EVN symposium
Granada, 8 October 2018
Imaging pulsar echoes at low frequencies
• LOFAR
• The ghost in B1508+55
• Offline VLBI with LOFAR
• First attempt 2016
• Relative motion 2016–2018
• New deconvolution method
O. Wucknitz 2018 2/38
LOFAR station (Tautenburg)
O. Wucknitz 2018 3/38
Low-band antennas (10-80 MHz, Ireland)
O. Wucknitz 2018 4/38
High-band antennas (110-250 MHz)
O. Wucknitz 2018 5/38
B1508+55: a pulsar and its ghost?
0.0 0.2 0.4 0.6 0.8 1.00.20.00.20.40.60.81.01.21.41.6
0.0 0.2 0.4 0.6 0.8 1.0pulse phase [periods]
0.0000.0050.0100.0150.0200.025
• ‘ghost’ component found by Stefan Os lowski with LOFAR
• moving relative to main component
• interpretation: scattering ‘echo’ [ Os lowski & Macquart in prep. ]
O. Wucknitz 2018 6/38
Interstellar scattering: geometric delay
Ds
Dds
Dd
ob
se
rve
r
θ
pu
lsa
r
sca
tte
rin
g s
cre
en
cτ =1
2θ2D D =
Ds Dd
Dds
Does the echo have a positional offset?
O. Wucknitz 2018 7/38
Can we localise the echo of B1508+55 ?
• τ ≈ 50msec (period ≈ 0.74 sec)
• Ds = 2.13kpc = 2.19 ·1011 sec · c
• assumption: Dd ≈ Dds D = Ds
• θ =
√2cτ
D= 0.′′14 (more if closer to us)
• at high SNR this can be measured with LOFAR-VLBI !
• can test echo hypothesis and maybe determine D
• later: use two paths as interstellar interferometer
O. Wucknitz 2018 8/38
VLBI: German LOFAR (GLOW) baselines
length, fringe-spacing at 150 MHz
[km] [arcsec]DE601–DE602 390 1.06DE601–DE603 344 1.20DE601–DE604 476 0.87DE601–DE605 53 7.80DE601–DE609 412 1.00DE602–DE603 277 1.49DE602–DE604 455 0.91DE602–DE605 440 0.94DE602–DE609 585 0.70DE603–DE604 186 2.22DE603–DE605 372 1.11DE603–DE609 325 1.27DE604–DE605 487 0.85DE604–DE609 248 1.66DE605–DE609 394 1.05
O. Wucknitz 2018 9/38
Offline VLBI with LOFAR
• LOFAR correlator limited (e.g. time resolution)
• need more flexibility
? arbitrary resolution
? pulsar gating
? re-correlations
record locally, correlate centrally! (non-e VLBI)
? GLOW recording in Bonn, Julich
? other stations recording locally (3 Gbps / station)
? core centrally in Groningen
? demanding logistics, huge effort
O. Wucknitz 2018 10/38
Correlation and calibration
• own software correlator
? standard FX architecture
? flexibility, not efficiency!
• calibration (own software)
? pulsar gating, main pulse as reference
? full station-based fringe-fitting for phases
with dispersive/non-dispersive delays, rates, DFR
? bandpass calibration
• imaging and non-imaging analysis
O. Wucknitz 2018 11/38
GLOW Oct 2016: Pulses (DE603–DE605)
O. Wucknitz 2018 12/38
Folded amplitudes and phases (DE603–DE605)
O. Wucknitz 2018 13/38
Echo position(s)
0.4 0.5 0.6 0.7
120
140
160
180
freq [
MH
z]
x [arcsec]
1.20
1.05
0.90
0.75
0.60
0.45
0.30
0.15
0.00
0.15
0.4 0.5 0.6 0.7pulse phase [periods]
120
140
160
180
freq [
MH
z]
y [arcsec]
1.20
1.05
0.90
0.75
0.60
0.45
0.30
0.15
0.00
0.15
0.4 0.5 0.6 0.71.0
0.8
0.6
0.4
0.2
0.0
0.2
x [
arc
sec]
0.4 0.5 0.6 0.70.8
0.6
0.4
0.2
0.0
0.2
y [
arc
sec]
0.4 0.5 0.6 0.7
0.00
0.01
0.02
0.03
0.04
0.05
implic
it f
lux
0.4 0.5 0.6 0.7pulse phase [periods]
120
140
160
180
freq [
MH
z]
preliminary distance: 124 pc, very close to us!
O. Wucknitz 2018 14/38
The full array: LOFAR + KAIRA
O. Wucknitz 2018 15/38
Main pulse and echoes (dirty maps)
October 2016 GLOW
210122
1
0
1
2Oct 2016 main pulse
0.005
0.000
0.005
0.010
0.015
0.020
0.025
0.030
± 0
.00
00
2
210122
1
0
1
2Oct 2016 echo 1
0.001
0.000
0.001
0.002
0.003
0.004
0.005
0.006
0.007
0.008
± 0
.00
00
6
210122
1
0
1
2Oct 2016 echo 2
0.00025
0.00000
0.00025
0.00050
0.00075
0.00100
0.00125
0.00150
0.00175
± 0
.00
00
6
February 2018 international
210122
1
0
1
2Feb 2018 main pulse
0.1
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
± 0
.00
00
6
210122
1
0
1
2Feb 2018 echo 1
0.003
0.000
0.003
0.006
0.009
0.012
0.015
0.018
0.021
± 0
.00
00
4
210122
1
0
1
2Feb 2018 echo 2
0.0006
0.0000
0.0006
0.0012
0.0018
0.0024
0.0030
0.0036
0.0042
± 0
.00
00
3
O. Wucknitz 2018 16/38
Delayed-profile-aware CLEAN
• gating mixes intrinsic tail and echo
• deconvolve dirty beam and intrinsic profile
• standard CLEAN components
? explicit: position
? implicit: flux
• generalised CLEAN components
? explicit: position (offset), delay
? implicit: flux, spectrum
O. Wucknitz 2018 17/38
Delayed-profile-aware CLEAN (1 iteration)
1.00.50.00.51.0∆RA [arcsec]
1.0
0.5
0.0
0.5
1.0
∆D
EC
[arc
sec]
signif. for best time per pix
0.6
1.2
1.8
2.4
3.0
3.6
4.2
4.8
5.4
1e7
1.00.50.00.51.0∆RA [arcsec]
1.0
0.5
0.0
0.5
1.0best time per pix
0.00050
0.00025
0.00000
0.00025
0.00050
0.00075
0.00100
1.00.50.00.51.0∆RA [arcsec]
1.0
0.5
0.0
0.5
1.0significance and time
0.6 0.4 0.2 0.0 0.2 0.4 0.6signed radius [arcsec]
0.00
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
dela
y [
sec]
0.04 0.02 0.00 0.02 0.04 0.06 0.08delay [sec]
0.00
0.01
0.02
0.03
0.04
flux
allcentrerest
0.04 0.02 0.00 0.02 0.04 0.06 0.08time [sec]
0.0
0.2
0.4
0.6
0.8
1.0
flux c
onv
profilemodelmodel centremodel rest
1 its
O. Wucknitz 2018 18/38
Delayed-profile-aware CLEAN (10 iterations)
1.00.50.00.51.0∆RA [arcsec]
1.0
0.5
0.0
0.5
1.0
∆D
EC
[arc
sec]
signif. for best time per pix
1000000
2000000
3000000
4000000
5000000
6000000
7000000
8000000
1.00.50.00.51.0∆RA [arcsec]
1.0
0.5
0.0
0.5
1.0best time per pix
0.0000
0.0025
0.0050
0.0075
0.0100
0.0125
0.0150
0.0175
0.0200
1.00.50.00.51.0∆RA [arcsec]
1.0
0.5
0.0
0.5
1.0significance and time
0.6 0.4 0.2 0.0 0.2 0.4 0.6signed radius [arcsec]
0.00
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
dela
y [
sec]
0.04 0.02 0.00 0.02 0.04 0.06 0.08delay [sec]
0.00
0.01
0.02
0.03
0.04
flux
allcentrerest
0.04 0.02 0.00 0.02 0.04 0.06 0.08time [sec]
0.0
0.2
0.4
0.6
0.8
1.0
flux c
onv
profilemodelmodel centremodel rest
10 its
O. Wucknitz 2018 19/38
Delayed-profile-aware CLEAN (20 iterations)
1.00.50.00.51.0∆RA [arcsec]
1.0
0.5
0.0
0.5
1.0
∆D
EC
[arc
sec]
signif. for best time per pix
150000
300000
450000
600000
750000
900000
1050000
1.00.50.00.51.0∆RA [arcsec]
1.0
0.5
0.0
0.5
1.0best time per pix
0.000
0.008
0.016
0.024
0.032
0.040
0.048
0.056
1.00.50.00.51.0∆RA [arcsec]
1.0
0.5
0.0
0.5
1.0significance and time
0.6 0.4 0.2 0.0 0.2 0.4 0.6signed radius [arcsec]
0.00
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
dela
y [
sec]
0.04 0.02 0.00 0.02 0.04 0.06 0.08delay [sec]
0.00
0.01
0.02
0.03
0.04
flux
allcentrerest
0.04 0.02 0.00 0.02 0.04 0.06 0.08time [sec]
0.0
0.2
0.4
0.6
0.8
1.0
flux c
onv
profilemodelmodel centremodel rest
20 its
O. Wucknitz 2018 20/38
Delayed-profile-aware CLEAN (30 iterations)
1.00.50.00.51.0∆RA [arcsec]
1.0
0.5
0.0
0.5
1.0
∆D
EC
[arc
sec]
signif. for best time per pix
20000
40000
60000
80000
100000
120000
140000
1.00.50.00.51.0∆RA [arcsec]
1.0
0.5
0.0
0.5
1.0best time per pix
0.000
0.008
0.016
0.024
0.032
0.040
0.048
0.056
0.064
1.00.50.00.51.0∆RA [arcsec]
1.0
0.5
0.0
0.5
1.0significance and time
0.6 0.4 0.2 0.0 0.2 0.4 0.6signed radius [arcsec]
0.00
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
dela
y [
sec]
0.04 0.02 0.00 0.02 0.04 0.06 0.08delay [sec]
0.00
0.01
0.02
0.03
0.04
flux
allcentrerest
0.04 0.02 0.00 0.02 0.04 0.06 0.08time [sec]
0.0
0.2
0.4
0.6
0.8
1.0
flux c
onv
profilemodelmodel centremodel rest
30 its
O. Wucknitz 2018 21/38
Delayed-profile-aware CLEAN (40 iterations)
1.00.50.00.51.0∆RA [arcsec]
1.0
0.5
0.0
0.5
1.0
∆D
EC
[arc
sec]
signif. for best time per pix
8000
16000
24000
32000
40000
48000
56000
64000
1.00.50.00.51.0∆RA [arcsec]
1.0
0.5
0.0
0.5
1.0best time per pix
0.000
0.008
0.016
0.024
0.032
0.040
0.048
0.056
0.064
1.00.50.00.51.0∆RA [arcsec]
1.0
0.5
0.0
0.5
1.0significance and time
0.6 0.4 0.2 0.0 0.2 0.4 0.6signed radius [arcsec]
0.00
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
dela
y [
sec]
0.04 0.02 0.00 0.02 0.04 0.06 0.08delay [sec]
0.00
0.01
0.02
0.03
0.04
flux
allcentrerest
0.04 0.02 0.00 0.02 0.04 0.06 0.08time [sec]
0.0
0.2
0.4
0.6
0.8
1.0
flux c
onv
profilemodelmodel centremodel rest
40 its
O. Wucknitz 2018 22/38
Delayed-profile-aware CLEAN (50 iterations)
1.00.50.00.51.0∆RA [arcsec]
1.0
0.5
0.0
0.5
1.0
∆D
EC
[arc
sec]
signif. for best time per pix
4000
8000
12000
16000
20000
24000
28000
32000
1.00.50.00.51.0∆RA [arcsec]
1.0
0.5
0.0
0.5
1.0best time per pix
0.000
0.008
0.016
0.024
0.032
0.040
0.048
0.056
0.064
1.00.50.00.51.0∆RA [arcsec]
1.0
0.5
0.0
0.5
1.0significance and time
0.6 0.4 0.2 0.0 0.2 0.4 0.6signed radius [arcsec]
0.00
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
dela
y [
sec]
0.04 0.02 0.00 0.02 0.04 0.06 0.08delay [sec]
0.00
0.01
0.02
0.03
0.04
flux
allcentrerest
0.04 0.02 0.00 0.02 0.04 0.06 0.08time [sec]
0.0
0.2
0.4
0.6
0.8
1.0
flux c
onv
profilemodelmodel centremodel rest
50 its
O. Wucknitz 2018 23/38
Delayed-profile-aware CLEAN (60 iterations)
1.00.50.00.51.0∆RA [arcsec]
1.0
0.5
0.0
0.5
1.0
∆D
EC
[arc
sec]
signif. for best time per pix
2500
5000
7500
10000
12500
15000
17500
20000
1.00.50.00.51.0∆RA [arcsec]
1.0
0.5
0.0
0.5
1.0best time per pix
0.000
0.008
0.016
0.024
0.032
0.040
0.048
0.056
0.064
1.00.50.00.51.0∆RA [arcsec]
1.0
0.5
0.0
0.5
1.0significance and time
0.6 0.4 0.2 0.0 0.2 0.4 0.6signed radius [arcsec]
0.00
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
dela
y [
sec]
0.04 0.02 0.00 0.02 0.04 0.06 0.08delay [sec]
0.00
0.01
0.02
0.03
0.04
flux
allcentrerest
0.04 0.02 0.00 0.02 0.04 0.06 0.08time [sec]
0.0
0.2
0.4
0.6
0.8
1.0
flux c
onv
profilemodelmodel centremodel rest
60 its
O. Wucknitz 2018 24/38
Delayed-profile-aware CLEAN (70 iterations)
1.00.50.00.51.0∆RA [arcsec]
1.0
0.5
0.0
0.5
1.0
∆D
EC
[arc
sec]
signif. for best time per pix
1500
3000
4500
6000
7500
9000
10500
1.00.50.00.51.0∆RA [arcsec]
1.0
0.5
0.0
0.5
1.0best time per pix
0.000
0.008
0.016
0.024
0.032
0.040
0.048
0.056
0.064
1.00.50.00.51.0∆RA [arcsec]
1.0
0.5
0.0
0.5
1.0significance and time
0.6 0.4 0.2 0.0 0.2 0.4 0.6signed radius [arcsec]
0.00
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
dela
y [
sec]
0.04 0.02 0.00 0.02 0.04 0.06 0.08delay [sec]
0.00
0.01
0.02
0.03
0.04
flux
allcentrerest
0.04 0.02 0.00 0.02 0.04 0.06 0.08time [sec]
0.0
0.2
0.4
0.6
0.8
1.0
flux c
onv
profilemodelmodel centremodel rest
70 its
O. Wucknitz 2018 25/38
Delayed-profile-aware CLEAN (80 iterations)
1.00.50.00.51.0∆RA [arcsec]
1.0
0.5
0.0
0.5
1.0
∆D
EC
[arc
sec]
signif. for best time per pix
800
1600
2400
3200
4000
4800
5600
6400
7200
1.00.50.00.51.0∆RA [arcsec]
1.0
0.5
0.0
0.5
1.0best time per pix
0.000
0.008
0.016
0.024
0.032
0.040
0.048
0.056
0.064
1.00.50.00.51.0∆RA [arcsec]
1.0
0.5
0.0
0.5
1.0significance and time
0.6 0.4 0.2 0.0 0.2 0.4 0.6signed radius [arcsec]
0.00
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
dela
y [
sec]
0.04 0.02 0.00 0.02 0.04 0.06 0.08delay [sec]
0.00
0.01
0.02
0.03
0.04
flux
allcentrerest
0.04 0.02 0.00 0.02 0.04 0.06 0.08time [sec]
0.0
0.2
0.4
0.6
0.8
1.0
flux c
onv
profilemodelmodel centremodel rest
80 its
O. Wucknitz 2018 26/38
Delayed-profile-aware CLEAN (90 iterations)
1.00.50.00.51.0∆RA [arcsec]
1.0
0.5
0.0
0.5
1.0
∆D
EC
[arc
sec]
signif. for best time per pix
600
1200
1800
2400
3000
3600
4200
4800
1.00.50.00.51.0∆RA [arcsec]
1.0
0.5
0.0
0.5
1.0best time per pix
0.00
0.01
0.02
0.03
0.04
0.05
0.06
0.07
1.00.50.00.51.0∆RA [arcsec]
1.0
0.5
0.0
0.5
1.0significance and time
0.6 0.4 0.2 0.0 0.2 0.4 0.6signed radius [arcsec]
0.00
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
dela
y [
sec]
0.04 0.02 0.00 0.02 0.04 0.06 0.08delay [sec]
0.00
0.01
0.02
0.03
0.04
flux
allcentrerest
0.04 0.02 0.00 0.02 0.04 0.06 0.08time [sec]
0.0
0.2
0.4
0.6
0.8
1.0
flux c
onv
profilemodelmodel centremodel rest
90 its
O. Wucknitz 2018 27/38
Delayed-profile-aware CLEAN (100 iterations)
1.00.50.00.51.0∆RA [arcsec]
1.0
0.5
0.0
0.5
1.0
∆D
EC
[arc
sec]
signif. for best time per pix
400
800
1200
1600
2000
2400
2800
3200
1.00.50.00.51.0∆RA [arcsec]
1.0
0.5
0.0
0.5
1.0best time per pix
0.00
0.01
0.02
0.03
0.04
0.05
0.06
0.07
1.00.50.00.51.0∆RA [arcsec]
1.0
0.5
0.0
0.5
1.0significance and time
0.6 0.4 0.2 0.0 0.2 0.4 0.6signed radius [arcsec]
0.00
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
dela
y [
sec]
0.04 0.02 0.00 0.02 0.04 0.06 0.08delay [sec]
0.00
0.01
0.02
0.03
0.04
flux
allcentrerest
0.04 0.02 0.00 0.02 0.04 0.06 0.08time [sec]
0.0
0.2
0.4
0.6
0.8
1.0
flux c
onv
profilemodelmodel centremodel rest
100 its
O. Wucknitz 2018 28/38
Delayed-profile-aware CLEAN (110 iterations)
1.00.50.00.51.0∆RA [arcsec]
1.0
0.5
0.0
0.5
1.0
∆D
EC
[arc
sec]
signif. for best time per pix
300
600
900
1200
1500
1800
2100
2400
1.00.50.00.51.0∆RA [arcsec]
1.0
0.5
0.0
0.5
1.0best time per pix
0.00
0.01
0.02
0.03
0.04
0.05
0.06
0.07
1.00.50.00.51.0∆RA [arcsec]
1.0
0.5
0.0
0.5
1.0significance and time
0.6 0.4 0.2 0.0 0.2 0.4 0.6signed radius [arcsec]
0.00
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
dela
y [
sec]
0.04 0.02 0.00 0.02 0.04 0.06 0.08delay [sec]
0.00
0.01
0.02
0.03
0.04
flux
allcentrerest
0.04 0.02 0.00 0.02 0.04 0.06 0.08time [sec]
0.0
0.2
0.4
0.6
0.8
1.0
flux c
onv
profilemodelmodel centremodel rest
110 its
O. Wucknitz 2018 29/38
Delayed-profile-aware CLEAN (120 iterations)
1.00.50.00.51.0∆RA [arcsec]
1.0
0.5
0.0
0.5
1.0
∆D
EC
[arc
sec]
signif. for best time per pix
250
500
750
1000
1250
1500
1750
2000
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O. Wucknitz 2018 30/38
Delayed-profile-aware CLEAN (130 iterations)
1.00.50.00.51.0∆RA [arcsec]
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O. Wucknitz 2018 31/38
Delayed-profile-aware CLEAN (140 iterations)
1.00.50.00.51.0∆RA [arcsec]
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O. Wucknitz 2018 32/38
Delayed-profile-aware CLEAN (150 iterations)
1.00.50.00.51.0∆RA [arcsec]
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O. Wucknitz 2018 33/38
Ionised matter around hot stars?
• Walker et al. (2017): Extreme Radio-wave Scattering
Associated with Hot Stars
• IDV sources with (hot) stars near l.o.s.
? J1819+3845 with Vega
? PKS 1322–110 with Spica (8.′5)
? PKS 1257–326 with Alhakim
• ‘dense’ neutral matter around star, ionised by UV
• elongated ‘elephant’s trunks’ may cause transverse lensing
• distances and orientation fit
O. Wucknitz 2018 34/38
Stars around B1508+55 ?
• A0 star Hip 74377 at 2.73 pc from l.o.s.
? distance from us ca. 260 pc
• A2 star Hip 74458 at 1.37 pc from l.o.s.
? π = (8.36±0.57)mas
? distance (120±8.2)pc
• compare with Dd = 124pc
• thanks to Mark Walker and Artem Tuntsov
O. Wucknitz 2018 35/38
Elephant’s trunk lensing ?
PSR
star
O. Wucknitz 2018 36/38
Thanks to all people involved!
Mostly informal collaboration, great VLBI spirit!
GLOW: Andreas Horneffer, Caterina Tiburzi, Jorn Kunsemoller,
Julian Donner, Natasha Porayko
FR606: Jean-Mathias Grießmeier
SE607: Tobia Carozzi
UK608: Aris Karastergiou
PL610: Mariusz Pozoga, Barbara Matyjasiak, Hanna Rotkaehl
PL611: Marian Soida, Wojciech Lewandowski,
Bartosz Smierciak
PL612: Tomasz Sidorowicz, Leszek Blaszkiewicz,
Andrzej Krankowski
KAIRA: Derek McKay
O. Wucknitz 2018 37/38
Summary
• offline-VLBI with LOFAR works!
• data can be calibrated
• ghost of B1508+55 really is echo
• distance of screen determined
• alignment with proper motion
• ongoing monitoring (data approaching 300 TB)
• will include GMRT, maybe others
other objects and projects
O. Wucknitz 2018 38/38
Bonus: Relative alignment in nature
O. Wucknitz 2018 39/38
Bonus: Cloud: no alignment
pulsarcloud
O. Wucknitz 2018 40/38
Bonus: Filament: relative alignment
pulsarghost image
O. Wucknitz 2018 41/38
