Evolution of the scattering screen of PSR B0834+06 Dana Simard, - - PowerPoint PPT Presentation

Evolution of the scattering screen of PSR B0834+06

Dana Simard, Caltech

J.-P. Macquart, Ue-Li Pen, Franz Kirsten, Robert Main, Marten van Kerkwijk, Walter Brisken

Scintillometry 2019 MPIfR @ Bonn, November 2019

PSR B0834+06 has long been used for scintillation arc studies

Dana Simard 6 November 2019 Scintillometry 2019 @ MPIfR

FAINT SCATTERING AROUND PULSARS: PROBING THE INTERSTELLAR MEDIUM ON SOLAR SYSTEM SIZE SCALES Stinebring et al. 2001 ApJ 549 L97

Dana Simard Scintillometry 2019 @ MPIfR

PSR B0834+06 has long been used for scintillation arc studies

• Brisken et al. 2010 measured the first VLBI distance to a pulsar

scattering screen using PSR B0834+06

Brisken et al. 2010 ApJ 708 232 6 November 2019

PSR B0834+06 shows evidence for compact structures

Dana Simard Scintillometry 2019 @ MPIfR

• Evidence for compact lensing structures:
• No detectable dependence of location of sub-images on pulsar

position & very small dependence on observing frequency

Hill et al. 2005 ApJ 619 L171 Arclet Apex Group γ τ ∼ 1 ms fD < 0 0.062 ± 0.006 0.1 ms τ 0.4 ms 0.01 ± 0.01 τ > 0.4 ms fD > 0 0.019 ± 0.004

∆θ ∝ λγ

Brisken et al. 2010 ApJ 708 232 6 November 2019

Models of pulsar scintillation arcs rely on geometry

Dana Simard Scintillometry 2019 @ MPIfR

pulsar

• bserver

lens

i

Pen & Levin 2014 (MNRAS 442 3338); Simard & Pen 2018 (MNRAS 478 983) Inclined corrugated sheets Gwinn 2019 (MNRAS 486 2809); Gwinn & Sosenko 2019 (MNRAS 489 3692) Noodle model for scintillation arcs Also confined turbulence in filaments (e.g. ESEs associated with hot stars Walker et al. 2017) or sheets (e.g. SNe remnants) 6 November 2019

Models of pulsar scintillation arcs rely on geometry

Dana Simard Scintillometry 2019 @ MPIfR

pulsar

• bserver

lens

i

Simard & Pen 2018 MNRAS 478 983 6 November 2019

The corrugated sheet model predicts evolution of secondary spectrum

Dana Simard Scintillometry 2019 @ MPIfR

3 simple predictions:

• Asymmetric lens profile: See a

different set of images from a different set of crests after a corrugated region passes by the pulsar

• Frequency evolution: At higher

frequencies, a steeper gradient is needed -> if underdense (overdense), separation between the pulsar and the image decreases (increases)

• Temporal evolution: As the crest

moves away from the pulsar, a steeper gradient is needed -> if underdense (overdense), separation between the pulsar and image decreases (increases) (Underdense)

Simard & Pen 2018 MNRAS 478 983 6 November 2019

The corrugated sheet model predicts evolution of secondary spectrum

Dana Simard Scintillometry 2019 @ MPIfR

3 simple predictions:

• Asymmetric lens profile: See a

different set of images from a different set of crests after a corrugated region passes by the pulsar

• Frequency evolution: At higher

frequencies, a steeper gradient is needed -> if underdense (overdense), separation between the pulsar and the image decreases (increases)

• Temporal evolution: As the crest

moves away from the pulsar, a steeper gradient is needed -> if underdense (overdense), separation between the pulsar and image decreases (increases) (Overdense)

Simard & Pen 2018 MNRAS 478 983 6 November 2019

*For a lensed image with magnification 0.01 and angular separation 10 mas at 314.5 MHz

𝛿

Underdense sheet 0.019 Overdense sheet

• 0.022

and fit a power law of the form

∆θ ∝ λγ

∆θ(λ)

Calculate Brisken et al. 2010 find small positive dependence of the angular separation

• n wavelength for one group of arclets.

Arclet Apex Group γ τ ∼ 1 ms fD < 0 0.062 ± 0.006 0.1 ms τ 0.4 ms 0.01 ± 0.01 τ > 0.4 ms fD > 0 0.019 ± 0.004

Frequency evolution consistent with Brisken et al. 2010 measurement

Dana Simard Scintillometry 2019 @ MPIfR Brisken et al. 2010 ApJ 708 232 Simard & Pen 2018 MNRAS 478 983 6 November 2019

Multi-epoch observations of PSR B0834+06

Dana Simard Scintillometry 2019 @ MPIfR

50 100 150 τ (µs) −20 20 fD (mHz) 50 100 150 τ (µs) −20 20 fD (mHz) −20 20 fD (mHz) −20 20 fD (mHz) −20 20 fD (mHz)

PI J.-P . Macquart 10 Arecibo Observations, 4 VLBA + Ar + VLA + Ef observations

Simard et al. in prep. 6 November 2019

Evidence of asymmetric lens profiles in PSR B0834+06

Dana Simard Scintillometry 2019 @ MPIfR

−20 20 fD (mHz) 50 100 150 τ (µs) −20 20 fD (mHz) −20 20 fD (mHz)

−20 20 fD (mHz) 50 100 150 τ (µs)

Two arclets approaching pulsar: One arclet leaving pulsar:

Simard et al. in prep. 6 November 2019

Evolution of PSR B0834+06

FOE, August 2019

−20 20 fD (mHz) 50 100 150 τ (µs) −20 20 fD (mHz) −20 20 fD (mHz) −20 20 fD (mHz) 50 100 150 τ (µs)

Two arclets approaching pulsar: One arclet leaving pulsar:

2 4 6 ∆θ (mas) 10 20 30 40 50 60

day 0 day 9 day 21 day 30 day 42 day 51 day 59 day 66 day 68 day 89

Dana Simard Scintillometry 2019 @ MPIfR

After avg. motion of the screen removed

To compare with models we need the distance to the screen

Dana Simard 4 November 2019 Scintillometry 2019 @ MPIfR

−20 −10 10 20 fD (mHz) 20 40 60 80 100 120 delay (µs) −20 −10 10 20 fD (mHz)

−20 −10 10 20 fD (mHz) −100 100 phase (deg) −20 −10 10 20 fD (mHz)

Simard et al. in prep.

Veff,|| = 270 +/- 30 km s-1 Angle of 8 +/- 2 degrees W of N

To compare with models we need the distance to the screen

Dana Simard 4 November 2019 Scintillometry 2019 @ MPIfR

−20 −10 10 20 fD (mHz) 20 40 60 80 100 120 delay (µs) −20 −10 10 20 fD (mHz)

−20 −10 10 20 fD (mHz) −100 100 phase (deg) −20 −10 10 20 fD (mHz)

Simard et al. in prep.

Veff,|| = 270 +/- 30 km s-1 Angle of 8 +/- 2 degrees W of N

0.4 0.6 0.8 η (s3) 0.25 0.50 0.75 1.00 1.25 1.50 average power per pixel ×1014

Curvature of 0.537 +/- 0.010 s3

To compare with models we need the distance to the screen

Dana Simard 4 November 2019 Scintillometry 2019 @ MPIfR

−20 −10 10 20 fD (mHz) 20 40 60 80 100 120 delay (µs) −20 −10 10 20 fD (mHz)

−20 −10 10 20 fD (mHz) −100 100 phase (deg) −20 −10 10 20 fD (mHz)

Simard et al. in prep.

Veff,|| = 270 +/- 30 km s-1 Angle of 8 +/- 2 degrees W of N

0.4 0.6 0.8 η (s3) 0.25 0.50 0.75 1.00 1.25 1.50 average power per pixel ×1014

Curvature of 0.537 +/- 0.010 s3 Derive a distance to the screen of Dscr = 390 +/- 20 pc

η = λ2 2c Deff V 2

eff,k

To compare with models we must remove the motion of the screen

Dana Simard Scintillometry 2019 @ MPIfR

−5 5 u (Mm) −8 −6 −4 −2 2 4 6 8 v (Mm)

Vpsr * 0.5 min Vearth * 5 min

Day 0 Day 89

αs

20 40 60 80 day 0.52 0.54 0.56 0.58 η (s3) η 0.23 0.24 0.25 0.26 0.27

dfD dt (mHz d−1) dfD dt

dfD dt = 1 2ην ✓ 1 − νfD dη dt ◆

Simard et al. in prep. 6 November 2019

Temporal evolution suggests underdense structures

Dana Simard Scintillometry 2019 @ MPIfR

2 4 6 8 |β| (mas) −0.4 −0.2 0.0 0.2 0.4 (|∆θ| − |β|) − (|∆θ| − |β|)0 (mas)

Structure A 0.008 cm−3

• 0.008 cm−3

0.0008 cm−3

• 0.0008 cm−3

2 4 6 8 |β| (mas)

Structure B

• Largest uncertainty is the curvature of the parabola in the secondary spectrum
• Combining VLBI w/ incoherent distance measurement will improve constraints on

distance to, velocity of the screen & the orientation of the scattering * for the same model, Δ ne = -0.007 cm-3 was consistent with the frequency evolution of the scattering screen measured by Brisken et al. 2010 (see previous slide)

Simard et al. in prep. 6 November 2019

Dana Simard Scintillometry 2019 @ MPIfR

Precise curvature measurements are crucial!

• We need precise curvatures to remove the motion of the screen and

measure the motion of the images within the screen

• We also need precise measurements to monitor changes in the screen
• ver time - in thin screen model these mean change in orientation of

screen

• Discrepancy between measurements from different observations of PSR

B0834+06: Evolution over time? Hard to explain by changes in screen parameters.

6 November 2019

VLBI observations & special transformations can improve curvature

Dana Simard Scintillometry 2019 @ MPIfR 6 November 2019

−20 20 fD (mHz) 50 100 150 τ (µs)

0.4 0.6 0.8 η (s3) 0.25 0.50 0.75 1.00 1.25 1.50 average power per pixel ×1014

Hough Transform

VLBI observations & special transformations can improve curvature

Dana Simard Scintillometry 2019 @ MPIfR 6 November 2019

−20 20 fD (mHz) 50 100 150 τ (µs)

0.4 0.6 0.8 η (s3) 0.25 0.50 0.75 1.00 1.25 1.50 average power per pixel ×1014

Hough Transform

𝜾j, l 𝜾j, m 𝜾k, l 𝜾k, m

Example on 2005 data from Brisken et al. 2010 ApJ 708 232

1-D screen models & position-position spectrum See talks by Olaf Wucknitz & Daniel Baker Power profiles used by Daniel Reardon VLBI + intensities

Summary

Dana Simard 6 November 2019 Scintillometry 2019 @ MPIfR

• Predictive models of scintillation can be tested using the frequency and

temporal evolution of substructure in the scintillation pattern

• PSR B0834+06 frequency (Brisken et al. 2010 ApJ 708 232) and temporal

evolution (Simard et al. in prep.) consistent with the underdense corrugated sheet model (Pen & Levin 2012 MNRAS 442 3338; Simard & Pen 2018 MNRAS 478 983)

• PSR B0834+06 temporal evolution shows asymmetric lensing structures
• Improved precision in the screen geometry, specifically the curvature, are

necessary for precise tests of scintillation arc models