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Compact structures of interstellar plasma in the Galaxy revealed by Radioastron Compact structures of interstellar plasma in the Galaxy revealed by Radioastron

Mikhail Popov On behalf of the Radioastron Pulsar Group

(Andrianov A., Bartel N., Burgin M., Fadeev E., Gwinn C., Joshi B.C., Smirnova T., Soglasnov V., Rudnitskyi A. et al.)

Mikhail Popov On behalf of the Radioastron Pulsar Group

(Andrianov A., Bartel N., Burgin M., Fadeev E., Gwinn C., Joshi B.C., Smirnova T., Soglasnov V., Rudnitskyi A. et al.)

Scintjllometry Workshop 4-8 November 2019, Bonn, Germany

ASC LPI

Radioastron Mission Radioastron Mission

The largest in the world 10-m deployable space radio telescope.

Launched on the 18th of July, 2011

• Daily Space-VLBI observatjons
• Support from more than 40 ground radio telescopes around the world
• Orbit around the Earth up to 300 000 km
• More than 7 years of successful operatjon
• Capable of multj-frequency observatjons

(18392 – 25112 MHz)

Studies on:

• AGN+QSO (imaging, surveys)
• Masers (imaging, surveys)
• Pulsars (ISM, scatuering efgects, etc.)
• Gravitatjonal redshifu

Frequency bands: 316 MHz, 1660 MHz, 4868 MHz, 22220 MHz

More informatjon: htup://radioastron.ru/

Basic parameters

Observing bands (cm) Frequency MHz SEFD kJy Gain mK/Jy Sensitivity 10 σ (mJy) Fringe spacing μatas

92 (P) 316-332 13.5 11 140 500 18 (L) 1636-1692 3.0 15 30 100 6 (C) 4804-4860 11.6 13 50 35 1.3 (K) 18372- 25132 40 3 160 7

Observed Pulsars

Source NOBS TRA, (hrs) TGND, (hrs) Correlatjon B0329+54 8 19 33.5 8 Corr. with RA B0525+21 4 6.5 6.5 1 Corr. with RA, 3 No corr. B0531+21 (CRAB) 17 37 53.5 3 Ground only, 6 Corr. with RA, 3 Failed B0809+74 3 3.5 3.5 2 Corr. with RA, 1 No corr. B0823+26 10 23 32 6 Corr. with RA, 4 No corr. B0833-45 (VELA) 4 9 9 4 Corr. with RA B0834+06 6 9.5 9.5 4 Corr. with RA, 2 No corr. B0919+06 2 4 4 1 Ground only, 1 Corr. with RA B0950+08 3 4.5 4.5 2 Corr. with RA, 1 No corr. B1133+16 5 8.5 8.5 3 Corr. with RA, 2 No corr. B1237+25 7 12 12 1 Ground only, 5 Corr. with RA, 1 No corr. B1508+55 3 5.5 5.5 1 Ground only, 2 No corr. B1641-45 1 5 10.5 Ground only

Observed Pulsars

Source NOBS TRA, (hrs) TGND, (hrs) Correlatjon B1642-03 1 2 2

• Corr. with RA

B1749-28 1 3 6

• Corr. with RA

B1919+21 1 2 2

• Corr. with RA

B1929+10 4 7 7 1 Ground only, 2 Corr. with RA, 1 Failed B1933+16 1 1.5 1.5

• Corr. with RA

B1937+21 1 3 3 Ground only B2016+28 1 1 1

• Corr. with RA

B2021+51 3 4.3 10 2 No corr., 1 Corr. with RA B2111+46 3 4 4 3 Ground only B2217+47 6 10 10 5 Ground only, 1 Corr. with RA B2255+58 1 1 5 Ground only B2319+60 1 1.5 7.5 Ground only

Mission Time Line

Year Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun 2011-12 In Orbit Check-out Fringe Search 2012-13 Early Science Program (10 projects) 2013-14 AO-1 (16 projects) 2014-15 AO-2 (14 projects) 2015-16 AO-3 (12 projects) 2016-17 AO-4 (13 projects) 2017-18 AO-5 (12 projects) 2018-19 AO-6 (11 projects) 2019-20 AO-7 (10 projects)

List of Projects

Code Title

• P. I.

Fringe Search Program: RAFS01 Fringe Search Observatjons at L band (Crab) RAFS12 Fringe Search Observatjons: Pulsar at P-band Early Science Program: RAES04 Crab Giant Pulses with RadioAstron at 18 cm

• C. Gwinn & M. Popov

RAES06 RadioAstron Pulsar Observatjons

• C. Gwinn & M. Popov

RAES07 RadioAstron/LBA Vela Pulsar Observatjons

• C. Gwinn & M. Popov

RAES10 RadioAstron Pulsar Observatjons (B0329+54)

• C. Gwinn & M. Popov

Key Science Program: RAKS02 Studies of Pulsars with RadioAstron

• C. Gwinn

RAGS04 Substructure in Pulsar Scatuering Disks

• M. Popov

“RadioAstron-VLBI observatjons: Study of Local Scatuering Material

• T. Smirnova

RAGS10 Crab Pulsar Giant Pulse Study with RadioAstron

• A. Rudnitskiy

RAGS20 Angular diameters of pulsar scatuering disks and the distributjon of interstellar plasma fmuctuatjons

• M. Popov

RAGS29 Monitoring of substructure in scatuering disks of pulsar radio emission

• C. Gwinn & M. Popov

RAGS36 Two-dimensional mapping of the interstellar scatuering screen for Crab pulsar

• R. Main & A. Rudnitskiy

Distance to scattering screens

τ 𝑡𝑑= 1 2𝑑𝐸∫

𝐸

𝑒𝑨 𝑨 (𝐸−𝑨 )ψ (𝑨 ) θ𝐼

2 = 4 ln2

𝐸

2 ∫ 𝐸

𝑒𝑨 𝑨

2𝜔 (𝑨)

Scattering of pulsar radiation by the interstellar medium causes angular and temporal broadening. Temporal broadening: Angular broadening:

Distance to scattering screen

τ 𝑡𝑑= 1 2𝑑𝐸∫

𝐸

𝑒𝑨 𝑨 (𝐸−𝑨 )ψ (𝑨 ) θ𝐼

2 = 4 ln2

𝐸

2 ∫ 𝐸

𝑒𝑨 𝑨

2ψ (𝑨 )

Scattering of pulsar radiation by the interstellar medium causes angular and temporal broadening. Temporal broadening: Angular broadening: Simple models:

• Uniformly distributed medium: ψ (𝑨 )=𝑑𝑝𝑜𝑡𝑢 ⇒

θH=(16ln 2𝑑 τsc/ 𝐸 )

1/2

• Thin screen:

ψ (𝑨 )=δ ( 𝑒) ⇒

θH=[8ln 2𝑑 τsc (𝐸−𝑒)/𝐸𝑒]

1/2

Brituon, Gwinn & Ojeda ApJ 501, L 101, 1998

Dynamic spectrum PSR B0919+06

The cross-power spectrum is the product of Fourier transforms of the Impulse-response functions:

~

𝑊 𝑏𝑐

~

𝑊 𝐵𝐶 (ω)=~ 𝑕 𝐵 (ω )~ 𝑕𝐶

∗(ω )

2D auto-correlation function

𝐶~

𝑊 (Δ𝑢 , Δ 𝑔 )= ∑ 𝑘=− ∞ ∞

∑

𝑙=−∞ ∞ ~

𝑊 𝑘, 𝑙~ 𝑊 𝑘− 𝑜, 𝑙− 𝑛

∗

Dynamic spectrum (B0916+06)

𝑢𝑒𝑗𝑔 = ρdif 𝑊 ⊥

𝑔 𝑒𝑗𝑔= 1 2 π τ sc

Decorrelation bandwidth fdif – HWHM Scintillation time tdif is the half-width at 1/e level.

Structure function

𝐸𝑡 (Δ𝑢 ,0 )=

(𝐶 (0,0 )−𝐶 (Δ 𝑢 ,0))

𝐶(0,0 )

𝐶 (0,0)

𝐶 (Δ𝑢 ,0 )

Slope of the time structure function shows the spectral index

• f the power-law spectrum of

electron density fluctuations. For Δ t < tdif

𝐸𝑡∼ Δ𝑢𝑜 −2

𝑜=11/3for Kolmogorov spectrum

Delay-fringe rate diagram for B0329+54

Gwinn et al., ApJ 822,2,2016 Popov et al., MNRAS 465, 978, 2017

Sections of delay-fringe rate diagram (B0329+54)

Visibility amplitude versus baseline

𝑊 (𝑐 )=exp[− 1 2( π

√2ln 2

θH𝑐 λ )

𝑜−2

]

𝑐−baseline θH −FWHM of Scattering Disk 𝑜=11/3for Kolmogorov spectrum

Too hard to calibrate visibility function

Average correlation function

PSR B0834+06. Average correlation function from complex cross-spectra (RA-AR).

Off-pulse

𝐾 (𝐜, Δ 𝑔 > 𝑔 𝑒𝑗𝑔 )

𝐾 (𝐜 ,0)

𝐾 (𝐜 , Δ 𝑔 > 𝑔 𝑒𝑗𝑔 ) 𝐾 (𝐜,0) = |𝐶𝑣(𝐜)|

2

1+|𝐶𝑣 (𝐜 )|

2

𝐜− baseline 𝐶𝑣(𝐜 )

– the spatial field-coherence function

𝐶𝑣 (𝐜 )=exp[− 1 2(

|𝐜|

ρdif )

𝑜 −2

]

Visibility magnitude versus baseline (Vela)

The scintillation pattern time delay between ground telescopes

𝑊 ⊥

PSR B0823+26, WB-GB B=4900 km Dt=8 s Vobs=610 km/s Vpm=190 km/s ds= 0.77 D

Variation of time delay (B0823+26,WB-GB)

Model Fit

Fitting of all 3 parameters

𝐵⋅sin( 2 π 𝑢 1(day )+δ)+𝐶

We suppose that . So we fixed B and and fit only A.

𝑊 ⊥∥𝑊 𝑞

Secondary spectra

Secondary spectra (B1929+10)

τ= 𝐸 2𝑑 λ2 𝑊 ⊥

2

𝑒 𝐸−𝑒 ν

2≈ 𝐸 λ2

2𝑑𝑊 𝑞

2

𝐸−𝑒 𝑒 ν

2

Fitting arc by function τ=𝑏 (ν −ν0)

2−𝑏 ν0 2

We do not suppose that a parabola always runs through the origin. We are fitting two values:

• curvature of parabola a,
• shift parabola top from the origin ν0

Stjnebring et al., ApJ 549, L97, 2001

Frequency

Cosmic

Prism

Pulsar

D=2 kpc

Cosmic Prism+Weak Scattering Screen

Perturbation depends on ν: Δν/ν<100%, ΔI/I<<100%

Time or

Position

Weak

Scattering

Screen

Frequency

Cosmic Prism+Weak Scattering Screen

Perturbation depends on ν: Δν/ν<100%, ΔI/I<<100%

Structure Function

The Structure Function shows that the

electric field at the spacecraft equals that at the Earth, but with a frequency shift that increases with time.

Time or

Position

Smirnova et al 2014, ApJ 786, 115

Diagram of scatuering layers in the directjon to the PSR B1919+21

Dz=1 kpc Dz2=440 pc Dzpr=1.4 pc Dz1=0.14 pc

Shishov et al., MNRAS, 468, 3709, 2017

Diagram of scatuering layers in the directjon to the PSR B0834+06

R= 620pc r2= 12 pc r1= 250 pc Rprism> 300 pc Smirnova et al, MNRAS 2019. (submitued)

Cosmic Prisms

Conclusions

• Cosmic prisms appear along most lines of sight

where we can detect them.

• The magnitude and direction of the gradient

vary with time.

• They tend to lie within ≈100 pc of the Sun. (A

selection effect may make the closest prism most easily detectable.)

• Cosmic prisms also affect pulsar timing, and are

likely detected in some observations.

Sky region near the VELA PSR

VELA supernova remnant in X-ray

ROSAT, MPE, NASA

PSR B0833-45

• Gl

Gb µ⍺ µ 𝜀 R(pc) V(km/s) 263

• 2.8
• 49.7

29.9 290 78 DM Spic(Jy) 𝛖(μs*s) Θ(mas) Δf(kHz*f(kHz) Rscr(pc) 67.97 60 4-20 4-8 10-50 40-60 Date T(hours) Radio telescopes 10.05.2012 3.0 HH,HO,MP,PA,TB 18.05.2012 1.5 AT,HH,HO,MP,PA 15.12.2013 2.5 AT,CD,HH,HO

Observatjons Parameters

UV-coverage

Visibility magnitude versus baseline

Fitting with Lorentzian function

Isotropic scatuering Anisotropic scatuering

UV-coverage

X-ray image of VELA PSR

Chandra High Resolutjon Camera

Pulsar Distance, kpc ∆tsc, s

∆νd, kHz

τsc, μats

θH, mas

Screen distance, kpc (Arc) Screen distance, kpc

B0329+54 1.03 108 15 4.1 и 22.5 5.0 0.41 B0525+21

(18 см)

1.6 160 3900 0.041 0.028 1.44 B0823+26 0.36 70 140 0.44 1.8 0.26 0.23 B0833-45

(18 см)

0.28 9.64 9.3 17.1 >3 ≤ 0.25 B0834+06 0.62 12 4 8 0.78 0.61 0.42 0.62 220 280 0.76 1.2 0.40 0.42 B0950+08 0.262 1000 4000 / ? 0.40 / ? 0.097 / 0.01 B1237+25 0.85 247 490 ≤ 0.098 ≤ 0.8 ≥ 0.22 0.23 B1641-45

(18 см)

4.9 0.2 0.062 2600 27 3.0 B1749-28

(18 см)

1.3 220 410 0.31 0.5 0.91 B1919+21 1 290 330 0.48 0.7 0.44 B1929+10 0.33 233 619 ≤ 0.106 0.63 0.24 0.19 B1933+16 3.7 0.25 600 12.3 2.6 B1933+16

(18 см)

3.7 41.6 50.4 3.2 0.84 2.7 1.3 / 3.1 B2016+28 0.95 2125 43 2.5 2.1 ≤ 0.01

Distance to the scattering screens

Positions of detected scattering screens

Conclusions

• A new scatuering efgect was discovered - a substructure of the scatuering disk. The

efgect of the substructure should be taken into account when analyzing the data of interferometric observatjons with extreme angular resolutjon.

• Layers of interstellar plasma close to the solar system were detected for the fjrst tjme,

which can cause rapid variability of compact extragalactjc radio sources.

• The distances to the efgectjve scatuering screens were determined for a dozen of
• pulsars. An analysis of these measurements indicates a possible layered structure of

the interstellar plasma in our Galaxy.

• Anisotropic scatuering was found in the directjon to the VELA pulsar. It can be

explained by the specifjc propertjes of the turbulent layers in the super-nova remnant.

• VLBI analysis of giant pulses from the CRAB pulsar revealed notable epoch-to-epoch

variatjon in the screen positjon explained by the dominant infmuence of the Crab Nebula.

The END

Publicatjons

• Anisotropic Scatuering of the Radio Emission of the Pulsar B0833–45 in the Vela Supernova Remnant.

Popov, M. V., Andrianov, A. S., Burgin, M. S., Zuga, V. A., Rudnitskiy, A. G., Smirnova, T. V., Soglasnov, V. A., & Fadeev, E. N. Astronomy Reports, 63, 391 (2019)

• Uncertainty in measurements of the distances of scatuering screens in pulsar observatjons.

Fadeev, E. Research in Astronomy and Astrophysics, 18, 103 (2018)

• Revealing compact structures of interstellar plasma in the Galaxy with RadioAstron.

Fadeev, E. N., Andrianov, A. S., Burgin, M. S., Popov, M. V., Rudnitskiy, A. G., Shishov, V. I., Smirnova, T. V., Soglasnov, V. A., & Zuga, V. A. MNRAS, 480, 4199 (2018)

• Interstellar scintjllatjons of PSR B1919+21: space-ground interferometry.

Shishov, V. I., Smirnova, T. V., Gwinn, C. R., Andrianov, A. S., Popov, M. V., Rudnitskiy, A. G., & Soglasnov, V. A. MNRAS, 468, 3709 (2017)

• Distributjon of Interstellar Plasma in the Directjon of PSR B0525+21 from Data Obtained on a Ground–Space

Interferometer. Andrianov, A. S., Smirnova, T. V., Shishov V. I., Gwinn, C. & Popov, M. V. Astronomy Reports, 61, 513 (2017)

• Giant Pulses of the Crab Nebula Pulsar as an Indicator of a Strong Electromagnetjc Wave.

Popov, M. V., Rudnitskii, A. G., & Soglasnov, V. A. Astronomy Reports, 61, 178 (2017)

Publicatjons

• RadioAstron Studies of the Nearby, Turbulent Interstellar Plasma with the Longest Space-Ground Interferometer Baseline.

Smirnova, T. V., Shishov, V. I., Popov, M. V., Gwinn, C. R., Anderson, J. M., Andrianov, A. S., Bartel, N., Deller, A., Johnson, M. D., Joshi, B. C., Kardashev, N. S., Karuppusamy, R., Kovalev, Y. Y., Kramer, M., Soglasnov, V. A., Zensus, J. A., Zhuravlev, V. I. Astrophysical Journal, 786, 115 (2014)

• Studies of Cosmic Plasma using RadioAstron VLBI Observatjons of Giant Pulses of the Pulsar B0531+21.

Rudnitskiy, A. G, Karuppusamy, R., Popov, M. V., & Soglasnov, V. A. Astronomy Reports, 60, 211 (2016)

• Study of Scatuering Material with RadioAstron-VLBI Observatjons.

Andrianov, A., Smirnova, T. V., Shishov, V. I., Popov, M. V., Kardashev, N. S., Soglasnov, V. A., Gwinn, C., Johnson, M., Bignall, H., Deller, A., & Kramer, M. Proceedings of Science, EVN 2014, 064 (2014) Conference paper

• Preliminary Results of Giant Pulse Investjgatjons from Crab Pulsar with RadioAstron.

Rudnitskiy, A. G., Popov, M. V., & Soglasnov, V. A. Proceedings of Science, EVN 2014, 065 (2015) Conference paper

• Distributjon of Inhomogeneitjes in the Interstellar Plasma in the Directjons of Three Distant Pulsars from Observatjons with

the RadioAstron Ground–Space Interferometer. Popov, M. V., Andrianov, A. S., Bartel, N., Gwinn, C., Joshi, B. C., Jauncey, D., Kardashev, N. S., Rudnitskii, A. G., Smirnova, T. V., Soglasnov, V. A., Fadeev, E. N., & Shishov, V. I. Astronomy Report, 60, 792 (2016)

Publicatjons

• PSR B0329+54: Statjstjcs of Substructure Discovered within the Scatuering Disk on RadioAstron Baselines of up to 235,000

km. Gwinn, C. R., Popov, M. V., Bartel, N., Andrianov, A. S., Johnson, M. D., Joshi, B. C., Kardashev, N. S., Karuppusamy, R. , Kovalev,

• Y. Y., Kramer, M., Rudnitskii, A. G., Safutdinov, E. R., Shishov V. I., Smirnova T. V., Soglasnov V. A., Steinmassl, S. F., Zensus, J. A.,

& Zhuravlev, V. I. Astrophysical Journal, 822, 2, 96 (2016)

• RadioAstron Five Years Afuer Launch: Main Science Results.

Kardashev, N. S., Alakoz, A. V., Andrianov, A. S., Artyukhov, M. I., Baan, W., Babyshkin, V. Е., Bartel, N., Bayandina, O. S., Val’tus,

• I. E., Voitsik, P. A., Vorobyov, A. Z., Gwinn, C., Gomez, J. L., Giovannini, G., Jauncey, D., Johnson, M., Imai, H., Kovalev, Y. Y., Kurtz,
• S. E., Lisakov, M. M., Lobanov, A. P., Molodtsov, V. А., Novikov, B. S., Pogodin, A. V., Popov, M. V., Privesenzev, A. S., Rudnitski, A.

G., Rudnitski, G. M., Savolainen, T., Smirnova, T. I., Sobolev, A. M., Soglasnov, V. A., Sokolovsky, K. V., Filippova, Е. N., Khartov, V. V., Churikova, M. E., Shirshakov, A. E., Shishov, V. I., & Edwards, P. Solar System Research, 51, 535 (2017)

• PSR B0329+54: Substructure in the scatuer-broadened image discovered with RadioAstron on baselines up to 330,000 km.

Popov, M.V., Bartel, N., Gwinn, C. R., Johnson, M. D., Andrianov, A. S., Fadeev, E., Joshi, B. C., Kardashev, N. S., Karuppusamy, R., Kovalev, Y. Y., Kramer, M., Rudnitskii, A. G., Shishov V. I., Smirnova T. V., Soglasnov V. A., & Zensus, J. A. MNRAS, 465, 978 (2017)

• Probing Cosmic Plasma with Giant Pulses from the Crab Pulsar.

Rudnistkiy, A., Popov, M., & Soglasnov, V. Astronomy Reports, 61, 393 (2017)