Compact structures of interstellar Compact structures of interstellar plasma in the Galaxy revealed by plasma in the Galaxy revealed by Radioastron Radioastron Mikhail Popov Mikhail Popov On behalf of the Radioastron Pulsar Group On behalf of the Radioastron Pulsar Group (Andrianov A., Bartel N., Burgin M., Fadeev E., Gwinn C., Joshi B.C., Smirnova T., (Andrianov A., Bartel N., Burgin M., Fadeev E., Gwinn C., Joshi B.C., Smirnova T., Soglasnov V., Rudnitskyi A. et al.) Soglasnov V., Rudnitskyi A. et al.) Scintjllometry Workshop 4-8 November 2019, Bonn, Germany Milky Way, photo by Zach Flaxbeard ASC LPI
Radioastron Mission Radioastron Mission The largest in the world 10-m deployable space radio telescope. Launched on the 18 th 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 Frequency SEFD Gain Sensitivity Fringe bands MHz kJy mK/Jy 10 σ spacing (cm) (mJy) 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- 40 3 160 7 25132
Observed Pulsars Source N OBS T RA , (hrs) T GND , (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 N OBS T RA , (hrs) T GND , (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 Substructure in Pulsar Scatuering Disks M. Popov RAGS04 “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 M. Popov fmuctuatjons 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 Scattering of pulsar radiation by the interstellar medium causes angular and temporal broadening. Temporal broadening: Angular broadening: 𝐸 2 = 4 ln2 𝐸 1 2 𝜔 ( 𝑨 ) θ 𝐼 𝑒𝑨 𝑨 2 ∫ 𝑒𝑨 𝑨 ( 𝐸 − 𝑨 ) ψ ( 𝑨 ) τ 𝑡𝑑 = 2 𝑑𝐸 ∫ 𝐸 0 0
Distance to scattering screen Scattering of pulsar radiation by the interstellar medium causes angular and temporal broadening. Temporal broadening: Angular broadening: 𝐸 𝐸 1 2 = 4 ln2 2 ψ ( 𝑨 ) τ 𝑡𝑑 = 𝑒𝑨 𝑨 ( 𝐸 − 𝑨 ) ψ ( 𝑨 ) θ 𝐼 𝑒𝑨 𝑨 2 𝑑𝐸 ∫ 2 ∫ 𝐸 0 0 Simple models: 1 / 2 ● Uniformly distributed medium: ψ ( 𝑨 ) = 𝑑𝑝𝑜𝑡𝑢 ⇒ θ H = ( 16ln 2 𝑑 τ sc / 𝐸 ) 1 / 2 ψ ( 𝑨 ) = δ ( 𝑒 ) ⇒ θ H = [ 8ln 2 𝑑 τ sc ( 𝐸 − 𝑒 ) / 𝐸𝑒 ] ● Thin screen: Brituon, Gwinn & Ojeda ApJ 501 , L 101, 1998
Dynamic spectrum PSR B0919+06 ~ 𝑊 𝑏𝑐 The cross-power spectrum is the product of Fourier transforms of the Impulse-response functions: ~ 𝑊 𝐵𝐶 ( ω ) = ~ 𝐵 ( ω ) ~ 𝐶 ∗ ( ω ) 2D auto-correlation function ∞ ~ ∞ 𝑊 𝑘 , 𝑙 ~ 𝑊 ( Δ 𝑢 , Δ 𝑔 ) = ∑ 𝐶 ~ 𝑊 𝑘 − 𝑜 , 𝑙 − 𝑛 ∑ ∗ 𝑘 = − ∞ 𝑙 = −∞
Dynamic spectrum (B0916+06) Decorrelation bandwidth f dif – HWHM 1 𝑔 𝑒𝑗𝑔 = Scintillation time t dif is 2 π τ sc the half-width at 1/e level. 𝑢 𝑒𝑗𝑔 = ρ dif 𝑊 ⊥
Structure function ( 𝐶 ( 0,0 ) − 𝐶 ( Δ 𝑢 , 0 ) ) Slope of the time structure function 𝐸 𝑡 ( Δ 𝑢 , 0 ) = 𝐶 ( 0,0 ) shows the spectral index of the power-law spectrum of 𝐸 𝑡 ∼ Δ 𝑢 𝑜 − 2 electron density fluctuations. For Δ t < t dif 𝑜 = 11 / 3for Kolmogorov spectrum 𝐶 ( 0,0 ) 𝐶 ( Δ 𝑢 , 0 )
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 𝑜 − 2 θ H 𝑐 𝑊 ( 𝑐 ) = exp [ − 1 ] π 2 ( λ ) √ 2ln 2 Too hard to calibrate visibility function 𝑐 − baseline θ H − FWHM of Scattering Disk 𝑜 = 11 / 3for Kolmogorov spectrum
Average correlation function 2 𝐾 ( 𝐜 , Δ 𝑔 > 𝑔 𝑒𝑗𝑔 ) = | 𝐶 𝑣 ( 𝐜 ) | Off-pulse 𝐾 ( 𝐜 , 0 ) 2 1 + | 𝐶 𝑣 ( 𝐜 ) | 𝐾 ( 𝐜 , 0 ) 𝐜 − baseline 𝐶 𝑣 ( 𝐜 ) – the spatial field-coherence function 𝐾 ( 𝐜 , Δ 𝑔 > 𝑔 𝑒𝑗𝑔 ) 𝑜 − 2 | 𝐜 | 𝐶 𝑣 ( 𝐜 ) = exp [ − 1 ] 2 ( ρ dif ) PSR B0834+06. Average correlation function from complex cross-spectra (RA-AR).
Visibility magnitude versus baseline (Vela)
The scintillation pattern time delay between ground telescopes PSR B0823+26, WB-GB 𝑊 ⊥ B=4900 km Dt=8 s V obs =610 km/s V pm =190 km/s d s = 0.77 D
Variation of time delay (B0823+26,WB-GB) Model 𝑊 ⊥ ∥𝑊 𝑞 We suppose that . So we fixed B and and fit only A . Fit Fitting of all 3 parameters 2 π 𝑢 𝐵⋅ sin ( 1 ( day ) + δ ) + 𝐶
Secondary spectra
Secondary spectra (B1929+10) λ 2 2 ≈ 𝐸 λ 2 τ = 𝐸 𝑒 𝐸 − 𝑒 2 𝐸 − 𝑒 ν ν Stjnebring et al., ApJ 549, L97, 2001 2 𝑑 2 2 𝑒 𝑊 ⊥ 2 𝑑𝑊 𝑞 2 − 𝑏 ν 0 2 Fitting arc by function τ = 𝑏 ( ν −ν 0 ) 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 ν 0
Cosmic Prism+Weak Scattering Screen Perturbation depends on ν: Δν/ν<100%, ΔI/I<<100% Cosmic Position Prism Time or Pulsar D=2 kpc Frequency Weak Scattering Screen
Cosmic Prism+Weak Scattering Screen Perturbation depends on ν: Δν/ν<100%, ΔI/I<<100% Structure Function Position Time or The Structure Function shows that the Frequency electric field at the spacecraft equals that at the Earth, but with a frequency shift that increases with time. Smirnova et al 2014, ApJ 786, 115
Diagram of scatuering layers in the directjon to the PSR B1919+21 D z =1 kpc D z2 =440 pc D zpr =1.4 pc D z1 =0.14 pc Shishov et al., MNRAS, 468 , 3709, 2017
Diagram of scatuering layers in the directjon to the PSR B0834+06 R= 620pc r 2 = 12 pc r 1 = 250 pc R prism > 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
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