probing cosmic plasma with giant radio pulses june 22, 2006 “scattering and scintillation in radio...

Probing cosmic plasma with Giant Radio Pulses

June 22, 2006 “Scattering and Scintillation in Radio Astronomy’’

Vladislav Kondratiev, Michael Popov, Vladimir Soglasnov

Norbert Bartel, Wayne Cannon, Alexander Novikov

Astro Space Center

York University, Toronto, Canada


Outline

• ISM: observing effects

• Properties of giant radio pulses (GRP)

• Measurements of pulse broadening and decorrelation bandwidth

• VLBI of GRPs


• dispersion• Faraday rotation• scattering

Influence of ISM

diffraction in radio spectra pulse broadening scintillations image angular smearing multiple imaging events (“superresolution”)


Properties of GRPs

1. “GIANT” Intensity

B1937+21

May 30, 1999Tidbinbilla (Aus)@1650 MHzB = 2×16 MHz

Speak = 65000 Jy

Speak ≈ 5 mln. Jy

March 2005

Kalyazin (Rus)@2244 MHzB = 16 MHz

∆t = 31.25 ns



CRAB Pulsar

CRAB at Kalyazin @2244 MHz ∆t = 31.25 ns




2. Short Duration

May 30, 1999Tidbinbilla (Aus)@1650 MHzB = 2×16 MHz

B1937+21

Giant pulses of B1937+21 are

extremely short, generally < 15 ns


2. Short Duration

Jun 6, 2005100-m GBT@2100 MHzBtot = 64 MHz

B1937+21

GP intrinsic width < 8ns

CRAB

Hankins et al., 2003, Nature, 422, 141

Arecibo @5.5 GHzB = 500 MHz∆t = 2 ns


2. Short Duration


3. High Degree of Polarization

Pulsar was observed as a calibrator for the project GBT03A-002 (Kardashev et al.)

GBT 100-m March 26, 2004 @1400 MHz B = 26 MHz

B1937+21

Nov 24-26, 2003 64-m Kalyazin @594 MHz B = 8 MHz

CRAB


3. High Degree of Polarization


Measurements of pulse broadening and decorrelation bandwidth

f (MHz) Speak (Jy) Duration (μs) Energy (Jy·μs) Telescope

CRAB Pulsar23 150 4·106 6·108 UTR-2 (Kharkov)

111 700 1.5·104 107 BSA (Puschino)

430 4·105 150 6·107 NCRT (Medicina)

600 5·104 50 2.5·105 64-m (Kalyazin)

1200 105 8 8·105 93-m WSRT

2200 5·106 0.1 5·105 64-m (Kalyazin)

8500 1000 0.002 2 Arecibo

Millisecond Pulsar B1937+21430 40 25 1000 Arecibo

430 200 25 5000 Arecibo

1420 6000 1 6000 Arecibo

1650 6.5·104 0.07 4000 70-m (Tidbinbilla)

2100 6300 0.08 500 100-m GBT

2380 200 0.4 80 Arecibo

LCPRCP


GRPs Instant Spectra B1937+21


Average ACF/CCF of GRPs Instant Spectra

B1937+21

NGP = 22

Speak > 1.2 kJy

νd ≈ 4 MHz


Dynamic spectrum of regular emission

B1937+21

RCPLCP


B1937+21

2D CCF between dynamic spectrain LCP and RCP

frequency:Δνd=3.79±0.04 MHz

large scaleΔνd=16.5±0.8 MHz

time:

ts=10.4±0.1 min

large scale

ts=46.2±0.4 min


τs= 40±4 ns

C = 2πτsΔνd = 0.95±0.1

Τbroad ≈ 94±5 ns


CRAB PulsarPopov et al., Astron.Rep. 2006, 50, 562

(astro-ph/0606025)UTR-2 @23 MHzBSA @111 MHzKalyazin @600 MHz


–4.2±0.3

B1937+21CRAB

–3.5±0.1

τ–ν Dependence

VLBI of GRPs


` WHY?

Precise instant measurements of the phase of visibility(high SNR 100÷1000, no integration) -> this simplifies calibration of space-ground radio interferometer (e.g., RADIOASTRON)

Measuring short-term variations of visibility function to study interstellar scintillations


VLBI: KL–ARO

The first ever !!!

Algonquine 46-m

Kalyazin 64-m

July 19-20, 2005@ 2244 MHzB = 2×16 MHz

S2 VLBI Recorder

Sources: DA193 (4×10min) CRAB Pulsar (2×3 hours)

RCP + LCP, USB

LCP, LSB + USB


VLBI: Examples of GRPs

VLBI: Software correlation


• delay compensation τg(t) = a + b(t-t0) + c(t-t0)2 + d(t-t0)3

• decoding• dedispersion H(ν) = H(ν0+Δν) = exp

DM = 56.737 pc/cm3 τDM = 660 μs dt = 8192 μs (N = 262144)

• fractional bit correction• fringe compensation exp (–j2πν0τg(t))

• correlation via FFT dT = 32 μs (m = 1024) σCCF = 1/√m σCCF = 0.031 6σ = 0.186 detection rate is about 5GPs per minute

• postcorrelation to determine delay and phase residuals

–

i2πDΔν2

ν02(νo+Δν)( )


VLBI: CCF Example

module (SNR = 56)

real part

imaginary part

VLBI: Expected angular broadening


Θd2 = cτ / d, d = 2kpc, τ = 200 ns => θd ≈ 0.2 mas

Θres = λ / s, s – baseline ARO-KL ~ 6500 km, λ = 13 cm

Θres ≈ 4 mas – 20 times larger θd

=> We can consider Crab Pulsar as a point source


VLBI: Residual phase behavior

July 20, 2005

CRAB Pulsar

glitch in fLO ≈ 6.6 mHz

Δν/ν = 3×10-12


VLBI: Residual

phase and delay behavior

± 30ns

regular drift in phase is not accompanied

by the corresponding drift in delay!!


VLBI: Residual phase / delay

Quasar DA193

Δt = 1 s (SNR=30)

rms = 2 ns

–3 ÷ 6 ns

D(τ) = <[φ(t) – φ(t + τ)]2>


VLBI: Structure functions

Crab

DA193

3 10-min sets


VLBI: Diffraction GPs spectra

Kalyazin

LCP

ARO-KLLCP


VLBI: Average CCFFor all 25 strong GPs

ARO-KLLCP

KL LCP-RCP

There is no notable correlation between diffraction spectra

for the LCP and RCP channels!

Δνd ≈ 1MHz


VLBI: Individual CCF

ARO-KL

KLLCP-RCP

Shifted to coincide with ARO-KL

The CCFs are in a good agreement

when being shifted in frequency lag by the half period of

the regular pattern


Summary

Measurements of scintillation parameters for the CRAB Pulsar and B1937+21

First VLBI observations of GRPs from the CRAB Puzzling absence of correlation between LCP and RCP diffraction spectra


Thank you

Polarization ― the Crab Pulsar

Kalyazin (Russia)Nov 24-26, 2003F = 594 MHzB = 8 MHzΔt = 125 ns

Arecibo Observatory Library ColloquiumNRAO Green Bank ColloquiumJune 17, 2004

May 15, 2006 363rd Heraeus Seminar

GPs Polarization

May 15, 2006 363rd Heraeus Seminar

LCP RCP

GPs Polarization

The spectrum of the strong GP at 10:18:03

LCP

RCP

probing cosmic plasma with giant radio pulses june 22, 2006 “scattering and scintillation in radio...

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