VSOP-2 Observations of Pulsars Carl Gwinn * With D.L. Jauncey 2, S. Dougherty 3, H. Hirabayashi 4, J.E. Reynolds 2, A. K. Tzioumis 2, E.A. King 2, B. Carlson.

Slides:



Advertisements
Similar presentations
Radio Astronomy By looking at the radio part of the EM spectrum, we can get a different perspective on the nature of the universe. the atmospheric window.
Advertisements

For centuries, astronomers learned about the sky by studying the light coming from astronomical objects, first by simply looking at the objects, and later.
Arecibo 40th Anniversary Workshop--R. L. Brown The Arecibo Astrometric/Timing Array Robert L. Brown.
NAIC-NRAO School on Single-Dish Radio Astronomy. Arecibo, July 2005
WHY STUDY ASTROPHYSICS?  To gain an understanding of our universe and our role in it Learn about how the universe operates --> modern science  Observations.
Activity 1: Properties of radio arrays © Swinburne University of Technology The Australia Telescope Compact Array.
How Do Astronomers Learn About the Universe?
LECTURE 7, SEPTEMBER 14, 2010 ASTR 101, SECTION 3 INSTRUCTOR, JACK BRANDT 1ASTR 101-3, FALL 2010.
Measuring Dispersion in Signals from the Crab Pulsar Jared Crossley National Radio Astronomy Observatory Tim Hankins & Jean Eilek New Mexico Tech Jared.
Probing cosmic plasma with Giant Radio Pulses June 22, 2006 “Scattering and Scintillation in Radio Astronomy’’ Vladislav Kondratiev, Michael Popov, Vladimir.
Probing the field of Radio Astronomy with the SKA and the Hartebeesthoek Radio Observatory: An Engineer’s perspective Sunelle Otto Hartebeesthoek Radio.
Radio `source’ Goals of telescope: maximize collection of energy (sensitivity or gain) isolate source emission from other sources… (directional gain… dynamic.
Radio Telescopes Large metal dish acts as a mirror for radio waves. Radio receiver at prime focus. Surface accuracy not so important, so easy to make.
Very Long Baseline Interferometry (VLBI) – Techniques and Applications Steven Tingay ATNF Astronomical Synthesis Imaging Workshop Narrabri, 24 – 28 September,
Astronomy Science combining all sciences. What is the Science of Astronomy? Astronomy is the scientific study of celestial objects (such as stars, planets,
Land Based Telescopes. Telescopes: "light buckets" Primary functions: 1. ___________ from a given region of sky. 2. ______ light. Secondary functions:
The Smiley Radio Telescope R.M. Blake, M. Castelaz, L. Owen, Pisgah Astronomical Research Institute J. Daugherty University of North Carolina Asheville.
History of the Universe. If the universe was 1 year old...
Random Media in Radio Astronomy Atmospherepath length ~ 6 Km Ionospherepath length ~100 Km Interstellar Plasma path length ~ pc (3 x Km)
03/000 Future operations of the AuScope network Australian Government Geoscience Australia.
An African VLBI network of radio telescopes as an SKA precursor Michael Gaylard Hartebeesthoek Radio Astronomy Observatory (HartRAO) P. O. Box 443, Krugersdorp.
(Spectral Line) VLBI Chris Phillips CSIRO ATNF Chris Phillips CSIRO ATNF.
Section 7.3. Hubble’s Ideas...  Edwin Hubble ( )  An American astronomer  One of the first to study galaxies  Two of his major findings changed.
8 th EVN Symposium: Exploring the universe with the real-time VLBI. 26 – 29 September 2006.Giuseppe Cimò – JIVE Interstellar Scintillation and IDV Twinkle,
Chapter 5: Light.
Radio Propagation Technician License Class Session 3 N1AW revised 4/2013.
Single Pulse Investigations at the Decameter Range O.M. Ulyanov 1, V.V. Zakharenko 1, V.S. Nikolaenko 1, A. Deshpande 2, M.V. Popov 3, V.A. Soglasnov 3,
The investigations of the solar wind with the large decametric radio telescopes of Ukraine Falkovych I.S. 1, Konovalenko A.A 1, Kalinichenko N.N. 1, Olyak.
What is Astrometry? Definition: To study the universe through positions and motions of celestial objects Acronym: Fund./Classical/Positional Astr. Related.
Investigation of different types radio sources by IPS method at 111MHz S.A.Tyul’bashev Pushchino Radio Astronomy Observatory, Astro Space Center of P.N.Lebedev.
RadioAstron space VLBI mission: early results. XXVIII GA IAU, Beijing, August RadioAstron space VLBI mission: early results. XXVIII GA IAU, Beijing,
Adaptive Filters for RFI Mitigation in Radioastronomy
Astronomy Big Idea: The sun is one of billions of stars in one of billions of galaxies in the universe.
Observing Strategies at cm wavelengths Making good decisions Jessica Chapman Synthesis Workshop May 2003.
S/X receiver for Parkes geodetic VLBI program 29 October 2012 ATNF, Sydney 29 October 2012 Оleg Titov (Geoscience Australia)
SUBDIFFUSION OF BEAMS THROUGH INTERPLANETARY AND INTERSTELLAR MEDIA Aleksander Stanislavsky Institute of Radio Astronomy, 4 Chervonopraporna St., Kharkov.
Scintillation from VERY Small-Scale HI Carl Gwinn (UCSB), John Reynolds (CSIRO), Warwick Wilson (CSIRO) Theory: CG, ApJ 2001 See also:
Galaxies, Gas and Radio Telescopes: Eric Wilcots prepared by Ruth Howes Marquette University with support from the Wisconsin Space Grant Consortium.
VLBI: The telescope the size of the planet
GBT Future Instrumentation Workshop Fixing the frequency coverage hole in C-Band Jagadheep D. Pandian Cornell University.
Interstellar turbulent plasma spectrum from multi-frequency pulsar observations Smirnova T. V. Pushchino Radio Astronomy Observatory Astro Space Center.
I.F.Malov Pushchino Radio Astronomy Observatory, Lebedev Physical Institute RUSSIA Do «magnetars» really exist? AXPs and SGRs Magnetars (dP.
Global Structure of the Inner Solar Wind and it's Dynamic in the Solar Activity Cycle from IPS Observations with Multi-Beam Radio Telescope BSA LPI Chashei.
Measuring the Near-Nothingness of Interstellar Space with Radio Astronomy Steven R. Spangler University of Iowa.
Lecture 13 Light: the Cosmic Messenger Telescopes and Observational Astronomy.
Oct. 9, Discussion of Measurement uncertainties (cont.) Measurements always have uncertainties, which can be estimated in our labs (and in your.
Section 7.3. Hubble’s Ideas...  ____________________________( )  An American astronomer  One of the first to study _______________  Two of.
Reflection distance,, and the change in the electron number density,, at the reflecting plasma boundary: We searched for but found no echo in simultaneously.
Single Dish Summer School, Green Bank 2007 Things to do with Single Dish: VLBI Tapasi Ghosh NAIC/Arecibo Observatory Outline: Interferometry Basic.
RADIO ASTRONOMY One Earth Foundation. Electromagnetic spectrum Whenever an electric charge changes speed or direction it gives off an electromagnetic.
WHAT CHANNEL IS THIS? Topic 5. Electromagnetic Radiation Electromagnetic radiation: varying types of energy waves emitted by stars.
Variability of a Sample of Potential meerKAT/SKA Calibrators Faith Hungwe – RU/HartRAO Advisers: R.Ojha – United States Naval Observatory (USNO)‏ (Alan.
Cosmic Masers Chris Phillips CSIRO / ATNF. What is a Maser? Microwave Amplification by Stimulated Emission of Radiation Microwave version of a LASER Occur.
Diffraction scintillation at 1.4 and 4.85GHz V.M.Malofeev, O.I.Malov, S.A.Tyul’bashev PRAO, Russia W.Sieber Hochschule Nederrhein, Germany A.Jessner, R.Wielebinski.
How can we measure turbulent microscales in the Interstellar Medium? Steven R. Spangler, University of Iowa.
IPS Observations Using the Big Scanning Array of the Lebedev Physical Institute: Recent Results and Future Prospects I.V.Chashei, V.I.Shishov, S.A.Tyul’bashev,
Atacama Large Millimeter/submillimeter Array Karl G. Jansky Very Large Array Robert C. Byrd Green Bank Telescope Very Long Baseline Array ngVLA: Reconfigurability.
Interplanetary scintillation of strong sources during the descending phase near the minimum of 23 solar activity cycle Chashei I1., Glubokova1,2 S., Glyantsev1,2.
28-1 A Closer Look at Light A. What is Light?
“Astrometry through beer goggles” Adam Deller Swinburne University
The Legacy of Supernovae
Tools of Astronomy.
Welcome to the 4th NAIC-NRAO School on Single Dish Radio Astronomy
Earth Science Ch. 24 The Sun.
Radio Astronomy Spectrum Management in practice – Australia (ATNF)
(National Astronomical Observatory of Japan)
Optical Telescopes, Radio Telescopes and Other Technologies Advance Our Understanding of Space Unit E: Topic Three.
Activity 1: Properties of radio arrays
How astronomers study space
Presentation transcript:

VSOP-2 Observations of Pulsars Carl Gwinn * With D.L. Jauncey 2, S. Dougherty 3, H. Hirabayashi 4, J.E. Reynolds 2, A. K. Tzioumis 2, E.A. King 2, B. Carlson 3, D. del Rizzo 3, H. Kobayashi 4, Y. Murata 4, P.G. Edwards 4, J.F.H. Quick 5, C.S. Flanagan 5, P.M. McCulloch 6 (*) University of California, Santa Barbara, (2) Australia Telescope National Facility, (3) Dominion Radio Astronomical Observatory, (2) Institute of Space and Astronautical Science, (5) Hartebeesthoek Radio Astronomy Observatory, (6) University of Tasmania

Why VLBI of Pulsars? Astrometry –Parallax –Proper Motion –Cosmological Rotation Scattering –Interstellar Plasma Turbulence –Structure of Radio Pulsar Emission Region

VLBI of Pulsars with VSOP-2 Pulsars are hard to observe –Weak at <20 cm –Pulsed emission: Flux density varies Gating can increase SNR Scintillation complicates spectra Noise can be important

Astrometry: Cosmological Rotation The local inertial reference frame is also the reference frame of the distant galaxies. This isn’t the case for all model universes that are consistent with General Relativity. Relative rotation of the frames can be measured using pulsar VLBI as an intermediary between the frames.

A room contains an ensemble of rotating, elastic spheres. All have equatorial bulges except one. It is perfectly round. That one is at rest, relative to the distant galaxies. -- Sciama, The Physical Foundations of General Relativity

The Solar System acts as a gyroscope, with accurately-measured motions, understood via Classical Mechanics –– in an inertial, non– rotating reference frame. Timing of pulsars yields their proper motions in that frame.

VLBI yields proper motions of pulsars in the frame of distant quasars. Comparison of proper motions from pulsar-timing with those from VLBI gives the relative rotation of local and cosmological frames. Star map by John Flamsteed, Linda Hall Library

Some Numbers: PSR Flux density –8 GHz: 16 mJy –22 GHz: 2 mJy Gain in SNR from Pulsar Gating:  2.5 Accuracy of timing proper motion: ≈10  as/yr

Scattering: Structure of Pulsar Emission Region Scattering of radio waves in the interstellar plasma acts as a large, but very corrupt, lens. This lens has a nominal resolution of about /D~100’s of km, for some pulsars. Pulsar VLBI allows measurement of the size of the emission region, if it is about this size.

Pulsars are Small * ****** Radio emission region≈300 km Neutron star≈15 km

Scintillation: Light Traveling Along Different Paths Interferes, and the Speckle Pattern Sweeps Past Earth Scotch tape The observed pattern changes with time, and observing frequency.

Speckle pattern depends on source position. Two sources (coded by stripes) produce different speckle patterns. Interstellar Plasma Statistics of the observed pattern give source size.

Vela Pulsar Size measurement works best for the Vela Pulsar: heavily scattered, strong enough to detect in 1 scintillation time  1 scintillation bandwidth 3 Important Things: –Distribution of Visibility (including source size effects) –Distribution of Noise –Speedy Fit of model to observations

Fit VSOP1: Calculate model visibility distribution (including source size – or none) Add noise: not a convolution Project to 1D: number N(Re[V]), mean square Im[V] Nonlinear fit to data VSOP-1 to Tidbinbilla, Gate 1 10:1 1:1

Distribution of Visibility for a Scintillating Point Source Zero Baseline Short Baseline Long Baseline For 0 baseline, the distribution of visibility is exponential along Re[V] (=distribution of intensity for a single dish). As the baseline lengthens, the distribution broadens in Im[V]. For long baselines, the distribution is circular (phase is random). “Interferometric Visibility of a Scintillating Source” ApJ 2001, 1197 Probability

If the source is resolved, the peak is “softer”, and shifted toward +Re[V]; the distribution is wider in Im[V]. Added instrumental and source noise, soften the peak and widen the distribution, but the centroid remains near 0. Effects of Source Structure+Noise Point source Resolved source Point source Resolved source No Noise With Noise (as Measured) Probability

Distribution of Noise We assess all of the noise by comparing samples within one element of the scintillation pattern. Excellent correlator design and performance are critical for stable and understandable noise. Noise includes source noise (self-noise), which changes with intensity and visbility; And sky, instrumental, and other noise, which don’t. Mopra-Tidbinbilla baseline VSOP-1 - Tidbinbilla baseline

VSOP-2 Observations Resolution is lower at shorter wavelength Scale of scintillation pattern: ~10 4 km Scintillation Time x Bandwidth at 8 GHz: –9 MHz x 45 sec –Pulsar flux density is ~ 0.13 Jy (no gating) –SNR ~ 5 in 1 scintillation element on VSOP-2 to Tidbinbilla Baseline –5x better with pulsar gating

Summary Pulsar VLBI is hard The results can sometimes be interesting VSOP-2 can make some interesting pulsar observations This requires: oHigh-sensitivity observations: big antennas! –Pulsar gate would help oControl of noise at the correlator oLots of work by investigators