Pulsar Scattering, Lensing and Gravity Waves

Introduction
Convergent Plasma Lenses
Gravity Waves
Black Holes/Fuzzballs
Summary

Ue-Li Pen, Lindsay King, Latham Boyle
CITA

Feb 15, 2012

Introduction

Gravity Waves
Summary

Overview

Pulsar Scattering VLBI ISM holography, distance measures Enhanced Pulsar Timing Array gravity waves fuzzballs

Introduction

Gravity Waves
Summary

Pulsar Scattering

Pulsars scintillate strongly due to ISM propagation Lens of geometric size ∼ AU Can be imaged with VLBI (Brisken et al 2010) Deconvolved by interstellar holography (Walker et al 2008)

Introduction

Gravity Waves
Summary

Scattering Image

Data from Brisken et al, Holographic VLBI.

Introduction

Gravity Waves
Summary

ISM enigma

Scattering angle observed mas, 10⁻⁸rad.

Snell’s law: sin(θ₁)/ sin(θ₂) = n₂/n₁

n − 1 ∼ 10⁻¹²

.
4 orders of magnitude mismatch.

Introduction

Gravity Waves
Summary

Possibilities

turbulent ISM: sum of many small scatters. Cannot explain discrete images.

conﬁnement problem: super mini dark matter halos, cosmic strings?

Geometric alignment: Goldreich and Shridhar (2006) Snell’s law at grazing incidence: ∆α = (1 − n₂/n₁)/α grazing incidence is geometry preferred at 2-D structures

Introduction

Gravity Waves
Summary

Current Sheets

generic outcome of reconnection Pang et al 2010 highly uncertain size, time scale Petschek vs Sweet-Parker long standing controversies

Introduction

Gravity Waves

Lenses

Summary

Gaussian Lens

Romani et al 1987, Clegg et al 1998 General highly triaxial system projected into highly elliptical pattern

Introduction

Gravity Waves

Lenses

Summary

Geometry

D_dsD_s

β = θ −

αˆ(D_dθ) = θ − α~(θ) ψ(θ) = σ_θ²κ₀exp(−θ²/2σ_θ²)

Introduction

Gravity Waves

Lenses

Summary

Plasma lensing

c_ph= c/ (1 − ω_p²/ω²)

n_ee²/ꢀ₀m_e

Φ ≈ ω_p²c²/4ω²

critical points and caustics in large convergence limit:

√ ꢁ

θ_c= ± 1 +

β_c= ±

2κ₀

magniﬁcations:

1 + κ₀2 log(−κ₀) − 1

Introduction

Gravity Waves

Lenses

Summary

Time light curves

Introduction

Gravity Waves

Lenses

Summary

Time light curves

Introduction

Gravity Waves

Lenses

Summary

Fiedler Event

2.7 and 8.1 GHz light curves of QSO 0954+658 (Fiedler et al. 1994)

Introduction

Gravity Waves

Lenses

Summary

Holographic Secondary Spectrum

Introduction

Gravity Waves

Lenses

Summary

Pre/post-dictions

plasma underdensity in current sheets (not generic?) weak (logarithmic) frequency dependence of ESE (Fiedler et al 1987)

unresolved ESE VLBI image increase during ﬂux decrement (Lazio et al 2000)

pulsar inverse parabolic arc cross sections

Introduction

Gravity Waves

Lenses

Summary

Lensing applications

Use ISM lens as a giant AU scale interferometer! straightforward to resolve the pulsar beam reﬂex motion. measure pulsar spin axis parallactic angle may be able to resolve pulsar emission region precise pulsar distance measurements

Introduction

Gravity Waves

Summary

Pulsar Gravity Wave Observatory

Major resolution and sensitivity boost compared to PTA Boyle and Pen 2010: resolution is λ/L, where λ ∼ 10ly and L ∼ 10kly, typically arc minute localization of sources

No longer in source confused limit, able to use pulsar intrinsic GW term

distances needed, from the lens distance reconstruction! during ESE, uses two screens to solve all unknowns.

Introduction
Gravity Waves

Summary

Black Holes Tests

Lai and Raﬁkov BH reconstruction: not possible to measure spin.

neglects coherent interference between images time delay measured to ∼ ns instead of ∼ms. 10,000 σ spin detection instead of < 1. what are we really testing? Einstein? no alternatives in strong ﬁeld?

Introduction
Gravity Waves

Summary

Fuzzballs

proposed by S. Mathur as alternatives to Black Holes has substantial cult following in stringy community resolves Hawking’s information paradox plausible argument due to failure of no-hair “theorem”

Introduction
Gravity Waves

Summary

classical no-hair: decay of perturbations on dynamical time (ms)

Thermal hair: Boltzman factor supression?

exp(−∆E/kT) ∼ exp(−Mc²/kT) ∼ 10⁻¹⁰: macroscopic excitation most unlikely thing ever considered? (including boltzman brains!)

Introduction
Gravity Waves

Summary

Correction Factors

thermodynamic partition function weights by degeneracy of states: (n₁/n₂) exp(−(E₁− E₂)/kT).

entropy S = log n, proportionate to area cancels the Boltzman factor! round black holes have the least area – least likely state! generic black hole should be fractal, i.e. fuzzball

Introduction
Gravity Waves

Summary

Quantum Gravity

Stringy interpretation: quantum mechanics is unitary, fuzzball violate Hawking calculation premise

order unity deviations near schwarzschild radius deviations fall oﬀ as (r_s/r)^l: unlikely to be tested with accretion ﬂows at ꢀ 2M

pulsar-BH binary lensing: results in modiﬁed or absent fringes!

Introduction
Gravity Waves

Summary

Conclusions

Physics: Underdense current sheets. New input for reconnection plasma studies

Pulsar kinematics: emission region physics, spin axis precise distance measurements: multi-frequency VLBI monitoring of pulsars

increased sensitivity coherent precision gravity wave astrometry

tests of quantum gravity: need to ﬁnd inclined BH-PSR binary

Pulsar Scattering, Lensing and Gravity Waves

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