X-ray and gamma-ray polarimetry: A new look ... - Confluence

X-ray and gamma-ray polarimetry: A new look at the

high-energy universe Fabian Kislat

Astrophysics Seminar, DESY, July 7, 2017

© 2014 Warner Bros. Ent.

2𝑟𝐼𝐼𝐼𝐼

7/7/2017 Fabian Kislat – X-ray and gamma-ray polarimetry: A new look at the high-energy universe 3

X-ray & gamma-ray Polarimetry Polarimetry Basics

Science Goals Techniques X-Calibur

Future Prospects

Polarization of Light


𝐸𝑥 𝑡 = 𝐸1 sin 𝜔𝑡 𝐸𝑦 𝑡 = 𝐸2 sin (𝜔𝑡 − 𝛿)

3 Parameters of linear polarized light: • Intensity 𝐼 • Polarization angle 𝜓 • Linear polarization

fraction 𝑃𝐿

Photon Scattering Klein-Nishina Cross Section:

d𝜎dΩ

∝𝑘𝑘2

𝑘2𝑘𝑘𝑘

+𝑘𝑘𝑘− 2sin2𝜃 cos2 𝜂


Polarization Through Scattering



http://www.vsezaoci.si/ocala-za-ribolov

X-Ray Polarimetry of Black Holes


Get geometrical information for sources which are too small to be imaged: GRS1915+105: rg ~ 10-15˚!




Future Prospects

The Big Picture

• How do black holes grow? What is their influence on their surroundings? – Most extreme gravitational fields ⇒ Test General Relativity – Powerful jets ⇒ Profound influence on their environment.

• Is our understanding of the fundamental laws of Physics correct? – Neutron stars, magnetars ⇒ behavior of light and matter in extreme

magnetic fields ⇒ Test QED – Polarization tests Lorentz Invariance.

• What is the origin of cosmic rays? – Study particle acceleration in supernova remnants. – Acceleration mechanism in AGN jets.


X-ray & Gamma-ray Polarimetry


Synchrotron (e.g. Mrk 421)

Inverse Compton (e.g. 3C 273)

Inverse Compton (e.g. Mrk 421) Blazars

Pulsed & Unpulsed Broadband Emission

Cyclotron Lines

Vacuum Resonances Pulsars &

Neutron Stars

Corona

Fe K-α

Compton Hump

Supermassive Black Holes

Prompt Synchrotron or Inverse Compton Emission Afterglow

Gamma-ray Bursts

100 eV 1 keV 10 keV 100 keV 1 MeV 10 MeV 100 MeV 1 GeV

Supernova Remnants Nuclear Emission Lines

Synchrotron emission Inverse Compton

Hadronic Emission

Stellar-mass Black Holes Fe K-α Compton Hump

Precessing Corona Jet

Thermal Accretion Disk

Corona

Hard Power-law Tail

Resonant Cyclotron Emission

Thermal Emission

Magnetars

X-ray & Gamma-ray Polarimetry


Synchrotron (e.g. Mrk 421)

Inverse Compton (e.g. 3C 273)

Inverse Compton (e.g. Mrk 421) Blazars

Pulsed & Unpulsed Broadband Emission

Cyclotron Lines

Vacuum Resonances Pulsars &

Neutron Stars

Corona

Fe K-α

Compton Hump

Supermassive Black Holes

Prompt Synchrotron or Inverse Compton Emission Afterglow

Gamma-ray Bursts

100 eV 1 keV 10 keV 100 keV 1 MeV 10 MeV 100 MeV 1 GeV

Supernova Remnants Nuclear Emission Lines

Synchrotron emission Inverse Compton

Hadronic Emission

Stellar-mass Black Holes Fe K-α Compton Hump

Precessing Corona Jet

Thermal Accretion Disk

Corona

Hard Power-law Tail

Resonant Cyclotron Emission

Thermal Emission

Magnetars

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A Brief History


OSO-8 (Source: nasa.gov)

Mid-1970s: OSO-8 measures Crab polarization at 2.6keV and 5.2keV. Limits on polarization from Cyg X-1.

IKAROS (Source: wikipedia.org)

2010/11: IKAROS measures gamma-ray polarization of GRBs.

INTEGRAL (Source: esa.int)

2008: Gamma-ray polarization measurement of the Crab by INTEGRAL.

(Source: kth.se)

2014: First broad-band x-ray polarization measurement of the Crab by PoGOLite with low statistical significance. 2016: POGO+ flight with improved sensitivity. X-Calibur

2016: 1-day test flight of X-Calibur. On track for LDB flight.

From

Wei

ssko

pf e

t al.

2006

1971: First sounding rocket x-ray polarization measurement of the Crab.

Accreting Black Holes • Do black holes rotate? • Rotating black holes affect

spacetime geometry. • The event horizon cannot

move faster than the speed of light. – Black hole spin parameter: 𝑎 = 𝐽 𝑀2⁄

– No-hair-theorem ⇒ Black hole is completely described by:

• Mass M • Spin a • Electric charge Q

• Larger spin ⇒ smaller ISCO. • X-ray polarimetry measures

black hole spin. • Thermal X-ray emission from

disk in stellar mass black holes. 7/7/2017 Fabian Kislat – X-ray and gamma-ray polarimetry: A new look at the high-energy universe 14

Image: NASA

Accreting Black Holes • Do black holes rotate? • Rotating black holes affect

spacetime geometry. • The event horizon cannot

move faster than the speed of light. – Black hole spin parameter: 𝑎 = 𝐽 𝑀2⁄

– No-hair-theorem ⇒ Black hole is completely described by:

• Mass M • Spin a • Electric charge Q

• Larger spin ⇒ smaller ISCO. • X-ray polarimetry measures

black hole spin. • Thermal X-ray emission from

disk in stellar mass black holes. 7/7/2017 Fabian Kislat – X-ray and gamma-ray polarimetry: A new look at the high-energy universe 15

Schnittman &

Krolik (2009)

a=0

a=0.99

Schnittman & Krolik (2009), Krawczynski (2012)

a=0.99

a=0

colder ↔ hotter

Accreting Black Holes • Power-law emission from black hole ⇒ Corona = hot, highly ionized gas

• What is the shape and size of the corona?

• Main X-ray emission in AGN from corona!


Cygnus X-1

Tomsick et al. (2014)

Direct coronal emission Reflected coronal emission

Thermal disk emission

Accreting Black Holes


Wedge Corona Spherical Corona

X-ray spectro-polarimetry allows determination of the corona shape and size.

Simulations by Schnittman & Krolik (2012)



Science Goals Techniques

X-Calibur Future Prospects

X-rays: 2 – 10keV Photo-Electric Effect Polarimeters • Photo absorption

⇒ photo electron emitted preferentially parallel to PA 𝑑𝜎𝑑Ω

∝sin2 𝜃 cos2 𝜙1 − 𝛽 cos𝜃 4

• Typical approach: – Absorption in gaseous detector; – Track photo-electron in GPD or TPC.


IXPE / XIPE Praxys

Hard X-rays: 4 – 60keV

Example: X-Calibur • Photons scatter in scattering element:

– Use a low-Z material to maximize scattering probability;

– Photo-electric effect ~𝑍5. • Scattered photons absorbed in

surrounding detectors: – Use a high-Z material to maximize

detection efficiency. • Use focusing X-ray optics to improve

effective area. Example: POGO+

• Scattering and absorption in scintillator. • Collimator instead of focusing optics.


LiH C

Si CZT

Kraw

czyn

ski e

t al.

(201

2)

Gamma-rays: 200keV – 5MeV Compton Telescopes

• Compton scattering in (relatively) low-Z tracker

• Photo absorption in high-Z calorimeter

• Δ𝐸 and �⃗�scatter ⇒ Compton cone

• Recoil electron ⇒ Reduced arc

• Wide field of view – Transient events – Extended sources


Polarimetry Basics

• Sinusoidal modulation of azimuthal scattering distribution – Amplitude ∝ Polarization fraction – Minimum at polarization angle

• Modulation factor μ = Amplitude for a 100% polarized source • Minimum detectable polarization (MDP) at 99% confidence level:

MDP =4.29𝜇 𝑅𝐼

𝑅𝐼 + 𝑅𝐵𝐵𝑇


𝑅𝐼 = Signal rate 𝑅𝐵𝐵 = Background rate

Weisskopf et al. FK et al. (2015)

Degree of polarization

α 0 2π

# photons

Polarization angle

Scattering Photo-effect




Future Prospects

X-Calibur

7/7/2017 Fabian Kislat – X-ray and gamma-ray polarimetry: A new look at the high-energy universe 24 Guo et al. (incl. FK) (2012), Beilicke, FK, et al. (2013), FK et al. (2017)

Energy range: 20 – 60 keV Modulation factor: 0.5 Minimum detectable polarization (after optimization): 21%/ h (Crab)

X-Calibur

• 12 CZT Detectors – 2mm thick; – 2x2 cm² footprint; – 64 pixels each.

• Brookhaven ASIC (de Geronimo) – 32 channels; – 2 ASICs per CZT; – Readout noise 2keV

FWHM.


Brookhaven ASICs (de Geronimo)

12 CZT Detectors (0.2x2x2cm3)

Results from Cornell High Energy Synchrotron Source

Beilicke, FK, et al. (2013) 7/7/2017 Fabian Kislat – X-ray and gamma-ray polarimetry: A new look at the high-energy universe 29

• Synchrotron beam at Cornell High-Energy Synchrotron Source (CHESS)

• Bragg reflection ⇒ 2 Lines at 40keV and 80keV

• ~95% polarized beam

X-Calibur Results • 24 hours at float (>128kft

during the day) • WASP pointed with 1”

precision at night • Detector worked well during

most of the flight • Crab rate about 0.1Hz • Data analysis is ongoing

– Analysis with Stokes parameters [FK et al (2015)]

– Spectral unfolding [FK et al (2015)]


Ascent, 25 – 60keV

Count rate during ascent.

Counts of single-pixel events.















FK et al. (2017)








Future Plans for X-Calibur • New front-end electronics

– Lower noise – Lower energy threshold

• Replace scintillator with Be scatterer – Higher density – Lower atomic number – Better scattering efficiency

• Install active shield top – 3x background reduction

• Tail-end imaging CZT detector • 2018/19: Long-duration balloon

flight from McMurdo, Antarctica


Scintillator Beryllium

Detected Absorbed in scatterer




Future Prospects

Polarization Spectroscopic Telescope Array PolSTAR

Build-to-print: CZT detectors

New: scatterer

NuSTAR optics (one rather than two)

Mast and instrument benches LEOSTAR-II

NuSTAR optics bench

Focal plane

71% Built-to-Print 100% New Science

7/7/2017 Fabian Kislat – X-ray and gamma-ray polarimetry: A new look at the high-energy universe 42 Krawczynski et al. (incl. FK), 2015

Imaging X-ray Polarimetry Explorer • Photo-electric effect polarimeters • Photo-electron preferentially emitted

parallel to polarization vector • Map photo electron track with Gas Pixel

Detector • Energy range 2 – 8 keV • Imaging polarimetry • IXPE scheduled for launch in 2020 • XIPE: candidate for an ESA medium-size

mission


Weisskopf et al.

Vela X-1 Matt, Costa, et al.

The X-ray Polarimetry Probe (XPP)

Two telescopes, Three polarimeters each – Low-Energy Polarimeter (LEP): 0.2 – 1keV

• Bragg polarimeter • Critical angle transmission gratings + Laterally graded multi-layer mirrors

– Medium-Energy Polarimeter (MEP): 2 – 10keV • Photo-electric effect polarimeter • Technology developed for PRAXyS

– High-Energy Polarimeter: 5 – 60keV • Scattering polarimeter


H. Krawczynski, P. Ghosh, H. Marshall, M. McConnell, T. Kallman, P. Kaaret, F. Kislat, J. Miller, E. Kara, A. Fabian, J. Heyl, A. Harding, M. Böttcher, E. Cackett, J. Wilms, M. Weisskopf, M. Baring, D. Stern, T. Maccarone, J. Tomsick, V. Kaspi, D. Ballantyne, G. Madejski, K. Jahoda, T. Okajima, J. Schnittman, J. Dexter, A. Ingram

AMEGO • The All-sky Medium Energy Gamma-ray Observatory:

– Combined Compton and pair-production telescope. – DSSD Tracker (no converter foil), – CZT calorimeter (Frisch grid), – CsI calorimeter for high energy.

• Tracking the recoil electron: – Reduce Compton cone to arc.

• Polarization sensitivity: 20% MDP in 1 Ms for 10mCrab.


Capu

to, F

K, R

acus

in e

t al,

2017

Summary • Polarized photons produced by:

– scattering – emission mechanism: synchrotron and curvature radiation – propagation in magnetic fields

• X-ray and gamma-ray polarimetry provide geometrical information: – Inner accretion flows of black holes – Origin of quasi-periodic oscillations in black hole binaries – Structure of the accretion column of pulsars – Magnetic structure of AGN jets

• X-Calibur flown in 2016 • A bright future is ahead:

– X-Calibur LDB flight in 2018/19 – IXPE selected for launch in 2020 – XPP may provide detailed polarization measurements of many sources.


The X-Calibur Collaboration


P. Dowkontt G. Simburger D. Braun

F. Kislat H. Krawczynski

J. Hoorman B. Beheshtipour Q. Abarr

Takashi Okajima G. de Geronimo, S. Li

David Stuchlik, Jim Lanzi, et al.

X-ray and gamma-ray polarimetry: A new look ... - Confluence

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