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
7/7/2017 Fabian Kislat – X-ray and gamma-ray polarimetry: A new look at the high-energy universe 4
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
7/7/2017 Fabian Kislat – X-ray and gamma-ray polarimetry: A new look at the high-energy universe 5
Polarization Through Scattering
7/7/2017 Fabian Kislat – X-ray and gamma-ray polarimetry: A new look at the high-energy universe 6
7/7/2017 Fabian Kislat – X-ray and gamma-ray polarimetry: A new look at the high-energy universe 7
http://www.vsezaoci.si/ocala-za-ribolov
X-Ray Polarimetry of Black Holes
7/7/2017 Fabian Kislat – X-ray and gamma-ray polarimetry: A new look at the high-energy universe 8
Get geometrical information for sources which are too small to be imaged: GRS1915+105: rg ~ 10-15˚!
7/7/2017 Fabian Kislat – X-ray and gamma-ray polarimetry: A new look at the high-energy universe 9
X-ray & gamma-ray Polarimetry Polarimetry Basics
Science Goals Techniques X-Calibur
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.
7/7/2017 Fabian Kislat – X-ray and gamma-ray polarimetry: A new look at the high-energy universe 10
X-ray & Gamma-ray Polarimetry
7/7/2017 Fabian Kislat – X-ray and gamma-ray polarimetry: A new look at the high-energy universe 11
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
7/7/2017 Fabian Kislat – X-ray and gamma-ray polarimetry: A new look at the high-energy universe 12
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
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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!
7/7/2017 Fabian Kislat – X-ray and gamma-ray polarimetry: A new look at the high-energy universe 16
Cygnus X-1
Tomsick et al. (2014)
Direct coronal emission Reflected coronal emission
Thermal disk emission
Accreting Black Holes
7/7/2017 Fabian Kislat – X-ray and gamma-ray polarimetry: A new look at the high-energy universe 17
Wedge Corona Spherical Corona
X-ray spectro-polarimetry allows determination of the corona shape and size.
Simulations by Schnittman & Krolik (2012)
7/7/2017 Fabian Kislat – X-ray and gamma-ray polarimetry: A new look at the high-energy universe 18
X-ray & gamma-ray Polarimetry Polarimetry Basics
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.
7/7/2017 Fabian Kislat – X-ray and gamma-ray polarimetry: A new look at the high-energy universe 19
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.
7/7/2017 Fabian Kislat – X-ray and gamma-ray polarimetry: A new look at the high-energy universe 20
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
7/7/2017 Fabian Kislat – X-ray and gamma-ray polarimetry: A new look at the high-energy universe 21
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
7/7/2017 Fabian Kislat – X-ray and gamma-ray polarimetry: A new look at the high-energy universe 22
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
7/7/2017 Fabian Kislat – X-ray and gamma-ray polarimetry: A new look at the high-energy universe 23
X-ray & gamma-ray Polarimetry Polarimetry Basics
Science Goals Techniques X-Calibur
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.
7/7/2017 Fabian Kislat – X-ray and gamma-ray polarimetry: A new look at the high-energy universe 25
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)]
7/7/2017 Fabian Kislat – X-ray and gamma-ray polarimetry: A new look at the high-energy universe 36
Ascent, 25 – 60keV
Count rate during ascent.
Counts of single-pixel events.
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)]
7/7/2017 Fabian Kislat – X-ray and gamma-ray polarimetry: A new look at the high-energy universe 37
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)]
7/7/2017 Fabian Kislat – X-ray and gamma-ray polarimetry: A new look at the high-energy universe 38
FK et al. (2017)
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)]
7/7/2017 Fabian Kislat – X-ray and gamma-ray polarimetry: A new look at the high-energy universe 39
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
7/7/2017 Fabian Kislat – X-ray and gamma-ray polarimetry: A new look at the high-energy universe 40
Scintillator Beryllium
Detected Absorbed in scatterer
7/7/2017 Fabian Kislat – X-ray and gamma-ray polarimetry: A new look at the high-energy universe 41
X-ray & gamma-ray Polarimetry Polarimetry Basics
Science Goals Techniques X-Calibur
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
7/7/2017 Fabian Kislat – X-ray and gamma-ray polarimetry: A new look at the high-energy universe 43
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
7/7/2017 Fabian Kislat – X-ray and gamma-ray polarimetry: A new look at the high-energy universe 44
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.
7/7/2017 Fabian Kislat – X-ray and gamma-ray polarimetry: A new look at the high-energy universe 45
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.
7/7/2017 Fabian Kislat – X-ray and gamma-ray polarimetry: A new look at the high-energy universe 46
The X-Calibur Collaboration
7/7/2017 Fabian Kislat – X-ray and gamma-ray polarimetry: A new look at the high-energy universe 47
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.