Advancing X-ray polarimetry of compact objects with XL-Calibur - - PowerPoint PPT Presentation

Mark Pearce

KTH Royal Institute of Technology

Compact objects for all 10-11 February 2020, Lund Observatory

Advancing X-ray polarimetry of compact objects with XL-Calibur

X-Calibur

X-ray telescope

X-rays X-ray lens Detector, e.g. CZT Pixel co-ordinate Deposited energy Time Image Light curve Energy spectrum ..100110..

X-ray polarimeter

X-ray lens Polarimeter ..100110..

+

Polarisation Fraction (PA, %) Polarisation Angle (PF , °) (Image) Light curve Energy spectrum Pixel co-ordinate Deposited energy Time

{

Scattered beam

Source symmetry/geometry Source orientation

Be

CZT

X-rays

X-ray polarimeter

X-ray lens Polarimeter ..100110.. Pixel co-ordinate Deposited energy Time

{

Scattered beam

Be

CZT

Polarization fraction

a

2π

# photons

Distribution of azimuthal scattering angles (α) encodes the polarisation properties of the X-ray beam

dN dα = 1 2 (1 + μ cos α); ¯ μ ∼ 0.5

Modulation factor

Polarisation angle

X-rays

X-ray polarimeter 8 m long truss 
 (carbon fibre rods + aluminium joints) InFOCμS X-ray mirror 50 cm2 @ 30 keV (255 Pt/C coated Al shells) WASP: 
 Wallops ArcSecond Pointer Pointing stability < 1” (RMS)

X-Calibur: 15-60 keV spectroscopy, timing and polarization

McMurdo, Antarctica December 2018 Observation of GX301-2 apastron flare ApJ (to appear) / arXiv:2001.03581

X-Calibur → XL-Calibur

20 30 40 50 60 70 80 90 100 Energy [keV] 1 10

2

10 ]

2

Effective area [cm FFAST S µ InFOC

3-10 x larger effective area

XL-Calibur (Hitomi) X-Calibur (InFOC𝜈S)

(1) New X-ray mirror

• Focal length =12 m
• Half-power-diameter = ~1.7 arcmin
• Field-of-view = 10 arcmin

⇒ Improve source statistics
 
 (2) Upgrade polarimeter


• Energy range: 15-80 keV
• ΔE/E (40 keV): ~5 keV (FWHM)

• Thinner CZT detectors (2 mm→0.8 mm)
• Lower anticoincidence energy threshold

(atmospheric γ). More compact design. ⇒ Decrease background

Be scattering rod 17th CZT detector CZT detector Collimator CsI(Na) anticoincidence shield body CsI(Na) anticoincidence shield plug PC/104 computer Digitiser board Harvester board PMT PMT

{

K-edge Pt

300 cm2 180 cm2 130 cm2

XL-Calibur 
 ~2000 kg / ~500 W

X-ray mirror Polarimeter 12m long truss Carbon fibre tubes and Al joints Focal spot movement < 3 mm Pointing system Stability: 1” RMS Knowledge: <15” Alignment/star cameras

A new era in hard X-ray polarimetry 
 MDPday (500 mCrab) ~1%

Unpolarised beam has 1% probability of yielding PF > MDP

e.g. M. Chauvin et al., Nat. Sci. Rep. 7 (2017) 7816 / Nat. Astr. 2 (2018) 652 / MNRAS 477 (2018) L45/ MNRAS 483 (2019) L138.

Landing July 18th 2226 UT Launch July 12th 0317 UT

2016

Crab Cygnus X-1 PoGO+: “MDP” ~10% (~1 week)

Flight opportunities

McMurdo Esrange Victoria Island

~5-7 days (to Victoria Island) May/June/July ~8-55 days December/January 


NET end-2021 NET summer 2022 Several flights foreseen - flight programme TBD

• Cygnus X-1 (hard spectral state)
• Black hole binary
• Discern geometry of X-ray bright

black hole corona.

Esrange

• Crab pulsar
• Rotation powered pulsar
• Phase-resolved polarimetry
• Differentiate emission models

8 10 12 14 16 18 20 22 ]

• 1

s

• 2

erg cm

• 9

[10

E

E f Two-pole caustic model Outer gap model XL-Calibur 100ksec

• Min. Det. Polarization

PoGO+ (20 - 160keV) SPI (100 keV - 1 MeV) IBIS (200 - 800 keV) OSO-8 (2.6 & 5.2 keV)

10 20 30 40 50

• Pol. Fraction [%]

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 Phase 80 − 60 − 40 − 20 − 20 40 60 80

• Pol. Direction

100 1000 Flux [mCrab] 0.2 0.3 0.4 1 2 3 4 10 Polariztion [%] Cyg X-1, XL-Calibur 100ksec for 5% polarization σ 1 MDP 99% confidence PoGO+ Upper Limit

GX 301-2 and Vela X-1


• Highly magnetised neutron

stars

• Constrain beam geometry
• Tests of QED vacuum

polarization.

PF ~ 20% PF ~ 0%

McMurdo

σ(∥B,⊥B)

2 4 6 8 10 12 14 ]

• 1

s

• 2

erg cm

• 9

[10

E

E f XL-Calibur 300ksec X-Calibur 2018/19 0.2 0.4 0.6 0.8 1 X-Calibur [arb. units]

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 Phase 0.1 0.2 0.3 0.4 0.5

• Pol. Fraction

Fan beam Pencil beam

• Min. Det. Polarization

• NASA Small Explorer

mission, IXPE

• 2-8 keV (photoelectric polarimeter)
• 30” imaging
• Launch ~April 2021

(4 m)

IXPE

XL-Calibur

IXPE (2-8 keV) XL-Calibur (15-80 keV)

Outlook

• During the next decade X-ray

polarimetry will become an established tool in astrophysics


• The IXPE satellite (launch 2021) will

address the soft X-ray band 
 (2-8 keV)

• Balloon-borne missions play an

important role in the hard X-ray band (~15-80 keV). 


• XL-Calibur is a second-generation

balloon mission providing hard X-ray spectro-polarimetry for the IXPE era.

The X-Calibur & XL-Calibur Teams

• Q. Abarr, H. Awaki (Ehime), R. Bose, D. Braun, G. de Geronimo, P. Dowkontt,
• T. Enoto, 

• M. Errando,
• Y. Fukazawa,
• T. Gadson,
• V. Guarino, S. Gunji, K. Hayashida (GSFC), 

• S. Heatwole, M. Ishida (ISAS), N.K. Iyer, F. Kislat (UNH), M. Kiss,
• T. Kitaguchi, 

• H. Krawczynski (WUSTL, PI), R. Kushwah, R.J. Lanzi, S. Li, L. Lisalda,
• Y. Maeda (ISAS), 

• H. Matsumoto (Osaka),
• T. Miyazawa,
• T. Mizuno, T. Okajima (GSFC), M. Pearce (KTH), 

• Z. Peterson, B. Rauch, F. Ryde,
• Y. Saito,

T.-A. Stana, D. Stuchlik (WFF), H. Takahashi (Hiroshima), T. Tamagawa, K. Tamura (Nagoya), H. Tsunemi, M. Tsutsumi, N. Uchida, 


• K. Uchiyama, A.

West,

• Y. Zhou