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The X-ray polarization signal in accreting sources (as expected from - - PowerPoint PPT Presentation

Nov 12, 2022 337 likes •462 views

The X-ray polarization signal in accreting sources (as expected from MC simulations made with MoCA) Francesco Tamborra G. Matt, S. Bianchi, M. Dovciak, M. Bursa From the Dolomites to the event horizon, 10-14/07/2017 Few trivial considerations

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Francesco Tamborra The X-ray polarization signal in accreting sources

  • G. Matt, S. Bianchi, M. Dovciak, M. Bursa

From the Dolomites to the event horizon, 10-14/07/2017

(as expected from MC simulations made with MoCA)

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SLIDE 2

Few trivial considerations

  • geometry of the scattering material

Thomson/Compton scattering linear polarization

  • inclination
  • scattering regime (# of scatterings

allowed in the material) [optical thickness] (Spectral shape) Scattering induced polarization signal strongly depends on:

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  • 10

10 20 30 40 50 60 70 80 90 100 0.2 0.4 0.6 0.8 1 Polarization Angle [deg] µ Pol Angle (disc 6-500, mdot01, MBH10 ) SLAB kT100 tau = 2 tau = 1 tau = 0.5 1 2 3 4 5 6 7 8 9 10 0.2 0.4 0.6 0.8 1 Polarization Degree [%] µ Pol Degree (disc 6-500, mdot01, MBH10 ) SLAB kT100 tau = 2 tau = 1 tau = 0.5

3 scattering regimes for the SLAB

1000 10000 100000 1x106 1x107 0.01 0.1 1 10 100 1000 E x I(E) [arbitrary units] Energy [keV] Spectrum (disc 6-500, mdot01, MBH10 ) SLAB kT100 60 deg - 400 bins tau = 2 tau = 1 tau = 0.5

(BHB 10 Msun, mdot=0.1 / corona: tau=0.5,1,2 - kT=100 keV)

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1 2 3 4 5 6 7 8 9 10 0.2 0.4 0.6 0.8 1 Polarization Degree [%] µ Pol Degree (disc 6-500, mdot01, MBH10 ) SLAB tau2 kT100 - logN - 50 bins unscattered 1 scatt 2 scatt 3 scatt 4 scatt 5 scatt >5 scatt total

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SLIDE 5

A qualitative explanation

thin (tau<1) thick (tau~1-2) very thick (tau>5) ..but we will observe polarization in energy!

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SLIDE 6

SLAB VS SPHERE

(BHB / corona: tau=1, kT=100 keV)

unpolarised seed

1 2 3 4 5 6 7 8 9 10 0.1 1 10 100 Polarization Degree [%] Energy [keV] Pol Degree (disc 6-500, mdot01, MBH10 ) SLAB tau1 kT100 - 50 bins 75 deg 60 deg 45 deg 1 2 3 4 5 6 7 8 9 10 0.1 1 10 100 Polarization Degree [%] Energy [keV] Pol Degree (disc 6-500, mdot01, MBH10 ) SPHERE tau1 kT100 - 50 bins 75 deg 60 deg 45 deg

SLAB SPHERE

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SLIDE 7

5x106 1x107 1.5x107 2x107 2.5x107 0.2 0.4 0.6 0.8 1 2 4 6 8 10 12 counts

  • Pol. Degree [%]

µ SEED mu distribution / Polarization (disc 6-500, mdot01, MBH10) limb - 50 bins counts polarization

SLAB VS SPHERE

(BHB corona: tau=1, kT=100 keV)

polarised seed

1 2 3 4 5 6 7 8 9 10 0.1 1 10 100 Polarization Degree [%] Energy [keV] Pol Degree (disc 6-500, mdot01, MBH10 ) SPHERE tau1 kT100 limb - 50 bins 75 deg 60 deg 45 deg 1 2 3 4 5 6 7 8 9 10 0.1 1 10 100 Polarization Degree [%] Energy [keV] Pol Degree (disc 6-500, mdot01, MBH10 ) SLAB tau1 kT100 limb - 50 bins 75 deg 60 deg 45 deg

SLAB SPHERE

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SLIDE 8

KN VS THOMSON

(BHB SLAB corona: tau=1, kT=100 keV)

1 2 3 4 5 6 7 8 9 10 0.1 1 10 100 Polarization Degree [%] Energy [keV] Pol Degree (disc 6-500, mdot01, MBH10 ) SLAB tau1 kT100 limb Thom - 50 bins Thom 75 deg KN 75 deg Thom 60 deg KN 60 deg Thom 45 deg KN 45 deg

polarised seed

KN

0.000010 0.000100 0.001000 0.010000 0.100000 0.01 0.1 1 10 100 1000 E x I(E) [arbitrary units] Energy [keV] Spectrum (disc 6-500, mdot01, MBH10 ) SLAB tau1 kT100 - logN - 400 bins Thom 75 deg KN 75 deg Thom 60 deg KN 60 deg Thom 45 deg KN 45 deg

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GR EFFECTS

(BHB SLAB corona: tau=1, kT=100 keV)

polarised seed

2x1046 4x1046 6x1046 8x1046 1x1047 1.2x1047 1.4x1047 2 3 4 5 6 7 8 9 10 F(E) [erg / s cm2 keV] Energy [keV] Spectrum (a0, mdot01, MBH10 ) 10 kpc - 400 bins 75 deg 60 deg 45 deg

  • 10

10 20 30 40 50 60 70 80 90 100 0.1 1 10 100 Polarization angle [deg] Energy [keV] Pol Angle (a0, mdot01, MBH10 ) SLAB tau1 kT100 - 50 bins - limb 75 deg 60 deg 45 deg

1 2 3 4 5 6 7 8 9 10 0.1 1 10 100 Polarization Degree [%] Energy [keV] Pol Degree (disc 6-500, mdot01, MBH10 ) SLAB tau1 kT100 limb - 50 bins 75 deg 60 deg 45 deg

no GR

P R E L I M I N A R Y

1 2 3 4 5 6 7 8 9 10 0.1 1 10 100 Polarization Degree [%] Energy [keV] Pol Degree (a0, mdot01, MBH10 ) SLAB tau1 kT100 - 50 bins - limb 75 deg 60 deg 45 deg

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SLIDE 10

CONCLUSIONS

Scattering-induced polarization is not that obvious ! Together with spectroscopical (and time) analysis, however, gives 2 more

  • bservables which can be used to discriminate between geometries of the

scattering material (aka the corona in accreting sources) However knowing the inclination of the system and the polarization of seed photons is crucial For the case of accreting sources, IXPE/XIPE band is rewarding but also challenging (expecially for XRBs)

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SLIDE 11

Thanks for the attention