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

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 linear polarization Scattering induced polarization signal strongly depends on: • geometry of the scattering material • inclination • scattering regime (# of scatterings allowed in the material) [optical thickness] (Spectral shape) Thomson/Compton scattering

3 scattering regimes for the SLAB (BHB 10 Msun, mdot=0.1 / corona: tau=0.5,1,2 - kT=100 keV) Spectrum (disc 6-500, mdot01, MBH10 ) SLAB kT100 60 deg - 400 bins Pol Degree (disc 6-500, mdot01, MBH10 ) SLAB kT100 Pol Angle (disc 6-500, mdot01, MBH10 ) SLAB kT100 1x10 7 10 100 tau = 2 tau = 2 tau = 2 tau = 1 tau = 1 tau = 1 tau = 0.5 tau = 0.5 tau = 0.5 90 9 80 8 1x10 6 70 7 60 6 E x I(E) [arbitrary units] Polarization Degree [%] Polarization Angle [deg] 50 100000 5 40 4 30 3 20 10000 2 10 1 0 -10 1000 0 0 0.2 0.4 0.6 0.8 1 0.01 0.1 1 10 100 1000 0 0.2 0.4 0.6 0.8 1 µ Energy [keV] µ

Pol Degree (disc 6-500, mdot01, MBH10 ) SLAB tau2 kT100 - logN - 50 bins 10 unscattered 1 scatt 2 scatt 3 scatt 9 4 scatt 5 scatt >5 scatt total 8 7 6 Polarization Degree [%] 5 4 3 2 1 0 0 0.2 0.4 0.6 0.8 1 µ

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

SLAB VS SPHERE (BHB / corona: tau=1, kT=100 keV) unpolarised seed SLAB SPHERE Pol Degree (disc 6-500, mdot01, MBH10 ) SLAB tau1 kT100 - 50 bins Pol Degree (disc 6-500, mdot01, MBH10 ) SPHERE tau1 kT100 - 50 bins 10 10 75 deg 75 deg 60 deg 60 deg 45 deg 45 deg 9 9 8 8 7 7 6 6 Polarization Degree [%] Polarization Degree [%] 5 5 4 4 3 3 2 2 1 1 0 0 0.1 1 10 100 0.1 1 10 100 Energy [keV] Energy [keV]

SLAB VS SPHERE SEED mu distribution / Polarization (disc 6-500, mdot01, MBH10) limb - 50 bins 2.5x10 7 (BHB corona: tau=1, kT=100 keV) 12 counts polarization 10 2x10 7 polarised seed 8 1.5x10 7 Pol. Degree [%] SLAB SPHERE counts 6 Pol Degree (disc 6-500, mdot01, MBH10 ) SLAB tau1 kT100 limb - 50 bins Pol Degree (disc 6-500, mdot01, MBH10 ) SPHERE tau1 kT100 limb - 50 bins 1x10 7 10 10 75 deg 75 deg 60 deg 60 deg 4 45 deg 45 deg 9 9 5x10 6 8 8 2 7 7 0 0 0 0.2 0.4 0.6 0.8 1 Polarization Degree [%] 6 Polarization Degree [%] 6 µ 5 5 4 4 3 3 2 2 1 1 0 0 0.1 1 10 100 0.1 1 10 100 Energy [keV] Energy [keV]

KN VS THOMSON (BHB SLAB corona: tau=1, kT=100 keV) polarised seed Spectrum (disc 6-500, mdot01, MBH10 ) SLAB tau1 kT100 - logN - 400 bins Pol Degree (disc 6-500, mdot01, MBH10 ) SLAB tau1 kT100 limb Thom - 50 bins 0.100000 10 Thom 75 deg Thom 75 deg KN 75 deg KN 75 deg Thom 60 deg Thom 60 deg KN 60 deg KN 60 deg 9 Thom 45 deg Thom 45 deg KN 45 deg KN 45 deg � KN 8 0.010000 7 E x I(E) [arbitrary units] 6 Polarization Degree [%] 0.001000 5 4 3 0.000100 2 1 0.000010 0 0.01 0.1 1 10 100 1000 0.1 1 10 100 Energy [keV] Energy [keV]

P Spectrum (a0, mdot01, MBH10 ) 10 kpc - 400 bins GR EFFECTS R 1.4x10 47 E 75 deg 60 deg L 45 deg I M 1.2x10 47 (BHB SLAB corona: tau=1, kT=100 keV) I N A 1x10 47 polarised seed R Y F(E) [erg / s cm 2 keV] 8x10 46 Pol Angle (a0, mdot01, MBH10 ) SLAB tau1 kT100 - 50 bins - limb 6x10 46 Pol Degree (a0, mdot01, MBH10 ) SLAB tau1 kT100 - 50 bins - limb 100 10 75 deg 75 deg 60 deg 60 deg 45 deg 4x10 46 45 deg 90 9 2x10 46 80 8 0 2 3 4 5 6 7 8 9 10 70 Energy [keV] 7 60 6 Polarization angle [deg] Polarization Degree [%] no GR 50 5 40 Pol Degree (disc 6-500, mdot01, MBH10 ) SLAB tau1 kT100 limb - 50 bins 10 75 deg 4 60 deg 45 deg 30 9 3 8 20 2 7 10 Polarization Degree [%] 6 1 0 5 0 -10 0.1 1 10 100 4 0.1 1 10 100 Energy [keV] Energy [keV] 3 2 1 0 0.1 1 10 100 Energy [keV]

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

Thanks for the attention