Monte Carlo simulation of cyclotron resonant scattering features

Transcription

1 of cyclotron resonant scattering features Dr. Karl Remeis-Sternwarte Bamberg, Sternwartstraße 7, Bamberg, Germany Erlangen Centre for Astroparticle Physics (ECAP), Erwin-Rommel-Str. 1, Erlangen, Germany

2 Motivation: Measuring a neutron star s magnetic field Magnetic field variation 1 arbitrary flux [s 1 cm 2 kev 1 ] Magnetic field strength [Bcrit] Absorption features Fundamental line and higher harmonics 12-B-12 rule: E cyc 12 B 12 kev Complex line shape Energy [kev] 60 80

3 Outline 1 Accreting neutron star binary systems with cyclotron lines Origin of matter accreted to the neutron star The neutron star s magnetic field and its influence on the infalling plasma 2 Cyclotron emission from the accretion column

4 Accretion mechanisms Accretion column Accretion mechanisms in X-ray binary systems

5 Accretion mechanisms Accretion column Accretion mechanisms in X-ray binary systems WARNING Not to scale! R OB 7R sun Separation 25R sun

6 Accretion mechanisms Accretion column Accretion mechanisms in X-ray binary systems Kreykenbohm et al. (1999) Stellar Wind Vela X-1: B G

7 Accretion mechanisms Accretion column Accretion mechanisms in X-ray binary systems L1 Truemper et al. (1978) Roche Lobe Overflow Her X-1: B G

8 Accretion mechanisms Accretion column Accretion mechanisms in X-ray binary systems Santangelo et al. (1999) Be Accretion 4U : B G

9 Accretion mechanisms Accretion column Formation of an accretion column B B crit G

10 Accretion mechanisms Accretion column Formation of an accretion column B Matter couples to magnetic field lines

11 Accretion mechanisms Accretion column Formation of an accretion column B Seed photon sources: Blackbody Bremsstrahlung Cyclotron emission etc...

12 of CRSF formation X-ray binaries B θ k

13 of CRSF formation X-ray binaries Resonance energy: ω n = nBsin 2 θ m sin 2 e θ B n θ k p

14 of CRSF formation X-ray binaries Resonance energy: ω n = nBsin 2 θ m sin 2 e θ e e B n p = p + k cos(θ) θ k p n

15 of CRSF formation X-ray binaries Resonance energy: ω n = nBsin 2 θ m sin 2 e θ e e e B e n p = p + k cos(θ) k θ k p n

16 of CRSFs

17 of CRSFs

18 of CRSFs Inject Photon Iterate Sample MFP and propagate photon Store photon Araya 99 vs. Schwarm 12 (Slab1-1) 20 Did the photon escape? yes 15 no Sample electron momentum Sample final Landau level Sample scattering angle Flux [kev 1 ] τ = τ = Calculate final photon energy and electron momentum Next photon 10 τ = τ = Final Landau level >0? yes no Energy [MeV] Araya & Harding (1999) Sample decay Landau level Sample emission angle

19 of CRSFs Inject Photon Iterate Sample MFP and propagate photon Store photon Did the photon escape? yes no Sample electron momentum Sample final Landau level Sample scattering angle Calculate final photon energy and electron momentum Next photon Final Landau level >0? no yes Sample decay Landau level Schwarm et al. (2012) Sample emission angle

20 of CRSFs Inject Photon Harding 90 vs. Schwarm T = 5keV, ϑ = 85 Iterate Sample MFP and propagate photon Store photon Did the photon escape? yes 10 1 no Sample electron momentum Sample final Landau level Sample scattering angle Calculate final photon energy and electron momentum Next photon Thermally averaged scattering cross section [τt] T = 10keV, ϑ = 60 T = 50keV, ϑ = 60 Final Landau level >0? no yes Sample decay Landau level Sample emission angle Energy [ωres] Harding & Daugherty (1991)

21 Model parameters X-ray binaries cy, τ perp = 3.0E 04 τ Th, B = 0.04 B crit, T = 3 kev, µ = Flux [kev 1 ] Energy [kev]

22 Model parameters X-ray binaries cy, τ perp = 3.0E 04 τ Th, B = 0.06 B crit, T = 3 kev, µ = B [B crit ]: Flux [kev 1 ] Energy [kev]

23 Model parameters X-ray binaries cy, τ perp = 3.0E 04 τ Th, B = 0.06 B crit, T = 15 kev, µ = T [kev]: Flux [kev 1 ] Energy [kev]

24 Model parameters X-ray binaries cy, τ perp = 3.0E 04 τ Th, B = 0.06 B crit, T = 15 kev, µ = µ: Flux [kev 1 ] Energy [kev]

25 Model parameters X-ray binaries sl10, τ para = 8.0E 04 τ Th, B = 0.06 B crit, T = 15 kev, µ = geometry: cy sl10 3 Flux [kev 1 ] Energy [kev]

26 Model parameters X-ray binaries sl11, τ para = 1.6E 03 τ Th, B = 0.06 B crit, T = 15 kev, µ = geometry: sl10 sl11 3 Flux [kev 1 ] Energy [kev]

27 Model parameters X-ray binaries CRSF via RCL Green s function table 7/8 < µ < 8/8 4/8 < µ < 5/ Flux [kev 1 ] /8 < µ < 3/8 0/8 < µ < 1/ Energy [kev] Isenberg et al. (1998)

28 Simulated spectrum Her X-1 with B&W 07 continuum µ0 = µ1 = µ2 = B&W 07 seed photons Blackbody radiation Bremsstrahlung Cyclotron radiation arbitrary flux Optical Depth [τth] Her X 1 B = G Te = 6.00 kev M = gs 1 r0 = 44 m Energy [kev] Becker & Wolff (2007)

29 Simulated spectrum Her X-1 with B&W 07 continuum Energy [kev] Her X 1 B = G Te = 6.00 kev Ṁ = gs 1 r0 = 44 m 10-4 τcyc = τth 10-5 Flux [s 1 cm 2 kev 1 ] r0 = 44m B ϑ = 60 sin(x) Flux [s 1 cm 2 kev 1 ] Energy [kev]

30 Cyclotron emission from the accretion column B B critical luminosity model (Becker et al., 2012)

31 Cyclotron emission from the accretion column B B critical luminosity model (Becker et al., 2012)

32 Cyclotron emission from the accretion column B B critical luminosity model (Becker et al., 2012) Reflection model (Poutanen et al., 2013)

33 Cyclotron emission from the accretion column B B B 3, T 3 B 2, T 2 B 1, T 1

34 Cyclotron emission from the accretion column B B B 3, T 3 B 2, T 2 B 1, T 1

35 Cyclotron emission from the accretion column B B E B 3, T 3 B 2, T 2 B 1, T 1 E

36 Summary CRSFs exhibit fundamental physics of accreting XRBs Completely new Monte Carlo code Comparison to data has just begun Get the model now! Thank you for your attention!

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