Ron Remillard Kavli Center for Astrophysics and Space Research

1. INPE Advanced Course on Compact ObjectsCourse IV: Accretion Processes in Neutron Stars & Black Holes Ron Remillard Kavli Center for Astrophysics and Space Research Massachusetts Institute of Technology http://xte.mit.edu/~rr/INPE_IV.4.ppt

2. IV.4 Periodic Variability in X-ray Binaries • Long-Term X-ray Periods • Binary Orbits • Superorbital Periods • Classical X-ray Pulsars • Pulse Periods and Period Derivatives • Pulse Profiles and Physical Models • X-ray Spectra and Cyclotron Absorption Features • Magnetars • Soft Gamma Repeaters (SGRs) • Anomalous X-ray Pulsars (AXPs) • Transient AXP, XTEJ1810-197

3. Periods of X-ray Binary Systems • Type Period Range Success Rate • (methods to determine binary period) • ---------------------------------------------------------------------------------- • LMXB 11 min – several days ~25% • (X-rays: dippers and eclipsers ; optical photometry; optical spectra) • HMXB 4.8 hr –400 days~75% • (X-ray modulations due to changing line of sight through stellar wind ; • some cases with optical spectra) • Superorbital Periods 30 days - 450 days few • (both LMXB, HMXB; X-ray band; Cyg X-1 in optical; • precessing accretion disks or accretion rate waves)

4. HMXB Orbital Periods in X-rays 4-band folded light curves Of HMXB Supergiants Wen et al. 2006 variable absorption along line of sight through stellar wind, binary orbit progresses. Very helpful ID tool For INTEGRAL: (many highly variable and obscured sources show X-ray periods 5-100 days) Binary phase

5. HMXB Orbital Periods in X-rays HMXB systems withB-e stars show periodic outbursts from eccentric orbits Wen et al. 2006 Binary Phase

6. Super-Orbital Periods in XRBs

7. Super-Orbital Periods in XRBs • LMC X-4 • 30.29 +/- 0.02 d. LMC X-3 published periods: 200d ; 100d; 453 d.

8. X-ray Pulsars Sample: sources in ASM monitoring catalog (incomplete)

9. HMXB X-ray Pulsars • Spin Period vs. Orbital Period Corbet Diagram (2007) Corbet (1986) used this diagram  segregated HMXB accretion types:Roche Lobe overflow (R), OB star wind (W), B-e type in Galaxy (B), B-e in SMC (b) B-e in LMC(b)

10. Accreting X-ray Pulsars • magnetosphere scale (Rm): B2/8p ~ rv2

11. Accreting X-ray Pulsars • SAX J2103.5+4545 Camero Arranz et al. 2007) • Spin Period Changes • Spin-up torque (N) • Rm < Rcor = (G MxPspin2 / 4p2)1/3 • = • N = M (G MxRm)1/2 • tspinup = n/n • = • = 10-5 yr (M-10)-1Pspin-4/3 (Rcp/Rm)1/2 • Review: Bildsten et al. 1997 • (ApJS, 113, 367)

12. Accreting X-ray Pulsars • Spin Changes • Bildsten et al. 1997

13. Accreting X-ray Pulsars • Spin Changes • Why so complicated? • Interactions: • disk B and stellar B ? • MHD outflow & braking? • Wind-fed systems • and disk reversals ? •  problem unresolved

14. Accreting X-ray Pulsars • Pulse Profiles vs. Energy • A0535+26 (Caballero et al. 2007) • RXTE (top panels 2-20 keV) • IBIS (bottom; 20-200 keV)

15. Accreting X-ray Pulsars • Pulse Profiles vs. Intensity • SAX J2103.5+4545 (Camero Arranz et al. 2007) • (2-60 keV)

16. Accreting X-ray Pulsars • Pulse Profiles at same intensity SAX J2103.5+4545 (Camero Arranz et al. 2007) Pulse Profile at same intensity & binary phase (2-60 keV)

17. Accreting X-ray Pulsars • Models for X-ray Continuum Spectrum: • e.g. Wolf et al. 2007, AIPC, 924, 496: • complicated, unsolved problem • bulk and thermal Comptonization • from shocks in the accretion column • Models for Radiation from Rotation-Powered Pulsars • see Arons 2007, astro-ph/07081050 • another difficult, unsolved, problem • spectrum: radio to Gamma Rays • pulsar wind nebulae • radiation is minor portion of energy budget

18. Accreting X-ray Pulsars • Cyclotron Resonance Scattering Features • Ecyc = hcB/2pme • = 11.6 B12 keV • (where B12 = B / 1012 G) • Eobs = Ecyc * f(real NS world) • grav. redshift • viewing angle (q) • emitting volume withgradients in (B, T, t, q ) •  model simulations Heindl et al. 2004

19. Accreting X-ray Pulsars Broad Absorption Line(s) in 14 X-ray Pulsars 12 – 50 keV (1012 – 1013 G) • Observed Cyclotron Lines

20. Accreting X-ray Pulsars Fix B, kT, and vary q(angle: B and photon path) • Modeling Cyclotron Lines Schonherr et al. 2007

21. Accreting X-ray Pulsars • Modeling Cyclotron Lines Variations B change line center top: 1.0-1.1 B0 ; middle: B0 constant; bottom: 0.9-1.0 Bo. Simulated spectra for fixed B and (top, down) kT = 20, 15, 10, 5 keV Schonherr et al. 2007

22. Magnetars • Soft Gamma Repeaters • Typical SGR bursts: • 0.1 s duration • peak Lx1039 – 1042 erg/s Time (s)

23. Magnetars • Soft Gamma Repeaters • SGR 1806-20 • 27 December 2004 Time (s) • Giant SGR bursts: • hours duration • peak saturates instruments • can light up earth’s ionosphere to “daytime’ ionizations

24. Magnetars • Anomalous X-ray Pulsars Selected as X-ray pulsars with rapid spin-down ; see Kaspi 2007, ApSpSci 308,1

25. Magnetars • Soft Gamma Repeaters & • Anomalous X-ray Pulsars

26. Magnetars • AXPs also show • SGR-like Bursts AXPs 

27. Magnetars • Magnetar Model • Magnetized (1015G) NS rotating at 5-8 s • Bursts triggered by sudden shift • in magnetospheric foorprint, driven by fracture in crust • Radiation from cooling of optically thick pair-photon plasma

28. Magnetars • Transient AXP: • XTEJ1810-197 • Gotthelf & Halpern 2007

29. Magnetars • Transient AXP: XTEJ1810-197 X-ray spectra: 2 BBs  Hot spot after large burst (unseen) Gotthelf & Halpern (2007)