INPE Advanced Course on Compact Objects Course IV: Accretion Processes in Neutron Stars & Black Holes Ron Remillard Kavli Center for Astrophysics and Space Research Massachusetts Institute of Technology

IV.5 Variability in X-ray Binary Systems  msec X-ray Pulsars Sources and Significance Timing and Spectral Properties  Aperiodic Variability in Accreting Neutron Stars Type I X-ray Bursts Type II X-ray Bursts Superbursts kHz QPOs  Aperiodic Variability in Black Holes Impulsive Relativistic Jets Weaker Types of Impulsive Jets Wild Instability Cycles in GRS

Msec X-ray Pulsars Source Spin (Hz) Orbit (hr) Bursts (Hz) IGR J XTE J XTE J XTE J SAX J bursts (401) XTE J bursts (314); not wd? HETE J bursts Swift J Characteristics: Extremely compact binaries; wd companion (R c ~0.05 R o ; M c ~0.02 M o ) Tip of reservoir of accretion-spun-up pulsars visible in X-rays Key to spin-ID of burst oscillations Key to inventory of spin distributions Key toward a model for kHz QPOs

Msec X-ray Pulsars XTE J : typical, faint transient peak ~ 30 mCrab ( keV) outburst duration ~65 days HETE J : transient persists for 2+ years; brief turnoff ; early end of msec pulsations (Aug. 19, 2005)

Energy Spectra & Power Spectra of msec Pulsars msec X-ray pulsars resemble Atoll sources in hard state. So why don’t atolls pulse (burst oscillations  similar spin frequencies) B ranges different? accretion plasma buries B? HETEJ1900 may inform us!

Type I X-ray Bursts Number of bursters~80 Science Applications:  Neutron-star finder  Burst oscillations (  spin)  Radius-expansion bursts (  distance estimate)  Redshifted abs. lines? (Cottam et al, 2003: 1? Case)  Test burst models  Trace dM/dt at NS surface?  Topic for BH event horizon test (lack of bursts in BH)

Type I X-ray Bursts Burst Oscillations e.g., Strohmayer & Markwardt sources of BOs max = spin range: 45, Hz some frequency profiles are shorter or spotted (on/off) amplitudes increase with energy (Muno et al. 2003)

Type I X-ray Bursts Burst Oscillations multiple max measures From the same source give consistent results Muno et al. 2002

Msec X-ray Pulsars and Burst Oscillations Frequency (Hz) Spin Distribution Neutron Star Speed limit ~730 Hz (burst oscillations, radio pulsars, X-pulsars; Chakrabarty et al. 2003) Why is limit < breakup freq. magnetic-accretion spin equilibrium? Gravitational waves? (Wagoner 1984; Bildsten 1998)

Type I X-ray Bursts Radius Expansion Bursts e.g., Z-transient XTE J Isolate burst spectrum(t) Fit spectra to blackbody (R,t) See R expansion + dip in T evolution  Eddinton L x  distance estimate (assume M x, layer composition)  Look for consistent results

Rudimentary Elements of Bursts Models Paradigm: thermonuclear explosion of H, He from accumulated, accreted matter on NS surface  Use L x as a scale for dM/dt  Assume (vary) M NS and R NS  Assume (vary) composition  Calculate (vary) T of subsurface layer (NS cooling model)  Compute hydrostatic equilibrium  Monitor ( , T) for detonation conditions Many complexities, e.g. differential rotation and turbulent mixing in surface layer (Prio & Bildsten 2007)

Bursts Models Status of burst models (see Strohmayer & Bildsten 2006  many bursters on fast and slow side of burst rate expectations Burst Oscillation Models spot evolution ray tracing for osc. amplitude(t)) Spitkovsky et al 2002, ApJ, 566, 1018 Type I bursts: huge science comeback; 1990s poster-child for “old and boring”

Type II X-ray Bursts Number of sources2 ; events are NOT thermal 4U (rapid burster + type I) ; GRO J (bursting pulsar) Linear  E vs.  t  accretion instability Cause unknown (magnetic?; high-rate ADAF?) Time (s) Count rate Rapid Burster; Inoue 2004, Adv. Sp. Res., 34, 2550

SuperBursts in Accreting Neutron Stars Number of sources8 duration: few to 10 hr triggered by a type I burst recurrence rate: year(s) can excite transient pulsar at spin rate ( ) model: C detonation in accretion/burst residue in subsurface layers

kHz QPOs Number of sources 26 atolls16 Z-type 8 msec pulsars 2 Properties move in frequency ( Hz) often twin, sometime solo separation of twins varies slowly

kHz QPOs QPO Scales van der Klis 2006 Plot everything vs. upper kHz QPO interpretations controversial Upper kHz QPO

kHz QPOs Current kHz QPO Models Beat frequency model (Miller & Lamb) twin peaks: Keplerian vs. NS surface footprint with R NS < R ISCO twin peak separation interpreted as spin However, twin peak separation is spin or 0.5 spin Disk Resonance (Abramowicz & Kluzniak) TypIcial twin peaks are 600, 900 Hz  3:2 ratio Resonance model for NS disks

Impulsive, Relativistic Jets in BH Binaries GRS jets v > 0.9 c (Mirabel & Rodriguez 1994; Fender et al. 1999) Also GRO J , Cyg X-3, XTE J (see Fender 2006) Special relativity demo; nut beware of assumption of bipolar symmetry Ejection moment not observed in X-rays

Black Holes in the Milky Way Relativistic jets imaged in radio and also in X-rays (Chandra). (Hannikainen et al. 2001; Corbel et al. 2002). Baryonic content of MQ jets still uncertain, except for SS433

Impulsive, Relativistic Jets in BH Binaries Small-scale impulsive jets B-cycles of GRS (Eikenberry et al. 1998; Fender + Pooley 1998) strong evidence for disk:jet connection other LC types (Eikenberry et al. 2007; Rodriguez et al. 2007)

More Complications: Fast X-ray Novae SAX J (V4641 Sgr) black hole binary + relativistic radio jets ‘Fast X-ray Nova’ 20 min light curve, Sept 15, 1999 (RXTE)

RXTE Observations of GRS – 2006: 1351 obs. (public data; 4.77 Ms)  785 data intervals (4.43 Ms) Quasi-steady428 (rms < 16%; 1 s bins; 307 hard; 121 soft) Variable Light Curves357 (rms > 16%)

Light Curve Types: Steady Variable  hard-steady (  -var )  soft-steady 64 0  soft-rolling  soft+dips  fast flare sequence + long min  hard dip + trigger + soft spike 0 33  square waves 0 20 steady-flicker-dip sequence 0 5  flicker  steady switching 0 16 flare-dip sequence + long min  heartbeats (50 s) 0 89  dropouts to soft and variable 0 44 ….new or inter- combinations 0 35 _______ _______

Steady Conditions: Color-Color Diagrams

Steady Conditions & Radio Flux GRS : coded for radio flux (Ryle telescope, 15 GHz): x  (x S 75 mJy ;

BHB Color-Intensity Diagrams GRS /steady H GX339-4

Fast QPOs in GRS Hz: 28 (of 785) QPO detections (  > 4): Sample: Hz = 30.2 LC Type Detect (total) FrequencyQ ( freq./FWHM )  2 (64)66.23 (0.34) 16  8 (56)65.85 (0.24) 14  13 (31)66.72 (0.21) 11  4 (16)66.92 (0.70) 24  1 (20)68.60 (0.93) 20 QPO Frequencies: 41, 67, 113, 165 Hz  67 Hz in “agitated soft state” or thermal:SPL intermediate

QPO near 67 Hz in type-averaged PDS  [64]  [56]  [31]

QPOs in Variable States (avg. PDS; 2-40 kev)   [42]    [89]    [44]

GRS Light Curves:  Type bright-hard zone contains a high-frequency QPO

GRS : theta-blue Power Density Spectra, blue region QPO (9  ) at Hz; harmonic (330 Hz; 3.7  ) Q = 5, ampl = 2% (13-30 keV) Colors resemble steep power-law state

GRS Light Curves:  Type Long exposures, July 16-18, bright-hard zone: 113 Hz QPO at 6-40 keV

High Frequency QPOs from GRS Type  : bright-hard zone; keV Data Frequency Q ( freq./FWHM ) 1997 Sept Remillard et al (3) June - Oct.Belloni et al (7) 2 All Type  [44](all HID zones)165 (3)4.7 (0.5) Type  : bright-hard zone; 6-40 keV Data Frequency Q ( freq./FWHM ) 2001 July Remillard et al (5) 2 All Type [42](all HID zones)112 (4)2.2 (0.4)

GRS Light Curves:  Type Profile variations within the  group. MIT undergraduate thesis: J. Z. Gazak

GRS Light Curves:  Type Recurrence time and flare fractions for the  group. MIT undergraduate thesis: J. Z. Gazak

GRS Light Curves:  Type Cycle zones for the  group. MIT undergraduate thesis: J. Z. Gazak

GRS Light Curves:  Type [82] 67 Hz in zone1 151 (4) Hz QPO in zone 3 7  ; Q = 3.2 (8 +/- 3 % below 165 Hz) keV:

QPOs in Variable States (avg. PDS; 2-40 kev)   [42]    [89]    [44] 6-40 keV 6-40 keV15-40 keV

MIRAX Support of Astrophysics Properties Physical Models MIRAX Observations Black Holes: mass Binary dynamics locate transients; optical teams spin GR disk spectra thermal state measures & alerts GR resonance (high-n QPOs) SPL state transitions and alerts event horizon Type I burst models deep limits for burst function jets Blandford-Znajek obs. moment of ejection; hard GR MHD? Vertical B? state transitions; radio teams accretion structures GR MHD (P rad regime) measure SPL high-L x flares

MIRAX Support of Astrophysics Properties Physical Models MIRAX Observations Neutron Stars: mass Binary dynamics locate NS transients radius kHz QPO models? bursts; atoll specra? spin Binary evolution theory locate msxp transients burst osc.; superburst osc. magnetic field Mag. evol. models? pulsar cyclotron lines SGR bursts; AXP bursts internal structure NS structure models SGR oscillations & crust Burst Models? Burst and superburst archive jets MHD? hard state; transit.; radio team