1. 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 http://xte.mit.edu/~rr/INPE_IV.3.ppt

2. IV.3 X-ray States of Accreting NSs  Classifying Atolls, Z-sources, and X-ray Pulsars Spectral Shapes and X-ray Colors Color-color and color-intensity diagrams X-ray spectra and power-density spectra  Soft and Hard States of Atoll Sources X-ray Spectra and the Model Ambiguity Problem The L vs. T 4 question for NSs Hard State and Jets  Z Sources Identifications and the two Groups X-ray Power Density Spectra X-ray Spectral Models XTE J1701-462: the first Z-type transient

3. Accreting NS Subclasses HMXB/pulsar (o) Hard spectra: e.g., power-law photon index < 1.0 at 1-20 keV;  easiest distinguished via gross spectral shape weakly magnetized, accreting NS (  ) BH Binaries and candidates (squares) filled symbol: persistent open symbol: transient Cackett et al. (2006)

4. Energy Spectra & Power Spectra of Accreting NS

5. Accreting NS Subclasses Atolls and Z-sources: X-ray spectra steeper than HMXB pulsars; distinguished with color-color and color-intensity diagrams. choose 4 energy bands {A, B, C, D} in order of increasing energy soft color = B/Ahard color = D/C atoll transient bright atoll source Z source extreme island, island, banana branch horizontal, normal, and and banana branches (upper and lower) flaring (here curled) braches Top to bottom:

6. Atoll-type Transients: Aql X-1, 4U1608-52 RXTE ASM: 10 outbursts per source

7. Atoll-type Transients: combine all outbursts hard color: 8.6-18 / 5.0-8.6 keV ; soft color 3.6-5.0 / 2.0-3.6 keV  soft (banana), intermediate (island), hard (extreme island) states (Lin, Remillard, & Homan 2007)

8. Atoll Spectra: Model Ambiguity (25 year debate) Eastern Model: A multi-color disk (MCD) + Comptonized blackbody (BB) Western model: BB + Comptonized MCD For each, Comptonization can be a simple slab model (T seed, T corona ), or an uncoupled, broken power law (BPL). All fits are good! Hard state: hot corona; moderate opt. depth; cool BB or MCD; Compt. dominates L x Soft state: 3 keV corona; high opt. depth; thermal and Compt. share L x

9. Performance Test: L (BB or MCD) vs. T Eastern Model: MCD behavior unacceptable in soft state Western model: BB L x is not T 4, in soft state, but physics of boundary layer evolution is a complex topic. hard state: L x growth is closer to T 4 line (i.e., constant radius). L MCD (10 38 erg/s at 10 kpc) -------------- L BB (10 38 erg/s at 10 kpc)

10. Solution to problem with atoll soft state? soft state: BB + MCD + weak BPL (constrained  < 2.5 ; E break = 20) hard state: Western (BB + BPL) L MCD (i=60 o ) and L BB (10 38 erg/s at 10 kpc) top line: R = R burst lower line: R = 0.2 R burst  R ns < R ISCO ?

11. Power Continuum vs. Comptonization Double-themal model: atolls and BH very similar In rms power vs. Comptonization fraction rms power in power density spectrum vs. fraction of energy (2-20 keV) for Comptonization Black Holes: 2 Atoll transients

12. Double-thermal Model: View of the Hard State L BB may track the accretion rate at NS surface If dm/dt (disk) = dm/dt (BL), then the hard state has too much rad. efficiency (e.g. line at 0.01 L EDD ). Alternatively, along lines of constant L(BPL+MCD), the hard state shows 6X less dm/dt reaching the NS surface, compared to the soft state.

13. ASM Light Curves of Z Sources GX5-1 GX340+0 Cyg X-2 Sco X-1 GX349+2 GX17+2

14. Long-term color-color diagrams of Zs GX5-1 GX340+0 Cyg X-2

15. Long-term color-color diagrams of Zs Sco X-1 GX349+2 gx17+2

16. Properties of Z-branches Flaring Branch Normal Branch Horizontal Branch

17. Hard X-ray Components of Z Sources RXTE Obs. of Sco X-1 (D’Amico et al. 2001) Transient hard tail ; not fixed in color-color branches ; but spectral shape does vary with color-color position

18. Spectral Fits for Z Sources BeppoSAX Obs. of GX17+2 (Di Salvo et al. 2000) Horizontal Branch: 8% power law (1-200 keV). ; Normal branch: no hard tail upper HB lower NB

19. Spectral Fits for Z Sources BeppoSAX Obs. of GX349+2 (Di Salvo et al. 2001) Normal Branch vertex has hard tail ; Flaring branch is very soft

20. First Transient Z-Source: XTEJ1701-462 --t1 --t2 --t3 --t4 Homan et al. 2006 + Atels by Homan et al. in 2006 and 2007 t1: Zs like GX5-1 t2: Zs like Sco X-1 t3: X-ray bursts t4: Atoll behavior + efforts to model the X-ray spectra, for physical insights about Z-branches: HB, NB, FB