1. The diversity of High- Mass X-ray binaries Ignacio Negueruela Agios Nikolaos October 2010 where astrologers roam …

2. High-mass X-ray binaries High-mass X-ray binaries are systems containing a compact object accreting from a massive star. Good separation from LMXBs. Very few intermediate-mass objects: LMC X-3, V4641 Sgr Fundamental tools for astrophysics, cf. Cen X-3 & Cyg X-1. Massive star is the main (only) contributor to optical and infrared brightness.

3. X-ray pulsars Most massive X-ray binaries are X-ray pulsars  magnetised neutron stars We know of two black hole systems, one in the Milky Way (Cyg X-1; O9.7Iab), and one in the LMC (LMC X-1, O8III-V). Others are being found in nearby galaxies: M33 X-7 and IC 10 X-1 (talks by Fabbiano, Pietsch) Weird cases: Cyg X-3, SS433; HMXBs? Related to ULXs? (talk by Roberts) Presence of strong magnetic field somehow inhibits jet formation  no radio detections. Nature of donor determines main properties.

4. X-ray spectra of accreting pulsars The X-ray spectra of accreting pulsars are generally fitted to phenomenological models (power-law+cutoff) Increasing effort to interpret them in physical terms. Bulk Comptonisation of thermal components (e.g., Becker & Wolff 2007, ApJ 654, 435) Talk by Haberl

5. X-ray pulsars Modern version of Corbet’s diagram (Corbet 1986, MNRAS 220, 1047) Be star Supergiant

6. Accretion from the wind of a supergiant Accretion from the wind of a supergiant Roche-lobe overflow Roche-lobe overflow Classes of HMXBs Be/X-ray binaries

7. Classical HMXB Cen X-3 SMC X-1 LMC X-4 + LMC X-1 (BH)

8.  Short orbital periods (2-3 days)  Circularised orbits  Incipient Roche-lobe overflow  The stars may be bloated, and are over-luminous for their mass  Formation of an accretion disk results in high L X  detectable in other galaxies Classical HMXBs Van der Meer et al. (2007, A&A 473, 523)

9. Classical HMXB Incipient Roche-lobe overflow L X  10 38 erg s -1

10. Formation channel for HMXBs Case C mass transfer q << 1 Non-conservative evolution via common envelope Results in SG+BH Only way to make a BH in a binary? (talk by Casares) Wellstein & Langer (1999; A&A 350, 148)

11. Be/X-ray binaries Note: many more Be/X in the SMC Talk by Coe

12. a Be star is an early type (O7 to A1) star, not very evolved (luminosity class III-V), which shows - or has shown - emission in the H  line (see Porter & Rivinius 2003, PASP 115, 1153 for a review).  Other Balmer and singly-ionised metallic lines (Fe II, Cr II, etc) also seen in emission. He I in emission in stars earlier than B2. At sufficient resolution, all lines are double peaked.  There is also an infrared excess due to continuum emission. Be/X-ray binaries

13.  These characteristics can be explained by the presence of a disk of material expelled from the star.  Currently the model favoured is the decretion viscous disk ( Lee et al. 1991, MNRAS 250, 432 ), which can reproduce most observational characteristics ( Porter 1999, A&A 348, 512; Okazaki 2001, PASJ 53, 119 )  At a given time, around 10% of early-B stars are in a Be star phase  But the Be phenomenon is very variable. Stars move from Be to non–Be phase. Be/X-ray binaries

14. Therefore … A Be/X-ray binary is made of A Be star – observationally always O9-B1 both in the Galaxy and the LMC A compact object accreting material from the disk of the Be star – observationally always a neutron star ► X-ray pulses detected whenever one looks hard enough. Indistinguishable distribution in the SMC (McBride et al. 2008; MNRAS 388, 1198)

15. X-ray lightcurves Persistent sources  Relatively low L X (  10 34 erg s -1 ).  Small intensity fluctuations (factor  10) without an obvious temporal pattern. Transients  Quiescence: low ( ≤ 10 35 erg s -1 ) or non-detectable L X.  Series of outbursts with relatively high X-ray luminosity (L x  10 37 erg s -1 ), separated by the (suspected) orbital period (Type I or normal according to Stella et al. 1986, ApJ 308, 669 ).  Larger outbursts with L x > 10 37 erg s -1 (L x ≈ L Edd ), lasting several weeks and not showing modulation with the orbital period (giant or Type II).

16. X-ray lightcurve of the persistent Be/X-ray binary X Per (4U 0352+30), taken with the All Sky Monitor on board RossiXTE P orb = 250.0 d, P spin = 837.6 s, e = 0.11

17. X-ray lightcurves Persistent sources  Relatively low L X (  10 34 erg s -1 ).  Small intensity fluctuations (factor  10) without an obvious temporal pattern. Transients  Quiescence: low ( ≤ 10 35 erg s -1 ) or non-detectable L X.  Series of outbursts with relatively high X-ray luminosity (L x  10 37 erg s -1 ), separated by the (suspected) orbital period (Type I or normal according to Stella et al. 1986, ApJ 308, 669 ).  Larger outbursts with L x > 10 37 erg s -1 (L x ≈ L Edd ), lasting several weeks and not showing modulation with the orbital period (giant or Type II).

18. P orb = 46.0 d, P spin = 41.7s, e = 0.41 X-ray lightcurve of the prototype Be/X-ray transient EXO 2030+375, taken with the All Sky Monitor on board RossiXTE

19. P orb = ? d, P spin = 160.7s X-ray lightcurve of the Be/X-ray transient MXB 0656 -072, taken with the All Sky Monitor on board RossiXTE. The only previous recorded outburst took place in 1974 (but there was another one four years later).

20. Several transients display series of Type I outbursts after (and only after) a giant outburst. 2S 1417-624 P orb = 42.1 d, P spin = 17.6s, e = 0.45

21. Optical studies Reig et al. (2007, A&A 462, 1081) l These changes are generally accompanied by large photometric variability l They can be explained as large variations in the disk’s configuration l Optical monitoring reveals strong changes in the line profiles  tracers of the disk’s dynamics

22. The truncated disk model Okazaki & Negueruela (2001, A&A 377, 161) l If the disk is supported by viscosity, the neutron star exerts a torque on disk particles that makes them lose angular momentum. l The phenomenology observed implies strong interaction between the different system components. This can be easily understood in terms of the decretion disk model. l As a consequence, the disk can only grow up to a certain size, and will be truncated at one of the commensurabilities between the Keplerian orbital period of the neutron star and disk particles  the disk acts as reservoir of mass.

23. Model successes The model effectively explains two observational facts:  There is a good correlation between the orbital period and the maximum EW(H  ) measured ( Reig et al. 1997, A&A 322, 193 )  the neutron star controls the size of the disk.  Analysis of emission-line shapes and infrared excess indicates rather higher densities in the disks of Be/X-ray binaries than in those of isolated Be stars ( Zamanov et al. 2001, A&A 367, 884 ). The model predicts a strong dependence of the observed behaviour on the orbital eccentricity, which is generally observed to hold.

24. But there are exceptions … KS 1947+300 P orb = 40.4 d, P spin = 18.7s, e = 0.03 l The more Be/X-ray binaries we know, the more difficult it seems to find a common pattern in their behaviour. l I trust, however, that all those different behaviours arise from the very complex dynamical interplay between the components of the systems and can finally be reduced to the same physical processes.

25. Where do they come from? Be/X-ray binaries are descended from moderately massive binaries that undergo a phase of mass transfer They are believed to originate from relatively close systems with q<0.5 in which semi- conservative mass transfer is possible Typical age ≥ 10 Myr

26. Considered as a population, BeXBs can be used to set constraints on formation models and hence on basic physics. There is growing evidence that a substantial population of Be/X-ray binaries with low eccentricity exists. Inference of electron- capture SN  dependence on previous binary history. Podsiadlowski et al. 2004, ApJ 612, 1044 See Coe’s talk for SMC population

27. The Be + WD mystery Population synthesis models provide tools to analyse populations (e.g., Van Bever & Vanbeveren 1997, A&A 322, 116 ; Raguzova 2001 A&A 367, 848 ). All population synthesis models that have been elaborated predict that, for every Be + neutron star binary, there should be ~ 10 Be + WD binaries. No such system has been conclusively identified. They are very hard to pinpoint, but there should be many!

28. The Be + WD mystery Population synthesis models provide tools to analyse populations (e.g., Van Bever & Vanbeveren 1997, A&A 322, 116 ; Raguzova 2001 A&A 367, 848 ). All population synthesis models that have been elaborated predict that, for every Be + neutron star binary, there should be ~ 10 Be + WD binaries. No such system has been conclusively identified. They are very hard to pinpoint, but there should be many! This renders the models somewhat suspect! This renders the models somewhat suspect!

29. Be/X-ray binaries There’s a correlation here …

30. Equilibrium at which corotation velocity at the magnetospheric radius equals Keplerian velocity ( Corbet 1986, MNRAS 220, 1047; Waters & van Kerkwijk 1989, A&A 223, 196 ) Equilibrium at which corotation velocity at the magnetospheric radius equals Keplerian velocity ( Corbet 1986, MNRAS 220, 1047; Waters & van Kerkwijk 1989, A&A 223, 196 )

31. Equilibrium at which corotation velocity at the magnetospheric radius equals Keplerian velocity ( Corbet 1986, MNRAS 220, 1047; Waters & van Kerkwijk 1989, A&A 223, 196 ) Equilibrium at which corotation velocity at the magnetospheric radius equals Keplerian velocity ( Corbet 1986, MNRAS 220, 1047; Waters & van Kerkwijk 1989, A&A 223, 196 )

32. Evolved O8-B2 stars (luminosity class I) Evolved O8-B2 stars (luminosity class I)

33. Vela X-1: Short term flaring Long term variability by a factor of 4 Supergiant X-ray binaries Flare from 4U 1907+09 Fritz et al. 2006 (A&A 458, 885) Ribó et al. 2006 (A&A, 449, 687)

34. Supergiant X-ray binaries ObjectPulseCounterpartPeriod Typical L X (erg s -1 ) 2S 0114+65 10000 sB1 Iab11.6 d~ 10 36 Vela X-1 283 sB0.5 Iab8.9 d~ 10 36 1E 1145.1-6141 297sB2 Iae14.4 d~ 10 36 GX 301-02 698 sB1 Ia + 41.5 d~ 10 37 4U 1538-52 529 sB0 I3.7 d~ 10 36 OAO 1657-415 38 sOfpe/WNL10.4 d~ 10 36 4U 1700-37 NOO6.5 Iaf+3.4 d~ 10 36 EXO 1722-363 413 sB0-1 I9.7 d~ 10 36 SAX J1802.7-2017 140 sB1 Ib4.6 d ~ 10 36 XTE J1855-026 361 sB0 Iaep6.1 d ? 4U 1907+09 440 sO8 I8.4 d~ 10 36 X 1908+075 605 sB1 I IGR J19140+0951 NOB0.5 Ia13.6 d~ 10 36 Cyg X-1 BHO9.7 Iab5.6 d~ 10 37

35. Radiative winds from hot stars Heavy ions have large Thompson cross sections The  law   0.8 – 1.2 Review: Kudritzki & Puls 2000, ARA&A, 38, 613 Images stolen from Stan Owocki Line Scattering: Bound Electron Resonance

36. Development of instability Velocity Density smooth wind Images stolen from Stan Owocki Owocki & Rybicki 1984, ApJ, 284, 337 cf. Feldmeier et al. 1997, A&A, 322, 878

37. Wind clumping Clumping factor Size and geometry of clumps Shells or blobs Optically thin? 1D simulations Runacres & Owocki 2002, A&A, 381, 1015 2D simulations Dessart & Owocki 2003, A&A, 406, L1 Porous winds Owocki et al. 2004, ApJ, 616, 525 Oskinova et al. 2006, MNRAS, 372, 313 Constraints from spectra Prinja et al. 2005, A&A 430, L41 Bouret et al. 2005, A&A, 438, 301 Puls et al. 2006, A&A, 454, 625

38. Bondi-Hoyle-Lyttleton accretion Dependence of L X on eccentricity Reig et al. (2003, A&A 405, 285) See review: Edgar 2004, New Ast. Rev. 48, 843

39. But this also becomes unstable … Transverse instability close to stagnation point (Foglizzo et al. 2005; A&A 435, 397) Perturbed accretion flow (Frixell & Taam 1988, ApJ 335, 862) Can (transient) accretion disks form?

40. This is a complex problem A photo-ionization wake in Vela X-1 Kaper et al. (1994, A&A 289, 846)

41. A photo-ionization wake in Vela X-1 Kaper et al. (1994, A&A 289, 846) A tidally induced accretion stream forms in the models of Blondin et al. (1991, ApJ 371, 684), which incorporate a realistic representation of the physics. This is a complex problem

42. X-rays and winds A photo-ionization wake in Vela X-1 Kaper et al. (1994, A&A 289, 846)

43. There is feedback everywhere Quaintrell et al. (2003, A&A 401, 313) Tidally induced non-radial pulsations in Vela X-1

44. Formation channel for SGXBs  Case A mass transfer  q  1  Conservative evolution with two mass-transfer phases  Results in SG+NS Wellstein & Langer (1999; A&A 350, 148)

45. Supergiant Fast X-ray transients A group of flaring sources with very short outbursts and supergiant companions. Transient emission composed by many flares reaching L X  10 36 -10 37 erg s -1 Persistent emission at lower luminosity L X  10 33 -10 34 erg s -1 Deep quiescence at L X  10 32 erg s -1 ( Giunta et al. 2009, MNRAS 399, 744; Bozzo et al. arXiv:1004.2059 ; Sidoli et al. 2010 arXiv:1007.1091 ) e.g., Romano et al. 2010, Mem. SAI 81, 332

46. Parameters of SFXTs Optical counterpart to AX 1845.0-0433 (VLT+FORS1)

47. The real outbursts Outburst (series of flares) is  1 day. Single flare is  3 minutes Fastest doubling time is  4 seconds. Data and graphics by courtesy of D. M. Smith Three days of Suzaku observations of IGR J17544-2619

48. This leaves several options: Difference in wind structure Difference in wind geometry Difference in accretion process Looking for a difference

49. Clumpy wind INTEGRAL monitoring of Vela X-1 (Kreykenbohm et al. 2008, A&A 492, 511) First proposed by in’t Zand (2005, A&A 441, L1) to explain behaviour of IGR J17544-2619. All winds from OB stars are likely clumpy. Classical supergiant X-ray binaries also show flares.

50. Equatorial overdensity Model proposed by Sidoli et al. (2007, A&A 476, 1307) to explain behaviour of IGR J11215-5952. Not clear how to extend it to other sources. Are winds spherically symmetric?

51. Magnetic modulation of accretion Grebenev & Sunyaev (2007, Ast. Lett. 33, 149) proposed that the sudden flares could be related to centrifugal inhibition of accretion in neutron stars with P spin ≈ P crit. Bozzo et al. (2008, ApJ 683, 1031) studied the conditions for centrifugal and magnetic inhibition of accretion  magnetic inhibition can only happen if B > 10 14 G (neutron star is a magnetar).

52. Outbursts in IGR J16479-4514 seem to be in phase with eclipse ( Bozzo et al. 2009, A&A 502, 21; Jain et al. 2009, MNRAS 397, L11 ). Likewise, periodicity in IGR J17544-2619 hints at elliptical orbit ( Clark et al. 2009, MNRAS 399, L113 ) Elliptical orbits Note, however, measurable eccentricities in wide-orbit SGXBs.

53. A combination of several things … Number of clumps that will be inside the accretion radius of the neutron star in one orbit A model including clumpy wind and variable geometry was able to reproduce the overall characteristics of some systems ( Ducci et al. 2009, MNRAS 398, 2152 ). But adding more complexity means more free parameters.

54. Very high-energy sources Three systems are known. PSR B1259-63 Radio pulsar orbiting a Be star. X-ray emission due to shocks at the interface between pulsar wind and disk. Johnston et al. 1992, ApJL 387, L37 Tavani et al. 1994, ApJL 433, L37 LS 5039 Compact object orbiting an O6.5 V star. Clark et al. 2001, A&A 376,476 Casares et al. 2005, MNRAS 364, 899 Talk by Paredes

55. PSR B1259-63 Radial wind model used Waters et al. (1988, A&A 198, 200) Very far away from our current understanding of Be-star winds: Keplerian disks Very low radial velocity Okazaki & Negueruela (2001, A&A 377, 161) Standard model in Tavani & Arons (1997, ApJ 477, 439) Image taken from a on-line presentation by Masaharu Hirayama (UMBC/JCA), where they are uncredited,

56. Casares et al. (2005, MNRAS 360, 1105) LS I +61  303 Colliding pulsar wind nebula scenario Romero et al. 2007, A&A 474, 15 Acretion/ejection (microquasar) scenario

57. Quite neglected case: SAX J0635+0533 This is a 34 ms X-ray pulsar orbiting a B0.7 IIIe star ( Cusumano et al. 2000, ApJ 528, L25 ) Orbital solution gives period P orb = 12.7 d, e = 0.29 ( Kaaret et al. 2000, ApJ 542, L41 ) No radio detection ( Nicastro et al. 2000, A&A 362, L5 ) No VHE source We don’t know the ingredients for a VHE source SAX J0635+0533 H.E.S.S. image of area (Aharonian et al. 2006, A&A 469, L1)

58. 1A 0538-66 B0.5 III P orb = 16.6 d, P s = 69 ms (one detection) LMC source. Active during the early 80’s L X ~ 10 39 erg s -1

59. 1A 0538-66 P orb = 16.6 d, B0.5 III P s = 69 ms (one detection) Charles et al. 1983 (MNRAS 202, 657) Out of outburst In outburst

60. Tidally induced mass loss? Mass –loss rate with orbital angle in the model of Stevens (1988, MNRAS 232, 199) for A0535-66 (P orb = 17 d, e = 0.7)

61. 1A 0538-66 P orb = 16.6 d, B0.5 III P s = 69 ms (one detection) Photometric period of 421d likely stable over >80 years ( McGowan & Charles 2003; MNRAS 3359, 748 ) H  in 2004

62. Alternative channel for a Be/X  Case C  q << 1  Fully non- conservative case  Results in Be+NS

63. IGR J00370+6122

64. IGR J00370+6122 = BD +60° 73 Spectral type BN0.5 II-III Reig et al. (2005, A&A 440, 637) Already seen by ROSAT and BeppoSAX (1RXS J003709.6+612131) Modulation at 15.7 d believed to be orbital period ( in’t Zand et al. 2007, A&A 469, 1063 ) Possible spin period 346 ± 6 s. Light curve typical of wind accretor ( in’t Zand et al. 2007, A&A 469, 1063 )

65. IGR J00370+6122 = BD +60° 73 Light curve typical of wind accretor ( in’t Zand et al. 2007, A&A 469, 1063 )

66. IGR J11215-5952

67. P orb = 165 d, B0.5 Ia P s = 187 s Accretion from inner region of a spherically symmetric wind (clumpy wind, magnetic field, transient accretion disk) Accretion from a compressed equatorial disk region. Swift/XRT lightcurve of February 2007 outburst (Romano et al. 2007, A&A 469, L5)

68. IGR J11215-5952 P orb = 165 d, B0.5 Ia P s = 187 s FASTWIND analysis T eff = 24700 K log g = 2.7 @ 7.0 kpc M bol = -9.05 R * = 31 R  M spec = 18 M  M evol = 36 M  From Lorenzo et al. (in prep.) Analysis by A. Herrero & N. Castro (IAC)

69. IGR J11215-5952 ESO 2.2m + FEROS Dec 2006 to Feb 2007 X-ray outburst

70. High Mass X-ray binaries GX 301-2 P orb =41.5 d P s = 696 s B1 Ia + GX 301-2 P orb =41.5 d P s = 696 s B1 Ia + Kaper et al. (2006, A&A 457, 595)

71. A very dense wind and an eccentric orbit Folded X-ray lightcurve and system model, (Watson et al. 1982, MNRAS 199, 915)

72. Excellent fit with a wind + tidal stream model, (Leahy & Kostka 2008, MNRAS 384, 774)

73. It is possible to see the stream Time series for P-Cygni lines in Wray 977 (Kaper et al. 2006, A&A 457, 595)

74. And a disk must form Pulse period in GX301-2 (Koh et al. 1997, ApJ 479, 933) Radial velocities around orbit (Kaper et al. 2006, A&A 457, 595)

75. Summary HMXBs provide excellent laboratories to address a wide variety of astrophysical problems. Classical HMXBs are very bright and persistent. We’re starting to see them in nearby galaxies. SGXBs and SFXTs are likely two manifestations of the same phenomenon, giving us valuable insights into the physics of stellar winds. Be/X-ray binaries are an older population. They are much more numerous and trace star formation (as in the SMC; talk by Coe). Unusual system give us glimpses into the evolution of close binaries.

76. The diversity of High- Mass X-ray binaries Ignacio Negueruela Agios Nikolaos October 2010 where astrologers roam …

77. LS 5039 – orbital solution Casares et al. (2005, MNRAS 364, 899) Paredes 2008, arXiv:0803.1097

79. Where are the low luminosity SGXBs?

80. Bondi-Hoyle-Lyttleton accretion Numerical simulation by Richard Edgar See review: Edgar 2004, New Ast. Rev. 48, 843 Sketch from Foglizzo et al. (2005; A&A 435, 397)

81. Numerical simulations Density contours in complex simulations of wind accretion in a binary (Nagae et al. 2004; A&A 419, 335) Streamlines in complex simulations of wind accretion in a binary (Nagae et al. 2004; A&A 419, 335)

82. Outburst of XTE J1739-302 observed by INTEGRAL on 2003 March 22nd. Fast X-ray transients Long-term RossiXTE lightcurve for SAX J1818.6-1703 Outburst of IGR J16479-4514 observed by INTEGRAL on March 5th 2003 All data from Sguera et al. (2005, A&A 444, 221)

83. Supergiant Fast X-ray transients Optical counterpart to XTE J1739-302 is an O8Iab(f) supergiant at a distance of  2 kpc (Negueruela et al. 2006, ApJ 638,982) Optical counterpart to IGR J17544-2619 is an O9Ib supergiant at  3 kpc Identification of counterparts allows immediate definition of class ( Negueruela et al. 2006, ESA-SP 604 (1), 165 ).