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

The diversity of High-Mass X-ray binaries

Ignacio Negueruela

Agios Nikolaos October 2010

where astrologers roam …

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.

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.

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

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X-ray pulsarsModern version of Corbet’s diagram (Corbet 1986, MNRAS 220, 1047)

Be star

Supergiant

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Accretion from the wind of a supergiantAccretion from the wind of a supergiant

Roche-lobe overflow

Roche-lobe overflow

Classes of HMXBs

Be/X-ray binariesBe/X-ray binaries

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Classical HMXB

Cen X-3Cen X-3

SMC X-1SMC X-1

LMC X-4LMC X-4

+ LMC X-1 (BH)+ LMC X-1 (BH)

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 LX detectable in other galaxies

Classical HMXBs

Van der Meer et al. (2007, A&A 473, 523)

Classical HMXBIncipient Roche-lobe overflow

LX 1038 erg s-1

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)

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Note: many more Be/X in the SMCTalk by Coe

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

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

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)

X-ray lightcurvesPersistent sources Relatively low LX ( 1034 erg s-1). Small intensity fluctuations (factor 10) without

an obvious temporal pattern.Transients Quiescence: low (≤ 1035 erg s-1) or non-detectable LX. Series of outbursts with relatively high X-ray

luminosity (Lx 1037 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 Lx > 1037 erg s-1 (Lx ≈ LEdd ), lasting several weeks and not showing modulation with the orbital period (giant or Type II) .

X-ray lightcurve of the persistent Be/X-ray binary X Per (4U 0352+30), taken with the All Sky Monitor on board RossiXTE

Porb = 250.0 d, Pspin = 837.6 s, e = 0.11

X-ray lightcurvesPersistent sources Relatively low LX ( 1034 erg s-1). Small intensity fluctuations (factor 10) without

an obvious temporal pattern.Transients Quiescence: low (≤ 1035 erg s-1) or non-detectable LX. Series of outbursts with relatively high X-ray

luminosity (Lx 1037 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 Lx > 1037 erg s-1 (Lx ≈ LEdd ), lasting several weeks and not showing modulation with the orbital period (giant or Type II) .

Porb = 46.0 d, Pspin = 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

Porb = ? d, Pspin = 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).

Several transients display series of Type I outbursts after (and only after) a giant outburst.

2S 1417-624 Porb = 42.1 d, Pspin= 17.6s, e = 0.45

Optical studies

Reig et al. (2007, A&A 462, 1081)

These changes are generally accompanied by large photometric variability They can be explained as large variations in the disk’s configuration

Optical monitoring reveals strong changes in the line profiles tracers of the disk’s dynamics

The truncated disk modelOkazaki & Negueruela (2001, A&A 377, 161)

If the disk is supported by viscosity, the neutron star exerts a torque on disk particles that makes them lose angular momentum.

The phenomenology observed implies strong interaction between the different system components. This can be easily understood in terms of the decretion disk model.

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.

Model successesThe 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.

But there are exceptions …

KS 1947+300

Porb= 40.4 d, Pspin= 18.7s, e = 0.03

The more Be/X-ray binaries we know, the more difficult it seems to find a common pattern in their behaviour. 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.

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

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

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!

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!

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There’s a correlation here …

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)





Kerkwijk 1989, A&A 223, 196)





Kerkwijk 1989, A&A 223, 196)





Kerkwijk 1989, A&A 223, 196)

y = 0,8836x

R2 = 0,4892

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Evolved O8-B2 stars (luminosity class I)

Evolved O8-B2 stars (luminosity class I)

Vela X-1: Short term flaring Long term variability by a

factor of 4

Supergiant X-ray binaries

Flare from 4U 1907+09Fritz et al. 2006 (A&A 458, 885)

Ribó et al. 2006 (A&A, 449, 687)

Supergiant X-ray binaries

Object Pulse Counterpart PeriodTypical LX

(erg s-1)2S 0114+65 10000 s B1 Iab 11.6 d ~ 1036

Vela X-1 283 s B0.5 Iab 8.9 d ~ 1036

1E 1145.1-6141 297s B2 Iae 14.4 d ~ 1036

GX 301-02 698 s B1 Ia+ 41.5 d ~ 1037

4U 1538-52 529 s B0 I 3.7 d ~ 1036

OAO 1657-415 38 s Ofpe/WNL 10.4 d ~ 1036

4U 1700-37 NO O6.5 Iaf+ 3.4 d ~ 1036

EXO 1722-363 413 s B0-1 I 9.7 d ~ 1036

SAX J1802.7-2017 140 s B1 Ib 4.6 d~ 1036

XTE J1855-026 361 s B0 Iaep 6.1 d ?

4U 1907+09 440 s O8 I 8.4 d ~ 1036

X 1908+075 605 s B1 IIGR

J19140+0951NO B0.5 Ia 13.6 d ~ 1036

Cyg X-1 BH O9.7 Iab 5.6 d ~ 1037

Radiative winds from hot stars

Heavy ions have large Thompson cross sections

The law 0.8 – 1.2

r

Rvrv *

w 1)(

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*w

3at 7.0)(

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Rrvrv

Rrvrv

Review: Kudritzki & Puls 2000, ARA&A, 38, 613

Images stolen from Stan Owocki

Line Scattering: Bound Electron Resonance

Development of instability

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Height (R* )

Velocity

Density

smooth wind

Images stolen from Stan Owocki

Owocki & Rybicki 1984, ApJ, 284, 337cf. Feldmeier et al. 1997, A&A, 322, 878

Wind clumping

Clumping factor Size and geometry of clumps Shells or blobs Optically thin?

1D simulations Runacres & Owocki 2002, A&A, 381, 10152D simulations Dessart & Owocki 2003, A&A, 406, L1Porous 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

Bondi-Hoyle-Lyttleton accretion

r

Rvrv *

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rrvGMM

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2rel

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Dependence of LX on eccentricityReig et al. (2003, A&A 405, 285)

See review: Edgar 2004, New Ast. Rev. 48, 843

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?

This is a complex problem

A photo-ionization wake in Vela X-1 Kaper et al. (1994, A&A

289, 846)


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

X-rays and winds


289, 846)

There is feedback everywhere

Quaintrell et al. (2003, A&A 401, 313)

Tidally induced non-radial pulsations in Vela X-1

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)

Supergiant Fast X-ray transientsA group of flaring sources with very short outbursts and supergiant companions.

Transient emission composed by many flares reaching LX 1036 -1037 erg s-1

Persistent emission at lower luminosity LX 1033 -1034 erg s-1

Deep quiescence at LX 1032 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

Parameters of SFXTs

Optical counterpart to AX 1845.0-0433 (VLT+FORS1)

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

This leaves several options: Difference in wind structure Difference in wind geometry Difference in accretion process

Looking for a difference

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.

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?

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 Pspin ≈ Pcrit.

Bozzo et al. (2008, ApJ 683, 1031) studied the conditions for centrifugal and magnetic inhibition of accretion magnetic inhibition can only happen if B > 1014G (neutron star is a magnetar).

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.

A combination of several things …

Number of clumps that will be inside the accretion radius of the neutron star in one orbit

2rel

Xacc

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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.

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, L37Tavani et al. 1994, ApJL 433, L37

LS 5039 Compact object orbiting

an O6.5 V star.Clark et al. 2001, A&A 376,476Casares et al. 2005, MNRAS

364, 899

Talk by Paredes

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)

2

*0w )(

n

R

rvrv

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,

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

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 Porb= 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+0533H.E.S.S. image of area (Aharonian et al. 2006,

A&A 469, L1)

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1A 0538-66

B0.5 IIIPorb= 16.6 d,

Ps= 69 ms (one detection)

LMC source. Active during the early

80’s LX ~ 1039 erg s-1

1A 0538-66

Porb= 16.6 d, B0.5 III


Charles et al. 1983 (MNRAS 202, 657)

Out of outburst In outburst

Tidally induced mass loss?

Mass –loss rate with orbital angle in the model of Stevens (1988, MNRAS 232, 199) for A0535-66 (Porb= 17 d, e = 0.7)

1A 0538-66

Porb= 16.6 d, B0.5 III


Photometric period of 421d likely stable over >80 years (McGowan & Charles 2003; MNRAS 3359, 748)

H in 2004

Alternative channel for a Be/X

Case C q << 1 Fully non-conservative case Results in Be+NS

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IGR J00370+6122

IGR J00370+6122 = BD +60° 73

Spectral type BN0.5 II-IIIReig 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)

IGR J00370+6122 = BD +60° 73

Light curve typical of wind accretor (in’t Zand et al. 2007, A&A 469, 1063)

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IGR J11215-5952

IGR J11215-5952

Porb= 165 d, B0.5 Ia

Ps= 187 sAccretion 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)

IGR J11215-5952

Porb= 165 d, B0.5 Ia

Ps= 187 s

FASTWIND analysis

Teff = 24700 K

log g = 2.7

@ 7.0 kpc

Mbol = -9.05

R* = 31 R

Mspec= 18 M

Mevol= 36 M

From Lorenzo et al. (in prep.)Analysis by A. Herrero & N. Castro (IAC)

IGR J11215-5952

ESO 2.2m + FEROS Dec 2006 to

Feb 2007

X-ray outburst

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High Mass X-ray binaries

GX 301-2Porb=41.5 d Ps = 696 s

B1 Ia+

GX 301-2Porb=41.5 d Ps = 696 s

B1 Ia+

Kaper et al. (2006, A&A 457, 595)

A very dense wind and an eccentric orbit

Folded X-ray lightcurve and system model,

(Watson et al. 1982, MNRAS 199, 915)

Excellent fit with a wind + tidal stream model,

(Leahy & Kostka 2008, MNRAS 384, 774)

It is possible to see the stream

Time series for P-Cygni lines in Wray 977

(Kaper et al. 2006, A&A 457, 595)

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)

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.

The diversity of High-Mass X-ray binaries

Ignacio Negueruela

Agios Nikolaos October 2010

where astrologers roam …

LS 5039 – orbital solution

Casares et al. (2005, MNRAS 364, 899)

Paredes 2008, arXiv:0803.1097

Where are the low luminosity SGXBs?

1s km1000 v 1s km2000

v

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rel

w2X rv

rrvGMM

Bondi-Hoyle-Lyttleton accretion

r

Rvrv *

w 1)(

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rrvGMM

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XX R

MGML

2rel

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Numerical simulation by Richard Edgar

See review: Edgar 2004, New Ast. Rev. 48, 843

Sketch from Foglizzo et al.

(2005; A&A 435, 397)

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)

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)

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) .

Documents

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