the diversity of high- mass x-ray binaries ignacio negueruela agios nikolaos october 2010 where...
TRANSCRIPT
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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Be/X-ray binariesBe/X-ray binaries
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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Be/X-ray binariesBe/X-ray binaries
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)
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)
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)
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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3at 7.0)(
2at 5.0)(
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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
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rrvGMM
X
XX R
MGML
2rel
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2~
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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)
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
X-rays and winds
A photo-ionization wake in Vela X-1 Kaper et al. (1994, A&A
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
2~
v
GMr
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
Ps= 69 ms (one detection)
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
Ps= 69 ms (one detection)
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
X
XX R
MGML
2rel
Xacc
2~
v
GMr
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) .