ON THE ORIGIN OF

X-RAY /VHE CORRELATION IN LS I +61 303

Vıctor Zabalza

with Josep Maria Paredes and Valentı Bosch-Ramon

Departament d’Astronomia i Meteorologia,Institud de Ciencies del Cosmos (ICC),

Universitat de Barcelona (IEEC-UB)

December 2, 2010

Vıctor Zabalza On the Origin of X-ray/VHE Correlation in LS I +61 303 1 / 19

Contents

1 The γ-ray loud X-ray binary LS I +61 303

2 Model description

3 Results

4 Summary

Vıctor Zabalza On the Origin of X-ray/VHE Correlation in LS I +61 303 2 / 19

Contents

1 The γ-ray loud X-ray binary LS I +61 303

2 Model description

3 Results

4 Summary

Vıctor Zabalza On the Origin of X-ray/VHE Correlation in LS I +61 303 3 / 19

LS I +61 303

◮ Night-to-night variability in VHE, X-ray.

◮ Kilosecond/hour scale variability in X-ray

◮ Long-term four year superorbital radio peak modulation(Paredes 1987) on top of orbital varibility.

◮ SGR-like burst lasting ∼0.5 s in hard X rays (de Pasquale etal. 2008, GCN 8209).

Vıctor Zabalza On the Origin of X-ray/VHE Correlation in LS I +61 303 4 / 19

LS I +61 303

◮ Night-to-night variability in VHE, X-ray.

◮ Kilosecond/hour scale variability in X-ray

◮ Long-term four year superorbital radio peak modulation(Paredes 1987) on top of orbital varibility.

◮ SGR-like burst lasting ∼0.5 s in hard X rays (de Pasquale etal. 2008, GCN 8209).

◮ Orbital periodicity (26.5 d) in radio, X-ray, HE and VHE γ-ray.

◮ Periodic outbursts in X-ray and VHE in 0.6 < φ < 1.0, whilemaximum in HE is around 0.0 < φ < 0.4.

Vıctor Zabalza On the Origin of X-ray/VHE Correlation in LS I +61 303 4 / 19

LS I +61 303

Orbital phase

]-1

s-2

cm

-12

F(E

>400 G

eV) [10

0 0.2 0.4 0.6 0.8 0 0.2 0.4 0.6 0.8 1

10

5

0

-5

INTEGRAL Hard X-ray(Hermsen et al. 2006)

Fermi HE γ-ray(Abdo et al. 2009)

MAGIC VHE γ-ray(Albert et al. 2009)

Vıctor Zabalza On the Origin of X-ray/VHE Correlation in LS I +61 303 5 / 19

LS I +61 303

Orbital phase

]-1

s-2

cm

-12

F(E

>400 G

eV) [10

0 0.2 0.4 0.6 0.8 0 0.2 0.4 0.6 0.8 1

10

5

0

-5

INTEGRAL Hard X-ray(Hermsen et al. 2006)

Fermi HE γ-ray(Abdo et al. 2009)

MAGIC VHE γ-ray(Albert et al. 2009)

But NOT stable! See talks by Diego, Tobias, Gernot.

Vıctor Zabalza On the Origin of X-ray/VHE Correlation in LS I +61 303 5 / 19

VHE/X-ray Multiwavelength observations

0

5

10

15

20

25

[10−

12 c

m−

2 s−

1 ]

MAGIC

0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1

Orbital phase

54345 54350 54355 54360 54365MJD (JD−2400000.5)

0

5

10

15

20

25

[10−

12 e

rg c

m−

2 s−

1 ]

XMM−Newton Swift/XRT

N (

E>

300

GeV

)F

(0.

3−10

keV

)

◮ MAGIC, XMM-Newton andSwift campaign covering∼ 60% of an orbital periodin 2007 (Anderhub etal. 2009, ApJ, 706, L27).

◮ X-ray (XMM-Newton andSwift) and VHE (MAGIC)∼ 17 observations.

◮ Significant correlation:r = 0.81+0.06

−0.21 (r = 0.97 forfirst outburst)

Vıctor Zabalza On the Origin of X-ray/VHE Correlation in LS I +61 303 6 / 19

VHE/X-ray Multiwavelength observations

−1 −0.5 0 0.5 1 1.5 2x/a

−1

−0.5

0

0.5

1

1.5

2

y/

a

to observer0.275

0.775

0.313

0.081

◮ MAGIC, XMM-Newton andSwift campaign covering∼ 60% of an orbital periodin 2007 (Anderhub etal. 2009, ApJ, 706, L27).

◮ X-ray (XMM-Newton andSwift) and VHE (MAGIC)∼ 17 observations.

◮ Significant correlation:r = 0.81+0.06

−0.21 (r = 0.97 forfirst outburst)

Vıctor Zabalza On the Origin of X-ray/VHE Correlation in LS I +61 303 6 / 19

VHE/X-ray Multiwavelength observations

−5 0 5 10 15 20N (E> 300 GeV) [10

−12 cm

−2 s

−1]

10

15

20

25

F (

0.3−

10 k

eV)

[10−

12 e

rg c

m−

2 s−

1 ]

MAGIC/XMM−Newton MAGIC/Swift

FX/[10−12 erg/cm2/s] = 12.2+0.9−1.0 + (0.71+0.17

−0.14)× FTeV/[10−12 ph/cm2/s]

Vıctor Zabalza On the Origin of X-ray/VHE Correlation in LS I +61 303 7 / 19

Contents

1 The γ-ray loud X-ray binary LS I +61 303

2 Model description

3 Results

4 Summary

Vıctor Zabalza On the Origin of X-ray/VHE Correlation in LS I +61 303 8 / 19

Model description

◮ Emitter located at the position of the compact object.

◮ OZM: Homogeneous physical properties throughout theemitter.

◮ Constant magnetic field along the orbit.

Vıctor Zabalza On the Origin of X-ray/VHE Correlation in LS I +61 303 9 / 19

Model description

◮ Emitter located at the position of the compact object.

◮ OZM: Homogeneous physical properties throughout theemitter.

◮ Constant magnetic field along the orbit.

Simultaneous modulation: dominant adiabatic losses

◮ Ultimately related to (magneto)hydrodynamical processes in theaccelerator and emitter regions: naturally present in a variablepressure environment.

Khangulyan et al. (2007) and Takahashi et al. (2009) take the sameapproach for PSR B1259-63 and LS 5039.

Vıctor Zabalza On the Origin of X-ray/VHE Correlation in LS I +61 303 9 / 19

Model description

◮ Emitter located at the position of the compact object.

◮ OZM: Homogeneous physical properties throughout theemitter.

◮ Constant magnetic field along the orbit.

Simultaneous modulation: dominant adiabatic losses

◮ Ultimately related to (magneto)hydrodynamical processes in theaccelerator and emitter regions: naturally present in a variablepressure environment.

◮ Adiabatic losses inferred from X-ray flux above pedestal(F ped

X = 11.5 × 10−12 erg/cm2/s)

Khangulyan et al. (2007) and Takahashi et al. (2009) take the sameapproach for PSR B1259-63 and LS 5039.

Vıctor Zabalza On the Origin of X-ray/VHE Correlation in LS I +61 303 9 / 19

Model description

◮ Emitter located at the position of the compact object.

◮ OZM: Homogeneous physical properties throughout theemitter.

◮ Constant magnetic field along the orbit.

Simultaneous modulation: dominant adiabatic losses

◮ Ultimately related to (magneto)hydrodynamical processes in theaccelerator and emitter regions: naturally present in a variablepressure environment.

◮ Adiabatic losses inferred from X-ray flux above pedestal(F ped

X = 11.5 × 10−12 erg/cm2/s)

◮ X-ray photon index (ΓX ≃ 1.5) matches a αe = 2 injection spectrum

Khangulyan et al. (2007) and Takahashi et al. (2009) take the sameapproach for PSR B1259-63 and LS 5039.

Vıctor Zabalza On the Origin of X-ray/VHE Correlation in LS I +61 303 9 / 19

Model description: Derivation of t ad

0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2Orbital Phase

0

5

10

15

20

25

F(0.3

−10

keV)[

10−

12erg/cm

2/s]

XMM-NewtonSwift/XRT

Vıctor Zabalza On the Origin of X-ray/VHE Correlation in LS I +61 303 10 / 19

Model description: Derivation of t ad

0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2Orbital Phase

0

5

10

15

20

25

F(0.3

−10

keV)[

10−

12erg/cm

2/s]

XMM-NewtonSwift/XRT

Vıctor Zabalza On the Origin of X-ray/VHE Correlation in LS I +61 303 10 / 19

Model description: Derivation of t ad

0.2 0.4 0.6 0.8 1 1.2

Orbital Phase

101

102

103

104

t cool

[s]

Synchrotron

IC

Adiabatic

◮ Requirements for tad:◮ tad ∝ FX◮ tad < min(tIC, tsyn)

Obtained tad : tens to hundreds of seconds

Vıctor Zabalza On the Origin of X-ray/VHE Correlation in LS I +61 303 11 / 19

Model description (II)

◮ Constant injection spectrum: Power-law with high energycutoff at balance of tacc = ηRL/c and tcool:

Ee,max ≈ 9BGtadη−1 TeV for adiabatic

Ee,max ≈ 60(BGη)−1/2 TeV for synchrotron

◮ To obtain 10 TeV electrons: η . min(BGtad , 40B−1G )

Vıctor Zabalza On the Origin of X-ray/VHE Correlation in LS I +61 303 12 / 19

Model description (II)

◮ Constant injection spectrum: Power-law with high energycutoff at balance of tacc = ηRL/c and tcool:

Ee,max ≈ 9BGtadη−1 TeV for adiabatic

Ee,max ≈ 60(BGη)−1/2 TeV for synchrotron

◮ To obtain 10 TeV electrons: η . min(BGtad , 40B−1G )

◮ Steady state electron energy distribution at each phase:

n(φ, γe) =1|γ|

∫ γmaxe

γe

Q(γ′) dγ′

◮ Orbital parameters from Aragona et al. (2009, ApJ, 698, 514)and i = 45◦

Vıctor Zabalza On the Origin of X-ray/VHE Correlation in LS I +61 303 12 / 19

Contents

1 The γ-ray loud X-ray binary LS I +61 303

2 Model description

3 Results

4 Summary

Vıctor Zabalza On the Origin of X-ray/VHE Correlation in LS I +61 303 13 / 19

Results: MW lightcurveN(E

>30

0GeV

)[

10−

12ph/cm

2/s]

MAGIC

0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2Orbital Phase

0

0

5

5

10

10

15

15

20

20

25

F(0.3

−10

keV

)[

10−

12erg/cm

2/s]

XMM-NewtonSwift/XRT

B = 0.22 G η = 10 Linj ∼ 1035 erg/s

Vıctor Zabalza On the Origin of X-ray/VHE Correlation in LS I +61 303 14 / 19

Results: SED during outburst (0 .6 <φ< 0.7)

101 102 103 104 105 106 107 108 109 1010 1011 1012 1013 1014

Eph [eV]

1031

1032

1033

1034

1035

E2d

Nγ/d

E[e

rg/s

] ◮ SED averaged overthe phases of threeobservations duringthe first outburst.

◮ Best agreement:◮ αe = 2.1◮ η = 7–120

Vıctor Zabalza On the Origin of X-ray/VHE Correlation in LS I +61 303 15 / 19

Phase averaged ( 0 < φ < 1) SED: Fermi

108 109 1010 1011 1012 1013 1014

Eph [eV]

1031

1032

1033

1034

1035

E2d

Nγ/d

E[e

rg/s

]

MAGIC spectrum NOT simultaneous

Fermi data in 10–100 GeVrequire a harder particledistribution belowEe = 4 × 1011 eV.

αe

{

. 1.8 if Ee < Ebreak

= 2.1 if Ee > Ebreak

Vıctor Zabalza On the Origin of X-ray/VHE Correlation in LS I +61 303 16 / 19

Contents

1 The γ-ray loud X-ray binary LS I +61 303

2 Model description

3 Results

4 Summary

Vıctor Zabalza On the Origin of X-ray/VHE Correlation in LS I +61 303 17 / 19

Summary

◮ Simultaneous X-ray/VHE campaign provides great data toprobe emitter

◮ Adiabatically dominated OZM effective to isolate the emitter’sproperties:

◮ B ≃ 0.22 G◮ Adiabatic timescales from few tens to few hundreds of

seconds.◮ Efficient accelerator: η = 7 − 130

Vıctor Zabalza On the Origin of X-ray/VHE Correlation in LS I +61 303 18 / 19

Summary

◮ Simultaneous X-ray/VHE campaign provides great data toprobe emitter

◮ Adiabatically dominated OZM effective to isolate the emitter’sproperties:

◮ B ≃ 0.22 G◮ Adiabatic timescales from few tens to few hundreds of

seconds.◮ Efficient accelerator: η = 7 − 130

◮ Results are unable to clearly discern accreting/non-accreting,but poses constraint on future modeling.

◮ GeV component has different origin than the X-ray/VHEemission.

Vıctor Zabalza On the Origin of X-ray/VHE Correlation in LS I +61 303 18 / 19

Summary

◮ Simultaneous X-ray/VHE campaign provides great data toprobe emitter

◮ Adiabatically dominated OZM effective to isolate the emitter’sproperties:

◮ B ≃ 0.22 G◮ Adiabatic timescales from few tens to few hundreds of

seconds.◮ Efficient accelerator: η = 7 − 130

◮ Results are unable to clearly discern accreting/non-accreting,but poses constraint on future modeling.

◮ GeV component has different origin than the X-ray/VHEemission.

For more information: arXiv:1011.4489

Vıctor Zabalza On the Origin of X-ray/VHE Correlation in LS I +61 303 18 / 19

ON THE ORIGIN OF

X-RAY /VHE CORRELATION IN LS I +61 303

Vıctor Zabalza

with Josep Maria Paredes and Valentı Bosch-Ramon

Departament d’Astronomia i Meteorologia,Institud de Ciencies del Cosmos (ICC),

Universitat de Barcelona (IEEC-UB)

December 2, 2010

Vıctor Zabalza On the Origin of X-ray/VHE Correlation in LS I +61 303 19 / 19