On the location and properties ofthe GeV and TeV emitters of LS 5039
Vıctor Zabalza
Max-Planck Institut fur Kernphysik, Heidelberg
April 17, 2013
Workshop on Variable Galactic Gamma-Ray Sources
Vıctor Zabalza (MPIK) The GeV and TeV components of LS 5039 1 / 18
LS 5039
−3 −2 −1 0 1 2×1012
−3
−2
−1
0
1
2
×1012
to observer
Superior conjunction
Inferior conjunction
Vıctor Zabalza (MPIK) The GeV and TeV components of LS 5039 2 / 18
Multi-wavelength view: TeV
Orbital Phase0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2
]-1
s-2
ph
cm
-12
F >
1 T
eV
[1
0
0
1
2
3
4
5
Su
peri
or
Co
nju
ncti
on
Infe
rio
r
Co
nju
ncti
on
Infe
rio
r
Co
nju
ncti
on
Su
peri
or
Co
nju
ncti
on
Ap
astr
on
Peri
astr
on
Ap
astr
on
(Aharonian et al. 2005)
Vıctor Zabalza (MPIK) The GeV and TeV components of LS 5039 3 / 18
Multi-wavelength view: TeV
E (eV)
1110 121013
10 1410
)-1
s-2
F(E
) (e
rg c
m×
2E
-1310
-1210
-1110INFC
0.9≤ φ0.45 <
SUPC
> 0.9φ 0.45 and ≤ φ
(Aharonian et al. 2005)
Vıctor Zabalza (MPIK) The GeV and TeV components of LS 5039 3 / 18
Multi-wavelength view: GeV
2.5 year Fermi-LAT results:
Energy [MeV]
310 410
510
610 710
]1
s2
F(E
) [
erg
cm
2E
1310
1210
1110
1010
Fermi, 30 months
H.E.S.S., SUPC, 2004/05
H.E.S.S., INFC, 2004/05
(Hadasch et al. 2011)
Vıctor Zabalza (MPIK) The GeV and TeV components of LS 5039 4 / 18
Multi-wavelength view: GeV
2.5 year Fermi-LAT results:
Energy [MeV]
310 410
510
610 710
]1
s2
F(E
) [
erg
cm
2E
1310
1210
1110
1010
Fermi, INFC
Fermi, SUPC
H.E.S.S., SUPC, 2004/05
H.E.S.S., INFC, 2004/05
(Hadasch et al. 2011)
Vıctor Zabalza (MPIK) The GeV and TeV components of LS 5039 4 / 18
Is a single GeV/TeV emitter possible?
The GeV and TeV components are dicult to reconcile with a singleIC emitter,
Statistically signi cant exponential cuto at few GeV would requirecomplex injection spectrum.
In a binary pulsar scenario, most of the energy is injected inside theorbit, but γγ absorption precludes a deep TeV emitter.
and a synchroton/IC scenario would require an extremely highmagnetic eld (∼ 100 G).
Under synchrotron dominant losses, particle spectrum would evolvetowards a particle index of −3, resulting in too soft GeV and TeV spectra.
Vıctor Zabalza (MPIK) The GeV and TeV components of LS 5039 5 / 18
Is a single GeV/TeV emitter possible?
The GeV and TeV components are dicult to reconcile with a singleIC emitter,
Statistically signi cant exponential cuto at few GeV would requirecomplex injection spectrum.
In a binary pulsar scenario, most of the energy is injected inside theorbit, but γγ absorption precludes a deep TeV emitter.
and a synchroton/IC scenario would require an extremely highmagnetic eld (∼ 100 G).
Under synchrotron dominant losses, particle spectrum would evolvetowards a particle index of −3, resulting in too soft GeV and TeV spectra.
Vıctor Zabalza (MPIK) The GeV and TeV components of LS 5039 5 / 18
Is a single GeV/TeV emitter possible?
The GeV and TeV components are dicult to reconcile with a singleIC emitter,
Statistically signi cant exponential cuto at few GeV would requirecomplex injection spectrum.
In a binary pulsar scenario, most of the energy is injected inside theorbit, but γγ absorption precludes a deep TeV emitter.
and a synchroton/IC scenario would require an extremely highmagnetic eld (∼ 100 G).
Under synchrotron dominant losses, particle spectrum would evolvetowards a particle index of −3, resulting in too soft GeV and TeV spectra.
Vıctor Zabalza (MPIK) The GeV and TeV components of LS 5039 5 / 18
Is a single GeV/TeV emitter possible?
The GeV and TeV components are dicult to reconcile with a singleIC emitter,
Statistically signi cant exponential cuto at few GeV would requirecomplex injection spectrum.
In a binary pulsar scenario, most of the energy is injected inside theorbit, but γγ absorption precludes a deep TeV emitter.
and a synchroton/IC scenario would require an extremely highmagnetic eld (∼ 100 G).
Under synchrotron dominant losses, particle spectrum would evolvetowards a particle index of −3, resulting in too soft GeV and TeV spectra.
Vıctor Zabalza (MPIK) The GeV and TeV components of LS 5039 5 / 18
Is a single GeV/TeV emitter possible?
The GeV and TeV components are dicult to reconcile with a singleIC emitter,
Statistically signi cant exponential cuto at few GeV would requirecomplex injection spectrum.
In a binary pulsar scenario, most of the energy is injected inside theorbit, but γγ absorption precludes a deep TeV emitter.
and a synchroton/IC scenario would require an extremely highmagnetic eld (∼ 100 G).
Under synchrotron dominant losses, particle spectrum would evolvetowards a particle index of −3, resulting in too soft GeV and TeV spectra.
Vıctor Zabalza (MPIK) The GeV and TeV components of LS 5039 5 / 18
Requirements for TeV emitter
An injected particle spectrum with: High energy cuto at Ee ∼ 10 TeV→ extremely high accelerationeciency.
Dominant IC losses up to Ee ∼ 10 TeV to avoid KN TeV spectrumsoftening→ low B
A location distant from the star is needed to avoid τγγ ≫ 1. Flux at Eγ > 100 GeV likely modulated by γγ absorption: SUPC ↓, INFC ↑
Vıctor Zabalza (MPIK) The GeV and TeV components of LS 5039 6 / 18
Requirements for TeV emitter
An injected particle spectrum with: High energy cuto at Ee ∼ 10 TeV→ extremely high accelerationeciency.
Dominant IC losses up to Ee ∼ 10 TeV to avoid KN TeV spectrumsoftening→ low B
A location distant from the star is needed to avoid τγγ ≫ 1. Flux at Eγ > 100 GeV likely modulated by γγ absorption: SUPC ↓, INFC ↑
Vıctor Zabalza (MPIK) The GeV and TeV components of LS 5039 6 / 18
Requirements for TeV emitter
An injected particle spectrum with: High energy cuto at Ee ∼ 10 TeV→ extremely high accelerationeciency.
Dominant IC losses up to Ee ∼ 10 TeV to avoid KN TeV spectrumsoftening→ low B
A location distant from the star is needed to avoid τγγ ≫ 1. Flux at Eγ > 100 GeV likely modulated by γγ absorption: SUPC ↓, INFC ↑
Vıctor Zabalza (MPIK) The GeV and TeV components of LS 5039 6 / 18
Requirements for TeV emitter (II)
1012 1013
Distance to star [1013 cm]
10−3
10−2
10−1
100
Mag
net
icfi
eld[G]
ηacc = 20
ηacc =
5η
acc =10
ηacc =
20η
acc =50
ηacc =
100 0.01
0.1
1
10
100
min
(Eb
reak
,Em
ax)[T
eV]
Vıctor Zabalza (MPIK) The GeV and TeV components of LS 5039 7 / 18
Requirements for GeV emitter
High eciency in converting pulsar wind power into non-thermalluminosity.
Ecient pulsar wind con nement and particle acceleration, Ecient non-thermal emission mechanism (IC in dense radiation eld).
An injected particle spectrum with: High energy cuto at Ee ∼ 10 GeV→ low acceleration eciency Low energy cuto at Ee ∼ (10 − 100)MeV
A location close to the compact object provides good temporalbehaviour:
High emission during superior conjunction Low emission during inferior conjunction
Vıctor Zabalza (MPIK) The GeV and TeV components of LS 5039 8 / 18
Requirements for GeV emitter
High eciency in converting pulsar wind power into non-thermalluminosity.
Ecient pulsar wind con nement and particle acceleration, Ecient non-thermal emission mechanism (IC in dense radiation eld).
An injected particle spectrum with: High energy cuto at Ee ∼ 10 GeV→ low acceleration eciency Low energy cuto at Ee ∼ (10 − 100)MeV
A location close to the compact object provides good temporalbehaviour:
High emission during superior conjunction Low emission during inferior conjunction
Vıctor Zabalza (MPIK) The GeV and TeV components of LS 5039 8 / 18
Requirements for GeV emitter
High eciency in converting pulsar wind power into non-thermalluminosity.
Ecient pulsar wind con nement and particle acceleration, Ecient non-thermal emission mechanism (IC in dense radiation eld).
An injected particle spectrum with: High energy cuto at Ee ∼ 10 GeV→ low acceleration eciency Low energy cuto at Ee ∼ (10 − 100)MeV
A location close to the compact object provides good temporalbehaviour:
High emission during superior conjunction Low emission during inferior conjunction
Vıctor Zabalza (MPIK) The GeV and TeV components of LS 5039 8 / 18
Candidate locations in a binary pulsar
Typical view of pulsar binary:
shoc
ked pu
lsar wind
shoc
ked
stel
lar w
ind
pulsar wind
stellar wind
star pulsar
0.5 1.0 1.5 2.0 2.
Sketch from Szostek & Dubus (2011)
Vıctor Zabalza (MPIK) The GeV and TeV components of LS 5039 9 / 18
Candidate locations in a binary pulsar
However, considering orbital motion yields a dierent picture:
Star
Shocked pu
lsar wind
Shocked stellar wind
Orbitalmotion
Pulsar
Vıctor Zabalza (MPIK) The GeV and TeV components of LS 5039 10 / 18
Candidate locations in a binary pulsar
However, considering orbital motion yields a dierent picture:
Star
Shocked pu
lsar wind
Shocked stellar wind
Windstando
Coriolisturnover
Orbitalmotion
Pulsar
Vıctor Zabalza (MPIK) The GeV and TeV components of LS 5039 10 / 18
Location of the emitters
TeV emitter at Coriolis turnoverIts distance from the pulsar x0 can be approximated from the balance ofpulsar wind ram pressure,
x0 ≈ (Lsdvw
(2Ω)2cMw)
1/2∝ R2orb
GeV emitter at wind standoLocated at the balance location between the pulsar and stellar winds:
Rs =Rorb
1 +√η, where η =
Lsd/cMwvw
.
The postshock ow will have relativistic bulk velocity in the radialdirection away from the star. (Bogovalov et al. 2009)
Vıctor Zabalza (MPIK) The GeV and TeV components of LS 5039 11 / 18
Location of the emitters
TeV emitter at Coriolis turnoverIts distance from the pulsar x0 can be approximated from the balance ofpulsar wind ram pressure,
x0 ≈ (Lsdvw
(2Ω)2cMw)
1/2∝ R2orb
GeV emitter at wind standoLocated at the balance location between the pulsar and stellar winds:
Rs =Rorb
1 +√η, where η =
Lsd/cMwvw
.
The postshock ow will have relativistic bulk velocity in the radialdirection away from the star. (Bogovalov et al. 2009)
Vıctor Zabalza (MPIK) The GeV and TeV components of LS 5039 11 / 18
Location of the emitters
TeV emitter at Coriolis turnoverIts distance from the pulsar x0 can be approximated from the balance ofpulsar wind ram pressure,
x0 ≈ (Lsdvw
(2Ω)2cMw)
1/2∝ R2orb
GeV emitter at wind standoLocated at the balance location between the pulsar and stellar winds:
Rs =Rorb
1 +√η, where η =
Lsd/cMwvw
.
The postshock ow will have relativistic bulk velocity in the radialdirection away from the star. (Bogovalov et al. 2009)
Vıctor Zabalza (MPIK) The GeV and TeV components of LS 5039 11 / 18
Proposed emitter locations
Pulsar orbit
Wind stando
Coriolis turnover
−6 −4 −2 0 2 4×1012
−6
−4
−2
0
2
4×1012
to observer
Vıctor Zabalza (MPIK) The GeV and TeV components of LS 5039 12 / 18
A simple model to test the candidate locations
We consider a One Zone model at each of the proposed emitterlocations aligned with the star-pulsar axis as the pulsar orbits aroundthe star.
We consider the stationary electron spectrum owing to IC,synchrotron and escape losses, and compute synchrotron and ICspectra.
The injected luminosity required is of 7% and 4% of the pulsarspin-down luminosity for the stando and coriolis turnover locations,respectively.
Vıctor Zabalza (MPIK) The GeV and TeV components of LS 5039 13 / 18
A simple model to test the candidate locations
We consider a One Zone model at each of the proposed emitterlocations aligned with the star-pulsar axis as the pulsar orbits aroundthe star.
We consider the stationary electron spectrum owing to IC,synchrotron and escape losses, and compute synchrotron and ICspectra.
The injected luminosity required is of 7% and 4% of the pulsarspin-down luminosity for the stando and coriolis turnover locations,respectively.
Vıctor Zabalza (MPIK) The GeV and TeV components of LS 5039 13 / 18
A simple model to test the candidate locations
We consider a One Zone model at each of the proposed emitterlocations aligned with the star-pulsar axis as the pulsar orbits aroundthe star.
We consider the stationary electron spectrum owing to IC,synchrotron and escape losses, and compute synchrotron and ICspectra.
The injected luminosity required is of 7% and 4% of the pulsarspin-down luminosity for the stando and coriolis turnover locations,respectively.
Vıctor Zabalza (MPIK) The GeV and TeV components of LS 5039 13 / 18
Results: SED
108 109 1010 1011 1012 1013 1014
E [eV]
10−13
10−12
10−11
10−10
10−9
E2 d
N/d
E[e
rgcm−
2s−
1 ]
INFC SumSUPC SumINFC, FermiSUPC, FermiINFC, HESSSUPC, HESS
Vıctor Zabalza (MPIK) The GeV and TeV components of LS 5039 14 / 18
Results: lightcurves
Orbital phase (φ)0.00.20.40.60.81.01.21.41.6
F E>
100
MeV
[10−
6ph
cm−
2s−
1 ]
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0Orbital phase (φ)
02468
10121416
F 0.2−
5Te
V[1
0−12
erg
cm−
2s−
1 ] Sup
erio
rco
njun
ctio
n
Apa
stro
n
Peria
stro
n
Infe
rior
conj
unct
ion
Vıctor Zabalza (MPIK) The GeV and TeV components of LS 5039 15 / 18
Results
Good qualitative agreement with GeV/TeV spectra and lightcurves!
Doppler boosting at wind stando emitter is required to avoidsymmetrical lightcurve peak and much larger variability fraction. Agood t is obtained with vf ≈ 0.2c→ good test for the presence ofboosting!
However, X-ray emission is not well reproduced from neither emitter: A stronger magnetic eld than B ≈ 0.3 G at the Coriolis turnover wouldresult in too soft TeV spectra.
The lower electrons energies at wind stando position require unlikelyhigh magnetic elds to radiate at keV.
Vıctor Zabalza (MPIK) The GeV and TeV components of LS 5039 16 / 18
Results
Good qualitative agreement with GeV/TeV spectra and lightcurves! Doppler boosting at wind stando emitter is required to avoidsymmetrical lightcurve peak and much larger variability fraction. Agood t is obtained with vf ≈ 0.2c→ good test for the presence ofboosting!
However, X-ray emission is not well reproduced from neither emitter: A stronger magnetic eld than B ≈ 0.3 G at the Coriolis turnover wouldresult in too soft TeV spectra.
The lower electrons energies at wind stando position require unlikelyhigh magnetic elds to radiate at keV.
Vıctor Zabalza (MPIK) The GeV and TeV components of LS 5039 16 / 18
Results
Good qualitative agreement with GeV/TeV spectra and lightcurves! Doppler boosting at wind stando emitter is required to avoidsymmetrical lightcurve peak and much larger variability fraction. Agood t is obtained with vf ≈ 0.2c→ good test for the presence ofboosting!
However, X-ray emission is not well reproduced from neither emitter: A stronger magnetic eld than B ≈ 0.3 G at the Coriolis turnover wouldresult in too soft TeV spectra.
The lower electrons energies at wind stando position require unlikelyhigh magnetic elds to radiate at keV.
Vıctor Zabalza (MPIK) The GeV and TeV components of LS 5039 16 / 18
Conclusions
The binary pulsar scenario can provide a natural explanation for theorigin of the GeV and TeV components in LS 5039: the wind standoand Coriolis turnover locations.
Samemodel could be used in binaries with known stellar windproperties (i.e., 1FGL J1018.6−5956).
Turbulence could be included by using hydrodynamical simulationsas input for location and energetics of shocks.
Vıctor Zabalza (MPIK) The GeV and TeV components of LS 5039 17 / 18
Conclusions
The binary pulsar scenario can provide a natural explanation for theorigin of the GeV and TeV components in LS 5039: the wind standoand Coriolis turnover locations.
Samemodel could be used in binaries with known stellar windproperties (i.e., 1FGL J1018.6−5956).
Turbulence could be included by using hydrodynamical simulationsas input for location and energetics of shocks.
Vıctor Zabalza (MPIK) The GeV and TeV components of LS 5039 17 / 18
Conclusions
The binary pulsar scenario can provide a natural explanation for theorigin of the GeV and TeV components in LS 5039: the wind standoand Coriolis turnover locations.
Samemodel could be used in binaries with known stellar windproperties (i.e., 1FGL J1018.6−5956).
Turbulence could be included by using hydrodynamical simulationsas input for location and energetics of shocks.
Vıctor Zabalza (MPIK) The GeV and TeV components of LS 5039 17 / 18