Sin ttulo de diapositiva

1
Josep M. Paredes
HE AND VHE EMISSION FROM X-RAY BINARIES
Locating PeV Cosmic-Ray Accelerators Future
Detectors in Multi-TeV Gamma-Ray
Astronomy Adelaide, 6-8 December 2006
2
OUTLINE

• X-ray binaries
• How many microquasars we know
• µqs as HE and VHE ?-ray sources
• Theoretical
  point of view
• 
  Observational point of view
• 4. µqs, gamma-ray binaries,..
• 5. Summary

3
Microquasars X-ray binaries with relativistic
jets
XB A binary system containing a compact object
(NS or a stellar-mass BH) accreting matter from
the companion star. The accreted matter forms an
accretion disc, responsible for the X-ray
emission. A total of 280 XB (Liu et al. 2000,
2001). HMXBs (131) Optical companion with
spectral type O or B. Mass transfer via decretion
disc (Be stars) or via strong wind or Roche-lobe
overflow. LMXBs (149) Optical companion with
spectral type later than B. Mass transfer via
Roche-lobe overflow.
8 HMXBs 35 LMXBs
280 XB 43 (15) REXBs
At least 15 microquasars
Maybe the majority of RXBs are microquasars
(Fender 2001)
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MICROQUASARS IN OUR GALAXY High Energy Detections
Name Mcomp Radio Jet
INTEGRAL BATSE COMPTEL
EGRET Others (M?)
p/t ?app Size Note 30-50 keV
40-100 keV 20-100 keV 160-430 keV 1-30 MeV
gt100 MeV
(AU) (significance) (count/s)
(significance) (mCrab) High Mass X-ray
Binaries LS I 61 303 ? p ?
0.4 10 ?700 Prec ? 7.1 2.4 0.5
5.2 5.1 2.1 yes?
3EGJ02416103 MAGIC V4641 Sgr 9.6
t ? 9.5 ?
? ? ? ?
? ? LS 5039
5.4 p 0.18 10 ?1000 Prec
? 8.0 1.7 0.2 10.7 3.7
1.8 yes? 3EGJ1824 ?1514 HESS SS
433 115? p 0.26
104 ?106 Prec. 94.7 5.2 0.2
21.7 0.0 2.8 ?
?
Hadronic, X-ray jet Cygnus X-1
10.1 p ? 40
4651 876.7 0.3 1186.8 924.5 2.5
yes ? Cygnus X-3
? p 0.69 104 Radio outb.
1096 78.3 0.3 197.8 15.5 2.1
? ?
Low Mass X-ray Binaries

Circinus X-1 ?
t gt 15 gt104
99.1 0.6 0.2 3.8
0.3 2.6 ? ? XTE
J1550-564 9.4 t ? 2 103
X-ray jet 738 55.3 0.2 17.1
-2.3 2.5 ?
? Scorpius X-1 1.4 p 0.68
40 2422 24.7 0.3
460.6 9.9 2.2 ?
? GRO J1655-40 7.02 t 1.1
8000 Prec? 59 2.7 0.2 40.6
23.4 3.9 ? ?

GX 339-4 5.8 0.5 t ?
lt 4000 306 46.7 0.2
89.0 58.0 3.5 ?
? 1E 1740.7-2942 ? p ?
106 147.3 4.32
0.03 92.4 61.2 3.7 ?
? XTE J1748-288 gt 4.5? t
1.3 gt 104 ?
? -12.4 ?
? ? GRS 1758-258
? p ? 106
813 75.3 0.1 74.3
38.0 3.0 ?
? GRS 1915105 14 4 t 1.2
?1.7 10 ?104 Prec?2556 123.4 0.2
208.8 33.5 2.7 ?
?
The 3rd IBIS/ISGRI soft gamma-ray survey catalog
(Bird et al. 2006, ApJ, in press,
astro-ph/0611493) BATSE Earth Occultation
Catalog, Deep Sample Results (Harmon et al. 2004,
ApJS, 154, 585)
5
MULTIFREQUENCY EMISSION IN MICROQUASARS
Adapted from Chaty (Ph.D. Thesis)

• Compacts jets
• Radio ? IR
• ? X?
• ? gamma?
• (synchrotron)

• Donor star
• IR ? UV
• (thermal)

• Disc
• corona ?
• X ? IR
• therm non therm

• Large scale ejection
• Radio X
• gamma?
• Interaction with environment

• Dust ?
• IR ? mm
• (thermal)

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BLACK HOLE STATES

• Black holes display different X-ray spectral
  states
• Low/hard state (a.k.a. power-law state). Compact
  radio jet.
• High/soft state (a.k.a. steep power-law state).
  No radio emission.
• Intermediate and very high states ? transitions.
  Transient radio emission.

Fender 2001, ApSSS 276, 69
7
Corbel et al. 2000, AA 359, 251
Grebenev et al. 1993, AASS 97, 281
8
MQs as high-energy ? -ray sources Theoretical
point of view
Leptonic models
SSC Atoyan Aharonian 1999, MNRAS 302, 253
Latham et al. 2005, AIP CP745, 323
EC Kaufman Bernadó et al. 2002, AA 385, L10
Georganopoulos et al. 2002, AA
388, L25 SSCEC Bosch-Ramon et al. 2004 AA 417,
1075 Synchrotron jet emission
Markoff et al. 2003, AA 397, 645
Hadronic models Pion decay Romero et al.
2003, AA 410, L1
Bosch-Ramon et al. 2005, AA 432, 609
9
Leptonic high energy models
Synchrotron self Compton model
Rodríguez et al. 1995, ApJS 101, 173

• Non-thermal flares GRS1915105 (Atoyan
  Aharonian 1999, MNRAS 302, 253)
• Flares are caused by synchrotron radiation of
  relativistic e? suffering radiative, adiabatic
  and energy-dependent escape losses in
  fast-expanding plasmoids (radio clouds)

• Continuous supply or in-situ acceleration of
  radio e?

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• After limiting, from the radio data, the basic
  parameter characterizing the expanding plasmoids,
  the e? may be accelerated up to TeV energies,
  and the fluxes of synchrotron radiation could
  then extend beyond the X-ray region and the
  fluxes of the IC ?-rays to HE and VHE.

BATSE
0.05 G
0.1G
IR
0.2 G
sub-mm
Exponential cutoff energies 20 TeV
_____ 1 TeV _ _ _ _ 30
GeV _ . _ . _ B 0.05 G
GRS 1915105
radio
IC scattering or maybe even direct synchrotron
emission from the jets could dominate the
high-energy emission above an MeV or so Atoyan
Aharonian 1999, MNRAS 302, 253, and 2001

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External Compton Scattering - HMXB

• Jet exposed to star, disk and corona photon
  fields.
• Applied to Cygnus X-1 (Romero, Kaufman Bernadó
  Mirabel 2002, AA 393, L61)
• Corona (Klein-Nishina regime), disk and companion
  star (Thomson)
• The Compton losses in the different regions will
  modify the injected
• electron spectrum, introducing a break in the
  power law at the energy
• at which the cooling time equals the escape
  time.

Radiation absorbed in the local field trough
pair creation
Viewing angle of 30º Bulk Lorentz factor G5
Up-scattering of star photons (A) disk
(B) corona (C)
The recurrent and relatively rapid variability
could be explained by the precession of the jet,
which results in a variable Doppler amplification
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Hadronic jet models for microquasars

• Hadronic models (only) for gamma ?-ray emission
• Conical jet 1014 eV protons interacting with
  strong stellar wind protons,
• assuming efficient wind proton diffusion
  inside the jet.
• Protons are injected in the base of the jet and
  evolve adiabaticaly.
• Applied to explain gamma-ray emission from high
  mass microquasars
• (Romero et al. 2003, AA 410, L1).
• The ?-ray emission arises from the decay of
  neutral pions created in the
• inelastic collisions between relativistic
  protons ejected by the compact
• object and the ions in the stellar wind.

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The only requisites for the model are a windy
high-mass stellar companion and the presence of
multi-TeV protons in the jet. Spherically
symmetric wind and circular orbit
Romero,Torres, Kaufman, Mirabel 2003, AA 410, L1
Interactions of hadronic beams with moving clouds
in the context of accreting pulsars have been
previously discussed in the literature by
Aharonian Atoyan (1996, Space Sci. Rev. 75,
357).
14

• Models from radio to VHE
• Released 1014 eV protons from the jet that
  diffuse through and interact with the ISM.
• Computed the broadband spectrum of the emission
  coming out from the pp primary interactions
  (?-rays produced by neutral pion decay) as well
  as the emission (synchrotron, bremsstrahlung and
  IC scattering) produced by the secondary
  particles produced by charged pion-decay.
• All the respective energy losses have been taken
  unto account.
• Applied to impulsive and permanent microquasar
  ejections.

1) 100 yr 2) 1000 yr, 3) 10000 yr dMQ/cloud10pc M
cloud105Msun Ljet1037 erg/s
Bosch-Ramon et al. 2005, AA 432, 609
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MQs as high-energy ? -ray sources Observational
point of view
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EGRET candidate LS 5039
Orbital phase 0.2
LS 5039 could be related to the high energy
gamma-ray source 3EG J1824-1514
VLBA, 5 GHz
Jet parameters ? gt 0.15 , ? lt 81? TB
9.4 x 107 K
Equipartition Ee 5 x 1039 erg B 0.2 G
The photon spectral index is steeper than the a lt
2 values usually found for pulsars Merk et
al.1996, AASS 120, 465 L?(gt100 MeV)4?1035
ergs?1
It is the only simultaneous X-ray/radio source
within the 3EG J1824-1514 statistical contours.
Paredes et al. 2000, Science 288, 2340
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Radio, L0.1-100 GHz 1?1031 erg/s
Synchrotron Radiation
e-
e-
e-
g-ray, E gt 100 MeV, Lg 4?1035 erg/s
Inverse Compton Scattering
UV, E 10 eV
Lopt 1?1039 erg/s
e-

ge 103
X-ray L3-30 keV 5?1034 erg/s
O6.5V((f))
e-
vjet ? 0.15c
e-
Proposed scenario
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GRO J1823-12 (l/b 17.5/-0.5)
Summary complicated source region possible
counterparts - 3 known ?-sources (unid.
EGRET) (MeV emission superposition ?) -
micro quasar RX J1826.2-1450/LS 5039 (sug.
counterpart of 3EG J1824-1514 Paredes et
al. 2000) work in progress
Collmar 2003, Proc. 4th Agile Science Workshop
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Discovery of the TeV counterpart by HESS
(Aharonian et al. 2005). Good position agreement
with LS 5039. Good extrapolation of the EGRET
spectrum.
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A black hole in LS 5039 ?
Radial velocity curve of LS 5039
New spectroscopic observations of LS 5039 INT
2.5 m telescope (July 2002 and 2003)
New orbital ephemeris!!
P 3.9060 0.0002 d e 0.35
0.04 Periastron at phase 0.0 And assuming
pseudo-synchronisation at periastron i
20.3 4.0 Mcompact 5.4 (1.9-1.4) M?
Casares et al., 2005, MNRAS, 364, 899
21
With the new orbital ephemerides ? correlated TeV
and X-ray orbital variability. HESS RX
TE
(Casares et al. 2005),
22
3.9 day orbital modulation in the TeV gamma-ray
flux
Aharonian et al. 2006, AA, in press
(astro-ph/0607192)
VHE ?-rays can be absorbed by optical photons of
energy h?e, when their scattering angle ? exceeds
zero.
23
We have enough information to build up a Spectral
Energy Distribution that can be modeled to
extract physical information (Paredes et al.
2006, AA 451, 259).
24
EGRET candidate LSI61303
The radio emitting X-ray binary LSI61 303, since
its discovery, has been proposed to be associated
with the ?-ray source 2CG 13501 ( 3EG
J02416103)
The broadband 1 keV-100 MeV spectrum remains
uncertain (OSSE and COMPTEL observations were
likely dominated by the QSO 0241622 emission)
Harrison et al. 2000, ApJ 528, 454
The EGRET angular resolution is sufficient to
exclude the quasar QSO 0241622 as the source of
?-ray emission.
Hartman et al. 1999, ApJS 123, 79
Strickman et al. 1998, ApJ 497, 419
Periodic emission
Radio (P26.496 d) ? accretion at periastron
passage
TaylorGregory 1982, ApJ 255,
210 Optical and IR MendelsonMazeh 1989, MNRAS
239, 733
Paredes et al. 1994 AA 288, 519 X-rays Paredes
et al. 1997 AA 320, L25 ?-rays ???
25
3EG J02416103 variability
INTEGRAL variability
Tavani et al. 1998, ApJ 497, L89
EGRET observations of 3EG J02416103 shows
variability on short (days) and long (months)
timescales
Massi et al. 2005 (astro-ph/0410504)
Hermsen et al. 2006 Rome, keV to TeV
connectionWorkshop, 18 October 2006
26
Chandra Image of LSI61303
Chandra PSF
5
Obtained using the Chandra simulator
Surface brightness distribution
LSI61303
PSF
Flux changes on timescales of few hours. Factor
of two variability
Paredes et al. 2006
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Flux time variability

• MAGIC has observed LSI during 6 orbital cycles
• A variable flux (probability of statistical
  fluctuation 3?10-5) detected
• Marginal detections at phases 0.2-0.4
• Maximum flux detected at phase 0.6-0.7 with a
  16 of the Crab Nebula flux
• Strong orbital modulation ? the emission is
  produced by the interplay of the two objects in
  the binary
• No emission at periastron, two maxima in
  consecutive cycles at similar phases ? hint of
  periodicity!

Albert et al. 2006
28
LS I 61 303 the film
Albert et al. 2006

• The average emission has a maximum at phase 0.6.
  
• Search for intra-night flux variations (observed
  in radio and x-rays) yields negative result
• Marginal detections occur at lower phases. We
  need more observation time at periastron passage
• Parts of the orbit not covered due to
  similarities between orbital period (26.5 days)
  and Moon period

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Radio 15 GHz /Ryle, simultaneous with MAGIC obs.
The TeV flux maximum is detected at phases
0.5-0.6, overlapping with the X-ray outburst and
the onset of the radio outburst. Concerning
energetics, a relativistic power of several 1035
erg s-1 could explain the non thermal luminosity
of the source from radio to VHE gamma-rays. This
power can be extracted from accretion in a slow
inhomogeneous wind along the orbit (Bednarek
2006, MNRAS 268, 579).
This spectrum is consistent with that of EGRET
for a spectral break between 10 and 100 GeV.
The flux above 200 GeV corresponds to an
isotropic luminosity of 7 x 1033 erg s-1, at a
distance of 2 kpc. The intrinsic luminosity of
LS I 61 303 at its maximum is a factor 6 higher
than that of LS 5039, and a factor 2 lower than
the combined upper limit (lt8.8 x 10 -12 cm-2 s-1
above 500 GeV) obtained by Whipple (Fegan et al.
2005, ApJ 624, 638).
Spectrum for phases 0.4 and 0.7
30
LSI61303 VLBA images over full orbit
---------- 10 AU
Orbital Phase
New VLBI observations show a rotating jet-like
structure
Dhawan et al. 2006, VI MIcroquasars Workshop,
Como, Setember 2006
3.6cm images 3d apart. Beam 1.5x1.1mas
3x2.2 AU. Contours _0.2mJy,
increment sqrt(2).
31
(No Transcript)
32
Mirabel 2006, (Perspective) Science 312, 1759
A possible scenario comes from the application of
the pulsar wind nebulae formed with the
interaction of a relativistic pulsar wind with
the ISM but where the wind of the companion plays
the role of the ISM. The stagnation point, where
the pressure from the two winds is balanced, is
within the binary system. Particles are
accelerated at the termination shock and produce
the non-thermal synchrotron emission (Dubus 2006,
AA 456, 801).
33
UV photons from the companion star suffer inverse
Compton scattering by the same population of
non-thermal particles, leading to emission in the
GeV-TeV energy range. Particles move
downstream away from the pulsar at a speed v
(initially c/3). A cometary nebula of radio
emitting particles is formed. It rotates with the
orbital period of the binary system. We see this
nebula projected (Dubus 2006, AA 456, 801).
34
PSR B1259-63
PSR B1259-63 / SS 2883 is a binary system
containing a B2Ve donor and a 47.7 ms radio
pulsar orbiting it every 3.4 years, in a very
eccentric orbit with e0.87. No radio pulses are
observed when the NS is behind the circumstellar
disk (free-free absorption). VHE gamma-rays are
detected when the NS is close to periastron or
crosses de disk (Aharonian et al. 2005).
35
The VHE spectrum can be fit with a power-law and
explained by IC scattering processes. The
lightcurve shows significant variability and a
puzzling behavior not predicted by previously
available models (Aharonian et al. 2005).
36
Detection of new VHE sources?

• Three TeV sources (all HMXBs) discovered up to
  now
• LS 5039 OBH?
• LS I 61 303 BeNS?
• PSR B1259-63 BeNS

Since these sources are located in the Galactic
plane, a sensitivity better by a factor X with
respect to current instruments means detecting
3X sources.

• Binaries with short orbital periods, difficult
  for Be but likely for O donors, should be on
  all the time, although strong variability due to
  absorption is an issue. Detectable in deep enough
  surveys.
• Binaries with long orbital periods and high
  eccentricities should display an on/off
  behavior, more with higher values. Detectable in
  long monitorings.

37
but what about gamma-rays from
Colliding winds of massive stars ?
Binary pulsars ?
IC spectra of WR 147
Gamma-ray emission should be expected either
through Leptonic processes (IC) (Chen White
1991, ApJ 366, 512) Relativistic bremsstrahlung
(Pollock 1987, AA 171, 135) Hadronic
interactions of co-accelerated ions with the
dense wind material (White Chen 1992, ApJ 387,
81)
A. Reimer et al. 2006, ASS (astro-ph/0611647)
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Unidentified TeV source TeV J2032

• SIGNIFICANCE 6.1? by HEGRA
• STEADY in flux over 4 years of data taking
• EXTENDED with radius (6.2 ? 1.2 ? 0.9) arcmin
• HARD SPECTRUM with index -1.9 ? 0.1stat ? 0.3sys
• INTEGRAL FLUX gt 1 TeV at the level of 5 Crab

Aharonian et al. 2002, AA 293, L37
39
VLA, 20 cm
Paredes et al. 2006, ApJ Letters, in press
40
GMRT, 45cm
At 10 kpc, these objects would present
luminosities likely requiring the presence of a
compact object, and thus pointing to an X-ray
binary nature. (for a model of microquasars
-X-ray binaries with jets- powering extended TeV
hadronic emission, see Bosch-Ramon et al. (2005)).
41
Summary

• Microquasars are among the most interesting
  sources in the galaxy from the viewpoint of
  high-energy astrophysics.
• Models predict that radio jets could be natural
  sites for the production of high energy photons
  via both Compton scattering and maybe direct
  synchrotron emission.
• Leptonic and hadronic processes could be behind
  TeV emission.
• Up to now, above 500 keV, a handful of µqs have
  been detected
• Cygnus X-1 at ? 1
  MeV, GRO J1655-40 at 1 MeV,
• GRS 1915105 and
  Cygnus X-3 at TeV?
• LS 5039 and
  LSI61303 100 MeV - few TeV
• More microquasars will be detected soon with the
  Cherenkov telescopes and GLAST. This will bring
  more constraints to the physics of these systems.
• Multiwavelength (multi-particle) campaigns are of
  primary importance.