Gamma-ray binaries. Guillaume Dubus. HEPRO III, Barcelona 2011 Institut de Planétologie et d Astrophysique de Grenoble

Gamma-ray binaries Guillaume Dubus HEPRO III, Barcelona 2011 Institut de Planétologie et d Astrophysique de Grenoble

Gamma-ray binaries O/Be + compact object 4-1200d orbits dominant gamma-ray emission. most likely rotation powered by high E pulsar expected phase in binary evolution LS I +61 303 spectral energy distribution (Zdziarski et al. 2009)

Radio morphology along orbit milliarcsecond scales show comet-like behaviour Dhawan+ 2006, Albert+ 2008 (LS I +61 303); Ribó+ 2008 (LS 5039); Moldón+ 2011 (PSR B1259) Dhawan et al. 2006 LS I +61 303

Gamma-ray binaries detected detected + orbital variability system Porb radio X-ray GeV TeV PSR B1259-63 LS 5039 LS I +61 303 HESS J0632+057 1FGL J1018.6-5856 psr Be 1237? O 3.9? Be 26.5? Be 320? O 16.6 NB1: gamma-ray emission not dominant in Cyg X-3 & V407 Cyg NB2: PSR J1023+0038, XSSJ12270-4859 low-mass gamma-ray binaries? Tam et al. 2010, Hill et al. 2011

Gamma-ray binaries detected detected + orbital variability system Porb radio X-ray GeV TeV PSR B1259-63 LS 5039 LS I +61 303 HESS J0632+057 1FGL J1018.6-5856 psr Be 1237? O 3.9? Be 26.5? Be 320? O 16.6 Origin of orbital modulation in γ-ray?

γ-ray orbital modulations inverse Compton on star photons orbit seen face on apastron periastron apastron periastron apastron periastron inverse Compton (GeV)

γ-ray orbital modulations inverse Compton on star photons pair production on star photons (opacity) orbit seen face on apastron periastron apastron periastron apastron periastron inverse Compton (GeV) + pair production above threshold (TeV)

γ-ray orbital modulations inverse Compton on star photons: anisotropic pair production on star photons (opacity) orbit seen edge on inf conj sup conj inf conj sup conj inf conj sup conj to observer inverse Compton (GeV)

γ-ray orbital modulations inverse Compton on star photons: anisotropic pair production on star photons (opacity): anisotropic orbit seen edge on inf conj sup conj inf conj sup conj inf conj sup conj to observer inverse Compton (GeV) + pair production above threshold (TeV) studies by different groups: Bednarek et al.; Kirk et al; Khangulyan & Bosch-Ramon et al.; GD, Cerutti & Henri; Sierpowska-Bartosik & Torres; Takata & Taam; Yamaguchi & Takahara...

γ-ray orbital modulations inverse Compton on star photons: anisotropic pair production on star photons (opacity): anisotropic orbit seen edge on inf conj sup conj inf conj sup conj inf conj sup conj to observer inverse Compton (GeV) + pair production above threshold (TeV) identify emission mechanism distinguish intrinsic variability from variability due to observer geometry Bednarek ; Khangulyan & Bosch-Ramon, Sierpowska-Bartosik & Torres, GD Cerutti Henri, Takata & Taam, Yamaguchi & Takahara

Example: LS 5039 Cerutti et al. 2010 massive star radiation field + orbit fixes emission <B>~a few G

Possible complications significant pair cascade emission at superior conjunction total!!!! e -! e + e - e + e + e -!! pairs Cerutti et al. 2010

Possible complications significant pair cascade emission at superior conjunction bulk doppler boost in shocked wind modifies lightcurve VHE β=0 β=c/3 X-ray GD+ 2010

Puzzling lightcurve of PSR B1259-63 Fermi/LAT lightcurve (Abdo et al. 2011) orbit close to periastron 10 36 erg/s spindown pulsar in 3.5 year orbit around Be star Fermi/LAT detection at periastron mid-december 2010 brighter in February (near inf. conjunction)

Puzzling lightcurve of PSR B1259-63 Fermi/LAT lightcurve (Abdo et al. 2011) expected inverse Compton on star photons Pétri & GD 2011 what caused the brightening? Inv. Compton on star not enough Be disk (!0, free-free...)? HE sync? Doppler boost? IC on other fields?... high Lγ nearly all spindown power radiated away at peak

Puzzling spectrum of LS I +61 303 modulation: inverse Compton on star offset like PSR B1259-63 Abdo et al. 2009 0.7 au 26 d to observer HE peak offset from IC expectations HE and VHE long term variability

Puzzling spectrum of LS I +61 303 modulation: inverse Compton on star offset like PSR B1259-63 spectrum: two populations of HE particles? (also LS 5039) Abdo et al. 2009 HE peak offset from IC expectations HE and VHE long term variability exponential cutoff at GeV (like Fermi pulsars?!)

Puzzling spectrum of LS I +61 303 modulation: inverse Compton on star offset like PSR B1259-63 spectrum: two populations of HE particles? (also LS 5039) curvature radiation in magnetosphere no orbital modulation expected magnetosphere pulsar wind nebula exponential cutoff at GeV (like Fermi pulsars?!)

Puzzling spectrum of LS I +61 303 modulation: inverse Compton on star offset like PSR B1259-63 spectrum: two populations of HE particles? (also LS 5039) curvature radiation in magnetosphere no orbital modulation expected striped wind pulsar wind nebula Pétri & GD 2011 inverse Compton in striped wind? line-of-sight crosses stripes pulsed GeV emission exponential cutoff at GeV (like Fermi pulsars?!)

γ-ray binaries: conclusions 5 binaries with O/Be star + dominant γ-ray emission powered by spindown of companion pulsar (tbc) γ-ray orbital modulation natural outcome of inverse Compton pair production on stellar photons. complications: pair cascade, Doppler boosting... but fails to explain peak phase in PSR B1259, LS I +61 303 other radiative processes? related to both having a Be companion? striped wind pulsar wind nebula γ-ray spectrum indicates two particle populations striped wind at GeV + pulsar wind nebula at TeV?