The Gamma-ray Sky with ASTROGAM GAMMA-RAY BINARIES. Second Astrogam Workshop Paris, March Josep M. Paredes

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1 The Gamma-ray Sky with ASTROGAM GAMMA-RAY BINARIES Second Astrogam Workshop Paris, March 2015 Josep M. Paredes

2 Binary systems with HE and/or VHE gamma-ray emission Microquasars: Accreting XRBs with relativistic jets. SED peak at kev. Cygnus X-3, detected at HE by Fermi-LAT and AGILE (Abdo et al. 2009, Tavani et al. 2009) Gamma-ray binaries: Young non-accreting pulsars + massive star. SED peak at MeV-GeV. PSR B , detected at HE by Fermi- LAT and at VHE by H.E.S.S. (Abdo et al. 2011, Aharonian et al. 2005) Cygnus X-3 Zdziarski et al. 2012, MNRAS, 421, 2956 LS I Sidoli et al. 2006, A&A, 459, 901

3 Recycled non-accreting MS PSRs in binary systems: the Black Widow Pulsar PSR B , detected at HE by Fermi/LAT (Wu et al. 2012) Colliding wind binaries: Eta Carinae, detected at HE by Fermi-LAT and upper limit at VHE by H.E.S.S. (Reimer et al. 2012, Abramowski et al. 2012) Symbiotic novae: V407 Cygni, detected at HE by Fermi-LAT (Abdo et al. 2010) 3

4 Microquasars and Gamma-ray binaries Two scenarios to describe the electron acceleration 1. Jets of a microquasar powered by accretion 2. Shocks between the relativistic wind of a young non-accreting pulsar and the wind of the stellar companion Mirabel 2006, Science 312,

5 Microquasar Non-accreting pulsar Possible scenarios An accretion disk is formed by mass transfer. Display bipolar jets of relativistic plasma. The jet electrons produce radiation by synchrotron emission when interacting with magnetic fields. VHE emission is produced by inverse Compton scattering when the jet particles collide with stellar UV photons, or by hadronic processes when accelerated protons collide with stellar wind ions. [Bosch-Ramon et al. 2006, A&A, 447, 263; Paredes et al. 2006, A&A, 451, 259; Romero et al. 2003, A&A, 410, L1] Radio emission Synchrotron Radiation X-ray Disk black body or Corona power-law e - e - e - e - e - e - Γ e ~10 5 Gamma-ray Inverse Compton Scattering UV - Opt Donor star OB Star The relativistic wind of a young (ms) pulsar is contained by the stellar wind. Particle acceleration at the termination shock leads to synchrotron and inverse Compton emission. After the termination shock, a nebula of accelerated particles forms behind the pulsar. The cometary nebula is similar to the case of isolated pulsars moving through the ISM. [Maraschi & Treves 1981, MNRAS, 194, P1; Dubus 2006, A&A, 456, 801; Sierpowska-Bartosik & Torres 2007, ApJ, 671, L145] 5 Adapted from NASA/CXC/SAO

6 Source System Type Orbital Period (d) Radio Structure (AU) Radio X-ray GeV TeV Microquasar Non-accreting pulsar PSR B O9.5Ve + NS 1237 Cometary tail ~ 120 LS I B0Ve +? 26.5 Cometary tail? LS 5039 O6.5V((f)) +? 3.9 Cometary tail? HESS J B0Vpe +? 321 Elongated (few data) ~ 60 1FGL J O6.5V((f)) +? Cygnus X-1 O9.7I + BH 5.6 Jet 40 + ring P P T P P P P P persistent P P P V P? P? 16.6? P P P P Cygnus X-3 WR + BH? 4.8h Jet Persistent & burst SS 433 A3-7 I + BH? AGL J MWC 656??? B2IIIe + BH persistent P T? T? P P? 13.1 Jet V V Persistent? 60 T? T??

7 Different orbit configurations probe different ambient conditions and geometries in gamma-ray binaries Dubus 2013, A&Arv 21, 64 7

8 PSR B Young pulsar wind interacting with the companion star The first variable galactic source of VHE Dense equatorial circumstellar disk 47.7 ms radio pulsar O8.5-9 Ve +NS (Negueruela et al. 2011, ApJL, 732, L11) Orbital plane of the pulsar inclined with respect to the disk (Melatos et al. 1995, MNRAS 275, 381; Chernyakova et al. 2006, MNRAS 367, 1201) Radio emission is produced by the HE outflow reaching distances times larger than the binary system size. e = 0.87 Moldón et al. 2011, ApJ 732, L10 8

9 Binary pulsars PSR B / LS 2883 The observed X-ray/soft gamma-ray emission was consistent with the shock-powered highenergy emission produced by the pulsar/outflow interaction X-ray lightcurve is remarkably stable the X- ray emission is produced directly inside the binary system synchrotron IC Chernyakova et al. 2014, MNRAS 439, 432 PSR B1259 / LS 2883 HE flare PSR B Nearly all the spin-down power is released in HE gamma rays (Abdo et al. 2011). Doppler boosting suggested (Tam et al. 2011), but very fine tuning is needed and lack of concurrent variability. 9

10 Fermi LS I HMXB, B0Ve+NS? COS-B γ-ray source CG/2CG Hermsen et al. 1977, Nature 269, MAGIC Albert et al. 2006, Sci 312, 1771 Albert et al. 2009, ApJ 693, 303 VLBI observations show a rotating jet-like structure (Dhawan et al. 2006, VI Microquasars Workshop, 2006) Abdo et al. 2009, ApJ 701, L123 Correlated X-ray and VHE emission Anderhub et al. 2009, ApJ 706, L27 10

11 Zdziarski et al. 2010, MNRAS 403, 1873 Not resolved yet the issue of the momentum flux of the pulsar wind being significantly higher than that of the Be wind, which presents a problem for interpretation of the observed radio structures (as pointed out by Romero et al 2007, A&A 474, 15) Suggested that the emissions detected by the Fermi LAT from X-ray binary pulsars originate in the magnetosphere region of the pulsar Zhang et al 2014, Res. A&A 14,

12 Fermi COMPTEL H.E.S.S. LS 5039 HMXB, O6.5V+NS? Moldón et al. 2012, A&A 548, A103 Aharonian et al. 2006, A&A 460, 743 Abdo et al. 2009, ApJ 706, L56 - IC scattering will vary with radiation density Collmar & Zhang 2014, A&A 565, A38 12 Collmar & Zhang 2014, A&A 565, A38 - The flux will also depend on the geometry seen by the observer because the source of seed photons is anisotropic (Khangulyan et al. 2008; Sierpowska-Bartosik&Torres 2008b) - The emission is enhanced (reduced) when the highly relativistic e seen by the observer encounter the seed photons head-on (rear-on), i.e., at superior (inferior) conjunction - VHE absorption due to pair production will be maximum (minimum) at superior (inferior) conjunction

13 Zabalza et al. 2013, A&A 551, A17 Coriolis turnover location Wind standoff The pulsar/stellar wind interaction in a compact-orbit binary gives rise to two potential locations for particle acceleration: o the shocks at the head-on collision of the winds o the termination shock caused by Coriolis forces on scales larger than the binary separation Three different components Takata et al. 2014, ApJ 790,18 13

14 HESS J Skilton et al. 2009, MNRAS 399, 317 Hinton et al. 2009, ApJ 690, L101 Be star MWC 148 XMM-Newton Δ1RXS J Aliu et al., 2014, ApJ 780, 168 Moldón et al A&A 533, L7 14

15 1FGL J Flux modulated with a 16.6 d period 1FGL J is one of the brighter Fermi sources (Ackermann et al. 2012, Fermi Col., Science 335, 189) X-ray flare-like behaviour near phase 0, coinciding with gamma-ray maximum Optical counterpart ~O6V((f)), just like LS Orbital parameters unknown An spatially coincident variable radio source Radio structure? LAT spectrum similar to a pulsar - but no pulsations seen H.E.S.S. Coll. 2015, arxiv

16 Recycled non-accreting MS PSRs in binary systems Black widows and Redbacks: Eclipsing millisecond pulsars in close (P b < 1 day) binary systems Companion: Nearly Roche-lobe filling Heated by the pulsar which drives mass loss from the companion The pulsar wind shocks with this material just above the surface of the companion Fermi/LAT has detected γ-rays from more than a dozen black widows and redbacks (Roberts 2012, IAU Symp 291) Non-thermal emission from the intra-binary shock, detected in X-rays in these systems, could contribute to unpulsed gamma-ray emission (Bogdanov et al. 2005, ApJ 630, 1029) PSR B Wu et al. 2012, ApJ 761, 181 The system behaves like a low-mass gamma-ray binary Orbital modulation of the HE emission in the black widow pulsar PSR B The pulsar spectrum with a cutoff at E c 1GeV is not variable (pulsar magnetosphere) Modulation restricted to the component above 2.7 GeV, attributed to pulsar wind emission (IC of the thermal radiation of the companion star off a cold ultrarelativistic pulsar wind) 16

17 Bednarek 2014, A&A 561, A116 17

18 Summary Five gamma-ray binaries (SED peak at MeV-GeV) 2 binaries contain O stars, 3 binaries Be stars VLBI observations support the presence of young non-accreting pulsars Variability at all wavelengths Correlated X-ray/TeV emission suggest a leptonic origin (synchrotron+ic) Unclear location of the GeV and TeV emissions Black widow and Redback binaries might show modulated GeV/TeV γ-ray emission