Gamma-rays from black-hole binaries (?)

Transcription

1 Gamma-rays from black-hole binaries (?) Valentí Bosch-Ramon Dublin Institute for Advanced Studies Accretion and Outflow in Black Hole Systems IAU Symposium 275: Jets at all Scales Kathmandu, Nepal 13/10/2010 V. Bosch-Ramon (DIAS) Gamma-rays from black-hole binaries 13/10/ / 30

2 Outline 1 Introduction 2 Some new findings in CONFIRMED microquasars 3 Jet and black hole binary/microquasar emission models 4 Some issues of gamma-ray production in binaries 5 Final remarks V. Bosch-Ramon (DIAS) Gamma-rays from black-hole binaries 13/10/ / 30

3 Outline 1 Introduction 2 Some new findings in CONFIRMED microquasars 3 Jet and black hole binary/microquasar emission models 4 Some issues of gamma-ray production in binaries 5 Final remarks V. Bosch-Ramon (DIAS) Gamma-rays from black-hole binaries 13/10/ / 30

4 Emission in galactic and extragalactic black holes As in AGNs, jets in galactic black holes are non-thermal radio emitters. (e.g. Mirabel & Rodríguez 1999; Ribó 2005) This jet emission can also be in the OIR, and probably up to X-rays. (e.g. Russell & Fender 2010; Russell et al. 2010) Finally, also there is evidence that gamma-ray emission has been detected in galactic black holes. (Tavani et al. 2009, Abdo et al. 2009, Sabatini et al. 2010; Albert et al. 2007) But not quite, since we have only 4 σ detections in GeV and TeV for Cygnus X-1 and... we cannot say for sure that Cygnus X-3 contains a black hole. V. Bosch-Ramon (DIAS) Gamma-rays from black-hole binaries 13/10/ / 30

5 The controversy... Gamma-ray binaries do exist, but what are they? Unclear cases: LS I and LS 5039 (Mirabel 2006; see also Martocchia et al. 2005, Dubus 2006, Romero et al. 2007, Bosch-Ramon & Khangulyan ) V. Bosch-Ramon (DIAS) Gamma-rays from black-hole binaries 13/10/ / 30

6 Outline 1 Introduction 2 Some new findings in CONFIRMED microquasars 3 Jet and black hole binary/microquasar emission models 4 Some issues of gamma-ray production in binaries 5 Final remarks V. Bosch-Ramon (DIAS) Gamma-rays from black-hole binaries 13/10/ / 30

7 The X-ray-GeV-TeV connection in Cygnus X-3 The source was detected by Fermi and AGILE in a soft-high (radio) state and during strong radio outbursts. There is orbital variability anticorrelated with soft X-rays. (Tavani et al. 2009; Abdo et al. 2009) (Abdo et al. 2009, Aleksic et al. 2010) V. Bosch-Ramon (DIAS) Gamma-rays from black-hole binaries 13/10/ / 30

8 The X-ray-GeV-TeV connection in Cygnus X-1 AGILE and MAGIC detected a GeV and a TeV flare (4 σ) from Cyg X-1 in the low hard state but at very different orbital phases and X-ray states. The persistent GeV and TeV UL are compatible with the extrapolation of the spectrum at 1 MeV. (Sabatini et al. 2010; Saito et al. 2009) (Sabatini et al. 2010) V. Bosch-Ramon (DIAS) Gamma-rays from black-hole binaries 13/10/ / 30

9 Outline 1 Introduction 2 Some new findings in CONFIRMED microquasars 3 Jet and black hole binary/microquasar emission models 4 Some issues of gamma-ray production in binaries 5 Final remarks V. Bosch-Ramon (DIAS) Gamma-rays from black-hole binaries 13/10/ / 30

10 The black hole binary/microqusar scenario Ingredients: relativistic e ± /p, B (synchrotron), u ph (e.g. IC/SSC), n (e.g. pp)... V. Bosch-Ramon (DIAS) Gamma-rays from black-hole binaries 13/10/ / 30

11 Jets and blobs Continuous flow versus blobs. (Blandford & Koenigl 1979; van der Laan 1966) Jets and blobs can produce emission through internal shocks, (e.g. Kaiser et al. 2000; Bosch-Ramon et al. 2006b) Particle evolution in a blob is different from that in persistent jets. E r 1 vs r 2/3 ; B r 3/2 vs r 1 ; u ssc r 3 vs r 2 Jets and blobs can interact with the stellar wind (e.g. Perucho & Bosch-Ramon 2008; Araudo et al. 2009) Jets suffer stronger instabilities but both terminate similarly. (e.g. Bordas et al. 2009) V. Bosch-Ramon (DIAS) Gamma-rays from black-hole binaries 13/10/ / 30

12 Jets and blobs Continuous flow versus blobs. (Blandford & Koenigl 1979; van der Laan 1966) Jets and blobs can produce emission through internal shocks, (e.g. Kaiser et al. 2000; Bosch-Ramon et al. 2006b) Particle evolution in a blob is different from that in persistent jets. E r 1 vs r 2/3 ; B r 3/2 vs r 1 ; u ssc r 3 vs r 2 Jets and blobs can interact with the stellar wind (e.g. Perucho & Bosch-Ramon 2008; Araudo et al. 2009) Jets suffer stronger instabilities but both terminate similarly. (e.g. Bordas et al. 2009) V. Bosch-Ramon (DIAS) Gamma-rays from black-hole binaries 13/10/ / 30

13 Particle acceleration Fermi I: shocks (e.g. Bell 1978a, 1978b; Drury 1983) Fermi II: stochastic dispersions (e.g. Fermi 1949) Shear acceleration: velocity gradients (e.g. Berezhko & Krymskii 1981; Rieger & Duffy 2004) Converter mechanism: high Γ and dense photon fields (e.g. Derishev et al. 2003; Stern & Poutanen 2006) Magnetic reconection: turbulent strong field (e.g. Romanova & Lovelace 1992; Zenitani et al. 2001) Fermi I (Protheroe 1999) V. Bosch-Ramon (DIAS) Gamma-rays from black-hole binaries 13/10/ / 30

14 Basics: acceleration, transport and work The timescale of the acceleration process can be roughly characterized through η r g /c with η > 1. Acceleration time: t acc 10 2 η E TeV B 1 10 G s Particle transport due to jet advection and particle diffusion takes place. Diffusion time: t Bohm 15 Rj 2 10 B 10 G ETeV 1 s Advection time: t adv = 10 z j 11 /v j 10 s Adiabatic cooling is likely relevant, and can dominate the whole NT population. Adiabatic cooling: t ad 10(R j 10 /v exp 9 ) s (e.g. Takahashi et al. 2009) V. Bosch-Ramon (DIAS) Gamma-rays from black-hole binaries 13/10/ / 30

15 Basics: radiation processes Relativistic particles cool through synchrotron and IC emission. Stellar IC scattering: t cool 12 u E 1 10 GeV s Synchrotron emission: t sync 400 B 2 10 G E 1 10 GeV s Relativistic Bremsstrahlung and Coulombian cooling could be relevant in the jet base. Relativistic Bremsstrahlung: t br 10 6 n 1 9 s Ionization cooling: t ion E 10 MeV n 1 9 s Hadronic processes, like proton-proton collisions but also photomeson production could take place, both leading to ν-production. Photodisintegration cannot be fully discarded. (e.g. Levinson et al. 2001, Romero et al. 2003; Bednarek 2005; Kelner et al. 2006) pp interactions: t pp 10 6 n 1 9 s (see Bosch-Ramon & Khangulyan 2009 for a discussion on relevant timescales) V. Bosch-Ramon (DIAS) Gamma-rays from black-hole binaries 13/10/ / 30

16 Models for low-mass microquasars Synchrotron emission: radio-x-rays; Core (thick)+extended (thin) emission; continuous and blob-like. (e.g. Martí et al. 1992; Markoff et al. 2001) Synchrotron Self- and disk/corona inverse Compton: deep KN > GeV; steep spectrum; jet base or powerful blob (SSC); local γγ-absorption (e.g. Atoyan & Aharonian 1999; Bosch-Ramon et al. 2006b) Hadronic processes: jet base; pp or photomeson interactions, secondary emission, local γγ-absorption. (e.g. Romero & Vila 2009) V. Bosch-Ramon (DIAS) Gamma-rays from black-hole binaries 13/10/ / 30

17 Spectral energy distribution in LMMQs Leptonic models (Bosch-Ramon et al. 2006b) Hadronic models (Romero & Vila 2009) V. Bosch-Ramon (DIAS) Gamma-rays from black-hole binaries 13/10/ / 30

18 Models for high-mass microquasars The emission mechanisms in the inner-jet should be similar to those in LMMQ. (leptonic: Bosch-Ramon & Paredes 2004; hadronic: Romero et al. 2003, Aharonian et al. 2006) The stellar photon field makes an additional IC component to arise, favors VHE emission but also γγ-absorption. (Boettcher & Dermer 2005; Dermer & Boettcher 2006) The whole system may become a NT emitter due to secondary emission at high and low energies. (e.g. Bednarek 2000, Orellana et al. 2007; Bosch-Ramon et al. 2008a, Zdziarski et al. 2009) The dynamical interaction with the stellar wind cannot be avoided, which can affect strongly jet propagation and radiation. (Perucho & Bosch-Ramon 2008, Perucho et al. 2010; see also Romero & Orellana 2005, Araudo et al. 2009) V. Bosch-Ramon (DIAS) Gamma-rays from black-hole binaries 13/10/ / 30

19 Spectral energy distributions in HMMQs Leptonic models (Paredes et al. 2006) Hadronic models (Romero et al. 2003) V. Bosch-Ramon (DIAS) Gamma-rays from black-hole binaries 13/10/ / 30

20 Outline 1 Introduction 2 Some new findings in CONFIRMED microquasars 3 Jet and black hole binary/microquasar emission models 4 Some issues of gamma-ray production in binaries 5 Final remarks V. Bosch-Ramon (DIAS) Gamma-rays from black-hole binaries 13/10/ / 30

21 Constraining the accelerator properties The detection of photons > TeV energies already hints at a very efficient acceleration and provides information on the mechanism itself. LS 5039 (HMXB): Khangulyan et al V. Bosch-Ramon (DIAS) Gamma-rays from black-hole binaries 13/10/ / 30

22 Energy requirements in Cygnus X-3 Cyg X-3 was recently detected by Fermi. (Abdo et al. 2009) Conservative estimates in the leptonic scenario point to L nt > erg s 1. (see also Dubus et al. 2010) Hadronic requirements are even stronger ( erg s 1 ). Cyg X-3 could be a non-negligible contributor to PeV CRs. V. Bosch-Ramon (DIAS) Gamma-rays from black-hole binaries 13/10/ / 30

23 Energy budget: Cygnus X-1 There is significant emission around apastron-inf. conj. phases. Luminosity requirements: L nt = erg s 1. V. Bosch-Ramon (DIAS) Gamma-rays from black-hole binaries 13/10/ / 30

24 Gamma-ray absorption in HMMQs Detection of TeV emission in Cyg X-1 requires specific configurations of the emitter-star-observer system (e.g. far from the orbital plane). γγ absorption creates pairs, which should reradiate their emission. Cygnus X-1: Bosch-Ramon et al. 2008b; see also del Valle et al V. Bosch-Ramon (DIAS) Gamma-rays from black-hole binaries 13/10/ / 30

25 Secondary emission and electromagnetic cascading γγ absorption -> pair creation -> emission. Pair emission: synchrotron vs inverse Compton (EM cascading). An emitter at the compact object location is discarded by observations. LS 5039 (HMXB): Adapted from Aharonian et al V. Bosch-Ramon (DIAS) Gamma-rays from black-hole binaries 13/10/ / 30

26 Secondary emission and X-rays Synchrotron emission from the secondaries can easily reach X-rays. For moderate ambient B-values, secondary X-rays overcome observations. LS 5039 (HMXB): adapted from Bosch-Ramon et al. 2008b V. Bosch-Ramon (DIAS) Gamma-rays from black-hole binaries 13/10/ / 30

27 Radio emission from secondary pairs 5 GHz emission in the observer plane produced by secondary pairs created in a high-mass binaries (Bosch-Ramon & Khangulyan 2010, sub.) V. Bosch-Ramon (DIAS) Gamma-rays from black-hole binaries 13/10/ / 30

28 Stellar wind/jet interactions A normal O-star wind (Ṁ 10 6 M yr 1 ) easily deflects a jet of L j erg s 1. The jet can be disrupted even for L j erg s 1 through non-linear instabilities after a wind-reconfinment shock. Perucho et al V. Bosch-Ramon (DIAS) Gamma-rays from black-hole binaries 13/10/ / 30

29 Outline 1 Introduction 2 Some new findings in CONFIRMED microquasars 3 Jet and black hole binary/microquasar emission models 4 Some issues of gamma-ray production in binaries 5 Final remarks V. Bosch-Ramon (DIAS) Gamma-rays from black-hole binaries 13/10/ / 30

30 Final remarks Black hole binaries generate gamma-rays in their jets but... their origin may be very different from AGNs. Also, gamma-rays can be reprocessed and come from the whole binary. However, note that the GeV emitter should be far from the jet base due to absorption, and the TeV emitter even farther due to acceleration and absorption constraints. Black hole and other gamma-ray binaries are almost indistinguishable in gamma-rays. V. Bosch-Ramon (DIAS) Gamma-rays from black-hole binaries 13/10/ / 30