PoS(extremesky2009)050 http://pos.sissa.it/ -ray source classes and their γ ∗ -ray sources have emerged recently. Here I summarize the main observational results and γ [email protected] Speaker. Gamma-ray emission fromCherenkov stellar telescopes sources and/or at has high-energytion been gamma-rays to by detected the space-borne well-known at instruments. X-raystellar binaries very In systems addi- high detected by energies H.E.S.S.theoretical by and aspects MAGIC, of the new these types sources as of well as of the new potential candidates. ∗ Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licence. c

The Extreme sky: Sampling the UniverseOctober above 13-17 10 2009 keV Otranto (Lecce) Italy Josep M. Paredes Departament d’Astronomia i Meteorologia and InstitutUniversitat de de Ciències Barcelona del (UB/IEEC), Cosmos Martí (ICC), iE-mail: Franquès 1, 08028 Barcelona, Spain New stellar theoretical implications PoS(extremesky2009)050 -ray γ ]. It is 1 Josep M. Paredes -ray opacities are γ -ray emission from ] such structure was γ 4 -ray sky. In the high- γ -rays or are potential Car, or star forming regions γ , although no obvious correla- ]. Arc-minute extended radio η 2 ]. Its appearance was that of an 3 post-trial significance) of TeV emis- ]. A recent study of the opacity and σ 7 ]. The detection occurred slightly before 6 INTEGRAL 10 mag) that renders the optical counterpart ]. These TeV measurements were coincident 5 ≥ V 2 in the 1–10 keV range. At radio wavelengths the -ray sources. In the following sections we describe are detecting sources already observed at very high 1 γ − erg s Fermi ) during the low/hard state [ c 37 6 . and 0 > v AGILE ]. 15 mJy flux density and a flat spectrum, as expected for a relativistic compact 8 ∼ -ray range, γ -ray source classes γ Cygnus X-3 is among the most intensively studied microquasars in the Galaxy. The system is MAGIC observed Cygnus X-1, and strong evidence (4.1 Cygnus X-1 is the first binary system for which dynamic evidence for a BH was found [ In the last years, a major progress has taken place in the detection of undetectable in the visual domain.not The yet nature firmly of established. the The compact system object,flux undergoes strong black density radio hole increments flares or one of neutron or almost star, two times is three per orders year, with or magnitude above the normal quiescent level of elliptical ring-like shell with Cygnusrecognised X-1 as offset a jet-blown from ring the aroundthat center. Cygnus develops X-1. Later, at the in This location ring [ where couldsec be the scales, the pressure result is exerted by of balanced the aBremsstrahlung by strong collimated by shock the jet, ionized detected ISM. gas at behind The milliarc- the observed bow shock. radiation would besion produced was through found thermal during a short-lived flaring episode [ tion between the X-ray and the TeV emission was found [ acceleration models for the TeVthat flare an electromagnetic shows, cascading under model the cannot explain assumption its qualitatively exact of the shape observed negligible [ TeV magnetic spectrum, but field, a high-mass X-ray binary withstar an seen orbital through period a of high 4.8 interstellar hours, absorption with (A a WN Wolf-Rayet companion with an intense state of hard X-ray emission observed by stellar systems. The Cherenkovthe telescopes discovery H.E.S.S., of MAGIC stellar and sources VERITASenergy have as (HE) contributed a to class inenergies the and very discovering also high-energy new (VHE) ones.are Among several the binary sources systems found in that the containa HE high-mass a and bright compact VHE star. object, band, a More there like recently, black colliding Westerlund hole 2 wind (BH) binaries have or also like a turnedthe neutron out different star, to types and be of stellaremitters. sources that either have been detected at 2. Accreting X-ray binaries also the brightest persistent high-mass X-rayX-ray binary luminosity (HMXB) of in the a Galaxy, few radiating a times maximum 10 emission around Cygnus X-1 was also found using the VLA [ the superior conjunction of the compactexpected. object, phase at After which the computing highest theemitter VHE absorbed positions, it luminosity has that been issystem suggested caused not that by the to TeV pair violate emitter creation the is for X-ray located different at observational the constraints border [ of the binary source displays a jet (one-sided, with velocity Stellar 1. Introduction PoS(extremesky2009)050 ] ± 19 ]. stat 2 10 . , 0 9 ± 7 . ]. A leptonic =26.496 days 17 = 2 Josep M. Paredes orb P -ray source. At TeV VHE ]). A theoretical dis- γ Γ 29 ]. The discovery of this 28 ], which may be consistent with 23 ]. VLBA observations allowed the secondary particles [ ]. 27 ] for a critic review of this scenario). 30 , pp 25 -ray emission above 100 MeV associated 26 γ 3 ]; see nevertheless [ 1514 showing X-ray and radio emission, led Paredes and col- 24 − ), plus the emission from the ], in which it is shown that the X-ray and the TeV lightcurves can be satellites detected transient pp 18 ]. These results show that Cygnus X-3 is a new HE 12 , Fermi ]. The TeV lightcurve shows significant variability and the observed time- ]. These authors concluded that the star-pulsar wind interaction was the most 11 63 is a binary system containing a Be main sequence donor, known as LS 2883, 16 15 and ]. Presently, there is not strong evidence supporting the black hole or neutron star − 20 ] to propose their physical association. High-resolution (VLBI) radio observations of ]. The radiation mechanisms and interaction geometry in this pulsar/Be star system ] it was reported the discovery of an extended jet-like and apparently precessing radio 28 14 22 AGILE -ray source classes γ 87 [ . Different models have been recently proposed to try to explain these observations. In a . PSR B1259 LS I +61 303 shows periodic non-thermal radio outbursts on average every There are two X-ray binaries that produce variable GeV and TeV emission LS I +61 303 [ The radio emission of LS 5039 is persistent, non-thermal and variable but no strong radio out- The 0 ]. In [ ]. sys 2 0.1 Jy at cm wavelengths. Collimated relativistic jets from this microquasar were reported soon = . 21 13 0 hadronic scenario, the emission andbe lightcurve produced at by TeV, collisions as ofthe well the high as circumstellar energy in disk protons the ( accelerated radio/X-ray band, by the could pulsar wind and protons of cussion of the radio properties of LS 5039 can be found in [ laborators [ and LS 5039 [ [ bipolar radio structure, and theof fact the that EGRET LS source 5039 3EG was J1824 the only source in theLS field 5039 of along the the error orbit are box which necessary can for be the useful detection to of disentangle morphological and the astrometric nature changes, of the compact source (see [ emitting structure with angular extensions ofing 10–50 a milliarcseconds. full VLBA orbital images cycle obtained show dur- a rotating elongated morphology [ nature of the compact object. energies, Cygnus X-3 has not[ been detected yet by the new generation of Cherenkov telescopes scenario is presented in [ explained by an X-ray/IC scenario of non-thermal emission. 4. Dubious cases and new candidates a model based on the interactionthe between wind the of relativistic the wind stellar of companion a ([ young non-accreting pulsar and bursts or periodic variability havedetection been of detected an so elongated far radio [ structure, interpreted as relativistic jets [ feasible radiation powering mechanism. This was therays first discovered variable galactic [ source of VHEaveraged gamma- energy spectrum can be fitted with a power law with a photon index 3. Pulsar wind binaries and a 47.7 ms radioe pulsar orbiting its companionwere every studied 3.4 in years [ in a very eccentric orbit, with Stellar ∼ after some of these flaring episodes, flowing away in the North-South directionwith (see Cygnus e.g. X-3 [ [ PoS(extremesky2009)050 − 6 Car 100 − η ∼ ]). ]. The TeV 37 36 XMM-Newton Josep M. Paredes ]. Two of these detected very hard 46 , ]. The system would -ray binary. However, 45 γ 50 , 44 ]. Such region presents non- INTEGRAL data taken contemporaneously 40 . ,

39 ]) of this system makes it unlikely , Swift 48 38 30 M ∼ ]. The H.E.S.S. detection and the VERI- ] and 35 ]). Extensive spectral observations of 34 49 -ray variability. This seems to happen also in the 4 data [ γ -ray emission [ γ ] that HESS J0632+057 is likely a new ]. Based on specific radio information from some Wolf-Rayet XMM-Newton 34 43 ]. Its energy spectrum is consistent with a power law with photon , 33 42 , 9), with an O star companion of . 41 4 days, giving strong support to a binary scenario [ 0 ]. The long orbital period (1350 yr, [ ± ∼ 47 ]. The X-ray spectrum is hard, and can be fitted with an absorbed power-law e ]. VLA and GMRT radio observations have found a faint and unresolved source 34 53. No evidence of flux variability was found. Observations with 35 ]. . . These winds strongly affect the environment and shocks are expected to form, 2 ]. In this context, MAGIC data point to a high inclination for the WR 147 system. 1 32 − ]. Also, a thorough discussion of the different theoretical models for these systems is ≈ 46 yr 31

-ray source classes VHE γ Γ M -ray attenuation produces any distinctive feature in the spectrum. However, anisotropic IC Eta Car is one of the most remarkable objects of our Galaxy. It is a very massive star ( Some properties of LS 5039 and LS I +61 303 and an individual description of them can be A new TeV binary candidate, HESS J0632+057, was discovered by the H.E.S.S. telescope Massive hot stars can generate strong winds with high mass-loss rates at the level of 10 γ 5 ) showing strong mass-outflow eruptions (e.g., [ −

especially in massive star binaries, incolliding wind which region the can winds be from resolved both at stars radio wavelengths collide. [ In some cases, the revealed a variable X-raywith source, the massive XMMU B0pe J063259.3+054801, spectral type whichHESS star J0632+05 is MWC [ 148 positionally (HD coincident 259440) and compatible in position with M 5. Colliding winds in massive binary systems thermal radiation of synchrotron origin, indicatingtence the of presence relativistic of particles relativistic in electrons. anlosses environment unavoidable, The with and exis- a hence dense several photonbe authors field high-energy have makes sources suggested inverse [ that Compton colliding wind binaries should that scattering can produce flux variations thatinclination can [ allow one to estimate system parameters such as the yield a period of 2020 be highly eccentric ( (WR) binaries, some detailed models have been recently developed [ at the position of MWC 148, with a significant flux variability on month timescales [ TAS non detection seem to pointX-ray to band, a when long-term comparing the with VERITAS [ variability, as well as the X-raysupport to and the the idea radio proposed variability byfurther clearly [ observations associated are with necessary MWC to 148, determine the gives binarity of MWC 148 (see, e.g., [ 10 systems, WR 146 andobtained WR results 147, are compatible have with been backgroundits observed fluctuations, on with these these are the objects the [ MAGIC first telescope. experimental lim- Although the model. The spectral energyated distribution at of different HESS spectral bands J0632+057,LS are assuming I the that +61 real the 303 counterparts, sources and looksobtaining LS associ- similar no 5039. to significant that evidence VERITAS of observed for the HESS TeV J0632+057 binaries during three different epochs index found in [ Stellar presented in [ array as a point-like source [ PoS(extremesky2009)050 1 1 ± − − 37 ] and ( AGILE erg s erg s 60 33 34 10 10 × × Josep M. Paredes 4 . 100 MeV) is ], W3(OH) [ > 59 Car, which is well within the -ray flux ( η γ ], Cep A [ 58 -ray luminosity of 3 γ ]. Several sources that could be responsible 56 after few years of observations. At energies Car, if confirmed, would imply the first evidence ], HH 80-81 [ ]. 5 η 57 44 -ray lightcurve was roughly constant during all the source. The average ]. One of these sources is the massive binary system Fermi , γ 56 45 , 43 AGILE 5931 with , AGILE has observed extensively this region, reporting the detection of − -ray sources. 41 γ ]), and the produced emission should be added to that generated by 5931, consistent with the position of ]. The 55 AGILE 50 hours of observation time. − , ]. Several works have explored the possible production of gamma-rays 52 ∼ 54 62 , Car in the 22–100 keV energy range, with a luminosity of 7 , which corresponds to an average , 1 53 η − 61 s ]. These models predict that under certain conditions, the population of rela- 2 -ray emission from a colliding wind system. The results obtained by − γ 65 -ray satellite , γ 4247 [ − 64 , ph cm 8 63 -ray source classes − ]. γ 100 MeV 10 The H.E.S.S. telescope detected the source HESS J1023-575, which is coincident with the The Carina region was observed with EGRET in the past, with no positive detection above Massive protostars have associated bipolar outflows with velocities of hundreds of km/s. These The association of 1AGL J1043 Collective effects of the stellar winds of hot stars might play an important role in a rather young 45 , ]. > -ray source, 1AGL J1043 × γ ) -ray emission, that could be detectable by 43 51 for a distance of 2.3 kpc [ at the terminal points ofclouds jets [ that emanate fromtivistic massive particles protostars accelerated embedded at in the denseγ terminal molecular shocks of the protostellarabove jets 100 can GeV, the produce emission significant levelCherenkov telescopes expected for is of about 0.01 Crab, which could be detectable by young stellar cluster Westerlund 2 in theand well-known was HII detected complex with RCW49. a The high source statistical is significance extended [ of for the TeV emission have beenWR20a, proposed which [ is hostedemission by does the not open support cluster thisbased Westerlund binary 2. on as collective However, a stellar the possiblefeasible. winds extension counterpart. from of The On the the association the TeV massive ofopen other clusters and HESS a hand, hot J1023-575 new an class with stars scenario of Westerlund in VHE 2, the if Westerlund confirmed, 2 would could7. make be of Gamma-rays from massive protostars outflows can produce strong shocks whennon-thermal interact radio with emission. the ambient Athem medium non-thermal associated leading with component to massive has regions YSOs: of been Serpens found [ in some outflows, all of [ 95% confidence radius error box of the 5 observations, although a fewperiastron. day timescale gamma-ray flare was detected a few months before seems to agree with what is[ expected from IC and neutral pion processes in colliding wind binaries 6. Massive stellar associations OB association (e.g. [ individual colliding wind binaries [ IRAS 16547 a 100 MeV. The Stellar X-ray emission from PoS(extremesky2009)050 ], massive 67 , Josep M. Paredes 66 ], have chances to be detected by the -ray emitting sources that are deeply γ 64 63, in which the power comes from the pulsar − 6 -ray sources have emerged recently. In particular, colliding wind bi- γ ], and low-mass X-ray binaries [ -ray telescopes . 63 γ -ray source classes γ INTEGRAL can be particularly useful to find/study Several binary systems have been detected at HE and/or VHE gamma-rays. Two of them, New types of stellar The author acknowledges support of the Spanish Ministerio de Educación y Ciencia (MEC) [1] Gies et al D.R. Gies &[2] C.T. Bolton, Stirling, 1986, A. ApJ, M., 304, et 371 al., 2001,[3] MNRAS, 327, Martí, 1273 J., Rodríguez, L.F., Mirabel, I.F., &[4] Paredes, J.M. 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A Therebeen very are detected two both other at systems, HE and LS VHEAlthough I gamma-rays +61 the and 303 the power and nature mechanism LS of 5039, of theradio which compact and these have object X-ray systems is emitters not is known. and differentof have seed (accretion, a photons high-mass pulsar), for bright all IC companion scattering of (O and them or target nuclei are B) for star, hadronic which interactions. is a source current generation of embedded in a denseYSO, environment, high-mass mainly microquasars), sources since related theseX-rays to sources because massive of may strong star not free-free (e.g. be and easily photo-electric absorption. SFXT, detectable massive in radio orAcknowledgments soft under grant AYA2007-68034-C03-01 and FEDER funds.and I Gustavo am E. indebted Romero toThis Valentí for research Bosch-Ramon has a made careful use ofSIMBAD reading the database, of NASA’s operated Astrophysics at Data the CDS, System Strasbourg, manuscript Abstract France. 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