SS 433 is a binary system containing a supergiant star that is overflowing its Roche lobe with matter accreting onto a compact object (either a black hole or neutron star)1,2,3. Two jets of ionized matter with a bulk velocity of approximately 0.26c (where c is the speed of light in vacuum) extend from the binary, perpendicular to the line of sight, and terminate inside W50, a supernova remnant that is being distorted by the jets2,4,5,6,7,8. SS 433 differs from other microquasars (small-scale versions of quasars that are present within our own Galaxy) in that the accretion is believed to be super-Eddington9,10,11, and the luminosity of the system is about 1040 ergs per second2,9,12,13. The lobes of W50 in which the jets terminate, about 40 parsecs from the central source, are expected to accelerate charged particles, and indeed radio and X-ray emission consistent with electron synchrotron emission in a magnetic field have been observed14,15,16. At higher energies (greater than 100 gigaelectronvolts), the particle fluxes of γ-rays from X-ray hotspots around SS 433 have been reported as flux upper limits6,17,18,19,20. In this energy regime, it has been unclear whether the emission is dominated by electrons that are interacting with photons from the cosmic microwave background through inverse-Compton scattering or by protons that are interacting with the ambient gas. Here we report teraelectronvolt γ-ray observations of the SS 433/W50 system that spatially resolve the lobes. The teraelectronvolt emission is localized to structures in the lobes, far from the centre of the system where the jets are formed. We have measured photon energies of at least 25 teraelectronvolts, and these are certainly not Doppler-boosted, because of the viewing geometry. We conclude that the emission—from radio to teraelectronvolt energies—is consistent with a single population of electrons with energies extending to at least hundreds of teraelectronvolts in a magnetic field of about 16 microgauss.
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The datasets analysed during this study are available at a public repository maintained by the HAWC Collaboration: https://data.hawc-observatory.org/.
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Margon, B. Observations of SS 433. Annu. Rev. Astron. Astrophys. 22, 507–536 (1984).
Fabrika, S. The jets and supercritical accretion disk in SS433. Astrophys. Space Phys. Rev. 12, 1–152 (2004).
Cherepashchuk, A. M. et al. INTEGRAL observations of SS433: results of coordinated campaign. Astron. Astrophys. 437, 561–573 (2005).
Zealey, W. J., Dopita, M. A. & Malin, D. F. The interaction between the relativistic jets of SS433 and the interstellar medium. Mon. Not. R. Astron. Soc. 192, 731–743 (1980).
Margon, B. & Anderson, S. F. Ten years of SS 433 kinematics. Astrophys. J. 347, 448–454 (1989).
Safi-Harb, S. & Ögelman, H. ROSAT and ASCA observations of W50 associated with the peculiar source SS 433. Astrophys. J. 483, 868–881 (1997).
Eikenberry, S. S. et al. Twenty years of timing SS 433. Astrophys. J. 561, 1027 (2001).
Migliari, S., Fender, R. P. & Mendez, M. Iron emission lines from extended X-ray jets in SS 433: reheating of atomic nuclei. Science 297, 1673 (2002).
Mirabel, I. & Rodríguez, L. F. Sources of relativistic jets in the galaxy. Annu. Rev. Astron. Astrophys. 37, 409–443 (1999).
Begelman, M. C., King, A. R. & Pringle, J. E. The nature of SS433 and the ultraluminous X-ray sources. Mon. Not. R. Astron. Soc. 370, 399–404 (2006).
Fabrika, S., Ueda, Y., Vinokurov, A., Sholukhova, O. & Shidatsu, M. Supercritical accretion discs in ultraluminous X-ray sources and SS 433. Nat. Phys. 11, 551 (2015).
Cherepashchuk, A. M., Aslanov, A. A. & Kornilov, V. G. WBVR photometry of SS 433—spectra of the normal star and the accretion disk. Sov. Astron. 26, 697–702 (1982).
Tetarenko, B. E., Sivakoff, G. R., Heinke, C. O. & Gladstone, J. C. WATCHDOG: a comprehensive all-sky database of galactic black hole X-ray binaries. Astrophys. J. Suppl. 222, 15 (2016).
Geldzahler, B. J., Pauls, T. & Salter, C. J. Continuum observations of the supernova remnants W50 and G 74.9+1.2 at 2695 MHz. Astron. Astrophys. 84, 237–244 (1980).
Brinkmann, W., Pratt, G. W., Rohr, S., Kawai, N. & Burwitz, V. XMM-Newton observations of the eastern jet of SS433. Astron. Astrophys. 463, 611–619 (2007).
Safi-Harb, S. & Petre, R. Rossi X-ray timing explorer observations of the eastern lobe of W50 associated with SS 433. Astrophys. J. 512, 784–792 (1999).
Aharonian, F. et al. TeV gamma-ray observations of SS-433 and a survey of the surrounding field with the HEGRA IACT-System. Astron. Astrophys. 439, 635–643 (2005).
Hayashi, S. et al. Search for VHE gamma rays from SS433/W50 with the CANGAROO-II telescope. Astropart. Phys. 32, 112–119 (2009).
Ahnen, M. L. et al. Constraints on particle acceleration in SS433/W50 from MAGIC and H.E.S.S. observations. Astron. Astrophys. 612, A14 (2018).
Kar, P. VERITAS observations of high-mass X-ray binary SS 433. Proc. Sci. (35th Int. Cosmic Ray Conf.) ICRC2017, https://doi.org/10.22323/1.301.0713 (2018).
Bordas, P., Yang, R., Kafexhiu, E. & Aharonian, F. Detection of persistent gamma-ray emission toward SS433/W50. Astrophys. J. 807, L8 (2015).
Abeysekara, A. U. et al. The 2HWC HAWC Observatory Gamma Ray Catalog. Astrophys. J. 843, 40 (2017).
López-Coto, R. et al. Effect of the diffusion parameters on the observed γ-ray spectrum of sources and their contribution to the local all-electron spectrum: the EDGE code. Astropart. Phys. 102, 1–11 (2018).
Albert, J. et al. Variable very high energy gamma-ray emission from the microquasar LS I +61° 303. Science 312, 1771–1773 (2006).
Archambault, S. et al. Exceptionally bright TeV flares from the binary LS I + 61° 303. Astrophys. J. 817, L7 (2016).
Reynoso, M. M., Romero, G. E. & Christiansen, H. R. Production of gamma rays and neutrinos in the dark jets of the microquasar SS433. Mon. Not. R. Astron. Soc. 387, 1745–1754 (2008).
Panferov, A. A. Jets of SS 433 on scales of dozens of parsecs. Astron. Astrophys. 599, A77 (2017).
Ptuskin, V. S., Moskalenko, I. V., Jones, F. C., Strong, A. W. & Zirakashvili, V. N. Dissipation of magnetohydrodynamic waves on energetic particles: impact on interstellar turbulence and cosmic ray transport. Astrophys. J. 642, 902–916 (2006).
Moderski, R., Sikora, M., Coppi, P. S. & Aharonian, F. A. Klein-Nishina effects in the spectra of non-thermal sources immersed in external radiation fields. Mon. Not. R. Astron. Soc. 364, 1488 (2005).
Romero, G., Boettcher, M., Markoff, S. & Tavecchio, F. Relativistic jets in active galactic nuclei and microquasars. Space Sci. Rev. 207, 5–61 (2017).
Smith, A. J. HAWC: design, operation, reconstruction and analysis. Proc. Sci. (34th Int. Cosmic Ray Conf.) ICRC2015, https://doi.org/10.22323/1.236.0966 (2016).
Abeysekara, A. U. et al. Observation of the Crab Nebula with the HAWC Gamma Ray Observatory. Astrophys. J. 843, 39 (2017).
Younk, P. W. et al. A high-level analysis framework for HAWC. Proc. Sci. (34th Int. Cosmic Ray Conf.) ICRC2015, https://doi.org/10.22323/1.236.0948 (2016).
Vianello, G. et al. The multi-mission maximum likelihood framework. Proc. Sci. (34th Int. Cosmic Ray Conf.) ICRC2015, https://doi.org/10.22323/1.236.1042 (2016).
Gorski, K. M. et al. HEALPix—a framework for high resolution discretization, and fast analysis of data distributed on the sphere. Astrophys. J. 622, 759–771 (2005).
Wilks, S. S. The large-sample distribution of the likelihood ratio for testing composite hypotheses. Ann. Math. Stat. 9, 60–62 (1938).
Chaty, S. & Delautier, S. Microquasars. http://www.aim.univ-paris7.fr/CHATY/Microquasars/microquasars.html (Université Paris Diderot, 2006).
Aharonian, F. et al. Discovery of very high energy gamma rays associated with an X-ray binary. Science 309, 746–749 (2005).
Aliu, E. et al. Multiwavelength observations of the TeV binary LS I +61 303 with VERITAS, Fermi-LAT, and Swift/XRT during a TeV outburst. Astrophys. J. 779, 88 (2013).
Abeysekara, A. U. et al. Extended gamma-ray sources around pulsars constrain the origin of the positron flux at Earth. Science 358, 911–914 (2017).
Brinkmann, W., Aschenbach, B. & Kawai, N. ROSAT observations of the W 50/SS 433 system. Astron. Astrophys. 312, 306–316 (1996).
Feldman, G. J. & Cousins, R. D. A unified approach to the classical statistical analysis of small signals. Phys. Rev. D 57, 3873–3889 (1998).
Fuchs, Y., Mirabel, I. F. & Ogley, R. N. Mid-infrared observations of GRS 1915+105 and SS 433. Astrophys. Space Sci. Suppl. 276, 99–100 (2001).
Finke, J. D. & Dermer, C. D. Cosmic ray electron evolution in the supernova remnant RX J1713.7-3946. Astrophys. J. 751, 65 (2012).
Foreman-Mackey, D., Hogg, D. W., Lang, D. & Goodman, J. emcee: the MCMC hammer. Publ. Astron. Soc. Pacif. 125, 306–312 (2013).
Particle Data Group. Review of particle physics. Phys. Lett. B 592, 1–5 (2004).
Amato, E. & Blasi, P. Non linear particle acceleration at non-relativistic shock waves in the presence of self-generated turbulence. Mon. Not. R. Astron. Soc. 371, 1251–1258 (2006).
Malkov, M. A., Diamond, P. H., Sagdeev, R. Z., Aharonian, F. A. & Moskalenko, I. V. Analytic solution for self-regulated collective escape of cosmic rays from their acceleration sites. Astrophys. J. 768, 73 (2013).
We acknowledge support from: the US National Science Foundation (NSF); the US Department of Energy Office of High-Energy Physics; the Laboratory Directed Research and Development programme of Los Alamos National Laboratory; Consejo Nacional de Ciencia y Tecnología, México (grants 271051, 232656, 260378, 179588, 239762, 254964, 271737, 258865, 243290, 132197 and 281653) (Cátedras 873, 1563); Laboratorio Nacional HAWC de rayos gamma; L’OREAL Fellowship for Women in Science 2014; Red HAWC, México; DGAPA-UNAM (Dirección General Asuntos del Personal Académico—Universidad Nacional Autónoma de México; grants IG100317, IN111315, IN111716-3, IA102715, IN109916 and IA102917); VIEP-BUAP (Vicerrectoría de Investigación y Estudios de Posgrado-Benemérita Universidad Autónoma de Puebla); PIFI (Programa Integral de Fortalecimiento Institucional) 2012 and 2013; PRO-FOCIE (Programa de Fortalecimiento de la Calidad en Instituciones Educativas) 2014 and 2015; the University of Wisconsin Alumni Research Foundation; the Institute of Geophysics, Planetary Physics, and Signatures at Los Alamos National Laboratory; Polish Science Centre grant DEC-2014/13/B/ST9/945 and DEC-2017/27/B/ST9/02272; and Coordinación de la Investigación Científica de la Universidad Michoacana. We thank S. Delay, L. Díaz and E. Murrieta for technical support. We thank R. Mushotzky for providing the spectrum of the XMM-Newton data in the HAWC detection region.
Nature thanks A. Achterberg and M. Bowler for their contribution to the peer review of this work.
Extended data figures and tables
The colour scale indicates the statistical significance of the excess counts above the background of contaminating cosmic rays and γ-rays before accounting for statistical trials. The bright extended γ-ray source MGRO J1908+06 is shown at the centre of the left panel with SS 433/W50 at the bottom. The dark contours show X-ray emission from SS 433 and its jets41. The semicircular area indicates the region of interest used to fit the γ-ray observations. The right panel shows the γ-ray excess measured after the fitting and subtraction of γ-rays from the spatially extended source MGRO J1908+06. The dashed box indicates the region shown in Fig. 1. The jet termination regions e1, e2, e3, w1 and w2 observed in the X-ray data are indicated, as well as the location of the central binary.
The significance is defined as deviations from the background expectation, in the HAWC sky map (left panel), after fitting and subtraction of emission from MGRO J1908+06 (middle panel), and after fitting and removal of emission from MGRO J1908+06 and the γ rays from w1 and e1 (right panel).
Extended Data Fig. 3 Fraction of jet power needed to produce the observed VHE γ-rays in the hadronic scenario.
The blue-shaded region shows the energy injection rate of protons, in units of the kinetic luminosity of the jet, required to produce the observed VHE γ-rays by interacting with ambient gas, as a function of the proton confinement time. A gas density of 0.05 cm−3 is adopted for the source vicinity16,27. Most hadronic models require >100% jet power (above the red solid line) and are thus not allowed. Even when the diffusion coefficient is extremely small (for reference, the dashed grey lines show the source age and the confinement time of 200 TeV protons in a 30-pc region in the ISM with Kraichnan- and Kolmogorov-type diffusion) and when the spectral index is much harder than 2, the hadronic scenario still requires a large energy input from the jet.
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