A unique signature for the presence of massive black holes in very dense stellar regions is occasional giant-amplitude outbursts of multi-wavelength radiation from tidal disruption and subsequent accretion of stars that make a close approach to the black holes1. Previous strong tidal disruption event (TDE) candidates were all associated with the centres of largely isolated galaxies2,3,4,5,6. Here, we report the discovery of a luminous X-ray outburst from a massive star cluster at a projected distance of 12.5 kpc from the centre of a large lenticular galaxy. The luminosity peaked at ~1043 erg s−1 and decayed systematically over 10 years, approximately following a trend that supports the identification of the event as a TDE. The X-ray spectra were all very soft, with emission confined to be 3.0 keV, and could be described with a standard thermal disk. The disk cooled significantly as the luminosity decreased—a key thermal-state signature often observed in accreting stellar-mass black holes. This thermal-state signature, coupled with very high luminosities, ultrasoft X-ray spectra and the characteristic power-law evolution of the light curve, provides strong evidence that the source contains an intermediate-mass black hole with a mass tens of thousand times that of the solar mass. This event demonstrates that one of the most effective means of detecting intermediate-mass black holes is through X-ray flares from TDEs in star clusters.

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  1. 1.

    Rees, M. J. Tidal disruption of stars by black holes of 10 to the 6th–10 to the 8th solar masses in nearby galaxies. Nature 333, 523–528 (1988).

  2. 2.

    Komossa, S. & Bade, N. The giant X-ray outbursts in NGC 5905 and IC 3599: follow-up observations and outburst scenarios. Astron. Astrophys. 343, 775–787 (1999).

  3. 3.

    Gezari, S. et al. An ultraviolet-optical flare from the tidal disruption of a helium-rich stellar core. Nature 485, 217–220 (2012).

  4. 4.

    Zauderer, B. A. et al. Radio monitoring of the tidal disruption event Swift J164449.3 + 573451. II. The relativistic jet shuts off and a transition to forward shock X-ray/radio emission. Astrophys. J. 767, 152 (2013).

  5. 5.

    Miller, J. M. et al. Flows of X-ray gas reveal the disruption of a star by a massive black hole. Nature 526, 542–545 (2015).

  6. 6.

    Lin, D. et al. A likely decade-long sustained tidal disruption event. Nat. Astron. 1, 0033 (2017).

  7. 7.

    Connelly, J. L. et al. Exploring the diversity of groups at 0.1 < z < 0.8 with X-ray and optically selected samples. Astrophys. J. 756, 139 (2012).

  8. 8.

    Remillard, R. A. & McClintock, J. E. X-ray properties of black-hole binaries. Annu. Rev. Astron. Astrophys. 44, 49–92 (2006).

  9. 9.

    Done, C., Gierliński, M. & Kubota, A. Modelling the behaviour of accretion flows in X-ray binaries. Everything you always wanted to know about accretion but were afraid to ask. Astron. Astrophys. Rev. 15, 1–66 (2007).

  10. 10.

    Done, C., Davis, S. W., Jin, C., Blaes, O. & Ward, M. Intrinsic disc emission and the soft X-ray excess in active galactic nuclei. Mon. Not. R. Astron. Soc. 420, 1848–1860 (2012).

  11. 11.

    Maraston, C. Evolutionary population synthesis: models, analysis of the ingredients and application to high-z galaxies. Mon. Not. R. Astron. Soc. 362, 799–825 (2005).

  12. 12.

    Mieske, S., Hilker, M. & Misgeld, I. The specific frequencies of ultra-compact dwarf galaxies. Astron. Astrophys. 537, A3 (2012).

  13. 13.

    Drinkwater, M. J. et al. A class of compact dwarf galaxies from disruptive processes in galaxy clusters. Nature 423, 519–521 (2003).

  14. 14.

    Pfeffer, J. & Baumgardt, H. Ultra-compact dwarf galaxy formation by tidal stripping of nucleated dwarf galaxies. Mon. Not. R. Astron. Soc. 433, 1997–2005 (2013).

  15. 15.

    Phinney, E. S. in The Center of the Galaxy Vol. 136 (ed. Morris, M.) 543–553 (Springer, Dordrecht, 1989).

  16. 16.

    Krolik, J. H. & Piran, T. Jets from tidal disruptions of stars by black holes. Astrophys. J. 749, 92 (2012).

  17. 17.

    Guillochon, J. & Ramirez-Ruiz, E. A dark year for tidal disruption events. Astrophys. J. 809, 166 (2015).

  18. 18.

    Li, L.-X., Narayan, R. & Menou, K. The giant X-ray flare of NGC 5905: tidal disruption of a star, a brown dwarf, or a planet? Astrophys. J. 576, 753–761 (2002).

  19. 19.

    Komossa, S. et al. A huge drop in the X-ray luminosity of the nonactive galaxy RX J1242.6-1119A, and the first postflare spectrum: testing the tidal disruption scenario. Astrophys. J. 603, L17–L20 (2004).

  20. 20.

    Van Velzen, S. et al. A radio jet from the optical and X-ray bright stellar tidal disruption flare ASASSN-14li. Science 351, 62–65 (2016).

  21. 21.

    Baumgardt, H., Makino, J. & Ebisuzaki, T. Massive black holes in star clusters. II. Realistic cluster models. Astrophys. J. 613, 1143–1156 (2004).

  22. 22.

    Brockamp, M., Baumgardt, H. & Kroupa, P. Tidal disruption rate of stars by supermassive black holes obtained by direct N-body simulations. Mon. Not. R. Astron. Soc. 418, 1308–1324 (2011).

  23. 23.

    Stone, N. C. & Metzger, B. D. Rates of stellar tidal disruption as probes of the supermassive black hole mass function. Mon. Not. R. Astron. Soc. 455, 859–883 (2016).

  24. 24.

    Lin, D. et al. Large decay of X-ray flux in 2XMM J123103.2 + 110648: evidence for a tidal disruption event. Mon. Not. R. Astron. Soc. 468, 783–789 (2017).

  25. 25.

    Norris, M. A. et al. The AIMSS Project—I. Bridging the star cluster–galaxy divide. Mon. Not. R. Astron. Soc. 443, 1151–1172 (2014).

  26. 26.

    Seth, A. C. et al. A supermassive black hole in an ultra-compact dwarf galaxy. Nature 513, 398–400 (2014).

  27. 27.

    Kzltan, B., Baumgardt, H. & Loeb, A. An intermediate-mass black hole in the centre of the globular cluster 47 Tucanae. Nature 542, 203–205 (2017).

  28. 28.

    Farrell, S. A., Webb, N. A., Barret, D., Godet, O. & Rodrigues, J. M. An intermediate-mass black hole of over 500 solar masses in the galaxy ESO243-49. Nature 460, 73–75 (2009).

  29. 29.

    Servillat, M. et al. X-ray variability and hardness of ESO 243-49 HLX-1: clear evidence for spectral state transitions. Astrophys. J. 743, 6 (2011).

  30. 30.

    Godet, O. et al. Investigating slim disk solutions for HLX-1 in ESO 243-49. Astrophys. J. 752, 34 (2012).

  31. 31.

    Jansen, F. et al. XMM-Newton observatory. I. The spacecraft and operations. Astron. Astrophys. 365, L1–L6 (2001).

  32. 32.

    Strüder, L. et al. The European Photon Imaging Camera on XMM-Newton: the pn-CCD camera. Astron. Astrophys. 365, L18–L26 (2001).

  33. 33.

    Turner, M. J. L. et al. The European Photon Imaging Camera on XMM-Newton: the MOS cameras. Astron. Astrophys. 365, L27–L35 (2001).

  34. 34.

    Watson, M. G. et al. The XMM-Newton serendipitous survey. V. The second XMM-Newton serendipitous source catalogue. Astron. Astrophys. 493, 339–373 (2009).

  35. 35.

    Bautz, M. W. et al. X-ray CCD calibration for the AXAF CCD Imaging Spectrometer. Proc. SPIE 3444, 210–224 (1998).

  36. 36.

    Lin, D. et al. Discovery of the candidate off-nuclear ultrasoft hyper-luminous X-ray source 3XMM J141711.1 + 522541. Astrophys. J. 821, 25 (2016).

  37. 37.

    Freeman, P. E., Kashyap, V., Rosner, R. & Lamb, D. Q. A wavelet-based algorithm for the spatial analysis of Poisson data. Astrophys. J. Suppl. Ser. 138, 185–218 (2002).

  38. 38.

    Cuillandre, J.-C., Luppino, G. A., Starr, B. M. & Isani, S. Performance of the CFH12K: a 12K by 8K CCD mosaic camera for the CFHT prime focus. Proc. SPIE 4008, 1010–1021 (2000).

  39. 39.

    Burrows, D. N. et al. The Swift X-Ray Telescope. Space Sci. Rev. 120, 165–195 (2005).

  40. 40.

    Mason, K. O. et al. The XMM-Newton optical/UV monitor telescope. Astron. Astrophys. 365, L36–L44 (2001).

  41. 41.

    Roming, P. W. A. et al. The Swift Ultra-Violet/Optical Telescope. Space Sci. Rev. 120, 95–142 (2005).

  42. 42.

    Sirianni, M. et al. The photometric performance and calibration of the Hubble Space Telescope Advanced Camera for Surveys. Publ. Astron. Soc. Pacif. 117, 1049–1112 (2005).

  43. 43.

    Boulade, O. et al. MegaCam: the new Canada–France–Hawaii Telescope wide-field imaging camera. Proc. SPIE 4841, 72–81 (2003).

  44. 44.

    Puget, P. et al. WIRCam: the infrared wide-field camera for the Canada–France–Hawaii Telescope. Proc. SPIE 5492, 978–987 (2004).

  45. 45.

    Balogh, M. L. et al. The colour of galaxies in distant groups. Mon. Not. R. Astron. Soc. 398, 754–768 (2009).

  46. 46.

    Peng, C. Y., Ho, L. C., Impey, C. D. & Rix, H.-W. Detailed decomposition of Galaxy images. II. Beyond axisymmetric models. Astron. J. 139, 2097–2129 (2010).

  47. 47.

    Hook, I. M. et al. The Gemini–North multi-object spectrograph: performance in imaging, long-slit, and multi-object spectroscopic modes. Publ. Astron. Soc. Pacif. 116, 425–440 (2004).

  48. 48.

    Cappellari, M. & Emsellem, E. Parametric recovery of line-of-sight velocity distributions from absorption-line spectra of galaxies via penalized likelihood. Publ. Astron. Soc. Pacif. 116, 138–147 (2004).

  49. 49.

    Vazdekis, A. et al. Evolutionary stellar population synthesis with MILES—I. The base models and a new line index system. Mon. Not. R. Astron. Soc. 404, 1639–1671 (2010).

  50. 50.

    Schlegel, D. J., Finkbeiner, D. P. & Davis, M. Maps of dust infrared emission for use in estimation of reddening and cosmic microwave background radiation foregrounds. Astrophys. J. 500, 525–553 (1998).

  51. 51.

    Homan, J. et al. A strongly heated neutron star in the transient Z source MAXI J0556-332. Astrophys. J. 795, 131 (2014).

  52. 52.

    Degenaar, N., Ootes, L. S., Reynolds, M. T., Wijnands, R. & Page, D. A cold neutron star in the transient low-mass X-ray binary HETE J1900.1-2455 after 10 yr of active accretion. Mon. Not. R. Astron. Soc. 465, L10–L14 (2017).

  53. 53.

    Wijnands, R., Degenaar, N. & Page, D. Cooling of accretion-heated neutron stars. J. Astrophys. Astron. 38, 49 (2017).

  54. 54.

    Haensel, P. & Zdunik, J. L. Non-equilibrium processes in the crust of an accreting neutron star. Astron. Astrophys. 227, 431–436 (1990).

  55. 55.

    Brown, E. F., Bildsten, L. & Rutledge, R. E. Crustal heating and quiescent emission from transiently accreting neutron stars. Astrophys. J. 504, L95 (1998).

  56. 56.

    Levine, A. M. et al. First results from the All-Sky Monitor on the Rossi X-Ray Timing Explorer. Astrophys. J. 469, L33 (1996).

  57. 57.

    Page, D., Lattimer, J. M., Prakash, M. & Steiner, A. W. Minimal cooling of neutron stars: a new paradigm. Astrophys. J. Suppl. Ser. 155, 623–650 (2004).

  58. 58.

    Page, D. & Reddy, S. Forecasting neutron star temperatures: predictability and variability. Phys. Rev. Lett. 111, 241102 (2013).

  59. 59.

    Page, D. NSCool: Neutron Star Cooling Code (Astrophysics Source Code Library, 2016).

  60. 60.

    Foreman-Mackey, D., Hogg, D. W., Lang, D. & Goodman, J. emcee: the MCMC hammer. Publ. Astron. Soc. Pacif. 125, 306 (2013).

  61. 61.

    Armas Padilla, M., Degenaar, N. & Wijnands, R. The X-ray spectral properties of very-faint persistent neutron star X-ray binaries. Mon. Not. R. Astron. Soc. 434, 1586–1592 (2013).

  62. 62.

    Brown, E. F. & Cumming, A. Mapping crustal heating with the cooling light curves of quasi-persistent transients. Astrophys. J. 698, 1020–1032 (2009).

  63. 63.

    Deibel, A., Cumming, A., Brown, E. F. & Page, D. A strong shallow heat source in the accreting neutron star MAXI J0556-332. Astrophys. J. 809, L31 (2015).

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D.L. is supported by the National Aeronautics and Space Administration (NASA) through Chandra Award number GO6-17046X issued by the Chandra X-ray Observatory Center, which is operated by the Smithsonian Astrophysical Observatory for and on behalf of the NASA under contract NAS8-03060, and by the NASA ADAP grant NNX17AJ57G. A.J.R. was supported by National Science Foundation (NSF) grant AST-1515084, and as a Research Corporation for Science Advancement Cottrell Scholar. J.S. acknowledges support from NSF grant AST-1514763 and a Packard Fellowship. D.P. was partially supported by the Consejo Nacional de Ciencia y Tecnología with CB-2014-1 grant number 240512. N.A.W., O.G. and D.B. acknowledge CNES for financial support to the XMM-Newton Survey Science Center activities. R.W. acknowledges support from the Netherlands Organisation for Scientific Research through a TOP Grant, module 1. J.P.B. acknowledges support from NSF grant AST 1518294. We thank the former Swift principal investigator N. Gehrels for approving our target of opportunity request to observe J2150–0551. We thank Z. Jennings for assistance with the Suprime-Cam data. The findings in this paper are based on observations obtained from XMM-Newton, Chandra, Swift, HST, CFHT, Gemini, SOAR and Subaru.

Author information


  1. Space Science Center, University of New Hampshire, Durham, NH, USA

    • Dacheng Lin
  2. Center for Data Intensive and Time Domain Astronomy, Department of Physics and Astronomy, Michigan State University, East Lansing, MI, USA

    • Jay Strader
  3. Gemini Observatory/AURA, Southern Operations Center, La Serena, Chile

    • Eleazar R. Carrasco
  4. Instituto de Astronomía, Universidad Nacional Autónoma de México, Mexico City, Mexico

    • Dany Page
  5. Department of Physics and Astronomy, San José State University, San José, CA, USA

    • Aaron J. Romanowsky
  6. University of California Observatories, Santa Cruz, CA, USA

    • Aaron J. Romanowsky
    •  & Jean P. Brodie
  7. Eureka Scientific, Oakland, CA, USA

    • Jeroen Homan
  8. SRON, Netherlands Institute for Space Research, Utrecht, The Netherlands

    • Jeroen Homan
  9. Department of Physics and Astronomy, University of Alabama, Tuscaloosa, AL, USA

    • Jimmy A. Irwin
  10. MIT Kavli Institute for Astrophysics and Space Research, MIT, Cambridge, MA, USA

    • Ronald A. Remillard
  11. IRAP, Universit de Toulouse, CNRS, UPS, CNES, Toulouse, France

    • Olivier Godet
    • , Natalie A. Webb
    •  & Didier Barret
  12. School of Mathematics and Physics, University of Queensland, St Lucia, Queensland, Australia

    • Holger Baumgardt
  13. Anton Pannekoek Institute for Astronomy, University of Amsterdam, Amsterdam, The Netherlands

    • Rudy Wijnands
  14. Université de Strasbourg, CNRS, Observatoire Astronomique de Strasbourg, UMR 7550, Strasbourg, France

    • Pierre-Alain Duc
  15. Canadian Astronomy Data Centre, Herzberg Institute of Astrophysics, Victoria, British Columbia, Canada

    • Stephen D. J. Gwyn


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D.L. wrote the main manuscript and led the data analysis. E.R.C. helped reduce the GMOS spectra and pre-imaging. D.P. performed the MCMC simulations for NSCool. J.S. obtained the SOAR U-band image and fitted the HST image with ISHAPE. A.J.R. obtained the Subaru g′-band image. S.D.J.G. stacked the CFHT images. All authors discussed the results and commented on the manuscript.

Competing interests

The authors declare no competing interests.

Corresponding author

Correspondence to Dacheng Lin.

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