Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

A direct localization of a fast radio burst and its host


Fast radio bursts1,2 are astronomical radio flashes of unknown physical nature with durations of milliseconds. Their dispersive arrival times suggest an extragalactic origin and imply radio luminosities that are orders of magnitude larger than those of all known short-duration radio transients3. So far all fast radio bursts have been detected with large single-dish telescopes with arcminute localizations, and attempts to identify their counterparts (source or host galaxy) have relied on the contemporaneous variability of field sources4 or the presence of peculiar field stars5 or galaxies4. These attempts have not resulted in an unambiguous association6,7 with a host or multi-wavelength counterpart. Here we report the subarcsecond localization of the fast radio burst FRB 121102, the only known repeating burst source8,9,10,11, using high-time-resolution radio interferometric observations that directly image the bursts. Our precise localization reveals that FRB 121102 originates within 100 milliarcseconds of a faint 180-microJansky persistent radio source with a continuum spectrum that is consistent with non-thermal emission, and a faint (twenty-fifth magnitude) optical counterpart. The flux density of the persistent radio source varies by around ten per cent on day timescales, and very long baseline radio interferometry yields an angular size of less than 1.7 milliarcseconds. Our observations are inconsistent with the fast radio burst having a Galactic origin or its source being located within a prominent star-forming galaxy. Instead, the source appears to be co-located with a low-luminosity active galactic nucleus or a previously unknown type of extragalactic source. Localization and identification of a host or counterpart has been essential to understanding the origins and physics of other kinds of transient events, including gamma-ray bursts12,13 and tidal disruption events14. However, if other fast radio bursts have similarly faint radio and optical counterparts, our findings imply that direct subarcsecond localizations may be the only way to provide reliable associations.

This is a preview of subscription content, access via your institution

Relevant articles

Open Access articles citing this article.

Access options

Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Figure 1: VLA detection of FRB 121102.
Figure 2: Radio and optical images of the FRB 121102 field.
Figure 3: Broadband spectral energy distribution of the counterpart.


  1. Lorimer, D. R., Bailes, M., McLaughlin, M. A., Narkevic, D. J. & Crawford, F. A bright millisecond radio burst of extragalactic origin. Science 318, 777–780 (2007)

    Article  CAS  ADS  Google Scholar 

  2. Thornton, D. et al. A population of fast radio bursts at cosmological distances. Science 341, 53–56 (2013)

    Article  CAS  ADS  Google Scholar 

  3. Cordes, J. M. & Wasserman, I. Supergiant pulses from extragalactic neutron stars. Mon. Not. R. Astron. Soc. 457, 232–257 (2016)

    Article  CAS  ADS  Google Scholar 

  4. Keane, E. F. et al. The host galaxy of a fast radio burst. Nature 530, 453–456 (2016)

    Article  CAS  ADS  Google Scholar 

  5. Loeb, A., Shvartzvald, Y. & Maoz, D. Fast radio bursts may originate from nearby flaring stars. Mon. Not. R. Astron. Soc. 439, L46–L50 (2014)

    Article  ADS  Google Scholar 

  6. Williams, P. K. G. & Berger, E. No precise localization for FRB 150418: claimed radio transient is AGN Variability. Astrophys. J. 821, L22 (2016)

    Article  ADS  Google Scholar 

  7. Vedantham, H. K. et al. On associating fast radio bursts with afterglows. Astrophys. J. 824, L9 (2016)

    Article  ADS  Google Scholar 

  8. Spitler, L. G. et al. Fast radio burst discovered in the Arecibo pulsar ALFA survey. Astrophys. J. 790, 101 (2014)

    Article  ADS  Google Scholar 

  9. Spitler, L. G. et al. A repeating fast radio burst. Nature 531, 202–205 (2016)

    Article  CAS  ADS  Google Scholar 

  10. Scholz, P. et al. The repeating fast radio burst FRB 121102: multi-wavelength observations and additional bursts. Astrophys. J. (in the press); preprint at

  11. Petroff, E. et al. A survey of FRB fields: limits on repeatability. Mon. Not. R. Astron. Soc. 454, 457–462 (2015)

    Article  ADS  Google Scholar 

  12. Metzger, M. R. et al. Spectral constraints on the redshift of the optical counterpart to the γ-ray burst of 8 May 1997. Nature 387, 878–880 (1997)

    Article  CAS  ADS  Google Scholar 

  13. Bloom, J. S., Kulkarni, S. R. & Djorgovski, S. G. The observed offset distribution of gamma-ray bursts from their host galaxies: a robust clue to the nature of the progenitors. Astron. J 123, 1111–1148 (2002)

    Article  ADS  Google Scholar 

  14. Gezari, S. et al. Ultraviolet detection of the tidal disruption of a star by a supermassive black hole. Astrophys. J. 653, L25–L28 (2006)

    Article  CAS  ADS  Google Scholar 

  15. Law, C. J. et al. A millisecond interferometric search for fast radio bursts with the Very Large Array. Astrophys. J. 807, 16 (2015)

    Article  ADS  Google Scholar 

  16. Maoz, D. et al. Fast radio bursts: the observational case for a Galactic origin. Mon. Not. R. Astron. Soc. 454, 2183–2189 (2015)

    Article  CAS  ADS  Google Scholar 

  17. Cordes, J. M. & Lazio, T. J. W. NE2001.I. A new model for the galactic distribution of free electrons and its fluctuations. Preprint at (2002)

  18. Inoue, S. Probing the cosmic reionization history and local environment of gamma-ray bursts through radio dispersion. Mon. Not. R. Astron. Soc. 348, 999–1008 (2004)

    Article  CAS  ADS  Google Scholar 

  19. McQuinn, M. Locating the “missing” baryons with extragalactic dispersion measure estimates. Astrophys. J. 780, L33 (2014)

    Article  ADS  Google Scholar 

  20. Carilli, C. L. & Yun, M. S. The radio-to-submillimeter spectral index as a redshift indicator. Astrophys. J. 513, L13–L16 (1999)

    Article  ADS  Google Scholar 

  21. Condon, J. J. Radio emission from normal galaxies. Annu. Rev. Astron. Astrophys. 30, 575–611 (1992)

    Article  ADS  Google Scholar 

  22. Lonsdale, C. J., Diamond, P. J., Thrall, H., Smith, H. E. & Lonsdale, C. J. VLBI images of 49 radio supernovae in Arp 220. Astrophys. J. 647, 185–193 (2006)

    Article  CAS  ADS  Google Scholar 

  23. Pen, U.-L. & Connor, L. Local circumnuclear magnetar solution to extragalactic fast radio bursts. Astrophys. J. 807, 179 (2015)

    Article  ADS  Google Scholar 

  24. Lyubarsky, Y. A model for fast extragalactic radio bursts. Mon. Not. R. Astron. Soc. 442, L9–L13 (2014)

    Article  ADS  Google Scholar 

  25. Romero, G. E., del Valle, M. V. & Vieyro, F. L. Mechanism for fast radio bursts. Phys. Rev. D 93, 023001 (2016)

    Article  ADS  Google Scholar 

  26. Lundgren, S. C. et al. Giant pulses from the crab pulsar: a joint radio and gamma-ray study. Astrophys. J. 453, 433–445 (1995)

    Article  ADS  Google Scholar 

  27. Kinkhabwala, A. & Thorsett, S. E. Multifrequency observations of giant radio pulses from the millisecond pulsar B1937+21. Astrophys. J. 535, 365–372 (2000)

    Article  ADS  Google Scholar 

  28. Reines, A. E. & Deller, A. T. Parsec-scale radio emission from the low-luminosity active galactic nucleus in the dwarf starburst galaxy Henize 2-10. Astrophys. J. 750, L24 (2012)

    Article  ADS  Google Scholar 

  29. Elvis, M. et al. Atlas of quasar energy distributions. Astrophys. J. Suppl. Ser. 95, 1–68 (1994)

    Article  ADS  Google Scholar 

  30. Bühler, R. & Blandford, R. The surprising Crab pulsar and its nebula: a review. Rep. Prog. Phys. 77, 066901 (2014)

    Article  ADS  Google Scholar 

  31. McMullin, J. P., Waters, B., Schiebel, D., Young, W. & Golap, K. CASA Architecture and Applications. In Astronomical Data Analysis Software and Systems XVI (eds Shaw, R. A. et al.) 127–130 (ASP Conf. Ser. Vol. 376, Astronomical Society of the Pacific, 2007)

  32. Perley, R. A. & Butler, B. J. An accurate flux density scale from 1 to 50 GHz. Astrophys. J. Suppl. Ser. 204, 19 (2013)

    Article  ADS  Google Scholar 

  33. Zacharias, N. et al. The U.S. Naval Observatory Robotic Astrometric Telescope 1st Catalog (URAT1). In American Astronomical Society Meeting Abstracts Vol. 225, abstr. 433.01 (American Astronomical Society, 2015)

  34. Drew, J. E. et al. The INT Photometric Hα Survey of the Northern Galactic Plane (IPHAS). Mon. Not. R. Astron. Soc. 362, 753–776 (2005)

    Article  CAS  ADS  Google Scholar 

  35. van Dokkum, P. G. et al. Forty-seven Milky Way-sized, extremely diffuse galaxies in the Coma cluster. Astrophys. J. 798, L45 (2015)

    Article  ADS  Google Scholar 

  36. Lawrence, A. et al. The UKIRT Infrared Deep Sky Survey (UKIDSS). Mon. Not. R. Astron. Soc. 379, 1599–1617 (2007)

    Article  ADS  Google Scholar 

  37. Benjamin, R. A. et al. GLIMPSE. I. An SIRTF Legacy project to map the inner galaxy. Publ. Astron. Soc. Pac. 115, 953–964 (2003)

    Article  ADS  Google Scholar 

  38. Churchwell, E. et al. The Spitzer/GLIMPSE surveys: a new view of the Milky Way. Publ. Astron. Soc. Pac. 121, 213–230 (2009)

    Article  ADS  Google Scholar 

  39. 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)

    Article  ADS  Google Scholar 

  40. Schlafly, E. F. & Finkbeiner, D. P. Measuring reddening with Sloan Digital Sky Survey stellar spectra and recalibrating SFD. Astrophys. J. 737, 103 (2011)

    Article  ADS  Google Scholar 

  41. Bessell, M. S., Castelli, F. & Plez, B. Model atmospheres broad-band colors, bolometric corrections and temperature calibrations for O - M stars. Astron. Astrophys. 333, 231–250 (1998)

    ADS  Google Scholar 

  42. Fukugita, M. et al. The Sloan Digital Sky Survey photometric system. Astron. J. 111, 1748–1756 (1996)

    Article  CAS  ADS  Google Scholar 

  43. Hewett, P. C., Warren, S. J., Leggett, S. K. & Hodgkin, S. T. The UKIRT Infrared Deep Sky Survey ZY JHK photometric system: passbands and synthetic colours. Mon. Not. R. Astron. Soc. 367, 454–468 (2006)

    Article  CAS  ADS  Google Scholar 

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

    Article  ADS  Google Scholar 

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

    Article  ADS  Google Scholar 

  46. He, C., Ng, C.-Y. & Kaspi, V. M. The correlation between dispersion measure and X-Ray column density from radio pulsars. Astrophys. J. 768, 64 (2013)

    Article  ADS  Google Scholar 

  47. Körding, E., Falcke, H. & Corbel, S. Refining the fundamental plane of accreting black holes. Astron. Astrophys. 456, 439–450 (2006)

    Article  ADS  Google Scholar 

Download references


The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities. We thank the staff at the NRAO for their continued support of these observations, especially with scheduling and computational infrastructure. The Arecibo Observatory is operated by SRI International under a cooperative agreement with the National Science Foundation (AST-1100968), and in alliance with Ana G. Méndez-Universidad Metropolitana and the Universities Space Research Association. We thank the staff at Arecibo for their support and dedication that enabled these observations. Further acknowledgements of telescope facilities and funding agencies are included as Supplementary Information.

Author information

Authors and Affiliations



S.C. was principal investigator of the localization campaign described here. C.J.L. and S.B.-S. are principal investigators of the realfast project and performed the analysis that achieved the first VLA burst detections. S.C., C.J.L., R.S.W., S.B.-S., G.C.B., B.B. and P.D. performed detailed analysis of the VLA data. S.B.-S. and B.B. led the analysis of the VLA multi-band spectral data. J.W.T.H. was principal investigator of the EVN observations, which were analysed by Z.P. and B.M. G.C.B. was principal investigator of the VLBA observations, and led their analysis. J.W.T.H., A.S. and L.G.S. led the execution and analysis of the parallel Arecibo observing campaign. P.D. led the commissioning of fast-sampled VLA observing modes. S.C. was principal investigator of the ALMA observations. P.S. was principal investigator of the X-ray observations, and performed the X-ray analysis, along with S.B. S.P.T. was principal investigator of the Gemini observations, and along with C.G.B. led the analysis of Keck, Gemini and archival UKIDSS and GLIMPSE data. S.C. and C.J.L. led the writing of the manuscript, with substantial contributions from J.M.C. and J.W.T.H. All authors contributed substantially to the interpretation of the analysis results and to the final version of the manuscript.

Corresponding author

Correspondence to S. Chatterjee.

Ethics declarations

Competing interests

The authors declare no competing financial interests.

Additional information

Reviewer Information Nature thanks H. Falcke and G. Hallinan for their contribution to the peer review of this work.

Extended data figures and tables

Extended Data Figure 1 The offset of FRB 121102 from the persistent counterpart.

Five bursts detected at the VLA with the highest resolution (A-array, 3 GHz) are plotted (crosses), with epoch indicated by MJD values. The (right ascension (RA), declination (Dec)) coordinate difference (burst relative to counterpart) is shown with an ellipse indicating the 1σ error calculated as the quadrature sum of errors in the two sources. VLBA and EVN positions are indicated, with 1σ errors smaller than the symbols. The centroid of the Gemini optical counterpart is shown (red dot) with an estimated 1σ error circle of 100 mas (red) from fitting and radio-optical frame tie uncertainties.

Source data

Extended Data Figure 2 VLA spectrum of the persistent counterpart to FRB 121102.

The integrated flux density Fν is plotted for each epoch of observation (listed by MJD) over a frequency range ν from 1 GHz to 25 GHz. Error bars represent 1σ uncertainties. The spectrum is non-thermal and inconsistent with a single power law.

Source data

Extended Data Table 1 VLA detections of bursts from FRB 121102 and Arecibo constraints
Extended Data Table 2 VLA 3-GHz observations of the persistent counterpart to FRB 121102 over time
Extended Data Table 3 Flux density and position measurements of the persistent counterpart to FRB 121102

Supplementary information

Supplementary Information

This file contains extended acknowledgements. (PDF 62 kb)

PowerPoint slides

Source data

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Chatterjee, S., Law, C., Wharton, R. et al. A direct localization of a fast radio burst and its host. Nature 541, 58–61 (2017).

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI:

This article is cited by


By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.


Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing