A kilonova associated with GRB 070809

Article metrics

Abstract

For on-axis typical short gamma-ray bursts (sGRBs), the forward shock emission is usually so bright1,2 that it renders the identification of kilonovae (also known as macronovae)3,4,5,6 in the early afterglow (t < 0.5 d) phase rather challenging. This is why previously no thermal-like kilonova component has been identified at such an early time7,8,9,10,11,12,13 except in the off-axis dim GRB 170817A (refs. 14,15,16,17,18,19) associated with GW170817 (ref. 20). Here we report the identification of an unusual optical radiation component in GRB 070809 at t ~ 0.47 d, thanks plausibly to the very-weak/subdominant forward shock emission. The optical emission with a very red spectrum is well in excess of the extrapolation of the X-ray emission that is distinguished by an unusually hard spectrum, which is at odds with the forward shock afterglow prediction but can be naturally interpreted as a kilonova. Our finding supports the speculation that kilonovae are ubiquitous11, and demonstrates the possibility of revealing the neutron star merger origin with the early afterglow data of some typical sGRBs that take place well beyond the sensitive radius of the advanced gravitational wave detectors21,22 and hence the opportunity of organizing dedicated follow-up observations for events of interest.

Access optionsAccess options

Rent or Buy article

Get time limited or full article access on ReadCube.

from$8.99

All prices are NET prices.

Fig. 1: Keck and HST observations of GRB 070809.
Fig. 2: Light curves and SEDs of GRB 070809.
Fig. 3: The optical to X-ray SEDs of sGRBs.
Fig. 4: Comparison of kilonova signal of GRB 070809 with other kilonova event and candidates.

Data availability

The Keck, HST, Gemini and Swift observation data analysed/used in this work are all publicly available.

Code availability

The codes used in this analysis are standard in the community, as introduced in Methods.

References

  1. 1.

    Eichler, D., Livio, M., Piran, T. & Schramm, D. N. Nucleosynthesis, neutrino bursts and gamma-rays from coalescing neutron stars. Nature 340, 126–128 (1989).

  2. 2.

    Berger, E. Short-duration gamma-ray bursts. Annu. Rev. Astron. Astrophys. 52, 43–105 (2014).

  3. 3.

    Li, L. X. & Paczyński, B. Transient events from neutron star mergers. Astrophys. J. Lett. 507, L59–L62 (1998).

  4. 4.

    Kasen, D., Badnell, N. R. & Barnes, J. Opacities and spectra of the r-process ejecta from neutron star mergers. Astrophys. J. 774, 25 (2013).

  5. 5.

    Tanaka, M. & Hotokezaka, K. Radiative transfer simulations of neutron star merger ejecta. Astrophys. J. 775, 113 (2013).

  6. 6.

    Metzger, B. D. Kilonovae. Living Rev. Relativ. 20, 3 (2017).

  7. 7.

    Tanvir, N. R. et al. A ‘kilonova’ associated with the short-duration gamma-ray burst GRB 130603B. Nature 500, 547–549 (2013).

  8. 8.

    Berger, E., Fong, W. & Chornock, R. An r-process kilonova associated with the short-hard GRB 130603B. Astrophys. J. Lett. 744, L23 (2013).

  9. 9.

    Yang, B. et al. A possible macronova in the late afterglow of the long–short burst GRB 060614. Nat. Commun. 6, 7323 (2015).

  10. 10.

    Jin, Z. P. et al. The light curve of the macronova associated with the long–short burst GRB 060614. Astrophys. J. Lett. 811, L22 (2015).

  11. 11.

    Jin, Z. P. et al. The macronova in GRB 050709 and the GRB-macronova connection. Nat. Commun. 7, 12898 (2016).

  12. 12.

    Jin, Z. P. et al. Short GRBs: opening angles, local neutron star merger rate, and off-axis events for GRB/GW association. Astrophys. J. 857, 128 (2018).

  13. 13.

    Troja, E. et al. A luminous blue kilonova and an off-axis jet from a compact binary merger at z = 0.1341. Nat. Commun. 9, 4089 (2018).

  14. 14.

    Goldstein, A. et al. An ordinary short gamma-ray burst with extraordinary implications: Fermi-GBM detection of GRB 170817A. Astrophys. J. Lett. 848, L14 (2017).

  15. 15.

    Pian, E. et al. Spectroscopic identification of r-process nucleosynthesis in a double neutron-star merger. Nature 551, 67–70 (2017).

  16. 16.

    Drout, M. R. et al. Light curves of the neutron star merger GW170817/SSS17a: implications for r-process nucleosynthesis. Science 358, 1570–1574 (2017).

  17. 17.

    Kasliwal, M. M. et al. Illuminating gravitational waves: a concordant picture of photons from a neutron star merger. Science 358, 1559–1565 (2017a).

  18. 18.

    Arcavi, I. et al. Optical emission from a kilonova following a gravitational-wave-detected neutron-star merger. Nature 551, 64–66 (2017).

  19. 19.

    Cowperthwaite, P. S. et al. The electromagnetic counterpart of the binary neutron star merger LIGO/Virgo GW170817. II. UV, optical, and near-infrared light curves and comparison to kilonova models. Astrophys. J. Lett. 848, L17 (2017).

  20. 20.

    Abbott, T. D. et al. GW170817: observation of gravitational waves from a binary neutron star inspiral. Phys. Rev. Lett. 119, 161101 (2017).

  21. 21.

    Abbott, B. P. et al. Prospects for observing and localizing gravitational-wave transients with Advanced LIGO, Advanced Virgo and KAGRA. Living Rev. Relativ. 21, 3 (2018).

  22. 22.

    Li, X., Hu, Y. M., Fan, Y. Z. & Wei, D. M. GRB/GW association: long–short GRB candidates, time-lag, measuring gravitational wave velocity and testing Einstein’s equivalence principle. Astrophys. J. 827, 75 (2016).

  23. 23.

    Marshall, F. E. et al. Swift Observations of GRB 070809 Report 80 (GCN, 2007).

  24. 24.

    Perley, D. A., Thoene, C. C., Cooke, J., Bloom, J. S. & Barton, E. GRB 070809: Confirmation of Optical Transient Circular 6774 (GCN, 2007).

  25. 25.

    Berger, E. A short gamma-ray burst “no-host” problem? Investigating large progenitor offsets for short GRBs with optical afterglows. Astrophys. J. 722, 1946–1961 (2010).

  26. 26.

    Perley, D. A., Thoene, C. C. & Bloom, J. S. GRB 070809: Putative Host Galaxy and Redshift Circular 7889 (GCN, 2008).

  27. 27.

    Planck Collaboration. Planck 2018 results. VI. Cosmological parameters. Preprint at https://arxiv.org/abs/1807.06209 (2018).

  28. 28.

    Alexander, K. D. et al. A decline in the X-ray through radio emission from GW170817 continues to support an off-axis structured jet. Astrophys. J. Lett. 863, L18 (2018).

  29. 29.

    Piro, L. et al. A long-lived neutron star merger remnant in GW170817: constraints and clues from X-ray observations. Mon. Not. R. Astron. Soc. 483, 1912–1921 (2019).

  30. 30.

    de Ugarte Postigo, A. et al. Spectroscopy of the short-hard GRB130603B: the host galaxy and environment of a compact object merger. Astron. Astrophys. 563, 62 (2014).

  31. 31.

    Rykoff, E. S. et al. GRB 070809: ROTSE-III Optical Limits Circular 6279 (GCN, 2007).

  32. 32.

    Evans, P. A. et al. Methods and results of an automatic analysis of a complete sample of Swift-XRT observations of GRBs. Mon. Not. R. Astron. Soc. 397, 1177–1201 (2009).

  33. 33.

    Malesani, D. et al. Multicolor observations of the afterglow of the short/hard GRB050724. Astron. Astrophys. 473, 77–84 (2007).

  34. 34.

    Soderberg, A. M. et al. The afterglow, energetics, and host galaxy of the short-hard gamma-ray burst 051221a. Astrophys. J. 650, 261–271 (2006).

  35. 35.

    Burrows, D. N. et al. Jet breaks in short gamma-ray bursts. II. The collimated afterglow of GRB 051221A. Astrophys. J. 653, 468–473 (2006).

  36. 36.

    Mangano, V. et al. Swift observations of GRB 060614: an anomalous burst with a well behaved afterglow. Astron. Astrophys. 470, 105–118 (2007).

  37. 37.

    Stratta, G. et al. A study of the prompt and afterglow emission of the short GRB 061201. Astron. Astrophys. 474, 827–835 (2007).

  38. 38.

    Berger, E., Cenko, S. B., Fox, D. B. & Cucchiara, A. Discovery of the very red near-infrared and optical afterglow of the short-duration GRB 070724A. Astrophys. J. 704, 877 (2009).

  39. 39.

    Kocevski, D. et al. Limits on radioactive powered emission associated with a short-hard GRB 070724A in a star-forming galaxy. Mon. Not. R. Astron. Soc. 404, 963 (2010).

  40. 40.

    Antonelli, L. A. et al. GRB090426: the farthest short gamma-ray burst? Astron. Astrophys. 507, L45–L48 (2009).

  41. 41.

    Nicuesa Guelbenzu, A. et al. The late-time afterglow of the extremely energetic short burst GRB 090510 revisited. Astron. Astrophys. 538, 7 (2012).

  42. 42.

    Troja, E. et al. An achromatic break in the afterglow of the short GRB 140903A: evidence for a narrow jet. Astrophys. J. 827, 102 (2016).

  43. 43.

    Knust, F. et al. Long optical plateau in the afterglow of the short GRB 150424A with extended emission. Astron. Astrophys. 607, 84 (2017).

  44. 44.

    Kasliwal, M. M., Korobkin, O., Lau, R. M., Wollaeger, R. & Fryer, C. L. Infrared emission from kilonovae: the case of the nearby short hard burst GRB 160821B. Astrophys. J. Lett. 843, L34 (2017).

  45. 45.

    Coulter, D. A. et al. Swope Supernova Survey 2017a (SSS17a), the optical counterpart to a gravitational wave source. Science 358, 1556–1558 (2017).

  46. 46.

    Hjorth, J. et al. The distance to NGC 4993: the host galaxy of the gravitational-wave event GW170817. Astrophys. J. Lett. 848, L31 (2017).

  47. 47.

    Troja, E. et al. The outflow structure of GW170817 from late-time broad-band observations. Mon. Not. R. Astron. Soc. 478, L18–L23 (2018).

  48. 48.

    D’Avanzo, P. et al. The evolution of the X-ray afterglow emission of GW 170817/ GRB 170817A in XMM-Newton observations. Astron. Astrophys. 613, L1 (2018).

  49. 49.

    Schlafly, E. F. & Finkbeiner, D. P. Measuring reddening with Sloan Digital Sky Survey stellar spectra and recalibrating SFD. Astrophys. J. 737, 103–115 (2011).

  50. 50.

    Troja, E. et al. The afterglow and kilonova of the short GRB 160821B. Preprint at https://arxiv.org/abs/1905.01290 (2019).

  51. 51.

    Lamb, G. P. et al. Short GRB 160821B: a reverse shock, a refreshed shock, and a well-sampled kilonova. Preprint at https://arxiv.org/abs/1905.02159 (2019).

  52. 52.

    Piran, T. The physics of gamma-ray bursts. Rev. Mod. Phys. 76, 1143–1210 (2004).

  53. 53.

    Nakar, E., Ando, S. & Sari, R. Klein-Nishina effects on optically thin synchrotron and synchrotron self-Compton spectrum. Astrophys. J. 703, 675 (2009).

  54. 54.

    Fan, Y. Z., Zhang, B. & Proga, D. Linearly polarized X-ray flares following short gamma-ray bursts. Astrophys. J. Lett. 635, L129–L132 (2005).

  55. 55.

    Metzger, B. D. & Fernández, R. Red or blue? a potential kilonova imprint of the delay until black hole formation following a neutron star merger. Mon. Not. R. Astron. Soc. 441, 3444–3453 (2014).

  56. 56.

    Kasen, D., Fernández, R. & Metzger, B. D. Kilonova light curves from the disc wind outflows of compact object mergers. Mon. Not. R. Astron. Soc. 450, 1777–1786 (2015).

  57. 57.

    Smartt, S. J. et al. A kilonova as the electromagnetic counterpart to a gravitational-wave source. Nature 551, 75–79 (2017).

  58. 58.

    Chornock, R. et al. The electromagnetic counterpart of the binary neutron star merger LIGO/Virgo GW170817. IV. Detection of near-infrared signatures of r-process nucleosynthesis with Gemini-South. Astrophys. J. Lett. 848, L19 (2017).

  59. 59.

    Valenti, S. et al. The discovery of the electromagnetic counterpart of GW170817: kilonova AT 2017gfo/DLT17ck. Astrophys. J. Lett. 848, L24 (2017).

  60. 60.

    Fong, W. et al. The afterglow and early-type host galaxy of the short GRB 150101B at z = 0.1343. Astrophys. J. 833, 151 (2016).

Download references

Acknowledgements

This work was supported in part by NSFC under grants no. 11525313 (that is, Funds for Distinguished Young Scholars), no. 11433009 and no. 11773078, the Funds for Distinguished Young Scholars of Jiangsu Province (no. BK20180050), the Chinese Academy of Sciences via the Strategic Priority Research Programme (grant no. XDB23040000) and the Key Research Programme of Frontier Sciences (no. QYZDJ-SSW-SYS024). S.C. and P.D. have been supported by ASI grant I/004/11/0.

Author information

Y.-Z.F., Z.-P.J, S.C. and D.-M.W launched the project. Z.-P.J, N.-H.L, X.L. (from PMO), S.C. and P.D. (from INAF/OAB) carried out the data analysis. Y.-Z.F. and D.-M.W. interpreted the data. Y.-Z.F. and Z.-P.J. prepared the paper and all authors participated in the discussion.

Correspondence to Yi-Zhong Fan.

Ethics declarations

Competing interests

The authors declare no competing interests.

Additional information

Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Supplementary information

Supplementary Information

Supplementary Fig. 1, Tables 1, 2 and refs. 1–21.

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark