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.

  • Letter
  • Published:

Hard-X-ray emission lines from the decay of 44Ti in the remnant of supernova 1987A


It is assumed1,2,3 that the radioactive decay of 44Ti powers the infrared, optical and ultraviolet emission of supernova remnants after the complete decay of 56Co and 57Co (the isotopes that dominated the energy balance during the first three to four years after the explosion) until the beginning of active interaction of the ejecta with the surrounding matter. Simulations4,5 show that the initial mass of 44Ti synthesized in core-collapse supernovae is (0.02–2.5) × 10−4 solar masses (). Hard X-rays and γ-rays from the decay of this 44Ti have been unambiguously observed from Cassiopeia A only6,7,8, leading to the suggestion that values of the initial mass of 44Ti near the upper bound of the predictions occur only in exceptional cases9. For the remnant of supernova 1987A10,11, an upper limit to the initial mass of 44Ti of <10−3 has been obtained from direct X-ray observations12, and an estimate of (1–2) × 10−4 has been made from infrared light curves and ultraviolet spectra by complex and model-dependent computations13,14,15. Here we report observations of hard X-rays from the remnant of supernova 1987A in the narrow band containing two direct-escape lines of 44Ti at 67.9 and 78.4 keV. The measured line fluxes imply that this decay provided sufficient energy to power the remnant at late times. We estimate that the initial mass of 44Ti was (3.1 ± 0.8) × 10−4, which is near the upper bound of theoretical predictions.

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

Access options

Buy this article

Prices may be subject to local taxes which are calculated during checkout

Figure 1: Hard-X-ray images indicating the detection of 44 Ti emission lines from SNR 1987A.
Figure 2: Hard-X-ray spectra of SNR 1987A measured with IBIS/ISGRI in 2003–2011.
Figure 3: γ-ray spectrum of SNR 1987A measured with SPI in 2003–2011.

Similar content being viewed by others


  1. Suntzeff, N. B. The energy sources powering the late-time bolometric evolution of SN 1987A. Astrophys. J. 384, L33–L36 (1992)

    Article  ADS  Google Scholar 

  2. Clayton, D. D. et al. The 57Co abundance in SN 1987A. Astrophys. J. 399, L141–L144 (1992)

    Article  ADS  CAS  Google Scholar 

  3. Fransson, C. & Kozma, C. The freeze-out phase of SN 1987A: implication for the light curve. Astrophys. J. 408, L25–L28 (1993)

    Article  ADS  CAS  Google Scholar 

  4. Thielemann, F.-K., Hashimoto, M. & Nomoto, K. Explosive nucleosynthesis in SN 1987A. II. Composition, radioactivities, and the neutron star mass. Astrophys. J. 349, 222–240 (1990)

    Article  ADS  CAS  Google Scholar 

  5. Woosley, S. E. & Hoffman, R. D. 57Co and 44Ti production in SN 1987A. Astrophys. J. 368, L31–L34 (1991)

    Article  ADS  CAS  Google Scholar 

  6. Iyudin, A. F. et al. COMPTEL observations of 44Ti gamma-ray line emission from Cas A. Astron. Astrophys. 284, L1–L4 (1994)

    ADS  CAS  Google Scholar 

  7. Vink, J. et al. Detection of the 67.9 and 78.4 keV lines associated with the radioactive decay of 44Ti in Cassiopeia A. Astrophys. J. 560, L79–L82 (2001)

    Article  ADS  CAS  Google Scholar 

  8. Renaud, M. et al. The signature of 44Ti in Cassiopeia A revealed by IBIS/ISGRI on INTEGRAL. Astrophys. J. 647, L41–L44 (2006)

    Article  ADS  CAS  Google Scholar 

  9. The, L.-S. et al. Are 44Ti-producing supernovae exceptional? Astron. Astrophys. 450, 1037–1050 (2006)

  10. Arnett, W. D., Bahcall, J. N., Kirshner, R. P. & Woosley, S. E. Supernova 1987A. Annu. Rev. Astron. Astrophys. 27, 629–700 (1989)

    Article  ADS  CAS  Google Scholar 

  11. Imshennik, V. S. & Nadezhin, D. K. Supernova 1987A in the Large Magellanic Cloud: observations and theory. Sov. Sci. Rev. E 8, 1–147 (1989)

    Google Scholar 

  12. Shtykovskiy, P. E., Lutovinov, A. A., Gilfanov, M. R. & Sunyaev, R. A. Constraints on the luminosity of the central source in the SNR 1987A. Astron. Lett. 31, 258–262 (2005)

    Article  ADS  CAS  Google Scholar 

  13. Chugai, N. N., Chevalier, R. A., Kirshner, R. P. & Challis, P. M. Hubble Space Telescope spectrum of SN 1987A at an age of 8 years: radioactive luminescence of cool gas. Astrophys. J. 483, 925–940 (1997)

    Article  ADS  CAS  Google Scholar 

  14. Jerkstrand, A., Fransson, C. & Kozma, C. The 44Ti-powered spectrum of SN 1987A. Astron. Astrophys. 530, A45 (2011)

    Article  ADS  Google Scholar 

  15. Larsson, J. et al. X-ray illumination of the ejecta of supernova 1987A. Nature 474, 484–486 (2011)

    Article  ADS  CAS  Google Scholar 

  16. Ahmad, I. et al. Improved measurement of the 44Ti half-life from a 14-year long study. Phys. Rev. C 74, 065803 (2006)

    Article  ADS  Google Scholar 

  17. Iyudin, A. F. et al. Emission from 44Ti associated with a previously unknown Galactic supernova. Nature 396, 142–144 (1998)

    Article  ADS  CAS  Google Scholar 

  18. Borkowski, K. J. et al. Radioactive scandium in the youngest Galactic supernova remnant G1.9+0.3. Astrophys. J. 724, L161–L165 (2010)

    Article  ADS  CAS  Google Scholar 

  19. Sunyaev, R. A. et al. Discovery of hard X-ray emission from supernova 1987A. Nature 330, 227–229 (1987)

    Article  ADS  Google Scholar 

  20. Matz, S. M. et al. Gamma-ray line emission from SN1987A. Nature 331, 416–418 (1988)

    Article  ADS  Google Scholar 

  21. Sunyaev, R. A. et al. Hard X-ray radiation from SN 1987A. Roentgen observatory observations from 1987 to 1989. Sov. Astron. Lett. 16, 171–176 (1990)

    ADS  Google Scholar 

  22. Winkler, C. et al. The INTEGRAL mission. Astron. Astrophys. 411, L1–L6 (2003)

    Article  ADS  CAS  Google Scholar 

  23. Berezhko, E. G., Ksenofontov, L. T. & Völk, H. J. Expected gamma-ray emission of supernova remnant SN 1987A. Astrophys. J. 732, 58 (2011)

    Article  ADS  Google Scholar 

  24. Sturm, R., Haberl, F., Aschenbach, B. & Hasinger, G. High resolution X-ray spectroscopy of SN 1987A: monitoring with XMM-Newton. Astron. Astrophys. 515, A5 (2010)

    Article  ADS  Google Scholar 

  25. Thielemann, F.-K., Nomoto, K. & Hashimoto, M. Core-collapse supernovae and their ejecta. Astrophys. J. 460, 408–436 (1996)

    Article  ADS  CAS  Google Scholar 

  26. Park, S., Zhekov, S. A., Burrows, D. N. & McCray, R., SNR 1987A: opening the future by reaching the past. Astrophys. J. 634, L73–L76 (2005)

    Article  ADS  CAS  Google Scholar 

  27. Krivonos, R. et al. INTEGRAL/IBIS 7-year all-sky hard X-ray survey. I. Image reconstruction. Astron. Astrophys. 519, A107 (2010)

    Article  Google Scholar 

  28. Churazov, E. et al. Positron annihilation spectrum from the Galactic Centre region observed by SPI/INTEGRAL revisited: annihilation in a cooling ISM? Mon. Not. R. Astron. Soc. 411, 1727–1743 (2011)

    Article  ADS  CAS  Google Scholar 

  29. Meaburn, J., Bryce, M. & Holloway, A. J. The kinematics of the rings around SN 1987A. Astron. Astrophys. 299, L1–L4 (1995)

    ADS  CAS  Google Scholar 

Download references


We thank R. A. Sunyaev for reading the manuscript and for comments; V. S. Imshennik, D. K. Nadezhin and N. N. Chugai for discussions about aspects of the physics of the supernova 1987A explosion; R. A. Krivonos for information regarding the analysis of INTEGRAL/IBIS data; and M. Coe for allowing us access to his INTEGRAL data of the LMC observations (1 Ms) before the end of the proprietary period. This work is based on data obtained through the Russian and European INTEGRAL science data centres, and was supported by grants RFBR-11-02-12285ofi-m-2011 and RAS-P20 ‘The origin, structure and evolution of objects of the Universe’.

Author information

Authors and Affiliations



S.A.G. was Principal Investigator of the proposal requesting INTEGRAL time (3.5 Ms) to observe SNR 1987A; made a preliminary analysis of the IBIS/ISGRI data and detected an excess at the SNR 1987A position; and wrote a draft of the text. A.A.L. was Co-investigator of the proposal, and participated in the analysis of IBIS/SIGRI data and the verification of the result. S.S.T. carried out the analysis of SPI data. C.W. provided general support for this project and participated in its different aspects, and C.W. and A.A.L. contributed substantially to the final text. All authors discussed the results and their presentation.

Corresponding author

Correspondence to S. A. Grebenev.

Ethics declarations

Competing interests

The authors declare no competing financial interests.

PowerPoint slides

Rights and permissions

Reprints and permissions

About this article

Cite this article

Grebenev, S., Lutovinov, A., Tsygankov, S. et al. Hard-X-ray emission lines from the decay of 44Ti in the remnant of supernova 1987A. Nature 490, 373–375 (2012).

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