Nuclear ashes and outflow in the eruptive star Nova Vul 1670



CK Vulpeculae was observed in outburst in 1670–1672 (ref. 1), but no counterpart was seen until 1982, when a bipolar nebula was found at its location1,2,3. Historically, CK Vul has been considered to be a nova (Nova Vul 1670), but its similarity to ‘red transients’, which are more luminous than classical novae and thought to be the results of stellar collisions4, has re-opened the question of CK Vul’s status5,6. Red transients cool to resemble late M-type stars, surrounded by circumstellar material rich in molecules and dust7,8,9. No stellar source has been seen in CK Vul, though a radio continuum source was identified at the expansion centre of the nebula3. Here we report that CK Vul is surrounded by chemically rich molecular gas in the form of an outflow, as well as dust. The gas has peculiar isotopic ratios, revealing that CK Vul's composition was strongly enhanced by the nuclear ashes of hydrogen burning. The chemical composition cannot be reconciled with a nova or indeed any other known explosion. In addition, the mass of the surrounding gas is too large for a nova, though the conversion from observations of CO to a total mass is uncertain. We conclude that CK Vul is best explained as the remnant of a merger of two stars.

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Figure 1: Spectra of CK Vul with identifications of the main features.
Figure 2: The ionized nebula and the newly discovered molecular emission in CK Vul.


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We thank F. Wyrowski, A. Belloche, T. Csengeri, K. Immer, K. Young and the APEX staff for executing part of the observations reported here. APEX is a collaboration between the Max-Planck-Institut für Radioastronomie, the European Southern Observatory, and Onsala Space Observatory. The SMA is a joint project between the Smithsonian Astrophysical Observatory and the Academia Sinica Institute of Astronomy and Astrophysics. We thank the SMA director R. Blundell for granting us director’s discretionary time. The Effelsberg 100-m radio telescope is operated by the Max-Planck-Institut für Radioastronomie on behalf of the Max-Planck-Gesellschaft.

Author information




T.K. wrote the text. T.K. and K.M.M. obtained and reduced the APEX data. N.A.P. obtained and reduced the SMA data. A.K. obtained and reduced the Effelsberg data. All authors contributed to the interpretation of the data and commented on the final manuscript.

Corresponding author

Correspondence to Tomasz Kamiński.

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The authors declare no competing financial interests.

Extended data figures and tables

Extended Data Figure 1 Spectral energy distribution of CK Vul.

Flux measurements and 3σ upper limits were collected from the literature and include data points obtained with the SMA in this study — as listed in Extended Data Table 4. Best-fit Planck function and modified grey-body spectral distributions are also shown. See Methods for details.

Extended Data Table 1 List of detected transitions with Effelsberg and APEX telescopes
Extended Data Table 2 Spectral setups observed with the APEX telescope
Extended Data Table 3 Novae observed with APEX in search for CO(3-2) emission
Extended Data Table 4 Continuum measurements of CK Vul used in the analysis of its spectral energy distribution

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Kamiński, T., Menten, K., Tylenda, R. et al. Nuclear ashes and outflow in the eruptive star Nova Vul 1670. Nature 520, 322–324 (2015).

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