A1 Refereed original research article in a scientific journal
Luminous red novae: Stellar mergers or giant eruptions?
Authors: A. Pastorello, E. Mason, S. Taubenberger, M. Fraser, G. Cortini, L. Tomasella, M. T. Botticella, N. Elias-Rosa, R. Kotak, S. J. Smartt, S. Benetti, E. Cappellaro, M. Turatto, L. Tartaglia, S. G. Djorgovski, A. J. Drake, M. Berton, F. Briganti, J. Brimacombe, F. Bufano, Y.-Z. Cai, S. Chen, E. J. Christensen, F. Ciabattari, E. Congiu, A. Dimai, C. Inserra, E. Kankare, L. Magill, K. Maguire, F. Martinelli, A. Morales-Garoffolo, P. Ochner, G. Pignata, A. Reguitti, J. Sollerman, S. Spiro, G. Terreran, D. E. Wright
Publisher: EDP SCIENCES S A
Publication year: 2019
Journal: Astronomy and Astrophysics
Journal acronym: ASTRON ASTROPHYS
Article number: ARTN A75
Volume: 630
Number of pages: 30
ISSN: 1432-0746
eISSN: 1432-0746
DOI: https://doi.org/10.1051/0004-6361/201935999
Web address : https://www.aanda.org/articles/aa/abs/2019/10/aa35999-19/aa35999-19.html
Self-archived copy’s web address: https://research.utu.fi/converis/portal/detail/Publication/42791538
We present extensive datasets for a class of intermediate-luminosity optical transients known as luminous red novae. They show double-peaked light curves, with an initial rapid luminosity rise to a blue peak (at -13 to -15 mag), which is followed by a longer-duration red peak that sometimes is attenuated, resembling a plateau. The progenitors of three of them (NGC 4490-2011OT1, M 101-2015OT1, and SNhunt248), likely relatively massive blue to yellow stars, were also observed in a pre-eruptive stage when their luminosity was slowly increasing. Early spectra obtained during the first peak show a blue continuum with superposed prominent narrow Balmer lines, with P Cygni profiles. Lines of Fe II are also clearly observed, mostly in emission. During the second peak, the spectral continuum becomes much redder, H alpha is barely detected, and a forest of narrow metal lines is observed in absorption. Very late-time spectra (similar to 6 months after blue peak) show an extremely red spectral continuum, peaking in the infrared (IR) domain. H alpha is detected in pure emission at such late phases, along with broad absorption bands due to molecular overtones (such as TiO, VO). We discuss a few alternative scenarios for luminous red novae. Although major instabilities of single massive stars cannot be definitely ruled out, we favour a common envelope ejection in a close binary system, with possibly a final coalescence of the two stars. The similarity between luminous red novae and the outburst observed a few months before the explosion of the Type IIn SN 2011ht is also discussed.
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