Luminous red novae: Stellar mergers or giant eruptions?

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. BufanoY-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

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

33 Downloads (Pure)

Abstract

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.

Original languageEnglish
Article number75
Number of pages30
JournalAstronomy & Astrophysics
Volume630
DOIs
Publication statusPublished - 24 Sep 2019
MoE publication typeA1 Journal article-refereed

Keywords

  • binaries: close
  • stars: winds, outflows
  • stars: massive
  • supernovae: general
  • ELECTRON-CAPTURE SUPERNOVAE
  • CORE-COLLAPSE SUPERNOVA
  • SN HUNT 248
  • V838 MONOCEROTIS
  • LIGHT CURVES
  • ETA-CARINAE
  • DUSTY AFTERMATH
  • MASSIVE STARS
  • V4332 SGR
  • V1309 SCO

Cite this