Issue |
A&A
Volume 630, October 2019
|
|
---|---|---|
Article Number | A75 | |
Number of page(s) | 30 | |
Section | Stellar structure and evolution | |
DOI | https://doi.org/10.1051/0004-6361/201935999 | |
Published online | 24 September 2019 |
Luminous red novae: Stellar mergers or giant eruptions?⋆
1
INAF – Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, 35122 Padova, Italy
e-mail: andrea.pastorello@inaf.it
2
INAF – Osservatorio Astronomico di Trieste, Via G.B. Tiepolo 11, 34143 Trieste, Italy
3
Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Str. 1 85748 Garching, Germany
4
European Organisation for Astronomical Research in the Southern Hemisphere (ESO), Karl-Schwarzschild-Str. 2, 85748 Garching bei München, Germany
5
School of Physics, O’Brien Centre for Science North, University College Dublin, Belfield, Dublin 4, Ireland
6
Osservatorio Astronomico di Monte Maggiore, Via Montemaggiore 3, 47016, Predappio Forlì-Cesena, Italy
7
INAF – Osservatorio Astronomico di Capodimonte, Salita Moiariello 16, 80131 Napoli, Italy
8
Institute of Space Sciences (ICE, CSIC), Campus UAB, Camí de Can Magrans s/n, 08193 Cerdanyola del Vallès (Barcelona), Spain
9
Institut d’Estudis Espacials de Catalunya (IEEC), c/Gran Capità 2-4, Edif. Nexus 201, 08034 Barcelona, Spain
10
Department of Physics and Astronomy, University of Turku, Vesilinnantie 5, 20014 Turku, Finland
11
Astrophysics Research Centre, School of Mathematics and Physics, Queen’s University Belfast, Belfast BT7 1NN, UK
12
The Oskar Klein Centre, Department of Astronomy, Stockholm University, AlbaNova 10691 Stockholm, Sweden
13
California Institute of Technology, 1200 E. California Blvd, Pasadena, CA 91125, USA
14
Finnish Centre for Astronomy with ESO (FINCA), University of Turku, Quantum, Vesilinnantie 5 20014, Finland
15
Aalto University Metsähovi Radio Observatory, Metsähovintie 114, 02540 Kylmälä, Finland
16
Lajatico Astronomical Centre, Via dei Mulini a Vento, 56030, Lajatico Pisa, Italy
17
Coral Towers Observatory, Unit 38 Coral Towers, 255 Esplanade, Cairns 4870, Australia
18
INAF – Osservatorio Astrofisico di Catania, Via S. Sofia 78, 95123 Catania, Italy
19
Dipartimento di Fisica e Astronomia, Università di Padova, Vicolo dell’Osservatorio 3, 35122 Padova, Italy
20
INFN – Sezione di Padova, Via Marzolo 8, 35131 Padova, Italy
21
Center for Astrophysics, Guangzhou University, Guangzhou 510006, PR China
22
Lunar and Planetary Lab, Department of Planetary Sciences, University of Arizona, Tucson, AZ 85721, USA
23
Osservatorio Astronomico di Monte Agliale, Via Cune Motrone, 55023 Borgo a Mozzano, Lucca, Italy
24
Las Campanas Observatory – Carnagie Institution of Washington, Colina el Pino, Casilla 601, La Serena, Chile
25
INAF – Osservatorio Astronomico di Brera, via E. Bianchi 46, 23807 Merate, LC, Italy
26
Osservatorio Astronomico del Col Druscié, 32043 Cortina d’Ampezzo, Italy
27
School of Physics & Astronomy, Cardiff University, Queens Buildings, The Parade, Cardiff CF24 3AA, UK
28
Gemini Observatory, Southern Operations Center, c/o AURA, Casilla 603, La Serena, Chile
29
School of Physics, Trinity College Dublin, The University of Dublin, Dublin 2, Ireland
30
Department of Applied Physics, University of Cádiz, Campus of Puerto Real, 11510 Cádiz, Spain
31
Departamento de Ciencias Fisicas, Universidad Andres Bello, Avda. Republica 252, Santiago, Chile
32
Millennium Institute of Astrophysics (MAS), Nuncio Monseor Sótero Snz 100, Providencia, Santiago, Chile
33
Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA) and Department of Physics and Astronomy, Northwestern University, Evanston, IL 60208, USA
34
Minnesota Institute for Astrophysics, University of Minnesota, Minneapolis, MN 55455, USA
Received:
31
May
2019
Accepted:
5
August
2019
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, Hα is barely detected, and a forest of narrow metal lines is observed in absorption. Very late-time spectra (∼6 months after blue peak) show an extremely red spectral continuum, peaking in the infrared (IR) domain. Hα 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.
Key words: binaries: close / stars: winds / outflows / stars: massive / supernovae: general
Tables A.1–A.6 are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/630/A75
© ESO 2019
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