A study in scarlet
Astronomy and Astrophysics, vol. 695, pp. A43
Abstract
Aims. We investigate the spectroscopic characteristics of intermediate-luminosity Red Transients (ILRTs), a class of elusive objects with peak luminosity between that of classical novae and standard supernovae. Our goal is to provide a stepping stone in the path to unveiling the physical origin of these events based on the analysis of the collected datasets. Methods. We present the extensive optical and near-infrared (NIR) spectroscopic monitoring of four ILRTs, namely NGC 300 2008OT-1, AT 2019abn, AT 2019ahd and AT 2019udc. First we focus on the evolution of the most prominent spectral features observed in the low-resolution spectra. We then present a more detailed description of the high-resolution spectrum collected for NGC 300 2008OT-1 with the Very Large Telescope equipped with UVES. Finally, we describe our analysis of late-time spectra of NGC 300 2008OT-1 and AT 2019ahd through comparisons with both synthetic and observed spectra. Results. Balmer and Ca lines dominate the optical spectra, revealing the presence of slowly moving circumstellar medium (CSM) around the objects. The line luminosity of H α , H β , and Ca II NIR triplet presents a double peaked evolution with time, possibly indicative of interaction between fast ejecta and the slow CSM. The high-resolution spectrum of NGC 300 2008OT-1 reveals a complex circumstellar environment, with the transient being surrounded by a slow (∼30 km s −1 ) progenitor wind. At late epochs, optical spectra of NGC 300 2008OT-1 and AT 2019ahd show broad (∼2500 km s −1 ) emission features at ∼6170 Å and ∼7000 Å which are unprecedented for ILRTs. We find that these lines originate most likely from the blending of several narrow lines, possibly of iron-peak elements.
Authors 66
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G. Valerin corresponding
Osservatorio Astronomico di Padova
Affiliation as printed
INAF – Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, I-35122 Padova, Italy
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Osservatorio Astronomico di Padova
Affiliation as printed
INAF – Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, I-35122 Padova, Italy
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National Institute for Astrophysics
Affiliation as printed
INAF – OATS, Via G.B. Tiepolo 11, 34143 Trieste, Italy
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Brera Astronomical Observatory · Osservatorio Astronomico di Padova
Affiliation as printed
INAF – Osservatorio Astronomico di Brera, Via E. Bianchi 46, 23807 Merate (LC), Italy
INAF – Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, I-35122 Padova, Italy
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Osservatorio Astronomico di Padova
Affiliation as printed
INAF – Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, I-35122 Padova, Italy
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Chinese Academy of Sciences · Yunnan Observatories
Affiliation as printed
International Centre of Supernovae, Yunnan Key Laboratory, Kunming 650216, P.R. China
Key Laboratory for the Structure and Evolution of Celestial Objects, Chinese Academy of Sciences, Kunming 650216, P.R. China
Yunnan Observatories, Chinese Academy of Sciences, Kunming 650216, P.R. China
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Affiliation as printed
Graduate Institute of Astronomy, National Central University, 300 Jhongda Road, 32001 Jhongli, Taiwan
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Radboud University Nijmegen · Space Research Organisation Netherlands
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Department of Astrophysics/IMAPP, Radboud University Nijmegen, P.O. Box 9010 6500 GL Nijmegen, The Netherlands
SRON, Netherlands Institute for Space Research, Niels Bohrweg 4, 2333 CA Leiden, The Netherlands
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Institute of Space Sciences · Osservatorio Astronomico di Padova
Affiliation as printed
INAF – Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, I-35122 Padova, Italy
Institute of Space Sciences (ICE, CSIC), Campus UAB, Carrer de Can Magrans s/n, E-08193 Barcelona, Spain
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Affiliation as printed
School of Physics, O’Brien Centre for Science North, University College Dublin, Belfield Dublin 4, Ireland
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Hiroshima University · Stockholm University · AlbaNova
Affiliation as printed
Hiroshima Astrophysical Science Center, Hiroshima University, Hiroshima, Japan
The Oskar Klein Centre, Department of Astronomy, Stockholm University, AlbaNova, SE-10691 Stockholm, Sweden
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Affiliation as printed
Department of Physics, Florida State University, 77 Chieftan Way, Tallahassee, FL 32306, USA
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Las Cumbres Observatory Global Telescope Network · University of California, Santa Barbara
Affiliation as printed
Department of Physics, University of California, Santa Barbara, CA 93106, USA
Las Cumbres Observatory, 6740 Cortona Dr. Suite 102, Goleta, CA 93117, USA
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Affiliation as printed
Cardiff Hub for Astrophysics Research and Technology, School of Physics & Astronomy, Cardiff University, Queens Buildings, The Parade, Cardiff CF24 3AA, UK
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University of Copenhagen · Astronomical Observatory of Capodimonte · National Institute for Astrophysics
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DARK, Niels Bohr Institute, University of Copenhagen, Jagtvej 128, 2200 Copenhagen, Denmark
INAF, Osservatorio Astronomico di Capodimonte, Salita Moiariello 16, I-80131 Napoli, Italy
Københavns Universitet, Faculty of Science, Niels Bohr Institute, DARK, DK
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California Institute of Technology · Infrared Processing and Analysis Center
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Caltech/IPAC, Mailcode 100-22, Pasadena, CA 91125, USA
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Affiliation as printed
Tuorla Observatory, Department of Physics and Astronomy, University of Turku, 20014 Turku, Finland
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Affiliation as printed
Tuorla Observatory, Department of Physics and Astronomy, University of Turku, 20014 Turku, Finland
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Stockholm University · AlbaNova
Affiliation as printed
Department of Astronomy, AlbaNova University Center, Stockholm University, SE-10691 Stockholm, Sweden
The Oskar Klein Centre, Department of Astronomy, Stockholm University, AlbaNova, SE-10691 Stockholm, Sweden
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Max Planck Institute for Astrophysics · Liverpool John Moores University
Affiliation as printed
Astrophysics Research Institute, Liverpool John Moores University, IC2, Liverpool Science Park, 146 Brownlow Hill, Liverpool L3 5RF, UK
Max-Planck-Institut für Astrophysik, Karl-Schwarzschild Str. 1, D-85748 Garching, Germany
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Aryabhatta Research Institute of Observational Sciences
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Aryabhatta Research Institute of Observational Sciences (ARIES), Manora Peak, Nainital 263001, India
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Instituto de Alta Investigación, Universidad de Tarapacá, Casilla 7D, Arica, Chile
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School of Physics, Trinity College Dublin, College Green, Dublin 2, Ireland
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Affiliation as printed
Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721-0065, USA
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Queen's University Belfast · University of Oxford
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Astrophysics Research Centre, School of Mathematics and Physics, Queens University Belfast Belfast BT7 1NN, UK
Department of Physics, University of Oxford, Keble Road, Oxford OX1 3RH, UK
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Affiliation as printed
Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, DK-8000 Aarhus C, Denmark
Aarhus University, Natural Sciences, Department of Physics and Astronomy, DK
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Collurania Teramo Observatory · National Institute for Astrophysics
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INAF – Osservatorio Astronomico d’Abruzzo, Via M. Maggini snc, Teramo I-64100, Italy
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University of California, Davis
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Department of Physics, University of California, Davis, CA 95616, USA
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Millennium Institute of Astrophysics · European Southern Observatory
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European Southern Observatory, Alonso de Córdova 3107, Casilla 19, Santiago, Chile
Millennium Institute of Astrophysics, Nuncio Monsenor Sótero Sanz 100, Providencia, 8320000 Santiago, Chile
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Affiliation as printed
Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721-0065, USA
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Affiliation as printed
Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721-0065, USA
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Stockholm University · AlbaNova
Affiliation as printed
The Oskar Klein Centre, Department of Astronomy, Stockholm University, AlbaNova, SE-10691 Stockholm, Sweden
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Stockholm University · AlbaNova
Affiliation as printed
The Oskar Klein Centre, Department of Astronomy, Stockholm University, AlbaNova, SE-10691 Stockholm, Sweden
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Osservatorio Astrofisico di Catania
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INAF-Osservatorio Astrofisico di Catania, Via Santa Sofia 78, I-95123 Catania, Italy
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Stockholm University · AlbaNova
Affiliation as printed
The Oskar Klein Centre, Department of Astronomy, Stockholm University, AlbaNova, SE-10691 Stockholm, Sweden
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Osservatorio Astronomico di Padova
Affiliation as printed
INAF – Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, I-35122 Padova, Italy
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Universidad Andrés Bello · Millennium Institute of Astrophysics
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Instituto de Astrofísica, Universidad Andres Bello, Fernandez Concha 700, Las Condes, Santiago RM, Chile
Millennium Institute of Astrophysics, Nuncio Monsenor Sótero Sanz 100, Providencia, 8320000 Santiago, Chile
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Astronomical Observatory of Capodimonte · International Center for Relativistic Astrophysics · National Institute for Astrophysics
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ICRANet, Piazza della Repubblica 10, I-65122 Pescara, Italy
INAF, Osservatorio Astronomico di Capodimonte, Salita Moiariello 16, I-80131 Napoli, Italy
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Goethe University Frankfurt · Istituto Nazionale di Fisica Nucleare, Trento Institute for Fundamental Physics And Applications · Osservatorio Astronomico di Padova
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INAF – Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, I-35122 Padova, Italy
INFN-TIFPA, Trento Institute for Fundamental Physics and Applications, Via Sommarive 14, I-38123 Trento, Italy
Institut für Theoretische Physik, Goethe Universität, Max-von-Laue-Str. 1, 60438 Frankfurt am Main, Germany
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Affiliation as printed
Astrophysics Research Centre, School of Mathematics and Physics, Queens University Belfast Belfast BT7 1NN, UK
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Institute of Space Sciences · Institut d'Estudis Espacials de Catalunya
Affiliation as printed
Institut d’Estudis Espacials de Catalunya (IEEC), E-08034 Barcelona, Spain
Institute of Space Sciences (ICE, CSIC), Campus UAB, Carrer de Can Magrans s/n, E-08193 Barcelona, Spain
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Affiliation as printed
Astronomical Observatory, University of Warsaw, Al. Ujazdowskie 4, 00-478 Warszawa, Poland
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Affiliation as printed
Tuorla Observatory, Department of Physics and Astronomy, University of Turku, 20014 Turku, Finland
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Florida State University · Las Cumbres Observatory Global Telescope Network · Center for Astrophysics Harvard & Smithsonian · The NSF AI Institute for Artificial Intelligence and Fundamental Interactions
Affiliation as printed
Center for Astrophysics, Harvard & Smithsonian, Cambridge, Massachusetts MA 02138, US
Department of Physics, Florida State University, 77 Chieftan Way, Tallahassee, FL 32306, USA
Las Cumbres Observatory, 6740 Cortona Dr. Suite 102, Goleta, CA 93117, USA
The NSF AI Institute for Artificial Intelligence and Fundamental Interactions, 77 Massachusetts Avenue, Cambridge, USA
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Stockholm University · Aarhus University · AlbaNova
Affiliation as printed
Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, DK-8000 Aarhus C, Denmark
The Oskar Klein Centre, Department of Astronomy, Stockholm University, AlbaNova, SE-10691 Stockholm, Sweden
Aarhus University, Natural Sciences, Department of Physics and Astronomy, DK
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Affiliation as printed
Finnish Centre for Astronomy with ESO (FINCA), University of Turku, Väisäläntie 20, 21500 Piikkiö, Finland
Tuorla Observatory, Department of Physics and Astronomy, University of Turku, 20014 Turku, Finland
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DTU Space · Technical University of Denmark
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DTU Space, National Space Institute, Technical University of Denmark, Elektrovej 327, 2800 Kongens Lyngby, Denmark
Technical University of Denmark, Department of Space Research and Technology, DK
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Kavli Institute for the Physics and Mathematics of the Universe · Astronomical Observatory of Rome · Istituto Nazionale di Fisica Nucleare, Sezione di Perugia · The University of Tokyo · National Institute for Astrophysics
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INFN, Sezione di Perugia, Via A. Pascoli s/n, I-06125 Perugia, Italy
Istituto Nazionale di Astrofisica – Osservatorio Astronomico di Roma, Via Frascati 33, I-00040 Monteporzio Catone, Italy
Kavli Institute for the Physics and Mathematics of the Universe (WPI), The University of Tokyo Institutes for Advanced Study, The University of Tokyo, Kashiwa, Chiba 277-8583, Japan
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Affiliation as printed
Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721-0065, USA
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Las Cumbres Observatory Global Telescope Network
Affiliation as printed
Las Cumbres Observatory, 6740 Cortona Dr. Suite 102, Goleta, CA 93117, USA
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Institute of Space Sciences · Institut d'Estudis Espacials de Catalunya
Affiliation as printed
Institut d’Estudis Espacials de Catalunya (IEEC), E-08034 Barcelona, Spain
Institute of Space Sciences (ICE, CSIC), Campus UAB, Carrer de Can Magrans s/n, E-08193 Barcelona, Spain
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Affiliation as printed
Astrophysics Research Centre, School of Mathematics and Physics, Queens University Belfast Belfast BT7 1NN, UK
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University of Padua · Osservatorio Astronomico di Padova
Affiliation as printed
Dipartimento di Fisica e Astronomia “G. Galilei”, Università degli studi di Padova Vicolo dell’Osservatorio 3, I-35122 Padova, Italy
INAF – Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, I-35122 Padova, Italy
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Las Cumbres Observatory Global Telescope Network · University of California, Santa Barbara
Affiliation as printed
Department of Physics, University of California, Santa Barbara, CA 93106, USA
Las Cumbres Observatory, 6740 Cortona Dr. Suite 102, Goleta, CA 93117, USA
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National Observatory of Athens · Institute for Astronomy, Astrophysics, Space Applications and Remote Sensing
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IAASARS, National Observatory of Athens, Metaxa & Vas. Pavlou St., 15236 Penteli, Athens, Greece
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Affiliation as printed
Department of Astronomy, University of Virginia, Charlottesville, VA 22904, USA
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Max Planck Institute for Extraterrestrial Physics
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Max-Planck-Institut für Extraterrestrische Physik, Giessenbachstraße 1, 85748 Garching, Germany
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University of North Carolina at Chapel Hill
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Department of Physics and Astronomy, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
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Osservatorio Astronomico di Padova
Affiliation as printed
INAF – Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, I-35122 Padova, Italy
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Space Telescope Science Institute · Johns Hopkins University
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Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218, USA
Space Telescope Science Institute, Baltimore, MD, USA
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Indian Institute of Astrophysics
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Indian Institute Of Astrophysics, 100 Feet Rd, Santhosapuram, 2nd Block, Koramangala, Bengaluru, Karnataka 560034, India
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Stockholm University · AlbaNova
Affiliation as printed
The Oskar Klein Centre, Department of Astronomy, Stockholm University, AlbaNova, SE-10691 Stockholm, Sweden
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Osservatorio Astronomico di Padova
Affiliation as printed
INAF – Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, I-35122 Padova, Italy
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Osservatorio Astronomico di Padova
Affiliation as printed
INAF – Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, I-35122 Padova, Italy
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Affiliation as printed
Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721-0065, USA
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Affiliation as printed
Astrophysics Research Centre, School of Mathematics and Physics, Queens University Belfast Belfast BT7 1NN, UK
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