Year: 2025
Type: article
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 Hα, Hβ, 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: G. Valerin, A. Pastorello, E. Mason, A. Reguitti, S. Benetti, Y.-Z. Cai, T.-W. Chen, D. Eappachen, N. Elias-Rosa, M. Fraser, A. Gangopadhyay, E. Y. Hsiao, D. A. Howell, C. Inserra, L. Izzo, J. Jencson, E. Kankare, R. Kotak, P. Lundqvist, P. A. Mazzali, K. Misra, G. Pignata, S. J. Prentice, D. J. Sand, S. J. Smartt, M. D. Stritzinger, L. Tartaglia, S. Valenti, J. P. Anderson, J. E. Andrews, R. C. Amaro, C. Barbarino, S. Brennan, F. Bufano, E. Callis, E. Cappellaro, R. Dastidar, M. Della Valle, A. Fiore, M. D. Fulton, L. Galbany, M. Gromadzki, T. Heikkilä, D. Hiramatsu, E. Karamehmetoglu, H. Kuncarayakti, G. Leloudas, M. Limongi, M. Lundquist, C. McCully, T. E. Müller-Bravo, M. Nicholl, P. Ochner, E. Padilla Gonzalez, E. Paraskeva, C. Pellegrino, A. Rau, D. E. Reichart, T. M. Reynolds, R. Roy, I. Salmaso, M. Shahbandeh, M. Singh, J. Sollerman, M. Turatto, L. Tomasella, S. Wyatt, D. R. Young
Institutions: Radboud University Nijmegen, Space Research Organisation Netherlands, Institute of Space Sciences, University College Dublin, Hiroshima University, Stockholm University, AlbaNova, Florida State University, Las Cumbres Observatory Global Telescope Network, University of California, Santa Barbara, Cardiff University, University of Copenhagen, Astronomical Observatory of Capodimonte, National Institute for Astrophysics, California Institute of Technology, Infrared Processing and Analysis Center, University of Turku, Max Planck Institute for Astrophysics, Liverpool John Moores University, Aryabhatta Research Institute of Observational Sciences, University of Tarapacá, Trinity College Dublin, University of Arizona, Queen's University Belfast, University of Oxford, Collurania Teramo Observatory, University of California, Davis, Millennium Institute of Astrophysics, European Southern Observatory, Osservatorio Astrofisico di Catania, Universidad Andrés Bello, Goethe University Frankfurt, Institut d'Estudis Espacials de Catalunya, Istituto Nazionale di Fisica Nucleare, Trento Institute for Fundamental Physics And Applications, International Center for Relativistic Astrophysics, Center for Astrophysics Harvard & Smithsonian, University of Warsaw, Technical University of Denmark, Aarhus University
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W6959513760
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