Hertzsprung gap stars in nearby galaxies and the quest for luminous red nova progenitors
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1.
University of Barcelona
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2.
Institut d'Estudis Espacials de Catalunya
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3.
California Institute of Technology
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4.
Radboud University Nijmegen
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5.
University of Cape Town
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6.
South African Radio Astronomy Observatory
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7.
University of Amsterdam
Abstract
Context. After the main sequence phase, stars more massive than 2.5 M⊙ rapidly evolve through the Hertzsprung gap as yellow giants and yellow supergiants (YSGs) before settling into the red giant branch. Identifying Hertzsprung gap stars in nearby galaxies is crucial for pinpointing progenitors of luminous red novae (LRNe) – astrophysical transients attributed to stellar mergers. In the era of extensive transient surveys like the Vera C. Rubin Observatory’s Legacy Survey of Space and Time (LSST), this approach offers a new way to predict and select common envelope transients.
Aims. This study investigates potential progenitors and precursors of LRNe by analysing Hubble Space Telescope (HST) photometry of stellar populations in galaxies within ∼20 Mpc to identify YSG candidates. Additionally, we use the Zwicky Transient Facility and MeerLICHT/BlackGEM to identify possible precursors, preparing for future observations by the LSST.
Methods. We compiled a sample of 369 galaxies with HST exposures in the F 475W, F 555W, F 606W, and F814W filters. We identified YSG candidates using MESA stellar evolution tracks and statistical analysis of colour–magnitude diagrams.
Results. Our sample includes 154 494 YSG candidates with masses between 3 M⊙ and 20 M⊙ and is affected by various contaminants, notably foreground stars and extinguished main sequence stars. After excluding foreground stars using Gaia proper motions, contamination is estimated at 1% from foreground stars (based on TRILEGAL simulations) and ∼20% from extinction affecting main sequence stars. Combining our YSG candidates with time-domain catalogues yielded several interesting candidates. In particular, we identified 12 LRN precursor candidates for which follow-up is encouraged.
Conclusions. We highlight the importance of monitoring future transients that match YSG candidates to avoid missing potential LRNe and other rare transients. LSST will be a game changer in the search for LRN progenitors and precursors; it is predicted to discover over 300 000 new YSG candidates and 100 LRN precursors within 20 Mpc.
Copyright and License
© The Authors 2025.
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Acknowledgement
H. T. and N. B. acknowledge to be funded by the European Union (ERC, CET-3PO, 101042610). Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or the European Research Council Executive Agency. Neither the European Union nor the granting authority can be held responsible for them. PJG is supported by NRF SARChI grant 111692. We thank Zeljko Ivezic and the anonymous referee for their valuable comments, which significantly enhanced the quality of this paper. We thank Rick White and Bernie Shiao for their assistance in retrieving the HSCv3 data. We acknowledge the extensive use of the MAST database to conduct this study. Based on observations with the MeerLICHT telescope. MeerLICHT is built and run by a consortium consisting of Radboud University, the University of Cape Town, the South African Astronomical Observatory, the University of Oxford, the University of Manchester and the University of Amsterdam. MeerLICHT is hosted by SAAO. Based on observations with the BlackGEM telescopes. BlackGEM is built and run by a consortium consisting of Radboud University, the Netherlands Research School for Astronomy (NOVA), and KU Leuven with additional support from Armagh Observatory and Planetarium, Durham University, Hamburg Observatory, Hebrew University, Las Cumbres Observatory, Tel Aviv University, Texas Tech University, Technical University of Denmark, University of California Davis, the University of Barcelona, the University of Manchester, University of Potsdam, the University of Valparaiso, the University of Warwick, and Weizmann Institute of science. BlackGEM is hosted and supported by ESO. Supported by the National Science Foundation under Grants No. AST-1440341 and AST-2034437 and a collaboration including current partners Caltech, IPAC, the Oskar Klein Center at Stockholm University, the University of Maryland, University of California, Berkeley, the University of Wisconsin at Milwaukee, University of Warwick, Ruhr University, Cornell University, Northwestern University and Drexel University. Operations are conducted by COO, IPAC, and UW. Based on observations made with the NASA/ESA Hubble Space Telescope, and obtained from the Hubble Legacy Archive, which is a collaboration between the Space Telescope Science Institute (STScI/NASA), the Space Telescope European Coordinating Facility (ST-ECF/ESAC/ESA) and the Canadian Astronomy Data Centre (CADC/NRC/CSA).
Data Availability
The full versions of Tables 3 and 4 are available in electronic form at the CDS via anonymous ftp to cdsarc.cds.unistra.fr (130.79.128.5) or via https://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/695/A226
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Additional details
- European Research Council
- 101042610
- National Research Foundation
- 111692
- National Science Foundation
- AST-1440341
- National Science Foundation
- AST-2034437
- Accepted
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2024-12-18
- Available
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2025-03-20Published online
- Caltech groups
- Division of Physics, Mathematics and Astronomy (PMA)
- Publication Status
- Published