The emergence of a [WC] star in Sakurai's object
Abstract
Sakurai's object provides a rare opportunity to observe stellar evolution on human timescales. Since its born-again event and detection in 1996, its evolution has been extensively monitored, and recent optical spectroscopy has suggested the emergence of [WR]-type emission features. In this Letter, we present a secure spectroscopic identification of its central star based on new VLT/FORS2 observations and NLTE expanding atmosphere models. Several observed emission lines arise in a [WR]-type stellar wind, establishing the central star as a [WR] object. The strongest stellar features are due to C II-III and He I. We derive the stellar and wind parameters of Sakurai's object and discuss its evolutionary status. The [WR] star is much cooler (Teff ~ 30.5 kK) than the born-again star V605 Aql (Teff} ~ 95 kK), which erupted about 80 years earlier. The inferred temperature is lower than predicted by models suppressing convective mixing efficiency during the VLTP, but is consistent with higher time-resolution calculations involving slightly lower-mass (<~ 0.6Msun) remnants. Continued spectroscopic monitoring and atmospheric modelling will be crucial for tracing its reheating curve and constraining the physics of this rapid evolutionary phase.
Versions
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BibTeX
@misc{marcolino2026emergence,
title = {{The emergence of a [WC] star in Sakurai's object}},
author = {W. Marcolino and P. A. M. van Hoof and V. C. Maria and H. Todt and G. C. Van de Steene and J. A. Toalá and S. Kimeswenger and M. Hajduk and J. -C. Bouret and D. Tafoya and D. Barría and A. A. Zijlstra},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.18645},
eprint = {2609.18645},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.18645},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - The emergence of a [WC] star in Sakurai's object
AU - W. Marcolino
AU - P. A. M. van Hoof
AU - V. C. Maria
AU - H. Todt
AU - G. C. Van de Steene
AU - J. A. Toalá
AU - S. Kimeswenger
AU - M. Hajduk
AU - J. -C. Bouret
AU - D. Tafoya
AU - D. Barría
AU - A. A. Zijlstra
PY - 2026
DA - 2026/09/16
PB - arXiv
DO - 10.48550/arxiv.2609.18645
UR - https://arxiv.org/abs/2609.18645
AB - Sakurai's object provides a rare opportunity to observe stellar evolution on human timescales. Since its born-again event and detection in 1996, its evolution has been extensively monitored, and recent optical spectroscopy has suggested the emergence of [WR]-type emission features. In this Letter, we present a secure spectroscopic identification of its central star based on new VLT/FORS2 observations and NLTE expanding atmosphere models. Several observed emission lines arise in a [WR]-type stellar wind, establishing the central star as a [WR] object. The strongest stellar features are due to C II-III and He I. We derive the stellar and wind parameters of Sakurai's object and discuss its evolutionary status. The [WR] star is much cooler (Teff ~ 30.5 kK) than the born-again star V605 Aql (Teff} ~ 95 kK), which erupted about 80 years earlier. The inferred temperature is lower than predicted by models suppressing convective mixing efficiency during the VLTP, but is consistent with higher time-resolution calculations involving slightly lower-mass (<~ 0.6Msun) remnants. Continued spectroscopic monitoring and atmospheric modelling will be crucial for tracing its reheating curve and constraining the physics of this rapid evolutionary phase.
ER -