VVV-WIT-13: an eruptive young star with cool molecular features
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arXiv
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2025
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| author | Guo, Zhen Lucas, Philip Yurchenko, Sergey N. Kaminski, Tomasz Montesinos, Matias Nayakshin, Sergei Elbakyan, Vardan Osses, Javier Garatti, Alessio Caratti o Zhao, He Kurtev, Radostin Borissova, Jura Morris, Calum Minniti, Dante Alonso-García, Javier Fermiano, Vitor Saito, Roberto K. Miller, Niall Zsidi, Gabriella Muthu, H. D. S. Briceño, Cesar Peña, Carlos Contreras Lynas-Gray, A. E. Tennyson, Jonathan Wang, Lingzhi Yu, Lixin Benitez-Palacios, Diego Yang, Jinyi Kuhn, Michael Wang, Sharon X. |
| author_facet | Guo, Zhen Lucas, Philip Yurchenko, Sergey N. Kaminski, Tomasz Montesinos, Matias Nayakshin, Sergei Elbakyan, Vardan Osses, Javier Garatti, Alessio Caratti o Zhao, He Kurtev, Radostin Borissova, Jura Morris, Calum Minniti, Dante Alonso-García, Javier Fermiano, Vitor Saito, Roberto K. Miller, Niall Zsidi, Gabriella Muthu, H. D. S. Briceño, Cesar Peña, Carlos Contreras Lynas-Gray, A. E. Tennyson, Jonathan Wang, Lingzhi Yu, Lixin Benitez-Palacios, Diego Yang, Jinyi Kuhn, Michael Wang, Sharon X. |
| contents | Here we investigate an infrared eruptive source, identified from the decade-long VISTA Variables in the Via Lactea survey (VVV). We named this target after a group of variable sources discovered by VVV, as VVV-WIT-13, with WIT standing for "What Is This?", due to its unique photometric variation behaviour and the mysterious origin of the outburst. This target exhibited an outburst with a 5.7 mag amplitude in the Ks-band, remained on its brightness plateau for 3.5 years, and then rapidly faded to its pre-eruptive brightness afterwards. We aim to reveal the variable nature and outburst origin of VVV-WIT-13 by presenting our follow-up photometric and spectroscopic observations along with theoretical models. We gathered photometric time series in both near- and mid-infrared wavelengths. We obtained near-infrared spectra during the outburst and decaying stages on XSHOOTER/VLT and FIRE/Magellan, and then fitted the detected molecular absorption features using models from ExoMol. We applied 2D numerical simulations to re-create the observables of the eruptive phenomenon. We observe deep AlO absorption bands in the infrared spectra of VVV-WIT-13, during the outburst stage, along with other more common absorption bands (e.g. CO). Our best-fit model suggests a 600 K temperature of the AlO absorption band. In the decaying stage, the AlO bands disappeared, whilst broad blue-shifted H2 lines arose, a common indicator of stellar wind and outflow. The observational evidence suggests that the CO and TiO features originate from an outflow or a wind environment. We find that VVV-WIT-13 is an eruptive young star with instability occurring in the accretion disk. One favoured theoretical explanation of this event is a disrupted gas clump at a distance of 3 au from the source. If confirmed, this would be the first such event observed in real time. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2509_15334 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | VVV-WIT-13: an eruptive young star with cool molecular features Guo, Zhen Lucas, Philip Yurchenko, Sergey N. Kaminski, Tomasz Montesinos, Matias Nayakshin, Sergei Elbakyan, Vardan Osses, Javier Garatti, Alessio Caratti o Zhao, He Kurtev, Radostin Borissova, Jura Morris, Calum Minniti, Dante Alonso-García, Javier Fermiano, Vitor Saito, Roberto K. Miller, Niall Zsidi, Gabriella Muthu, H. D. S. Briceño, Cesar Peña, Carlos Contreras Lynas-Gray, A. E. Tennyson, Jonathan Wang, Lingzhi Yu, Lixin Benitez-Palacios, Diego Yang, Jinyi Kuhn, Michael Wang, Sharon X. Solar and Stellar Astrophysics Here we investigate an infrared eruptive source, identified from the decade-long VISTA Variables in the Via Lactea survey (VVV). We named this target after a group of variable sources discovered by VVV, as VVV-WIT-13, with WIT standing for "What Is This?", due to its unique photometric variation behaviour and the mysterious origin of the outburst. This target exhibited an outburst with a 5.7 mag amplitude in the Ks-band, remained on its brightness plateau for 3.5 years, and then rapidly faded to its pre-eruptive brightness afterwards. We aim to reveal the variable nature and outburst origin of VVV-WIT-13 by presenting our follow-up photometric and spectroscopic observations along with theoretical models. We gathered photometric time series in both near- and mid-infrared wavelengths. We obtained near-infrared spectra during the outburst and decaying stages on XSHOOTER/VLT and FIRE/Magellan, and then fitted the detected molecular absorption features using models from ExoMol. We applied 2D numerical simulations to re-create the observables of the eruptive phenomenon. We observe deep AlO absorption bands in the infrared spectra of VVV-WIT-13, during the outburst stage, along with other more common absorption bands (e.g. CO). Our best-fit model suggests a 600 K temperature of the AlO absorption band. In the decaying stage, the AlO bands disappeared, whilst broad blue-shifted H2 lines arose, a common indicator of stellar wind and outflow. The observational evidence suggests that the CO and TiO features originate from an outflow or a wind environment. We find that VVV-WIT-13 is an eruptive young star with instability occurring in the accretion disk. One favoured theoretical explanation of this event is a disrupted gas clump at a distance of 3 au from the source. If confirmed, this would be the first such event observed in real time. |
| title | VVV-WIT-13: an eruptive young star with cool molecular features |
| topic | Solar and Stellar Astrophysics |
| url | https://arxiv.org/abs/2509.15334 |