VVV-WIT-13: An eruptive young star with cool molecular features

Context. Outburst phenomena are observed at different stages of stellar evolution, due to the enhancement of the mass accretion rate on protostars or even stellar merger events. In the case of a young stellar object (YSO), the episodic mass accretion event plays an important role in the pre-main-sequence stellar mass assembly. Here we investigate an infrared eruptive source (RA = 16:53:44.38; Dec = − 43:28:19.47), identified from the decade-long VISTA Variables in the Vía Láctea survey (VVV). We named this target after a group of variable sources discovered by VVV, as VVV-WIT-13, where WIT stands 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 K s -band, remained on its brightness plateau for 3.5 years, and then rapidly faded to its pre-eruptive brightness afterwards. Aims. Our aim is 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. Methods. 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. Results. 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 H 2 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. Conclusions. 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.

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Publication Details

Journal
Astronomy and Astrophysics
Published
2025-10-08
DOI
https://doi.org/10.1051/0004-6361/202556048
Citations
1
Primary Topic
Astronomy and Astrophysical Research
Type
article
Field-Weighted Citation Impact
1.19
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article

VVV-WIT-13: An eruptive young star with cool molecular features

G. Zsidi, D. Minniti, R. K. Saito, P. W. Lucas et al.
1 citations
Astronomy and Astrophysics
Astronomy and Astrophysical Research
1.19
article

VVV-WIT-13: An eruptive young star with cool molecular features

G. Zsidi, D. Minniti, R. K. Saito, P. W. Lucas, N. Miller, Sergei N. Yurchenko, A. Caratti o Garatti, L. Wang, Sergei Nayakshin, Jing Yang, A. E. Lynas-Gray, Carlos Contreras Peña, C. S. Morris, J. Alonso-García, Matías Montesinos, Jonathan Tennyson, S.X. Wang, J. Borissova, R. Kurtev, T. Kamiński, Michael Kuhn, Vardan G. Elbakyan, Zhen Guo, L. Yu, H.D.S. Muthu, V. Fermiano, H. Zhao, C. Briceño, Diego Benitez-Palacios, Javier Osses
article en
1 citations

Abstract

Context. Outburst phenomena are observed at different stages of stellar evolution, due to the enhancement of the mass accretion rate on protostars or even stellar merger events. In the case of a young stellar object (YSO), the episodic mass accretion event plays an important role in the pre-main-sequence stellar mass assembly. Here we investigate an infrared eruptive source (RA = 16:53:44.38; Dec = − 43:28:19.47), identified from the decade-long VISTA Variables in the Vía Láctea survey (VVV). We named this target after a group of variable sources discovered by VVV, as VVV-WIT-13, where WIT stands 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 K s -band, remained on its brightness plateau for 3.5 years, and then rapidly faded to its pre-eruptive brightness afterwards. Aims. Our aim is 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. Methods. 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. Results. 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 H 2 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. Conclusions. 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.

Astronomy and AstrophysicsVol. 703
University of Wyoming (US), Universidad de Antofagasta (CL), Southern Federal University (RU), Seoul National University (KR), University of Hertfordshire (GB), Valparaiso University (US), University of Leicester (GB), Vatican Secret Archives (VA), University of Oxford (GB), Universidade Federal de Santa Catarina (BR), Millennium Institute of Astrophysics (CL), Wyoming Department of Education (US), Nicolaus Copernicus Astronomical Center (PL), Cerro Tololo Inter-American Observatory (CL), Astronomy and Space (AU), National Astronomical Observatories (CN), University College London (GB), Fundación Ciencias Exactas y Naturales (AR), University of Duisburg-Essen (DE), University of Chile (CL), Federico Santa María Technical University (CL), University of the Western Cape (ZA), National Institute for Astrophysics (IT), Tsinghua University (CN), Polish Academy of Sciences (PL)
Openalex Percentile: Top 17%
Astronomy and Astrophysical Research
1.19
DOIOpen Access PDFOpenAlex
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