Optical and infrared light curves for the V1741 Sgr over a period of approximately 8 years, from 2015 to mid-2023. Credit: arXiv (2024). DOI: 10.48550/arxiv.2401.09522
Using various ground-based facilities and space telescopes, astronomers observed an accretion burst that recently occurred on a young variable star known as V1741 Sgr. Observation results, published on January 17 on the preprint server arXivshed more light on the nature of this star.
V1741 Sgr (other designations: SPICY 71482 and Gaia22dtk) is a classical T Tauri variable star located near the young star cluster NGC 6530, nicknamed the Lagoon Nebula. The source was first reported as variable in 1957 and after years of stability, its first explosion was recorded in mid-2022 with ESA’s Gaia satellite.
Studies of the recent explosion of V1741 Sgr suggest that it may be a young stellar object (YSO), a star at an early stage in its evolution. Observations show that episodic accretion processes occur in YSOs, so these objects can experience accretion-driven explosions.
Astronomers generally divide these events into EX Lup (also known as EXors) and FU Ori (or FUors) explosions. EXors have an amplitude of a few magnitudes and last from a few months to one or two years; Borers are more extreme and rarer, can reach magnitudes of 5 to 6 magnitudes, and last for decades or even centuries.
A team of astronomers led by Michael A. Kuhn from the University of Hertfordshire, United Kingdom, carried out V1741 Sgr photometry and spectroscopy, using instruments such as Gaia, Zwicky Transient Facility (ZTF) or the telescope infrared (IRTF) from NASA. The primary objective of their study was to explore the observed explosion, in hopes of determining the true nature of the V1741 Sgr.
The study found that the V1741 Sgr explosion was an EX Lup-like event of moderate amplitude – about 3.0 mag in the optical and 1-2 mag in the infrared. The explosion spectrum shows strong atomic and molecular emission, as well as brightening throughout the observed range.
According to the researchers, the most notable change in the spectrum of V1741 Sgr was the appearance and then disappearance of the titanium oxide (TiO) absorption as it continued to fade, which could be due to the cooling of circumstellar gas.
“In April 2023, as the explosion began to subside, strong TiO absorption appeared, indicating a cooler temperature T ∼ 3,600 K. However, once the source returned to its previous flow the explosion in August 2023, the absorption of TiO and the emission of CO disappeared. (…) The cooling of the circumstellar gas would explain the appearance of TiO, which then disappeared once this gas disappeared and the stellar spectrum reappeared”, explain the authors of the article.
Analyzing the light burst curve, Kuhn’s team identified an increase of 60 days and a plateau of 280 days, followed by a decay lasting about 110 days. The study found that the explosion made the spectral energy distribution (SED) bluer at wavelengths below 1.6 μm and redder at wavelengths above 1.6 μm.
The collected data also allowed astronomers to determine the fundamental properties of V1741 Sgr. It was found that the star is of spectral type K2, has an age of less than 3 million years and is located at a distance of about 4,100 light years.
The results suggest that V1741 Sgr formed on the outskirts of the Lagoon Nebula, near a subcluster designated G5.9-0.9, rather than the main cluster.
More information:
Michael A. Kuhn et al, The 2022-2023 accretion explosion of the young star V1741 Sgr, arXiv (2024). DOI: 10.48550/arxiv.2401.09522
Journal information:
arXiv
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Quote: Astronomers observe the accretion explosion of a young variable star (January 24, 2024) retrieved on January 25, 2024 from
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