Combined griJHKS light curves of Gaia20bdk obtained by several ground-based surveys and telescopes, and G, W1 and W2 light curves obtained by the Gaia and (NEO)WISE space telescopes. Credit: arXiv (2024). DOI: 10.48550/arxiv.2412.07697
An international team of astronomers analyzed multicolor photometric and spectroscopic observations of the star Gaia20bdk. As a result, they discovered that Gaia20bdk is a young FUor-type stellar object. The discovery is presented in an article published December 10 on the arXiv preprint server.
Young stellar objects (YSOs) are stars in the early stages of their evolution; in particular, protostars and pre-main sequence stars. They are usually observed embedded in dense molecular clusters, environments containing lots of molecular gas and interstellar dust.
Since episodic accretion processes occur in YSOs, 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; Fuors are more extreme and rarer. They can have an amplitude of up to 5 to 6 magnitudes and last for decades or even centuries.
Gaia20bdk was identified in March 2020 by the Gaia Photometric Science Alert system as a 1.2 mag brightening of a red star known as 2MASS 07101491-1827010. Closer inspection of this source revealed that it could be a YSO in the star-forming region Sharpless 2-301, located about 11,500 light years away. Gaia20bdk’s mass was determined to be around 2.67 solar masses, while its age was estimated at 1.6 million years. Archival data indicates that the explosion of this source began in 2018.
Now, a group of astronomers led by Michal Siwak of the Konkoly Observatory in Budapest, Hungary, has carried out an in-depth study of Gaia20bdk, hoping to shed more light on its nature.
“In order to study the star during the resting phase, we collected public domain visual and infrared photometry… We are using our (own) public domain optical and infrared photometry and spectroscopy to study the explosion,” the researchers wrote in the journal.
The study found that Gaia20bdk is a Class I YSO type G7 with an effective temperature of approximately 5,300 K and a bolometric luminosity of 11 solar luminosities. In general, Class I YSOs are those that have a thick envelope and a spectral index greater than 0.3.
The near-infrared spectra of Gaia20bdk studied by Siwak’s team show all the characteristics of typical FUors. In particular, astronomers have noted that these spectra show a carbon monoxide band head in absorption, a triangular shape of the H band spectrum, and mainly hydrogen and heavier elements in absorption.
Additionally, the Gaia20bdk lightcurve plateau exhibits small-scale photometric variability, typically associated with the disk flicker observed in other FUors. Gaia20bdk’s disk was found to have an interior radius of about four solar radii, a bolometric luminosity of about 133 to 165 solar luminosities, and a mass accretion rate of 0.000015 solar masses per year. These values are also typical of FUor type YSOs.
More information:
M. Siwak et al, Gaia20bdk — a new FUor in the Sh 2-301 star formation region, arXiv (2024). DOI: 10.48550/arxiv.2412.07697
Journal information:
arXiv
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