For the time period September 2020 to April 2021, light curve for V899 Mon. Credit: Park et al., 2021.
A photometric and spectroscopic observation of V899 Mon, a strange young star with unusual eruptions, was made by an international team of astronomers. The observational campaign provided more insight into the star's nature. This research was described in a paper that was published September 23rd on arXiv.org.
V899 Mon, also known as IRAS 06068–0641 and located around 2,600 light-years from the MonocerosR2 molecular cloud (Molecular Cloud R2), is an eruptive young star object (YSO). It is believed to be approximately two times larger than the sun, and has a radius between four and six solar radiations.
Previous observations have indicated that V899 Mon experienced a bright outburst in November 2009 that reached its peak brightness by 2010. It then returned to quiescence for a short time in 2011, and then brightened up again in 2012. The observations made during V899 Mon's bursting period have not given enough information to provide further insight into the nature of the object.
Generally, YSOs can be classified as either FU Orionis type objects (FUors), or EX Lupi type objects (EXors). FUors are brighter than magnitude 4 in the optical realm and stay brightened for many decades. EXors brighten also by a few magnitudes but, unlike FUors they stay in the high brightness stage for a few weeks to a few decades. It is not yet clear what V899 Mon means.
Sunkyung Park, an astronomer from Konkoly Observatory in Budapest (Hungary), led the multifilter optical photometric monitoring. They also made optical and near infrared spectroscopic observations on V899 Mon to determine if this YSO was a FUor and EXor.
According to observations, the 2018 year was the second peak for the V899 Mon outburst. The star's brightness has been decreasing at an average rate of 0.30 mag per years since then. The 2017-2018 season saw the strongest burst, lasting for approximately 200 days. In the 2020/2021 season, another shorter, but weaker, accretion burst occurred.
Astronomers observed that V899 Mon's increasing number of accretion explosions and disk brightness declines suggest that the YSO is slowly switching from the not yet understood accretion mechanism during enhanced accretion to magnetospheric accretion.
The study revealed that V899 Mon's small amplitude in photometric variations, rich emission line, measured mass loss rate and measured mass accretion rates all have similar properties to classical T Tauri-type star (CTTS) stars. The gradual decrease in V899 Mon indicates that it is nearing the end of its second outburst and is on the road to returning to the quiescent phase.
All the data being considered, researchers conclude that V899 Mon may be of the EXor type.
The paper's authors concluded that "our recent photometric and spectrum observations of V899 Mon during the current evolutionary stage reveal more features typical of EXors."
Sunkyung Park et. al., V899 Mon: A peculiar young star that is about to burst. arXiv.2109.11283v1 (astro-ph.SR). Sunkyung Park et. al., V899 Mon : A peculiar young star that is about to burst. arXiv.2109.11283v1 (astro-ph.SR). arxiv.org/abs/2109.11283
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