Multi-wavelength detection of an ongoing FUOr-type outburst on a low-mass YSO

Zhen Guo, P. W. Lucas, R. G. Kurtev, J. Borissova, V. Elbakyan, C. Morris, A. Bayo, L. Smith, A. Caratti o Garatti, C. Contreras Peña, D. Minniti, J. Jose, M. Ashraf, J Alonso-García, N. Miller, H. D. S. Muthu

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During the pre-main-sequence evolution, Young Stellar Objects (YSOs) assemble most of their mass during the episodic accretion process. The rarely seen FUOr-type events (FUOrs) are valuable laboratories to investigate the outbursting nature of YSOs. Here, we present multi-wavelength detection of a high-amplitude eruptive source in the young open cluster VdBH 221 with an ongoing outburst, including optical to mid-infrared time series and near-infrared spectra. The initial outburst has an exceptional amplitude of >6.3 mag in Gaia and 4.6 mag in K_s, with a peak luminosity up to 16 Lsun and a peak mass accretion rate of 1.4 x 10^{-5} Msun. The optical to infrared spectral energy distribution (SED) of this object is consistent with a low-mass star (0.2 Msun) with a modest extinction (A_V < 2 mag). A 100-d delay between optical and infrared rising stages is detected, suggesting an outside-in origin of the instability. The spectroscopic features of this object reveal a self-luminous accretion disc, very similar to FU Orionis, with a low line-of-sight extinction. Most recently, there has been a gradual increase in brightness throughout the wavelength range, possibly suggesting an enhancement of the mass accretion rate.
Original languageEnglish
Article numberslad201
Pages (from-to)115-122
Number of pages8
JournalMonthly Notices of the Royal Astronomical Society: Letters
Issue number1
Early online date26 Jan 2024
Publication statusE-pub ahead of print - 26 Jan 2024


  • astro-ph.SR
  • astro-ph.GA


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