While we are still working on restoring our server (update to follow next week), we have a look on a plot from the first published referee paper using HOYS data. It is called: “The 2014-2017 outburst of the young star ASASSN-13db: A time-resolved picture of a very low-mass star between EXors and FUors“.
This is actually the topic of research for which HOYS (Hunting Outbursting Young Stars) was originally started. It looks at an outbursting, low mas, young star and investigates its properties. I will copy the paper abstract below, so you can have a detailed look.
In the figure above, the HOYS data for the source is shown. Our data are the only ones that have managed to catch the decline in brightness in several filters, and thus allowed to study the colour changes during this phase of the evolution of the burst. We regularly check if the source has started another burts, but so far the source has remained more or less in its quiescent state since. But it will certainly erupt again, however it is not clear when this will happen. Thus, keep taking those images so that we do not miss the start of the next burst.
Paper Abstract:
Context: Accretion outbursts are key elements in star formation. ASASSN-13db is a M5-type star with a protoplanetary disk, the lowest-mass star known to experience accretion outbursts. Since its discovery in 2013, it has experienced two outbursts, the second of which started in November 2014 and lasted until February 2017.
Aims: We explore the photometric and spectroscopic behavior of ASASSN-13db during the 2014-2017 outburst.
Methods: We use high- and low-resolution spectroscopy and time-resolved photometry from the ASAS-SN survey, the LCOGT and the Beacon Observatory to study the light curve of ASASSN-13db and the dynamical and physical properties of the accretion flow.
Results: The 2014-2017 outburst lasted for nearly 800 days. A 4.15 d period in the light curve likely corresponds to rotational modulation of a star with hot spot(s). The spectra show multiple emission lines with variable inverse P-Cygni profiles and a highly variable blue-shifted absorption below the continuum. Line ratios from metallic emission lines (Fe I/Fe II, Ti I/Ti II) suggest temperatures of 5800-6000 K in the accretion flow.
Conclusions: Photometrically and spectroscopically, the 2014-2017 event displays an intermediate behavior between EXors and FUors. The accretion rate ([Ṁ]= 1-3 × 10-7 M⊙/yr), about two orders of magnitude higher than the accretion rate in quiescence, is not significantly different from the accretion rate observed in 2013. The absorption features in the spectra suggest that the system is viewed at a high angle and drives a powerful, non-axisymmetric wind, maybe related to magnetic reconnection. The properties of ASASSN-13db suggest that temperatures lower than those for solar-type stars are needed for modeling accretion in very-low-mass systems. Finally, the rotational modulation during the outburst reveals that accretion-related structures settle after the beginning of the outburst and can be relatively stable and long-lived. Our work also demonstrates the power of time-resolved photometry and spectroscopy to explore the properties of variable and outbursting stars.