HOYS stands for Hunting Outbursting Young Stars and one of our aims from the start was to provide long term, pre-outburst light curves for the largest of the know bursts, the FU-Ori type outbursts. We know they seem to occur roughly every few 10,000yr, but there are not that many known and most of them get only noticed when the object is in outburst.
As we have seen, in one of the latest papers (Paper VIII), we have excellent long term (~10yr) light curves now for about 3000 young stars in the HOYS clusters. This means in total we have observed ~30,000yr of a typical young star light curve, and should now roughly have a 50% chance to have such an outburst occur amongst out targets. Note that we do have the FU-Ori burst of Gaia17bpi amongst our targets (Paper also here), but that field was only added after we knew about it, so this cannot be counted for the statistics.
Then, last week, I had an excited email from one of our participants that an FU-Ori burst had been announced in the latest Astronomy Telegrams. The star in question is PR Ori, which is situated in the L1641N star forming region ,just south of the M42 Orion Nebula cluster.
It turns out that we knew about the object since 2021, when it was noted as the Gaia alert object Gaia21arx. We then wrote about it in week 109, and again in week 155. In the latter, not noticing we had looked at it prior. In any case, roughly speaking the statistics are right, we now have, as expected one burst amongst our targets. It won’t help to bin down the typical burst frequency, but it is a start. But have a read of the week 109 post to see why studying this one in detail with HOYS data is tricky – it is merged with a brighter star, which is its binary companion. Oh, and the light curves above are the two latest years of the HOYS data for the system in the R and I-band. It still seems to be slowly getting brighter, is still variable on short timescales, and we need to run some cleaning of the data to remove some of the outliers that are evident in the image.