This week we look back at the light curve of the Gaia alert object Gaia17bpi. The object increased its brightness by about 4 magnitudes over a period of about three years. With some ‘wiggles’, the brightness has remained high since. Our HOYS data has in part be used to classify this source as an FU-Ori type outburst. This is exactly the type of object for which HOYS was originally designed for. Unfortunately, we do not have any pre-outburst data, because the source was not a HOYS field prior to the burst. Even if it would have been, it would have been far too faint.
Our current light curve shows very good coverage of the field in several filters during the first few years after the burst. Over the last few seasons the number of observations has dropped. We can still see the source has not changed much, but it is important to have data points every now and again in multiple filters to keep an eye on these objects. Note that the other stars in the field are then also observed. And we do not know when the object will return to its pre-burst state. There are no definitive data that show how a FU-Ori type burst returns to its pre-burst state, since none of the known objects has done that. Thus, some estimates indicate that these burst last up to 100yr.