This week we show the light curve of the young star PR Ori, which is situated south of the Orion Nebula in the L1641N HOYS target region. This star is actually composed of two stars that form a binary, wit the components A and B. Note that A itself is a binary. But the two component A and B are too close together, so we only really have a combined light curve for the system.
Recently component B has undergone an FU-Ori outburst. Read all about it here. We show one decade (10yr) of B, V, R, and I data from HOYS for the system in the plot above. The last two years are not show (see below). One can see a general increase in the brightness over time, but far less than what is typically expected for such an outburst. Indeed the V magnitude only goes up by about half a magnitude. This is caused by component A being the dominant light source in the system during quiescence. Component B was between four and five magnitude fainter before the eruption. If one remembers that a five magnitude change means a hundred times flux change this becomes more clear. In other words, before the eruption B contributed only one percent of the light. A typical FU-Ori eruption might increase the flux for B by a factor of a hundred, making it roughly equally bright to A during the outburst. And doubling the flux of the system would increase the brightness by about 0.75mag. This is roughly in line with what we can see in the light curve.
This is yet another FU-Ori outburst in one of the HOYS fields. Thus, we should be able to revisit the FU-Ori statistics again at some point to work out at what rate these bursts are happening in a population of young stars.
The data shown above misses the last two years. We do have all the data, but the plot was made from the data already ingested in our new database, and not the one you all can see live. Note that we are making good progress with the switching to the new system. Almost all website functions have been rewritten and tested for the new system. Only admin tools remain to be adapted. Currently we are actively working on transferring as much of the data from the live system to the new as we can, without having to switch the website off-line. In preparation for the switch-over, which we can do hopefully very soon, please ensure that if you have uploaded data, that as much of it is fully processed. This will be making the downtime of the transfer to the new system much shorter. We will email every user once we have decided on the exact date of the transfer.