One aspect of young stars has so far not extensively investigated in the HOYS data. This is the mass accretion rate. The reason is that changes in the accretion rate cause usually larger changes in the U-band brightness, as well as in most cases, variations in the flux in the Halpha line. In both cases the data is usually sparse. Not many participants have a U-band filter. But even if they do, the young stars tend to be very faint at these short wavelengths and thus a large telescope and long exposure times are needed. While many people do have an Halpha filter, because it is narrow band, long exposure times are needed to measure the brightness of the objects accurately.
However, for several years now we do have accumulate for some fields a sufficient amount of Halpha and U-Band images to analyse. Thus, over the winter we plan to start with a small undergraduate student project to evaluate what can be done with the data we have. How many young stars have we observe, that show a clear indication of Halpha emission lines and what fraction varies? How many stars have sufficient U-band data and do their variations correlate with the variation in Halpha emission? We will see what we find and report back 🙂
Above is an example of a light curve of a young star over about 6yr. We only display the R-band and the Halpha data. The difference between the two (R-Halpha) is an indication of the brightness of the flux in the Halpha line itself. In this case it seems that other than the noise in the data, there are no significant changes, but a detailed analysis is needed to investigate this in detail.