This week we look at the light curve of LkHa137. This is a young star in the Pelican Nebula region. It is situated in a dark part of the molecular cloud and images show it is surrounded by a faint extended nebulosity (explaining the photometry outliers visible in the data). This is most likely light from the young system that gets scattered on the circumstellar material in the vicinity of it. Indeed the object is made up of two stars, called A and B, which are separated by about one arcsecond. Component A is by 2.5mag brighter than B and thus dominates the light we record. Due to the small separation, we cannot detect both stars separately in our data.
The light curve shows a variety of behaviours that keep changing over time. On short (day-to-day) timescales there is some scatter with amplitudes of a few percent, which increases at later times. These variations are correlated in the different filters, and hence represent real brightness variations. From 2015-2017 to object remained otherwise constant with very minor (percent changes) small systematic long term brightness shifts.
This was followed by two longer term dimming events in 2018 and 2019, of about half a magnitude. The source seems to have returned to its prior brightness after both of them and again remained about constant at this level in 2020. After this the brightness dropped by about half a magnitude in 2021. A further half magnitude drop is seen in early 2022, from which the source has recovered by now, but is still 0.5mag fainter than at the start of the HOYS observations of this object.
It will be interesting to see what the object is doing next….