This week we have a timely look at one of the Gaia photometric alerts. In particular Gaia21bkd, which was published in the evening of March 18. The Gaia light curve shows an almost 2mag drop in the brightness of the star, which seems generally a bit (0.5mag) variable, but no such deep dimming events have been observed before.

The star itself is a known young star in the IC348 young cluster in Perseus. At a distance of about 315pc it is one of the closest young star forming clusters. The star itself is a know emission line star, catalogued as LkHA99 and situated in the outskirts of the IC348 cluster. Thus, the object shows signs of ongoing accretion.

The HOYS light curve (for clarity we only show the I-Band data in the above plot) contains photometry of the source from the last six observing seasons. The 2020-21 season of visibility now almost comes to its end, with the object setting very soon after sunset.

In our data the brightness dip seen in Gaia is also evident. Furthermore, there are other dips, which are even deeper, that Gaia has missed. In particular about two years ago the source underwent two deep dimming events. They are missed by Gaia as they usually only last a few days. The two observed ones are shorter than 2 weeks. Thus, with the lower cadence (~30days) of Gaia, they tend to get missed.