YSO Bulletin
- March 2024 -

- BM And - one to watch! -

BM Andromedae

Andromeda is not usually thought of as a hunting ground for YSOs, but this one is worth following, especially as it is in the same area as the well-known Z And (prototype of the Z And stars of course) and furthermore in a rather attractive little cluster of bright stars. With a classification of UXOR/ROT and a K-type spectrum it is a member of the T Tauri group, stars of roughly Solar mass. The ROT part shows that it exhibits small-scale variations due to activity on the star itself, such as spotting. The period in this case is about 18 days which is relatively long for a young star; though in some YSOs such as DI Cep, the spot is in the accretion disc rather than the star itself. The smoothed visual light-curve for the past 200 days above demonstrates the rapidity of the variations when they happen, the fades (characteristic of UX Orionis stars) at JD2460260 and 320 are deep and rapid, taking only a day or two, and the rise at 2460280 is of 0.8m in just one day! This is clearly an unpredictable star that exhibits all sorts of changes, reminding me somewhat of the variations of RR Tauri.
Currently only about half a dozen AAVSO members are following this object, which is now becoming rather low in the sky. So this is essentially a call to include this object on your observing list at the next apparition!

New FUOR in Cygnus

SSTgbs J21470601+4739394 (henceforth 214747 for obvious reasons) is a young binary deeply embedded in a dark nebula. A large surge in the mid-IR has been seen on the fainter component of the system, which is a low-luminosity object (about a fourth of Solar preoutburst, but up to virtually equal to Solar at outburst. The rise in luminosity can be seen in 'before' and 'after' views in the right-hand column. Note that following the outburst there has been a discharge of material into the circumstellar environment as well.

K-band view of the FUOR outburst on 214747. Scale is the same in both pictures.

Baby Clusters!

A recent study of young clusters found that a remarkable fraction (up to 80%) of clusters younger than about 30 Myr is currently experiencing significant expansion, whereas older systems are mostly compatible with equilibrium configurations. The authors say "...we observe a trend where the expansion speed increases with the clustercentric distance, suggesting that clusters undergoing expansion will likely lose a fraction of their present-day mass. Also, most young expanding clusters show large sizes, possibly due to the expansion itself."...