YSO Bulletin
- July 2024 -

- SFN problems! -

Recently the professionally-based Star Formation Newsletter has appeared to be in difficulties, with no issue accessible since April. It is a vital resource for the YSO community and has in fact been the source of virtually all the content of this newsletter. One upshot of this is that our publication seems to be the only generally-available source of news in the field. Since it is not currently accessible, this YSON will contain articles from before our inception in January 2020. One reason why I will continue to ask for contributions from our subscribers, who I hope will take this none-too-subtle hint.

More on PDS 70

This object, also known av V1032 Cen, has been the subject of many studies which have revealed two forming planets - possibly others, including evidence for forming satellites - in this 5Myr-old, ¾-solar mass T Tauri star. Water vapour has also been detected, along with UV emission from the star's corona. This emission is one factor that contributes to the erosion of the protoplanetary disc. These discs are usually gone by 10Myr but since we are just halfway through that timescale there seems to be plenty of time for more planet formation!

V1686 Cyg

An Armenian study presents an analysis of the optical observations of the Herbig AeBe star V1686 Cyg, which is associated with a small isolated star-forming region around another HAeBe star, BD+40°4124. The normally-faint star that can outburst to magnitude 12 was observed as a part of a project on the investigation of young eruptive stars. Observations were made with the 2.6m telescope of Byurakan Observatory from 2015 to 2017.
In that period they obtained V1686 Cyg direct images and 14 medium- and low-resolution spectra. In the course of observations this star underwent an atypical outburst. After data reduction it was shown that the full rise and decline of V1686 Cyg had almost 3 magnitudes amplitude and lasted about 3 months. They were also able to trace the changes of the stellar spectrum during the outburst, which are correlated with the photometric variations.

With this in mind, it could make a good target for amateur observing, and imagers could try and capture the nebulous wisps in the area as well.

Starforming Relic

Several recent studies have shown that the Vela OB2 region hosts a complex array of sub-populations with ages in the range 10 to 50 Myr, which might represent the best example of the outcome of clustered star formation in Giant Molecular clouds (GMC). The area around the open cluster Collinder 135 reveals an area of several hundred parsecs and shows a new cluster named BBJ1 with the same age as NGC 2547 (30 to 35 Myr), but located at a distance of 260 pc from it. Deeper investigation has detected a filamentary structure of stars that bridges the two clusters. Given the extent in space and a similar age, this indicates that such a structure represents the detection of a 35 Myr-old outcome of a mechanism of filamentary star formation in a GMC.

HAeBe's again

The eighth-magnitude object Herbig Ae star HD 169142, near δ Sgr is known to have a gaseous disk with a large inner hole, and also a photometrically variable inner dust component in the sub-au region. A further analysis of the object looked at the evolution of inner dust around HD 169142, which may provide information on the evolution from late-stage protoplanetary disks to debris disks. They used near-IR to constrain the dust distribution at three epochs spanning six years, as well as studying the star's photometric variability using optical-IR observations and archival data. Results indicate that a dust ring at about 0.3AU formed at some time between 2013 and 2018, and then faded (but did not completely disappear) by 2019. The short-term variability resembles that observed in extreme debris disks, and is likely related to short-lived dust of secondary origin, though variable shadowing from the inner ring could be an alternative interpretation. If confirmed, this is the first direct detection of secondary dust production inside a protoplanetary disk.