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YSO Bulletin
- November 2020 -

Become a Disc Detective!

This is a project that would appear to be ideal for those times when observational astronomy is out (in the UK, that means most of the time!) It is run by Marc Kuchner, NASA's outreach guru, as part of the zooniverse scheme. Here is a quick description from their website:

Planets form from vast clouds of gas, dust, and chunks of rock - clouds in the shape of disks, with stars in the center. We can find out where planets are forming and where planets probably remain today by searching for stars that are surrounded by these disks. Finding these disks, called “debris disks” or “YSO disks” depending on their age and gas content, has been a major quest of astronomers for the last three decades.
NASA’s WISE mission observed more than two billion sources, including galaxies, stars, nebulae, and asteroids, not to mention image artifacts and noise. Among these two billion sources are thousands of new disks waiting to be discovered.
At Disk Detective, you will help astronomers find these disks, homes for extrasolar planets. You'll examine images of disk candidates from NASA's WISE mission, and compare them with images from four different astronomical surveys: the SkyMapper Southern Sky Survey, the Pan-STARRS survey, the Two Micron All Sky Survey (2MASS), and the unWISE coadds of data from the WISE mission. Many of them will be junk, but every now and then you'll find a nice clean image, with no background objects or noise overwhelming the signal. And some of those will be new circumstellar disks!
...To find these disks, we look for infrared excess - stars that have more infrared light than you would expect, which indicates the presence of material the gas and dust has warmed up. Here, we have selected a set of systems that have infrared excess, and we are looking for your help to make sure that these systems actually look the way we expect them to (rather than looking like galaxies, or material from the gas and dust between stars).

Resources and training (I realise that some of us here may not need training, but it's there for you) are all available through the DD website. It looks like a very worthwhile project.

Don't forget the UXOR!

Dirk van Dam (Leiden Observatory) and Dr. Matthew Kenworthy (Leiden Observatory) request AAVSO observer assistance in monitoring the UXOR ASASSN-V J181654.06-202117.6 in an exoplanet/planetary system study. This is AAVSO Alert Notice 710 and I include a section from that notice. Go to the YSO section on the forum to find the full text and threads:
van Dam writes: "This system is a recently discovered system by ASAS-SN, which shows a very deep eclipse (0.8 mag ~ 50%), that is not only asymmetric (indicative of a circumplanetary disk), but also exhibits substructure (could possibly be rings, or indicative of moon formation). The whole could also be an eclipsing dust cloud or other options, but only further analysis will reveal what this particular occultation is. The AAVSO observations would be helpful to fill out the eclipse and add more detail to the full transit to explore the possibility of rings, or to better constrain the modeling of the eclipse. The potential follow-up campaign would be to catch the whole eclipse and constrain the period of the system."
Observations are currently being made at Las Cumbres Observatory in Chile. AAVSO observers are requested to monitor the target. CCD photometry is requested (filters in order of priority: Sloan g, V, B, Rc, Ic). If observing with multiple filters, alternating filters is preferred. Filtered photometry is preferred, but if unfiltered observations are made, they should be reduced to a V filter (CV). Visual observations are also welcome.
Re the cadence of CCD observations, van Dam says: "There seems to be at least nightly variation of the target, but shorter cadence is preferred to fill out the light curve and see whether there is intranight variance. The shorter the cadence the better, with a minimum of twice per night. Time series would be the best and every hour would be fantastic, with a minimum SNR of 5."

Data Mining for Dippers

The AAVSO are running a data mining webinar on November 1st. It will concentrate on using data from TESS (Transiting Exoplanet Survey Satellite) to detect stellar variation.
The YSO connection emerges because the techniques can reveal the presence of 'dippers' which are young, low-mass stars which show periodic, or semi-periodic fades. Typically these are caused by the dust discs but may also reveal debris discs from planetary or planetesimal material around stars which have already formed or which are in the latter stages of formation. RZ Psc may be one such object, rather than the UXOR it was previously thought to be (its colours do not suggest it is UXORious)
A study by Tajiri et al used the same basic principle and also found, in addition to the more 'conventional' style of dipper:

"...three old dippers whose age exceeds ten million years, which is considered as the disk dissipation time. The color-color diagram indicates that these old dippers are likely to have an extreme debris disk. In particular, we found a runaway old dipper having a large three-dimensional velocity of 72 km s-1. The dippers in the field, which were probably escaping from their birth molecular clouds or were born outside the current area of star forming regions, are more common than previously considered."