YSO Bulletin
- August 2026 -

Report from the First Zoom Meeting

By their own admission, HQ forgot to send out a formal registration for the first meeting of the group so we had only half-a-dozen attendees! However, what was lacking in quantity was made up for in quality, and all items on the agenda were discussed, in this case possibly helped by the turnout. Chief take-away was that nobody felt any major changes were needed to the newsletter and it was generally felt to be a good thing. Since that time I have had some formal dates from HQ. We will meet quarterly on Zoom, on these Saturdays (note the times are not all the same):

• November 21, 2026 at 3pm ET/8pm UTC
• February 20, 2027 at 3pm ET/8pm UTC
• May 15, 2027 at 3pm ET/7pm UTC
• August 21, 2027 at 3pm ET/7pm UTC

Calendar reminders will be sent out at times nearer the dates, so now nobody has any excuses!
Since Josch Hambsch was present at the meeting we spent some time discussing TV Crt, where he presented a lightcurve of the beginning of the transit of the disc across the other pair in this double-double system. It wasn't only those present who were impressed - I sent the graphic to Prof. Amelia Bayo who is the head researcher on the project. She said These curves are sooo much cleaner than the ASASSN ones for instance! super interesting!! we can learn a lot combining those data with the spectroscopy, Halpha photometry, radio data, etc! This is great! I add Juliana and Seba in CC that are the full of energy people that will be able to extract everything that these data have to offer. So, bearing that in mind, it would be terrific if we could get a few more observers in on this campaign. The I data are important as they show the behaviour of the disc properties, but essentially as wide a waveband sweep as you can get. Amelia's team have access to several observational sources - ALMA, the VLT and CHARA for instance - hence the welcome comments on our optical results. Take a bow!

Another FUOR!

A recent Chinese study reports on the discovery of an FUor-like Class I protostar in NGC7538. The source, named NGC-7538-MIR, exhibited a giant luminosity burst of 5 magnitudes in the K band, and a prolonged high-luminosity state lasting at least five years. Its mid-infrared (mid-IR) light curves, constructed from WISE/NEOWISE multiepoch data, presented a rapid rise and slight fading after the peak, placing this event among long-duration eruptive phenomena observed in protostars, such as FUor events. The evolution of luminosity and colour can be naturally split into three phases, pre-burst, burst and post-burst, suggesting that different physical processes may dominate in each phase. The evolution of the object is consistent with a transition from variability influenced by circumstellar extinction (pre-burst) to a phase with greatly enhanced accretion luminosity (burst), and followed by a gradual relaxation of the circumstellar environment (post-burst). Overall, the observed IR variability is consistent with a FUor-like accretion event occurring at an early evolutionary stage, highlighting the importance of long-term monitoring for identifying episodic accretion events in deeply embedded protostars.
Large-amplitude IR brightening accompanied by systematic colour evolution provides strong evidence for enhanced disc accretion, particularly for deeply embedded Class I sources where optical spectroscopy is often unfeasible. Such photometric diagnostics have proven essential for extending the census of FUor-like objects beyond the classical, optically visible population.

Russian Jets!

No need to worry - because these are jets that a group of Russian researchers found emanating from the M-type YSO FN Tau, part of course of the Aur-Tau star formation area which is dominated by low-mass stars such as this. They have detected a microjet and four Herbig-Haro objects, whose positions and kinematics indicate the presence of a bipolar collimated outflow H-H 1267 from the star. The stellar jet does not propagate rectilinearly, and they discuss the possibility that the curved shape of the jet, whose axis is inclined to the line of sight at an angle of <20°, results from the precession of the inner regions of the FN Tau protoplanetary disc, with the whole system viewed almost pole-on. Approximately 60 years ago, the star underwent outbursts with an amplitude of around 2 magnitudes lasting several months, which they associate with the onset of the microjet.
Observers should note they also point out that since jets have been detected in fewer than 40% of CTTSs, targeting stars exhibiting large-amplitude photometric variability represents a well-motivated strategy for identifying new jet sources! It's not as though there is a shortage of T Tau stars up there, so someone could follow a few of them. The researchers overtly mention DF Tau which is one of the stars I look at.