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YSO Bulletin
- 1 February 2020 -

Major Campaign on V582 Mon (KH15D)

This month sees the start of an exciting campaign to observe the peculiar YSO V582 Mon, discovered by our own Bill Herbst and also known as KH15D. The system is composed of a pair of T Tauri stars enmeshed in a circumbinary dust ring which is tilted in respect to the orbit. Therefore the stars are periodically hidden and revealed depending on the system dynamics. When both are hidden the variable is at minimum and the only light comes from the ring. This ring is situated at a radius which in our Solar System corresponds to the asteroid belt. Bipolar outflows have been observed - but coming from the disk rather than the stars!
Observationally this is purely a CCD target, and even then as Bill says, it is 'not for the faint-hearted', being very close to a bright star and in a nebulous region (the Cone nebula) The need for monitoring is particularly urgent in the next month or two, since Bill's team have been assigned time on Gemini South to obtain infrared spectroscopy of the star, some time between Feb. 1 and April 30. The system has entered a new and interesting phase in which one star of the pair is currently emerging from behind the edge of the ring. A phased lightcurve of a past apparition appears below. Note the flat maxima, when both stars contribute to the curve. Nifty eh?
See the relevant thread in the YSO section of the forum (ignore the 'safari' alert box if it appears: say 'yes') for further links, and possible updates.

One for All!
CQ Tauri is without doubt one of the most rewarding of all variable stars to observe. Firstly, it is within the reach of small telescopes, possibly even good binoculars (at least around maximum). Secondly it is in the same low-power field as another very active star, RR tau, as well as a fainter and rather less-active object AD Tau. Thirdly - and most intriguingly - it is extremely active. On one occasion I saw this star fall by almost a whole magnitude within the space of a minute! Not seen before and not seen since, a warning against bias, now that I have said it! However this star changes from one day to the next - it's hard to keep up with!

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