(cba:news) ASASSN-18ey = MAXI J1820+070
jop at astro.columbia.edu
Thu Jun 14 18:29:05 EDT 2018
We're accumulating a great several-month light curve of this black-hole
transient. It was hard to discern a period - lots of wiggles appearing,
showing promise, and then disappearing - for ~2 months. Over the last 9
days the star got its act together and showed an impressive
large-amplitude wave with a period of 17 hours. Exactly what kind of
period it is - orbital? superhump? precession? outburst? - is still
unclear. And for an equatorial star that's a really awkward period,
since no one can get long runs and the pitfalls of daily aliasing are
Stephen Brincat, Josch Hambsch, and Geoff Stone have been carrying most
of the water in recent weeks. Malta, Chile, and California have pretty
great climates in June! But the upcoming 1-2 weeks are critical in
assessing the coherence (the stability) of this signal... and I hope
that other observers will pay special attention to this star now!
Observations from AU/NZ are of special value since that is a nearly
unrepresented longitude in our coverage. Nights are decently long down
there, the star is still mag 13.4, and the star transits near midnight.
No need for fast data - 30 s or even 60 s is just fine. The table is set!
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