Hi folks,
I've signed up for the Newsflash for T CrB observations, and I've noticed that different observers are doing different cadences. One observer reports a single measurement which looks like it's an average of several measurements with a proper error value; another submits 30 individual measurements within a one-hour window with reported errors of 0.000; a third does several observations over the night.
I wonder what is the best way to observe to provide useful data? How important is time resolution versus quality of measurement? Is it worth observing once a night, once an hour over the night, every ten minutes, or continuously? Are 30 observations in a hour useful, or do they just increase scatter in the data?
I have some ideas of potential answers to these questions, but clearly my answer is not the same as the three somewhat-hypothetical exemplars described above. It would be useful for some experienced folks to wade in and provide some specific guidance on cadence for this unusual star.
Thanks,
Scott
I am no expert, but the activity of T CrB occurs at both short and long timescales. This is an active close binary, so there is variation at short timescales like a 'typical' cv, where there is irregular(?) jitter in the brightness of the accretion stream from the cool component onto the hot companion. Observing that would benefit from dusk-to-dawn runs of fairly short exposures (< 1 minute), and most interesting with a B or preferably U filter (shorter wavelength is better). An alternative might be a narrowband H-alpha filter. Folks who get such data even now should _publish_ a report in the JAAVSO, and not simply dump the data into the database, where it is likely to be forgotten.
There is also the roughly 9-month variation in the M-giant component, where good _consistent_ data twice a week (say) would be sufficient if you were the only person observing it. The AAVSO database suggests that even after trimming out the poor/inconsistent data, the star is getting well observed in that aspect. Probably the most useful thing here (again if no one else were observing it) would be something like B,V,I filters to see the change in temperature as well as brightness. If one could get the Wing 1.04-micron continuum band in the near-IR, that would be even more useful as far as the luminosity of the star. The R filter is not particularly useful (my opinion) since any information you get from it (via V-R color-index) you can get better with the B-V and V-I color index.
What happens when it erupts? Seems like ideally you'd want spectra as fast as you can take them during the entire rise time and then maybe hourly in the days following, especially H-alpha and the violet portion of the spectrum, if possible. We don't know when that's going to happen (will there be precursor activity an hour or two ahead? dunno!). In lieu of spectra, perhaps some folks are simply getting a lot of photometric data on any particular night on the long chance they catch the action (dunno what the thinking is along those lines given limited resources). The first indication of the outburst might be from a security camera in a parking lot somewhere in Asia or other random location, so who knows.
If there is a Slack thread or similar for observers world-wide getting data on this thing, it would be nice to know about it. Is a bona-fide expert like Ulisse Munari in Italy coordinating observing of this event? Robin Leadbeater? Others?
\Brian
I know we have a bunch of new observers locally all interested in variable stars due to the impending eruption, and most won't go through all the courses and join the CV section before just shooting images. I'm making a one-pager for folks here to use, and I'll include your suggestions for cadence, Brian - many thanks.
Scott