i Andy - I lurk on the Convento mailing list and here are some thoughts
on XMM (which have got quite long as I type).
1) I agree - a longer, continuous chunk of data would be more useful than
sporadic shorter observations over the whole period (if you can get it,
though). The question in my mind is how long a continuous chunk it is
viable to go for.
4 days is 0.35Megasecs - that's a heck of a lot - definitely in the big
proposal league.
Looking at the XMM AO-11 results while there are quite a few individual
objects with >100ksec awarded but none with 200ksec (I think). Of
course, there are a few surveys with more time (LMC etc).
Would shorter chunks over a 4 day period be more likely to get time and
still achieve the goals? For example, 25 x 5 sec chunks. Not sure, I just
doubt whether you will get 350ksec on a single WR star. We need enough
photons in each block to get a decent RGS spectra in my view.
2) Why do this star? Answer: because of the evidence of optical
variability that is believed to be linked to wind clumping. There are
X-ray brighter WR stars, but can we make the case that WR134 is the best
use of this much time on WR stars. How unique is WR134? Important to make
that case that this is THE object.
WR134 would be easily detected by XMM and the counts (and the level of
sensitivity to variation) can be easily estimated for different exposures.
3) Why do this star now? Answer: because of the campaign of line profile
variability next year. The fact that the campaign is at one site is a
problem - it would be much better to have 24 hour coverage for the
duration of the XMM observations - that would be a weakness in my view if
it can't be fixed.
4) What will the X-rays tell us? This needs more thought too - to be
obvious - the star will be variable or not variable. If it is variable it
may be periodic (either with or without the same period as the optical).
What the different options means is unclear to me.
The system is listed in Simbad as an eclipsing binary, but I think that
is now not believed to be the case. X-ray emission is an integrated
quantity, whereas line profile variability can be more specific (ie at a
particular velocity). How many useful RGS spectra can we get (that could
be a game changer - are X-ray line profile changes coordinated with
optical).
Also, note that the Suzaku deadline is also coming along in the autumn.
Cheers
Ian
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Dr. Ian Stevens
School of Physics & Astronomy Tel. +44 121 414 6450
University of Birmingham, Edgbaston Fax +44 121 414 3722
Birmingham B15 2TT, UK E-mail irs@star.sr.bham.ac.uk
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On Tue, 11 Sep 2012, Andy Pollock wrote:
Zitat: Dear ConVentos,
Part of the initial thinking about this campaign concerned the desirability of getting complementary data at other wavelengths. In my case this means X-rays. The wonderful news reported by Thomas yesterday morning comes one month before the XMM proposal deadline for the period that covers the campaign known as XMM AO12. Given that there's little chance of getting 4 months' continuous X-ray coverage we need to decide what to do. WR134 and WR137 are well detected X-ray sources but not strong enough for current high-resolution instruments. WR135 has been invisible in X-rays so far. The CIR-type variability seen in the optical in WR134 with a period (or time scale) of 2.3 days would seem to me to suggest requesting continuous coverage of WR134 for 2 XMM satellite revolutions, each of which takes 2 days. WR134 is continuously visible with XMM in AO12 during the following windows
2013-04-05 to 2013-06-01
2013-10-07 to 2013-12-10
which limits simultaneous X-ray coverage of the optical spectroscopic campaign of WR134 to a couple of weeks at the beginning. This would seem to me more promising than shorter, piecemeal observations at different times during the 4-month campaign but I'm open to counter suggestions.
Andy
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