Forum der Vereinigung der Sternfreunde

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

Dear Andy,Thinking about too.
 So It seems to be necessary to support your X ray observations with time series spectra covering the whole optical domain at short cadence. Individual exposures can be combine after to do a 1h total exposure for the requirement of the optical campaign.
First question: At which cadence you recommend to get spectra, depending on the number and frequency of events yous will have ?
It could be done easily from IAC80 or after end of mission by amateurs who used to do so before in support of Chandra or XMM observations. Just ask for the precise time of coverage you need. I used to do spectral time series on different astrophysical subjects.


Cheer
Thierry Garrel
http://gabalou.canalblog.com/

2012/9/11 Andy Pollock <fg-spek-convento@vds-astro.de (fg-spek-convento@vds-astro.de)>

_________________
Thierry Garrel
Observatoire de Fontcaude, Montpellier, France
SpectroBlog http://gabalou.canalblog.com/

Hi Andy,

I hope that we get some more professional response on your great suggestion.

I am not an expert in X-ray observations and can only give my two cents. I understand that WR 135 is out of business for XMM. I basically agree to apply for a short but continuous coverage (no patchy shots during the 4 months). There is a concern from my side, though, I would like to address. Teide observations start at 2013-05-17. The overlap with 2013-04-05 to 2013-06-01 is only two weeks. I do not expect implementation difficulties as with Mons (two weeks hard work basically without data acquisition) but believe that we will deliver after ~2 nights. When asking for 2 XMM satellite revolutions we should mention the need to get time as late as possible in the intervall 2013-04-05 to 2013-06-01 just to be on the save side.

What about WR137? Is it a good idea to apply for time, as well, or should we stick on WR134?

Cheers, Thomas

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


-------------------------------------------------------------------------
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
-------------------------------------------------------------------------

On Tue, 11 Sep 2012, Andy Pollock wrote:

Hi Andy:

This would be great to get XMM data and in as concentrated a fashion as possible, even if limited to the beginning or end of the optical observations, which have to take place in the summer months, because of position in the sky. Unfortunately all 3 objects are (just) out of reach by MOST. Would a long observation of WR135 (the only WC star among the 3 targets) be a waste of time with XMM, the only X-ray telescope with enough surface area to do it! Or should we wait for nu-astro (or whatever it?s called) to look at higher energies for X-rays from WR135, i.e. away more from self absorption in the wind?

Cheers, Tony

From: Andy Pollock (fg-spek-convento@vds-astro.de)
Sent: Tuesday, September 11, 2012 10:42 AM
To: fg-spek-convento@vds-astro.de (fg-spek-convento@vds-astro.de)
Subject: [fg-spek] Thinking about the X-ray side of the 2013 WR campaign




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

_________________
Tony Moffat