WR140 aproaching periastron

[Robin Leadbeater]

Periastron of the binary system WR140 is due on 18th December so I took a final control spectrum last night for the Pro-Am campaign. (LHIRES III 1200 l/mm grating).

wr140_20160815_906-20161101_780.png (11 KiB) Viewed 10861 times

Nothing much has changed since August except for a just detectable blue shift in the WR star component countered by a small red shift in the O star features as the stars move in their orbit.

Cheers
Robin

[Robin Leadbeater]

Nothing much happening yet

wr140_ 20161110_756_Leadbeater.png (24.66 KiB) Viewed 10823 times

wr140_ 20161110_756_Leadbeater_detail.png (23.67 KiB) Viewed 10823 times

[Paul Luckas]

Hi Robin,

Forgive my lack of knowledge of the astrophysics of these types of objects, but I wonder if you could elaborate slightly on the means by which we can be sure the slight shift is 'real' and not an instrumental or processing artefact.

Cheers,

Paul

[Joan Guarro Flo]

Hello Paul :

Do not worry, it's very healthy to have doubts. But Robin graphics are very good. As you can see my match.
It would be hopeless were all bad ..

Friendly, Joan.

[Robin Leadbeater]

Hi Paul,

Hi Robin,

Forgive my lack of knowledge of the astrophysics of these types of objects, but I wonder if you could elaborate slightly on the means by which we can be sure the slight shift is 'real' and not an instrumental or processing artefact.

Cheers,

Paul

The spectrum is very reproduceable in the continuum away from the broad emission lines and the SNR is better than 200 so we can have confidence that variations larger than say ~ 2% are real.

The moving ripples on the top of the flat topped CIII 5696 line we are currently seeing are caused by variations in the stellar wind and occur continuously, even outside periastron. (The central blip is from the companion O star) There was a specific Pro-Am study of these wind variations recently in WR134
http://adsabs.harvard.edu/abs/2016MNRAS.460.3407A

Near periastron of WR140 + O star, the colliding winds from the two stars produce additional emission. You can see an animation of what I measured last periastron here
http://www.threehillsobservatory.co.uk/ ... tra_41.htm
Those observations were part of another Pro-Am campaign published here
http://adsabs.harvard.edu/abs/2011MNRAS.418....2F

The objective this time is to determine how repeatable the effects around periastron are.

Cheers
Robin

[Robin Leadbeater]

We can also have confidence in the red and blue shifts of the WR and O star components due to their orbits. The wavelength calibration can be verified to high precision using the narrow interstellar Na D lines. One key result of combining amateur and professional observations last periastron was an improved set of orbital parameters for the system. In fig 1 of the resulting paper
http://mnras.oxfordjournals.org/content ... 2.full.pdf
the quality of the amateur points are generally indistinguishable from the professional ones.

Cheers
Robin

[Paul Luckas]

Thanks Robin, much appreciate your detailed response. I have a few month's worth of CIII data of gam2 Vel taken back in late 2014 / early 2105 in which the orbital shift is very obvious, but have always presumed the error margin to be much higher (and therefore do not always trust the very small shifts I see from night to night).

http://jazzistentialism.com/blog/?p=1489

As you say, S/N is the key, together with signposts such as the interstellar Na, etc. I'll have to start trusting this a little more.

Paul

[Robin Leadbeater]

Hi Paul,

Yes the LHIRES is not the most stable of instruments but if a good wavelength reference can be found eg by superimposing lamp lines during the exposures as here
http://www.spectro-aras.com/forum/viewt ... 5010#p5011
or by using tellurics as here
https://arxiv.org/ftp/arxiv/papers/1206/1206.6754.pdf (fig 5)
I managed to get long term RV precision down to around 1-2km/s using the 2400 grating.

Though when the profile is changing so much, the limiting factor is probably just deciding what the line wavelength actually is !

Cheers
Robin

[Robin Leadbeater]

Great blog by the way . I had dipped in occasionally in the past but never fully realised how much useful and interesting stuff you have on there, particularly with your southern perspective. Now bookmarked in my favourites !

Cheers
Robin

[Robin Leadbeater]

I think the first signs of excess emission can be seen on the blue edge of the CIII line tonight

wr140_ 20161110_756_20161112_703_Leadbeater.png (25.8 KiB) Viewed 10693 times

Robin