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Wolf-Rayet star in a colliding wind binary system (WR140)

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#1 Organic Astrochemist

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Posted 18 December 2016 - 01:50 AM

WR140 is a binary system comprising a WC7 Wolf-Rayet star and an O5 companion. Both have extremely fast stellar winds (up to 3000 km/s) that carry away staggering amounts of material: ~2 trillion tonnes per millisecond for the former and ~200 billion tonnes per millisecond for the latter.

At closest approach, the winds of these stars collide with maximum energy releasing vast amounts of radiation from X-rays to radio waves.

Here is a great animation of the orbit of the two stars. The teal color cone is the surface where the two winds collide.

http://www.roe.ac.uk/~pmw/Wr140orb.htm

 

To the best of my knowledge, periastron passage occurs some time today December, 18 2016.

 

Thanks to a tip from Robin Leadbeater, I have been following this system with my simple Star Analyzer diffraction grating since November 25, 2016.

V1687 Cyg WR140.png

This article shows how the CIII peak at 569.6 nm increased around periastron passage (see Figure 2, page 16).

https://arxiv.org/pdf/1101.1430.pdf

Here is a comparison of the spectra I took on 11/25 (in blue) with one taken on 12/05 (in black with red dots for data points). At this point the stars were too far apart and I couldn't detect any increase in CIII emission around 570 nm.

V1687 Cyg WR1401.png  

Here is a more recent comparison of the spectra I took on 11/25 (in blue) with one taken on 12/15 (in black with red dots for data points). It's possible the results are an artifact of my crude data processing, but they are consistent with the predicted increase in CIII emission around 569.6 nm due to the closer approach of the stars and the more energetic collision of their stellar winds. Note all the red dots around 570 nm that are above the blue line.

WR140 CIII.png

Hopefully I'll be able to continue to observe this fascinating system. 


Edited by Organic Astrochemist, 18 December 2016 - 01:51 AM.

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#2 JRG2

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Posted 18 December 2016 - 02:28 AM

I hope you will be able to continue observing and reporting. Thanks for sharing.



#3 robin_astro

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Posted 18 December 2016 - 09:31 AM

Yes your latest result is consistent with what I am currently seeing at ~1A resolution. Impressive work at such low resolution !

Here are my results for the flat topped CIII line covering the same period.

 

WR140_Three_Hills_Observatory.png

 

Cheers

Robin

 

 



#4 Organic Astrochemist

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Posted 19 December 2016 - 11:52 AM

Thanks Robin.

I've been watching the spectra that you and others have been posting on other sites.

I did get a chance to observe again last night, but it really is a terrible time. Lately the clouds seem to show up about half an hour after sunset, which makes setting up difficult. It's also a time I'd rather be with my wife and kids. The upshot is that I didn't get very good focus. This once again confirms to me that if I can see something, it must be blindingly obvious. I think that is the case for this excess emission of CIII around 570 nm. Blue is from 11/25 and black is from 12/18.

WR140 compoared.png

I look forward to seeing more higher resolution spectra.




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