Wolf-Rayet stars

[jsandse]

Hi folks,

Just put up a blog on Wolf-Rayet stars and their spectra here:

http://stargazerslounge.com/blogs/jsandse/471-spectra-wolf-rayet-stars.html

There are several in Cygnus around mag 7 which those with star analysers can capture when we get nearer the summer and hopefully some clearer weather.

These stars are kind of neglected their isn't too much spectra of them out there - you have to go to the professional literature in the main.

Any comments or any spectra welcome on these "exotic beauties"

cheers

John

[JAO]

I am not equipped to do spectroscopy (would like to be) or Radio Astronomy but as a visual observer I love the DSOs in Cygnus. One of which is NGC 6888 which I believe has a Wolf Rayet star at its heart. NGC 6888 is a stunning object in a larger aperture scope.

Adrian

[jsandse]

Yep thats right the star I took the spectra of is the wolf-rayet star at the centre of NGC6888.

Incredible to think one star was responsible for that stunning nebula and my blog has a link in it to a stunning picture of the nebula

cheers

John

[JAO]

John

Yep that is great picture and the background in your blog is a good read.

Thanks for sharing.

Adrian

[Rob_Jn]

I took these two spectra a couple of years ago with the Staranalyser. I knew I had the correct star in the view immediately as I could see the emission lines straight away. Very different to other types of spectra, exciting stuff! I think it is WR136 at the centre of NGC6888.

Rob

[JAO]

Rob

It is exciting stuff, all that going on at the heart of 6888.

Adrian

PS Really good and useful stuff on your website, I will be following up this spectroscopy mularkey!

[jsandse]

Yep Rob some nice spectra you have there with your star analyser - I am impressed.

and that sure is a spectra of WR136 sitting in the middle of NGC6888:0)

Hamann produced a spectral atlas a while back on the Wolf-Rayet WN type stars and your spectra is consistent with his. If your interested you can find his paper at:

http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1995A%26AS..113..459H&data_type=PDF_HIGH&whole_paper=YES&type=PRINTER&filetype=.pdf

and thats a very nice spectra of WR 140 too :0)

I am going to try and capture a lot more WR stars this summer - there are about 40 under magnitude 12 visible from the northern hemisphere.

But I'll need to go to a lower resolution grating to capture those as my spectroscope with 1200 lines grating and resolution R approx 6000 won't go much above mag 8 I reckon - I was pushing it a bit with WR136 at mag 7.5

cheers

John

[TheThing]

Very interesting John, thanks for posting. A whole other area to explore. I'll be keeping an eye r developments and also having a look myself.

[Rob_Jn]

Thanks John, the paper should help me identify some more lines though I'm always a bit frustrated at the low resolution, lines overlap each other so it's not possible to give an unambiguous id. The Staranalyser does give you the opportunity to go faint though.

Have you got any interesting targets in the Winter sky?

Rob.

[jsandse]

Hi Rob,

In terms of Wolf-Rayet stars there are several candidates for Winter observation.

The following picture contains the list of northern wolf rayet stars I have

identified from the seventh catalogue of wolf-rayet stars and simbad.

I have put the constellations in to help - so stars in Cepheus are good at the moment and cassiopeia (getting better in a couple of months) and there are a couple of low ones in Canis Major.

I have a list of fainter WR stars but getting down to mag 12 would be a

good challenge to start with :0)

I am compiling a list of hot O stars at the moment which would be worth

a look and if you want to look at Be stars then the French ARASbeam website

provides a list at [ArasBeAM]

- they tend to be more frequently observed though.

There are plenty of other exciting things you can do with your star analyser.

Resolution isn't everything! - in fact lack of it has advantages.

Doing spectrophotometry. Low resolution allows you to capture most of the conitnuum in one shot. You can then calibrate your images against standard stars and allow for atmospheric extinction - you should be able then to compare your stars against the planck curve and chck temperature etc of the star.

Moving onto hotter stars you can look to see where local thermodynamic

equilibrium breaks down and compare against non-local thermodynamic

equilibrium in models like TLUSTY

With low resolution you can look to get spectra of supernova and probably

the "holy grail" in amateur long distance spectroscopy would be to check the swift related websites for gamma ray bursts and check for optical components of the burst - if you capture one of those it'll probably be the most

distant object an amateur has ever measured using any form of spectroscopy.

cheers

John

[jsandse]

Here is a working link to the list:

[Merlin66]

Good listing John!

BTW you can still use the spectroscope under light pollution and moonlight conditions.... so even when you can't take images you can still collect spectra! One of the benefits.

The SA100 and the Rainbow Optics ( 200 l/mm) are ideal lo res gratings for recording faint objects and have been used to record and measure redshift in distant qasars....

(John- You need to use that 300 l/mm classical spectroscope!)

Ken

[jsandse]

Yep can't wait to get going when the weather is a bit better.

And you are right ken quasars are distant objects the brightest one being in Virgo number 3C 273 . It has an average apparent magnitude of 12.8 and a distance from earth of 2.4 billion light years.

But GRBs can be a lot brighter! -GRB 080319B, was accompanied by an optical counterpart that peaked at a visible magnitude of 5.8 comparable to that of the dimmest naked-eye stars despite the burst's distance of 7.5 billion light years!!!!! - thats more than half the way across the 13.7 billion year universe

cheers

John

[Rob_Jn]

Nice list to work on John, thank you. I'd be very lucky indeed to get a GRB spectra!

I did produce a spectra of 3C273 and measured the red shift. I need to test my setup now I have put the SA in a filter wheel since getting an Atik383, did all the previous spectra with an Artemis 285. Lots to do and it's just turned cloudy here :-(

Rob.

[TheThing]

Although the universe is 13.7bn years old, isn't something like 40bn light years across? Something to do with expansion being faster that the speed of light initially?

Still fascinating to think you looking at the spectra of something that is nearly twice as old as the solar system.

[jsandse]

Ok to be pedantic then its is half the size of the OBSERVABLE universe.

Other figures beyond that are debatable unless you can point me to some indefatigable evidence....

John

[jsandse]

Also see Chris Lintotts video here:

What size is the Universe? Studying The Universe (About Astronomy)

[TheThing]

Yes, apologies. Back to pedants corner for me!

Still quite amazing that you're looking back in time over 7 billion years and those stars probably don't exist anymore.

[jsandse]

No need to apologise its a good point you bring up and its one of the big questions in physics! - big in all senses of he word :0)

For an excellent account of the limitations to what an astronomer can observe look at the lecture by Professor Susskind on youtube at time 1 hour into the lecture:

This lecture is amazing by the way - he does a good part of cosmology using only school maths.

cheers

John

[jsandse]

Yes Rob weather has been poor recently.

Out of interest how accurate was your redshift calculation? - that would be interesting to know.

And that Atik 383 is a very nice camera to use for spectra or visual.

cheers

John

[Rob_Jn]

I was very chuffed with my estimation, after calibration etc. measuring the peak wavelengths in VSpec compared to the rest wavelength for Ha gave z=0.157 and I think the published value is 0.158 (all this is form memory - I'll post the results later when I'm back home). Another project to do is some more of these. I think there are more quasars within reach with the SA.

Rob.

[jsandse]

Rob,

Very impressed with your estimate!

And there are 8 pulsars under mag 14 in Simbad. For instance

[VV98] J102613.9+523752 with VMag 13.99 but it is a whopping distance z = 0.259

cheers

John

[Rob_Jn]

Thanks John, my memory was correct. Here is the image and a crop of the spectrum, H-gamma was pointed out to me by Robin Leadbeater. To be fair the z value is less good on H beta or H gamma, but I'm not going to use those am I . Christian Buil notes the H beta is a combo of H beta and OIII at this resolution. I think mag 14 is do-able, I love a challenge and I see [VV98] J102613.9+523752 is well placed at the moment, you have set me going now!

Rob

[jsandse]

Very impressive results there.

Good luck with [VV98] J102613.9+523752

cheers

John

[FraserClarke]

And there are 8 pulsars under mag 14 in Simbad.

Just to be pedantic, I think you mean Quasars rather than Pulsars

I'm seriously impressed with the level of interest and achievement in spectroscopy on here. I do it professionally (building and using spectrographs), and it's absolutely fantastic to see what people can do as part of a hobby with relatively small telescopes. I really think it's got a big and exciting future ahead of it too.