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Wolf-Rayet Stars

The Wolf-Rayet stars are massive, hot  stars, whose spectra exhibit strong, broad emission lines. WR-stars are in an advanced stage of evolution where they have lost their atmospheres and are still ejecting hot gas at high speed (>1000 km/s). Their exposed cores show exceptional surface temperature of 40.000-70.000 K typical.  There are 2 classes of Wolf-Rayet stars: WN stars, where the ions of helium and nitrogen dominate and  WC stars, where the ions of carbon, oxygen and helium are found.

WR-stars are candidates for future supernova explosions.

 
The H-alpha image below shows NGC 6888 in constellation Cygnus, with WR 136 at the center.

Image data: Refractor 120 f/5, Astronimik H-alpha filter (13nm), ST8-E, exptime 600 sec, 1x1, detail, 08/21/03


 

The spectrum below is from WR 136.  Date:  05/15/2000, Equipment: 8"/F4.5 Newtonian, ST8-E camera in 2x2 binning mode, 9 images, exptime 45sec, Rainbow Optics grating at  nosepiece of  camera.

Spectrum of Wolf-Rayet star No.136 in dense star field of Cygnus Milky way. (Just below center, note the spectrum of carbon star RS Cyg in upper right corner)


Emission line spectrum of 7.44mag star  HD 192163 (WR-136).

This is an example of an WN6 star, where 6 stands for a spectral subtype. The spectrum shows emission lines of He II, N III, N IV and N V.

VIIth Catalogue of Galactic Wolf-Rayet Stars, van der Hucht, K.A. 2001, New Astronomy Reviews 45, 135

Atlas of optical spectrophotometry of Wolf-Rayet (WC and WO sequences)
Torres A.V., Massey. P. 1987 ApJ. Suppl. 65, 459. Available at CDS

Wolf-Rayet stars are very rare. No more than 150 were found in our galaxy. A list of Wolf-Rayet stars, brighter than 8.5mag, which are accessible from the northern hemisphere follows (J2000.0).
 
 

 WR       HD              R.A.            Dec.      Type        V

   6    50896       6 54 13.0      -23 55 42     WN5    6.74
111  165763      18 08 28.5      -21 15 11     WC5    7.68
133   190918     20 05 57.3     +35 47 17     WN4     6.78
134   191765     20 10 14.2     +36 10 35     WN6     8.02
135   192103     20 11 53.5     +36 11 51     WC8     8.51
136   192163     20 12 06.5     +38 21 17     WN6     7.44
137   192641     20 14 31.8     +36 39 39     WC7     7.95
138   193077     20 17 00.0     +37 25 23     WN5     8.06
139   193576     20 19 32.4     +38 43 54     WN5     8.27
140   193793     20 20 28.1     +43 51 17     WC7     6.88




First echelle spectra of WR136 and WR140 can be seen on my UFES-page

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