Wolf-Rayet stars
This is very much a work in progress, having only used the 200 l/mm
star analyser once before (On a few bright stars in Lyra) I was keen to
have a look at some Wolf-Rayet stars. I was very impressed by these
initial results.
Wolf-Rayet stars are quite scarce, and in the Northern
hemisphere the best known/easiest to observe are a group in Cygnus. The
table below shows the brightest ones... all below
naked-eye visibility.
WR
|
HIP
|
RA
|
Dec
|
Mag
|
Spec class
|
133
|
99002
|
20h5m57.3s
|
+35º46'18.2"
|
6.7
|
WN5 +O9I
|
134
|
99377
|
20h10m14.2s
|
+35º10'35.1"
|
8.23
|
WN6
|
135
|
99525
|
20h11m53.5s
|
+36º11'50.6"
|
8.36
|
WC8
|
136
|
99546
|
20h12m6.5s
|
+38º21'17.8"
|
7.65
|
WN6
|
137
|
99769
|
20h14m31.8s
|
+36º39'39.6"
|
8.15
|
WC7+O9
|
138
|
99982
|
20h17m0.0s
|
+37º25'23.8"
|
8.1
|
WN5+B?
|
139
|
100214
|
20h19m32.4s
|
+38º43'54.0"
|
8.1
|
WN5+O6III-V
|
140
|
100287
|
20h20m28.0s
|
+43º51'16.3"
|
7.07
|
WC7+O4-5
|
Below are the results taken with the equipment shown on Equipment page
, and processed with RSpec software. The coloured spectrum below each
graph is synthesized by the software from the graphical data as an
indication of the spectra appearance.
These images where take with the 500mm zoom lens. Exposure times vaired
from 15 - 30 seconds, with several exposures of each star taken;
dark fame subtraction, stacked, cropped with Deep Sky Stacker and IRIS
software, before being processed by RSpec.
I was surprised at the amount of detail that could be revealed in these
low resolution Spectroscopy pictures, especially as I was still
learning how best to use the star analyser.
The "fun" begins, trying to identify the lines and compare the results, I've referenced below the main sources I used for this.
Obviously with such low resolution spectra the wavelenghts shown on the graphs are indication only.
=========================================================================================
First, 2 stars of spectral type WN6, WR136 & WR134 which show a lot of common details on these 2 spectra.
WR 136
Above is an enlarged part of one of the frames showing the star WR136 and the spectrum it produced.
This immediately looks different from the other "normal" stars in the
image due to its distinctive bright emission points on its spectra. The
RSpec software converts that part of the image into the resulting
graphical dispaly (shown beow), allowing any emision/absorption lines
to be easily seen and documented. Finding out what is responsible for
each line is when the fun begins !
For those unfamilar with the notation:- He[II] = Ionized Helium
He⁺, C[IV] = triple ionized Carbon C⁺⁺⁺, N[III] = Nitrogen N⁺⁺,
etc.
WR 134
=========================================================================================
Then 3 Carbon rich, spectral type WC, stars. These clearly show the two
distinct CIII & CIV lines at 5690-5820 Angstroms, and that those
for WR135, which is a WC8 type are noticably narrower than the
WC7 type WR137 & WR140.
WR 135
WR 137
Enlarged part of image showing bright spots on the spectra of WR137.
WR 140
On-line sources used to aid line identification:-
Spectral atlas of the Galactic Wolf-Rayet stars (WN ssequence)
W,R, Hamann, L, Koesterke, & U, Wessolowski
An atlas at optical Spectrophotometery of Wolf-Rayet Carbon & Oxygen stars
A, V, Torres, & P, Messey
Web-page of "Wolf-Rayet type star spectroscpy"
J, Ferreira
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