Page 38 - spectroscopic-atlas-5_0-english_Neat
P. 38
Spectroscopic Atlas for Amateur Astronomers 38
Five of these WO stars are numbered with Sand 1... 5, named after Nicholas Sanduleak,
who was looking with objective prism for these “exotic stars” in the 70s of the 20th cen-
tury. These extremely rare and highly interesting objects are well researched and docu-
mented.
Compared to WR 136, WR 142 shows mainly extremely broad and highly ionised emis-
sions of oxygen. These obviously exorbitant amounts of energy, generated in the final stage
of a WO star, can be estimated wit help of the detected ionisation stages. The required en-
ergy to ionise oxygen to the stage O VI is 113.9 eV (Table sect. 34). This is as much as 4.6-
fold to generate He II and 8.3-fold to ionise hydrogen H II. In addition to the extremely high
temperatures, this is also caused due to the photoionisation by X-ray sources [235].
The Doppler analysis of the line widths obtained here stellar wind speeds of about 3600 up
to >5000 km/s, after all some 30 – 50% of the radial velocity of a typical SN explosion-
(see sect. 25) or ~1.6% of the speed of light! Suitable for own measurements is the rela-
tively isolated, unblended O VI line at λ5290.
The spectrum was recorded with Celestron C8/Atik 314L+/4x1300 seconds, 2x2 binned.
The line identification is here based on [242] [243] [2].
