Page 84 - spectroscopic-atlas-5_0-english_Neat

Spectroscopic Atlas for Amateur Astronomers 84

Alterf (320 ly) is a K5 III giant of the later K-class. Its surface temperature is 3,950 K, al-
most 340 K lower than that of Arcturus. The apparent rotation speed is indicated in [505]
with <17 km/s. Such low values are normal for late spectral types and have no detectable
effect on the spectra of this resolution.

Particularly the short-wave side of the Alterf profile is still dominated by discrete absorption
lines, which are mostly the same, as seen in the spectra of Pollux and Arcturus. However
the shape of the continuum in the yellow-red range is already similar to that of Betelgeuse
and Antares, albeit much less intense. This shows the beginning influence of the molecular
TiO absorption. At this spectral resolution, these absorption bands can be reliably identified
only in the near infrared part, close to the telluric A-line which is outside of the chart in Ta-
ble 50. The following detailed spectrum of Aldebaran, however, shows complementarily
this section. With K5 lll this star has the same spectral class like Alterf. The spectrum
shows here clearly the absorption bands of titanium oxide TiO and calcium hydride CaH.

Telluric O2 7186
TiO 7126

TiO 7088
TiO 7054

?

CaH 6921
CaH 6903/08
Telluric O2

CaH 6750
TiO 6713

Table 51: Pollux (α Gem)

Pollux (34 ly) is classified as K0 Illb, an early K-star already established on the Giant Branch
of the HRD. Its surface temperature is about 4,770 K. The apparent rotation speed is given
in [505] with <17km/s. On this table Pollux is documented with an overview spectrum
(200L grating) and a higher resolved profile in the blue area (900L grating).

The line identification is based amongst others on [1], [5], [50], [52], [53], [55], [58], [59]