The project of constructing a 188-cm telescope and a new observatory was under
way at the time. Osawa, as a member of the construction committee, contributed to
resolving technical problems, including the site search.
In 1960, the OAO was established and Osawa was appointed first director of this
observatory.
He then served as director of the TAO from 1963 up to his retirement in 1977.
Thereafter, he served as a professor of astronomy at Chiba University for 5 years.
Osawa died in 2005 at age 88.
3.7.2 Astrophysical Works
3.7.2.1 Theoretical Study of A-Type Star Atmospheres
During his stay at Yerkes Observatory, Osawa calculated model atmospheres of
A-type stars having effective temperatures of Te ¼ 8900 K and 7500 K and surface
gravity log g ¼ 3.5, 4.0 and 4.5. In this calculation he took into consideration the
continuous absorption by hydrogen, negative ion of hydrogen, and ionized hydrogen
molecule. The spectral energy distributions in two stellar types of A3V and A9V are
illustrated in Fig. 3.15. The Balmer discontinuity at λ 3647 Å is remarkable in A3
stars. Based on this model, he calculated the profiles of the Balmer H-gamma line
and compared with observed line profiles. He found fair agreement between model
and observations compared to existing models. He showed that this better agreement
Fig. 3.15 Spectral energy distribution of model atmosphere of A-type main-sequence stars
(A3 star, blue line: Te ¼ 8900 K, log g ¼ 4.5, and A9 star, red line: Te ¼ 7500 K, log g ¼ 4.5).
The abscissa is the wavelength (Å), and the ordinate is the energy flux (F ν Â 10
6
) (erg Hz
À1 cm
À2 s
À1
)
(Osawa 1956)
3.7 Osawa Kiyoteru and Stellar Physics
69
way at the time. Osawa, as a member of the construction committee, contributed to
resolving technical problems, including the site search.
In 1960, the OAO was established and Osawa was appointed first director of this
observatory.
He then served as director of the TAO from 1963 up to his retirement in 1977.
Thereafter, he served as a professor of astronomy at Chiba University for 5 years.
Osawa died in 2005 at age 88.
3.7.2 Astrophysical Works
3.7.2.1 Theoretical Study of A-Type Star Atmospheres
During his stay at Yerkes Observatory, Osawa calculated model atmospheres of
A-type stars having effective temperatures of Te ¼ 8900 K and 7500 K and surface
gravity log g ¼ 3.5, 4.0 and 4.5. In this calculation he took into consideration the
continuous absorption by hydrogen, negative ion of hydrogen, and ionized hydrogen
molecule. The spectral energy distributions in two stellar types of A3V and A9V are
illustrated in Fig. 3.15. The Balmer discontinuity at λ 3647 Å is remarkable in A3
stars. Based on this model, he calculated the profiles of the Balmer H-gamma line
and compared with observed line profiles. He found fair agreement between model
and observations compared to existing models. He showed that this better agreement
Fig. 3.15 Spectral energy distribution of model atmosphere of A-type main-sequence stars
(A3 star, blue line: Te ¼ 8900 K, log g ¼ 4.5, and A9 star, red line: Te ¼ 7500 K, log g ¼ 4.5).
The abscissa is the wavelength (Å), and the ordinate is the energy flux (F ν Â 10
6
) (erg Hz
À1 cm
À2 s
À1
)
(Osawa 1956)
3.7 Osawa Kiyoteru and Stellar Physics
69