Universe of Spectroscopy

Author: Koji Kawabata

What would you like to introduce to readers in this series?

According to the introductory book of astronomy, supernova is a large explosion that blows off a star. You may know that there are two types of supernova, one is a nuclear explosion type supernova that is shown by the white dwarf beyond the limits of mass. The other is gravitational collapse type supernova that is shown by the last-stage of in heavier star evolution. In more details textbook, it would say that the gravitational collapse type supernova is divided into some types. These are Type II which has rich hydrogen, Type Ib which is lacking of hydrogen but has rich helium, and Type Ic which is lacking both hydrogen and helium. It might say more particular types. So, what kind of parent star would become Type II, Type Ib, or Type Ic Supernova? What does the introductory book that you read say about it? The relations between parent stars and each type of supernovae is discussed very active right now.
This is really hot topic and interesting field, but it would not still get used to be appeared in the introductory book.

In 2002, I became involved in the supernova research. The beginning was to observe Type Ic Supernova SN 2002ap in the test observation of an instrument, FOCAS, of Subaru Telescope. After three years, from the suggestion by domestic and international joint researchers who have a detailed knowledge of supernova research, I started to observe Type Ib Supernova SN 2005cz. I did not imagine that the Type Ib Supernova SN 2005cz got attentions a lot as a candidate of the lightest of Type Ib Supernova category in gravitational collapse supernova. I admired the insight of fellows.
In this story, I want to tell you how I luckily that I had an allocation of precious observation time at Subaru Telescope in the best time that was past half a year after explosion, and the accomplishment of showing the picture of parent star of "peculiar" supernova reasonably. How was it?

My research field and current interests:

I want to continue to find out the relations between gravitational collapse supernova and the parent star. Then I want to figure out the evolution of massive star.
In recent years, I use Hiroshima University's 1.5 m telescope, Kanata Telescope (former infrared simulator of NAOJ), as a platform telescope to observe bright supernova at early-time explosion in visible and infrared, and then I use large aperture Subaru Telescope to observe the darkened supernova in late-time after explosion. At the same time, I advance unique observation in the world that is research about the magnetic field structure of radiative region of gamma ray burst afterglow in polarization observation with using specific instrument of Kanata Telescope (still I cannot get good sample). After this, I want to continue to the research of supernova and gamma ray burst. Also, I encourage to promote new observational astronomy by taking advantage of this "polarization". In the future, I want to complete visual polarization survey as soon as possible. And, I want to get basic data for various astronomy such as non-spherically symmetric mass radiate of stars, interstellar dust, interstellar magnetic field, and so on.


Koji Kawabata
Hiroshima Astrophysical Science Center, Hiroshima University
Job Title
Associate Professor
Field of Expertise
Stellar Astronomy