A DETACHED DUST SHELL SURROUNDING THE J-TYPE CARBON STAR Y CANUM VENATICORUM
This paper reports the first clear detection of a de- tached dust shell surrounding the prototypical J-type carbon star Y CVn in 90 m and 160 m maps taken with the ISO/ISOPHOT 1 . The projected inner radius of the shell is 180 -190 , corresponding to (6.4-7.1) 10 17 cm at a distance of 250 pc. The shell thickness is obtained to be (2-5) 10 17 cm. The mass-loss rate at the formation of the shell is estimated to be in the range (7-20) 10 6 M yr 1 , about two orders of magni- tude higher than the present-day mass-loss rate derived from CO gas observations. The obtained mass in the shell is (4-14) 10 2 M. It is concluded that the mass-loss rate decreased by two orders of magnitude on a short time scale 1.4 10 4 years ago as- suming an average shell expansion velocity of 15 km s 1 ,a nd that Y CVn has been staying at the low mass-loss state. The duration of the previous higher mass-loss phase would be at most 2 10 4 years even if the asymmetry in the shell geometry is taken into account. The evolutionary status of Y CVn is also discussed.
A half century of infrared astronomy — A personal recollection of the footprints in Japan
Since the new era of infrared astronomy was opened by the Two Micron Sky Survey by Neugebauer et al. in the early 1960s, about a half century has passed. During this time, observations have expanded rapidly and widely, to almost every field of astronomy, to reveal new perspectives on the universe. As a result, infrared astronomy has become one of the major branches of astronomy, along with optical, radio, X-ray as well as high-energy particle astronomy. In Japan, we started our infrared astronomical activities at a rather early time, under relatively poor technical and environmental conditions, and using somewhat unconventional methods to overcome these difficulties. Here, a brief survey is presented of developments concerning infrared astronomy during the past half century, while mainly recollecting our footprints in the stream of world activities.
Experimental transition probabilities for spectral lines of seventy elements
From introduction: "The goal of the work was to provide lists of the principal lines of the elements generally observed under ordinary conditions in arc spectra, together with their relative intensities on a true scale of relative energy."