Engineering topics

Kwok, Sun

Publications and source records attributed to Kwok, Sun.

21 records · Page 2

NASA NTRS1988

The high-latitude F supergiant IRAS 18095 + 2704 - A proto-planetary nebula

The paper reports the discovery of a new high-latitude F supergiant, IRAS 18095 + 2704, which shows a large excess in the far-infrared. Ground-based observations have identified it as a V = 10.4 mag F3 Ib star which displays light and velocity variability. Comparison with the post-asymptotic giant branch (AGB) evolution model of Volk and Kwok suggests that it is an excellent candidate for a protoplanetary nebula. Model fitting of the spectrum of 18095 + 2704 from 0.35 to 100 microns suggests that it evolved from the AGB approximately 265 yr ago and had a mass-loss rate of 0.00003 solar mass/yr at the end of the AGB.

Hrivnak, Bruce J.↗

NASA NTRS1987

Ground-based infrared observations of variable IRAS sources as candidates for late asymptotic giant branch stars

Analysis of the color distribution of OH/IR stars and IRAS low-resolution spectra class 30 objects suggests the presence of a well-defined evolutionary sequence which is populated by late asymptotic giant branch (LAGB) stars. The paper reports ground-based identification and infrared photometry of 10 candidates of news LAGB stars. None of the selected sources are found to have optical counterparts, and eight of the 10 show a strong 10-micron silicate absorption feature. It is suggested that these stars represent an invisible extension of extreme Mira variables and are some of the most evolved stars observed to date.

Kwok, Sun↗

NASA NTRS1987

Ground-based observations of IRAS candidates for late asymptotic giant branch stars

Ground-based IR photometric observations were obtained for 16 of the IRAS Circular No. 9 sources which have been suggested to be candidates of OH/IR stars. Five of these sources are confirmed to be OH/IR stars and three others as carbon stars. Two are young objects in an early stage of star formation and one, possibly two, are planetary nebulae. Two sources of very low color temperatures (about 180 K) are also found, and may represent objects in transition between the asymptotic giant branch and planetary nebula phases.

Kwok, Sun↗