Robert E. Stencel

Workstation-based preprocessing of IRAS sky-flux images

Computer algorithms to remove two types of degradations in IRAS sky-flux images, namely slowly varying background illumination (strongly effected by the presence of zodiacal light) and periodic stripes, are presented. This paper discusses both algorithms in detail and shows results of its use on various sky-flux images. Focus of the work was on the implementation within a workstation environment, and its value as a preprocessing tool for researchers. Speed of the process, usability of the programs, and correctness of the results were the main goals in developing these tools.

Far-infrared circumstellar 'debris' shell of red supergiant stars

Examination of IRAS data on late type evolved stars suggests that there is yet another transition line, between chromospheres and dust, which lies above and to the right of corona-wind transitions in the HR Diagram. The IRAS 60 µm data also appears to indicate the existence of very cool material extending tens of thousands of stellar radii around red supergiant stars. These circumstellar debris shells may prove useful in the analysis of the history of mass loss in given objects and larger scale galactic trends, such as metallicity.

The environments of cool stars

This review describes recent conclusions about the physical environment of red giant and supergiant stars. This includes coronae, chromospheres, dust formation and stellar winds. This knowledge can provide the boundary conditions for considering what role such objects play as members of binary star systems, where tidal forces and companion behavior alter observed characteristics.

MG II emission lines in the spectra of cool, high luminosity stars

We present the initial results of a survey of the Mg II emission lines in the spectra of K and M giants, bright giants, and supergiants. Profiles of the Mg II h and k lines in 12 such stars are shown in a relative spectral type/luminosity class grid. Plots based on the h-line data illustrate the existence of a Wilson-Bappu. effect in these lines and of a slight dependence of the line asymmetry on V-R color. A time series of Mg II profiles for the M3 giant Gamma Cru show that the Mg II profiles have not undergone the profile shape changes seen in the Fe II lines from this star over the same time period.

THE 1971 ECLIPSE OF 32 CYGNI: UBV AND SPECTROPHOTOMETRIC OBSERVATIONS

Standard UBV and 20 A spectrophotometry at four blue wavelengths obtained during the November 1971 eclipse of 32 Cyg is reported. Key words: photometry - eclipsing binary

Molecular catastrophes and circumstellar SiO masers

Understanding the complex SiO maser regions of highly evolved stars can be improved through multiwavelength studies of “pre-maser” stars, such as MO-M4 giants and semi-regular variables, which can be placed on normal H-R diagrams unlike most of the OH-IR stars. I argue that SiO masers are a key pant of the transformation of hot stellar plasma into cold circumstellas silicate dust, in the outflows from evolved, oxygen rich stars. Evidence for this statement rests on the following: (a) red giant mass loss originates in a stochastic, anisotropic manner; (b) SiO maser maps of Miras and red supergiants show numerous maser spots within a few stellar radii; (c) molecules and dust naturally form in a cooling outflow (e.g. SN1987A after 410 days showed strong shortwave infrared bands of CO and SiO molecular emission, and novae show dust production episodes after maximum light); (d) the IRAS Low Resolution Spectrometer provided evidence for diverse and variable 10 micron silicate features in Miras, and these shapes correlate well with the proposed maser chronology, suggesting a formation and annealing sequence. The theory for the occurence of SiO masers involving thermal instability, related “new” physics, recent calculations and a prediction axe discussed.

Oxygen-rich mass loss from carbon-rich stars---some implications

We have evaluated the degree of dust to gas coupling in the atmospheres of red giant stars, and find non‐zero drift velocities. Chemical fractionation of the stellar atmosphere on an evolutionary timescale is implied.

Summary of Final Discussion

The last session of the Colloquium was Chaired by Harry Nussbaumer and opened with statements from members of a panel comprised of Livio, Mikolajewska, Luud, Viotti, Magalhaes, Slovak, Kwok and Whitelock. Viotti began by comparing the available data for symbiotics historically and since IAU Colloquium 70 in 1981. He emphasized new UV, X-ray, infrared and radio observations. He also sketched the recent history of wavelength specific publications. Whitelock stated that it now seems clear all D-types probably contain Miras and that S-types do not evolve into D-types. Luud stated that his group intends to continue its near infrared observations with the 2 meter at Tartu, and that it is important to confirm conclusions based on IRAS data. He mentioned that masses for the Miras are needed given the discrepancy between observed and evolutionary masses.

THE SEARCH FOR THE ELUSIVE COMPANION OF EG ANDROMEDAE.

We report observations at opposite quadratures of the interacting symbiotic binary EG Andromedae (HD 4174, Period = 470 d ). Correcting for absolute motion at the system, it appears that many of the nebular lines arise from material that moves with the red giant star. The He II feature appears to track the hot component. It may be possible to use this feature in other, similar systems in order to “pin-down” the mass ratio.

Remarks on red giant and supergiant stars

The preceeding review paper by Hollis Johnson and these remarks summarize portions of a half-day meeting held immediately prior to the Fifth Cool Stars Workshop. This special session was held in order to allow the astronomers interested in problems related to the atmospheres and evolution of red giant and supergiant stars to share ideas on selected current topics and to obtain previews of some of the papers presented during the Workshop. Many of the talks presented are published in these Proceedings.