Raymond J. Talbot

Solar Models of Low Neutrino-Counting Rate: The Central Black Hole

Partial evolutionary sequences have been calculated for several solar models with central black holes of order 10

Solar models of low neutrino-counting rate - The depleted Maxwellian tail

sup -5

Interstellar Cloud Material: Contribution to Planetary Atmospheres

M/sub sun/. If these are assumed to radiate their Eddington limiting luminosity, the central temperature is depressed to the extent that the predicted count rate for the

COMPUTER RESULTS ON COMBINED HYDROGEN AND HELIUM BURNING

sup 37

ENCOUNTERS WITH INTERSTELLAR CLOUDS: THE EFFECT ON STELLAR WINDS AND THE POSSIBILITIES FOR ACCRETION*

Cl solar neutrino experiment nears the current upper limit of 1 SNU; this occurs when the auxiliary energy source provides about half of the solar luminosity. Count rates below this limit would result from an even larger black-hole luminosity. Consequences for stellar evolution of the occasional presence of black holes inside normal stars are discussed. (AIP)

Evolution Of Galaxies .2. Chemical Evolution Coefficients

Evolutionary sequences for the sun are presented which confirm that the Cl-37 neutrino counting rate will be greatly reduced if the high-energy tail of the Maxwellian distribution of relative energies is progressively depleted. Thermonuclear reaction rates and pressure are reevaluated for a distribution function modified by the correction factor suggested by Clayton (1974), and the effect of the results on solar models calculated with a simple Henyey code is discussed. It is shown that if the depletion is characterized by a certain exponential dependence on the distribution function, the counting rate will fall below 1 SNU for a distribution function of not less than 0.01. Suggestions are made for measuring the distribution function in the sun by means of neutrino spectroscopy and photography.

Evolution Of Galaxies .4. Highly Flattened Disks

A statistical analysis of the properties of dense interstellar clouds indicates that the solar system has encountered at least a dozen clouds of sufficient density to cause planets to accumulate nonnegligible amounts of some isotopes. The effect is most pronounced for neon. This mechanism could be responsible for much of the neon in Earths atmosphere. For Mars, the predicted amount of neon added by cloud encounters greatly exceeds the present abundance.

Some recent results from galactic and stellar evolution theory

Abundances in combined hydrogen helium burning in core edge of Population II red giant stars

Climatic effects during passage of the Solar System through interstellar clouds

McCrea’ has recalled the suggestion’ that terresterial Ice Ages may be produced by accretion of interstellar matter by the Sun. Subsequently several a ~ t h o r s j ~ have discussed further consequences o f encounters between stars and dense interstellar clouds. I n this report we summarize some results of an analysis that will be presented i n more detail e l ~ e w h e r e . ~ TABLE I presents an analysis of data from the literature concerning the properties of clouds i n the present interstellar medium. For each of several samples we display the number density n of hydrogen nuclei, the number nc of such clouds per cubic parsec in the disk of the Galaxy, the fraction f, of the disk of the Galaxy occupied by clouds of that class, the mean time 7 between encounters, and the number ofencounters N , with such an object expected for a disk star of solar age. A more detailed discussion of these and related quantities will appear elsewherc.’ The undertainties involved are such that the sample labeled 21 cm may represent the same class of object as Spitzer’s “standard cloud”; t h e CO observations and the more dense Lynds’ nebulae, however, appear to represent objects substantially diferent from the lower density clouds. I t is seen that while the less dense clouds occupy a fairly substantial fraction of the galactic disk, and encounters with such objects should be relatively routine for long-lived stars like the Sun , the very dense clouds occupy a much smaller fraction of the disk, and the Solar System could not be expected to have encountered many of them. This information has been summarized by the definition of the two integral distributions shown in FIGURE 1 . Here f ( 2 n ) is the fraction of the volume of the disk of the Galaxy occupied by clouds with density exceeding n , and N , (2 n ) is the number of encounters expected during 4.6 x 10’ yr with clouds of density greater than or equal to n. I t is not known whether the break at n lo3 (3m-j is real or due to some observational selection eKmt operating against the very dense clouds; i f the darkest clouds are underrepresented due to observational difficulties, their role may be considerably more important than is indicated by this analysis.