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Data from the IUE shows that the true central star of the giant planetary Longmore-Tritton 5 (339+88.1 deg) is a binary companion to the G5 star SAO 82570. The slope of the energy distribution curve indicates that the star may be one of the hottest known. The Mg II doublet associated with the G star is very strong, consistent with the existence of a close binary companion.
Infrared photometry and maps from 2 to 100 microns are presented for three of the principal far infrared sources in NGC 6334. Each region is powered by two or more very young stars. The distribution of dust and ionized gas is probably strongly affected by the presence of the embedded stars; one of the sources is a blister H II region, another has a bipolar structure, and the third exhibits asymmetric temperature structure. The presence of protostellar objects throughout the region suggests that star formation has occurred nearly simultaneously in the whole molecular cloud rather than having been triggered sequentially from within. Previously announced in STAR as N83-16263
The behavior of stochastic self-propagating star formation (SSPSF) in three dimensions is examined in simulation for the first time, emphasizing the effect of the added dimension on the sensitivity of spiral structure to the probability of star formation. The model produces global equilibrium spiral structure over a much more restricted range of star formation probabilities and relaxation times than in two dimensions. Spiral structure also occurs as a transient phenomenon in the runs which eventually fill or evolve to structured nonspiral states. The equilibrium spirals are not as distinctive as those produced by two-dimensional models. However, there are refinements which may modify these results, such as allowing for the depletion of gas in the interstellar medium due to conversion to long-lived low mass stars.
Infrared spectrophotometry of the R-type carbon star HD 19557 is presented. Two unusual spectroscopic features are seen: a 3.1 micron band is lacking and a 2.8 micron band is present. Identifications are proposed for three previously unreported stellar absorption bands with electronic sequences of C2, CN, and C2H. The latter is proposed to be responsible for the 2.8 micron feature. The atmospheric structure of the star is studied with synthetic spectra, and an effective temperature between 2600 K and 3000 K is suggested. No SiC emission is seen at 11.3 microns, indicating that grain formation is not a viable process around the star. The lack of dust in R stars may suggest a salient difference between R and N types.
A discussion is presented of the basic ideas underlying the use of star counts to determine galactic parameters. Previous work using star counts is reviewed, and possible future observational programs that will be important in increasing the knowledge of the stellar content of the galaxy are indicated. The techniques used in star counts are illustrated by applications to the differential number-magnitude counts in SA 57, the frequency-color diagrams in SA 57 and SA 68, the paucity of intermediate population stars in the range M(V) = 5-8, and the M/L ratio for the unseen matter in the halo.
Aspects of the current theory of molecular-cloud (MC) evolution and star formation are reviewed, with consideration of recent star and MC observations. The problem of MC collapse is discussed in terms of fragmentation in spherically symmetric collapse, the role of magnetic fields and density fluctuations, anisotropic collapse, and nonlinear interactions between fragments. Protostellar winds are identified as the source of the energy supporting MC against collapse, sweeping shells of mass into MC to produce low-mass stars continuously, and sustaining the production of massive stars once it is triggered by the collision of MCs, as in the spiral density-wave peaks. The clumping and coagulation processes are considered for the case of the MC in Orion. The protostellar-wind mass input required to inhibit systematic MC-core collapse is estimated at 10 to the -6th solar mass/cu pc year.
Enhanced X-ray emission from an early-type runaway star would be direct evidence for the presence of a collapsed companion, and thus for its origin as the result of a supernova explosion in a massive binary. To test this idea, measurements of X-ray fluxes in the 0.5-3 keV energy range from nine O and B type runaway stars were made with the Einstein Observatory. In each case, the X-ray luminosity observed does not exceed that expected from a normal OB star. Therefore we conclude that, if the runaway stars have collapsed companions, the separations of the components must be much greater than those in normal OB binaries.
Detailed far-IR observations and complemenary submillimeter, 5 GHz continuum and c(18)0 observations of a sample of far-IR selected luminous regions of star formation. The clouds and that the exciting stars lie deep within these condensations. The far-IR sources have diversely shaped 40 micron to 180 micron spectra even through their 60 micron to 100 micron color temperatures are similar. The radio and far-IR results together show that the exciting stars are in clusters containing either zero-age main sequence and pre-main sequence stars or consisting entirely of premain sequence objects. C(18)0 and submillimeter observations imply gas densities approximately .00005 - high enough to make t(sub dust) approximately t(sub gas).
Various projects on the topic of hot stars with circumstellar dust are reported. The surface temperature, wind speed, and interstellar reddening were determined for the variable WC7 star HD 193793. Circumstellar carbon monoxide molecules were detected around a hot star. The dust envelope of the star W90 in the young cluster NGC2264 is discussed, and the spectra of low-redshift and X-ray emitting quasars are mentioned.
A systematic redshift of the high ionization resonance emission lines with respect to the intercombination lines is found from an examination of the ultraviolet spectra of symbiotic stars obtained with IUE. After consideration of other possibilities, this is most probably explained by photon scattering in an expanding envelope optically thick to the resonance lines. Line formation in a wind, or at the base of a wind is therefore suggested. Reasons are also given indicating line formation of the most ionized species in a region with an electron temperature of the order of 100,000 K, probably around the cool star. The behavior of the emission line width with ionization energy seems to support this model. The cool components of symbiotic stars appear to differ from normal red giants, which do not have winds of this temperature. An explanation in terms of a higher rotation velocity due to the binary nature of these stars is suggested.
The concept of typing the Hipparcos optical and the JPL VLBI frames of reference by means of VLBI measurements of the positions and proper motions of the radio components of some bright stars is considered. The properties of the thermal and non-thermal radio-stars are discussed and 22 candidate stars are selected to achieve this tie. A description is given of the first VLBI attempt to detect these stars on the intercontinental baselines of the Deep Space Network with the Mark II recording system.
Photometric observations of 131 SAO stars for use in calibrating data obtained from the Near Infrared Photographic Sky Survey (NIPSS) are reported. The serial numbers of the primary NIPSS program fields in which the photometry was done are shown along with the approximate position of each field and the number of stars observed in each field. The observations are listed, showing the SAO numbers of the program stars, their 1950 equatorial coordinates, the V magnitudes, and the (V-R) and (V-I) color indices. The mean errors in magnitudes and color indices obtained by averaging deviations from the mean for each star are on the order of 0.02 mag.
It is pointed out that spectroscopic signatures of stellar chromospheric activity are readily observable. The present study is concerned with new photometric and spectroscopic observations of active-chromosphere RS CVn, BY Dra, and FK Com stars. Attention is given to the first results of a synoptic monitoring program of many active chromosphere stars. During the time from 1980 to 1982, photometric and spectroscopic observations of 10 known or suspected active-chromosphere objects were made. The results regarding the individual stars are discussed. Seven stars observed with the International Ultraviolet Explorer (IUE) are all spectroscopic binaries.
Attention is given to semidetached binaries of the Algol type and to related interacting systems, such as Beta Lyrae and the W Serpentis stars. A brief description is given of observational problems. The basic properties of the Algol variables are satisfactorily explained by means of evolutionary models that assume considerable mass transfer between the components. It is pointed out that ultraviolet spectra obtained with the IUE satellite corroborate the view that the present subgiant secondary component was initially the more massive star and that it has been stripped of a large fraction of its mass so that the deep layers affected by CNO processing are now denuded. It is believed that the present-day 'classical' Algols must have undergone a phase of rapid mass transfer in the past and that Beta Lyrae and the W Serpentis stars are probably closer to that stage than ordinary Algols. Around the accreting star a complex structure is formed, and an induced stellar wind may blow a large part of the transferred matter out of the system.
It is noted that when magnetic lines of force are present in the mantle of an early-type star, gyroresonance radiation at radio wavelengths may occur at detectable levels in addition to bremsstrahlung. An expression is derived for the effective value of the ratio of the emissivity in gyroresonance radiation to that in bremsstrahlung, and some numerical values are estimated using values of the parameters which may be typical for conditions in the mantles of early-type stars. The volume emissivity in gyroresonance radiation may exceed that for bremsstrahlung by a large factor. The implications of this result for the interpretation of the radio fluxes from early-type stars are discussed. It is shown that the radio-frequency radiation emerging from a hot star probably consists of gyroresonance radiation from an array of magnetic loops as well as bremsstrahlung from a low-density wind. It is argued that it is probable that the estimates of rate of mass loss made ignoring the possibility of gyroresonance radiation may be too large by a factor of at least 10.
Attention is given to the evolution of neutron stars whose magnetic fields are so weak that (1) the effects of the magnetosphere on the accretion disk are negligible, allowing it to extend to the surface of the star; and (2) the loss of energy and angular momentum by the pulsar mechanism is negligible compared with that provided by the accretion disk. The small nonaxisymmetric distortion of the neutron star should produce some modulation of the X-ray emission at the gravitational wave frequency, and it is hypothesized that this frequency will lie in the 200-800 Hz range. This is significantly below the rotational frequency of the neutron star.
Far-infrared (40-160 micron) observations of Herbig-Haro objects and their probable exciting stars are presented. The importance of these far-infrared observations is epitomized by the fact that, on average, 70 percent of the bolometric luminosity of a typical candidate star is radiated beyond the longest detected ground-based wavelength, even for those objects observed out to 20 micron from the ground. Extended far-infrared emission characterizes some of these regions. Some Herbig-Haro nebulae are themselves conspicuous 100 micron peaks (e.g., HH 1 and HH 25). A bipolar structure is found at 100 micron in the vicinity of the Cohen-Schwartz star. All the exciting stars must be low-mass objects (approximately less than 3 solar mass). It is argued that they might be approximately 1 solar mass protostars still in their accretion phase.
Ultraviolet observations of barium stars and other cool stars with peculiar element abundances are reported. Those observations attempted to find hot white dwarf companions. Among six real barium stars studied, only Zeta Cap was found to have a white dwarf companion. Among seven mild, or marginal, barium stars studied, at least three were found to have hot subluminous companions. It is likely that all of them have white dwarf companions.