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The discrepancy between values of Jupiter's dynamic oblateness as measured by space probes and via 1971 beta Sco occultations is re-examined. The indicated correction to the Io ephemeris is compared to corrections proposed by Aksnes and Franklin (1975, 1976). It is found that the latter corrections reduce the above discrepancy to a marginal level.
Effects of atmospheric turbulence on stellar-occultation inversion procedures are investigated using a heuristic scattering model that is believed to reproduce the essential features of turbulence. A quantitative estimate is made of the size of the error in deducing the mean refractivity profile of a planetary atmosphere, taking into account constant as well as exponential scattering. It is shown that ordinary turbulence has no important effect on the average intensity profile in a stellar occultation but could have an important instantaneous effect. A critical examination of possible manifestations of turbulent scattering during occultations of Beta Sco by Jupiter indicates that all observed phenomena during these events can be understood in terms of scintillations produced by turbulence.
Evaporation of gas from the surface of HZ Her by Her X-1 and its implications regarding the mass transfer process are examined further. The powerful soft X-ray flux results in an evaporation rate greater than previous estimates. The evaporative flow is shown to be subsonic at first, with the result that the capture of evaporated gas by Her X-1 may be efficient, and the self-excited wind mechanism is possible. A criterion for stabilization of mass transfer by stellar wind mass loss is derived. Possible mechanisms for the long-period variability of HZ Her are discussed. Evaporative winds are also estimated for Sco X-1 and Cyg X-2 spectra.
A Fabry-Perot interferometer was used to measure a 2-sigma upper limit of 0.39 mA for CH(plus) toward Tau Sco, a line of sight with a large amount of atomic hydrogen yet only a small amount of molecular hydrogen. The upper limit for the abundance of CH(plus) in a region where hydrogen is primarily atomic shows that no unexpectedly rapid CH(plus) formation processes are occurring and, conversely, that the CH(plus) destruction rate is not smaller than expected. It is argued that either CH(plus) is primarily formed in regions with large amounts of H2 or CH(plus) is formed at least as rapidly as the density-cubes in regions where hydrogen is mostly atomic.
The theory of perturbations, giving the diatomic effective Hamiltonian, is used for calculating actual molecular wave functions and intensity factors involved in transitions between states arising from Hund's coupling cases a,b, intermediate a-b, and c tendency. The Herman and Wallis corrections are derived, without any knowledge of the analytical expressions of the wave functions, and generalized to transitions between electronic states with whatever symmetry and multiplicity. A general method for studying perturbed intensities is presented using primarily modern spectroscopic numerical approaches. The method is used in the study of the ScO optical emission spectrum.
A single flare event with a rise time of about 7 s and a decay time of approximately 40 s was observed by the Goddard cosmic X-ray spectroscopy experiment on OSO-8 during observations of 3U 0614+09 in September 1975. The possibility is discussed that the source was 3U 0614+09, which has been compared with the low-mass binary Sco X-1. The spectra during the event could be fitted with blackbody (kT = 0.8-1.1 keV) or thermal bremsstrahlung (kT = 1.1-2.5 keV) models with absorption by cool material. In the blackbody model the source was of the order of 1 million cm in size.
The stars Alpha Aur (G5 III + G0 III), Alpha Boo (K2 IIIp), Alpha Ori (M1-M2 Ia-Ib), Alpha Sco (M1.5 Iab), Mu Gem (M3 III), and Alpha Her (M5 Ib-II) have been observed using interference filters in five photometric bands between 1.25 and 3.25 microns during seven flights with NASA's Lear Jet Infrared Observatory. The filters were designed to measure molecular features, primarily from CN and CO, and continuum fluxes. By calibrating the photometer in the laboratory against a stabilized blackbody source, relative flux curves have been derived. The energy distributions and the strength of molecular features are discussed. The most interesting result obtained is that the fluxes from Mu Gem and Alpha Her in the filter centered at 3.25 microns seem to be depressed by at least some tenths of a magnitude. Tentatively this depression is proposed to be due to the wings of the two vibration-rotation bands (about 2.7 microns) of hot water vapor. Since water vapor is an important opacity source and its abundance is a sensitive C/O indicator, the proposed interpretation makes renewed efforts to detect water bands in early M stars highly desirable.
Equatorial regions are well suited for studies of lower mesospheric response to X-rays because cosmic ray background effects are low there. In a sequence of rocket and balloon-borne observations conducted in Peru (12.5 S, 76.8 W), a direct measurement of a galactic X-ray source was made at an altitude of 65 km. Although no unusual X-ray activity was found above and below the region studied, the 65 km observations were consistent with known data for Sco X-1, i.e., its position and energy spectrum. In addition to showing that stellar X-rays do indeed affect the lower mesosphere, their transient nature leads also to the conclusion that the equatorial energetic electron belt is not a permanent feature of that region.
X-ray data on the sources 3U 1813-14 (GX 17+2) and 3U 1811-17 (GX 13+1), obtained by Copernicus between 1975 and 1977, are examined. These reveal correlated intensity and spectral-slope variations in GX 17+2 similar to those seen in Sco X-1 and four other galactic sources, 3U 0614+09, 3U 1702-36, 3U 1728-16, and 3U 1758-25. The data on GX 17+2 have been unsuccessfully searched for further evidence of a shallow 31.9-minute modulation. In the case of GX 13+1 no significant variability was seen in either intensity or spectrum. A simultaneous search made from the NRAO simultaneously with some of the X-ray observations revealed no significant radio emission from either source.
A measurement of Sco X-1 with the graphite-crystal polarimeters on the OSO 8 satellite yields upper limits (3 sigmas) to the linear polarization of 2.7% and 4.9% at 2.6 keV and 5.2 keV, respectively. The results are discussed in terms of an accretion-disk model.
Mg II h and k emission lines of the M2 giant beta Peg and the M5 supergiant alpha Her were detected in Copernicus observations. In the alpha Her profiles, similar to alpha Ori and alpha Sco profiles, the k line is asymmetric and the h line is symmetric. The possibility that the k line asymmetry is produced by overlying absorption is discussed. In beta Peg, both h and k lines are asymmetric, and line formation in an expanding chromosphere is indicated. The observations are in accord with one formulation of the Wilson-Bappu relation but deviate from another form of the Wilson-Bappu relation.
This paper reports preliminary results on the positions of X-ray sources obtained with the modulation collimator on the first NASA High Energy Astronomy Observatory, HEAO 1. Calibration on Sco X-1 establishes the experiment capabilities to be within 7 sec as limited by aspect errors. For the reported X-ray sources certain ambiguities in their positions are resolved and the previous optical identifications of four sources are confirmed, two of which are X-ray bursters and one of which is the black hole candidate Cir X-1. An accurate position for a new transient source is also presented.
During the summer of 1978 the recurrent transient X-ray source, Aquila X-1, underwent its first major outburst in two years. The results of extensive observations at X-ray and optical wavelengths throughout this event, which lasted for approximately two months are presented. The peak X-ray luminosity was approximately 1.3 times that of the Crab and exhibited spectral dependent flickering on timescales approximately 5 minutes. The observations are interpreted in terms of a standard accretion disk model withparticular emphasis on the similarities to Sco X-1 and other dward X-ray systems, although the transient nature of the system remains unexplained. It was found that Aquila X-1 can be described adequately by the semi-detached Roche lobe model and yields a mass ratio of less than or approximate to 3.5.
The paper presents the theory, design, performance parameters, and statistical limitations of dispersive-crystal and Thomson-scattering devices as X-ray polarimeters for solar and extrasolar observations. With reference to the Bragg crystal polarimeter, the instrument parameters of the OSO-8 polarimeter are reported along with estimates of the minimum detectable polarization for several sources as derived from measured values for the integral reflectivities, the known spectra for a number of X-ray sources, and crystal panel geometry. For the Thomson-scattering polarimeter, values are given for the scattering efficiency for hydrogen and lithium as a function of photon energy and for the spectra of the two brightest X-ray sources: Sco X-1 and the Crab Nebula.
Observations covering multiple orbital periods of the X-ray source Sco X-1 were carried out in 1975 and 1976 with the graphite crystal spectrometer aboard OSO 8. Time-averaged continuum spectra are featureless and are reasonably well described in terms of a Comptonized thermal bremsstrahlung spectrum in which kT is about 1.5-2 keV and in which the number of electron scatterings that each photon is assumed to have undergone is of the order of 100. Line limits, typically with equivalent widths of a few electron volts, are established for important emission lines of Si XIII, Si XIV, S XV, S XVI, and Fe XXV as a function of binary phase.
Faint blue stars are suggested as the optical counterparts of the X-ray bursters 4U (MXB) 1636-53 and 4U (MXB) 1735-44 as well as the 7-sec X-ray pulsar 4U 1626-67. The candidate stars have large UV excesses and were discovered well within the 20- and 30-arcsec error radii determined with the rotating modulation collimator aboard SAS 3. Photographic observations and photoelectric photometry of the candidate stars are discussed. It is shown that the candidates for 4U 1626-67 and 4U 1636-53 lie further from the reddened-supergiant or main sequence than any known X-ray source counterparts and have colors that are inconsistent with those of a reddened normal star, while the candidate for 4U 1735-44 has the colors of both Sco X-1 and a late O or BO star suffering about 1 mag of extinction.
The discovery of a faint X-ray source at approximately 282 deg galactic longitude, -9 deg galactic latitude with the rotation modulation collimator X-ray detectors aboard SAS 3 is reported. The source is designated 2S 0921-630 and is tentatively identified, on the basis of an optical search, with a 17th magnitude star exhibiting the He II line at 4686 A and H-beta in emission. The optical spectrum of this star is shown to be similar to those of the optical counterparts of Sco X-1 and other such galactic X-ray sources. It is suggested that 2S 0921-630 may belong to the class of low-luminosity galactic X-ray binaries.
Multiple Copernicus scans of two N2 band regions (near 958.5 and 960.2A) of Delta Sco and Epsilon Per are reported. The observations indicate upper limits for the number of N2 molecules equal to 1.0-3.8 times 10 to the -12th/sq cm and 1.2-4.4 times 10 to the -12th/sq cm, respectively; the limits depend on the cloud temperature. It is suggested that the limits are consistent with the column densities predicted by chemical models for diffuse interstellar clouds, and the predicted relative abundances are presented in terms of the ratio of N(N2)/(2N(H2) + N(Hl)).