Preliminary results of magnetic field measurements in vicinity of magnetosphere and interplanetary space from Mariner IV

During the encounter between Mariner IV and Mars on 14-15 July, no magnetic effect that could be definitely associated with the planet was evident in the magnetometer data. This observation implies that the Martian magnetic dipole moment is, at most, 3 x 10^-4 times that of the earth.

We demonstrate that the Oosterhoff II (Oo II) RR Lyrae ab variables are hotter by ~270 K, at the same period, than Oo I variables. Or, at the same (B– V)₀ value the Oo II variables have larger radii than Oo I variables. This accounts for the reason Oo II variables are brighter (0.12-0.20 mag) than Oo I variables. The dependence of the light amplitude of RR Lyrae variables on temperature is independent of Oo type. This makes it possible to derive an accurate set of equations to relate intrinsic (B – V)₀ color indices to light amplitudes, which in turn can be used to determine the interstellar reddening (E (B – V)). With just a few variables (~5), it is possible to determine the E (B – V) to an accuracy of <0.01 mag in the absence of systematic photometric errors. We discuss the errors introduced in color excess determinations by including the Blazhko stars in a solution. A comparison of color excess values of 23 globular clusters and two regions of the Large Magellanic Cloud (LMC), determined with the aid of our newly developed equations, are found to compare favorably (~0.01 mag) with color excess values found in the literature. Four new Oo III variables, some found in metal-poor clusters, are discussed. An analysis of the galactic-field variables indicates the majority are Oo I and Oo II variables, but a few short-period (log P < –0.36) metal-strong variables, so far not found in galactic globular clusters are evidently ~0.30 mag fainter than Oo I variables. Oo III variables may also be present in the field. We conclude that the RR Lyrae ab variables are primarily restricted to four sequences or groups. If we assume that the Oo I variables' mean absolute magnitude is Mv = 0.61, the mean absolute magnitudes of the other three sequences are: short-period variables Mv ~ 0.89 mag, Oo II Mv ~ 0.43 mag, and Oo III Mv ~ 0.29 mag. The Oo I fundamental RR Lyrae ab red edge (FRE) and fundamental blue edge (FBE) occur at approximately the following temperatures: FRE T ~ 6180 K and FBE T ~ 6750 K. There is a strong dependence of Mv on [Fe/H] as we proceed from the short-period variables to the Oo I variables and to the Oo II variables, but there seems to be little or no dependence of Mv on [Fe/H] for stars within a group, at least for the Oo I and Oo II groups. The Oo II variables exhibit a weak period luminosity relation in V in many globular clusters unlike the Oo II-like variables in Oo I clusters which do not exhibit a P-L relation. The properties of some intermediate LMC clusters are discussed.

The distances to four galaxies and two globular clusters which are derived with the aid of period-luminosity and period-color relations of delta Scuti and SX Phe stars are compared to the distances derived by other methods, in particular RR Lyrae stars. We examine the luminosities of horizontal branch or RR Lyrae stars in Oosterhoff I and II globular clusters. Observational data from a variety of sources indicate a discontinuous jump of similar to 0.2 mag in the luminosities of RR Lyrae variables at [Fe/H] approximate to -1.5 as we transition from Oosterhoff I to Oosterhoff II clusters. If Oosterhoff I clusters have RR Lyrae variables with average M-V values of M-V = 0.53 mag at [Fe/H] = -1.5, it implies that RR Lyrae stars in Oosterhoff II clusters average M-V values are similar to 0.34 mag. Unlike the Oosterhoff I clusters which show an increase in the V luminosity of RR Lyrae stars as [Fe/H] becomes smaller, little or no change in the V luminosity of RR Lyrae variables is evident in Oosterhoff II clusters in the interval of [Fe/H] from -1.5 to -2.2. We find distance moduli found with RR Lyrae variables agree to <= 0.04 mag with those found with the delta Scuti and/or SX Phe variables if the M-V values of RR Lyrae stars above are adopted. We find evidence of recent star formation (presence of near solar-metallicity delta Scuti stars with ages of 150 Myr to 1 Gyr) in the Large Magellanic Cloud (LMC), Small Magellanic Cloud, and the central region of the Fornax (dSph) galaxies. We also find an older population of metal-poor delta Scuti variables (SX Phe stars) in the LMC and Fornax galaxies. The Carina dSph is unique in that only an old population of metal-poor delta Scuti variables is evident. No evidence of recent delta Scuti star formation is found. The minimum periods observed for the SX Phe variables (blue stragglers) in the globular clusters M55 and omega Cen indicate that they could have been formed in a burst of metal-poor single star formation in the last 2.9-6 Gyr. If formed by the more acceptable scenario of stellar mergers, it is likely that the merged remnant resembles a normal star in a relatively advanced stage of main-sequence evolution with an enriched He core and ordinary He envelope. We present equations to calculate intrinsic-color indices for delta Scuti, SX Phe, and RR Lyrae stars at mean light. Finally, we show that the fundamental-radial-pulsating stars (delta Sct and SX Phe variables) have larger average light amplitudes than the first-overtone pulsating variables. The fundamental metal-poor variables (SX Phe stars) have the largest average and individual amplitudes.