BV(Rl) KC light curves are presented for 27 type la supemovae discovered during the course of the Calán/Tololo Survey and for two other SNe la observed during the same period. Estimates of the maximum hght magnitudes in the B, V, and I bands and the initial decline rate parameter Am 15 (B) are also given.

We present the first comparisons of a newly developed Galactic Structure and Kinematic Model to magnitude and color counts, as well as relative proper motions, in the fields of the open clusters NGC 188 ((l, b) = (122.8 o , +22.4 o )) and NGC 3680 ((l, b) = (286.8 o , +16.9 o )). In addition to determining the reddening toward these two clusters, it is shown that starcounts at intermediate Galactic latitudes in the range 11 ≤ V ≤ 17 allow us to constrain the model scale-height for disk subgiants. We obtain a mean value of 250 ± 32 pc, in agreement with previous determinations of the scale-height for red-giants. We are also able to constrain the scale-height of main-sequence stars, and the distance of the sun from the Galactic plane, ruling out the possibility of a value of +40 pc, in favor of a smaller value. Comparisons with the observed proper-motion histograms indicate that the velocity dispersion of disk main-sequence stars must increase with distance from the Galactic plane in order to match the observed proper-motion dispersion. The required increase is consistent with the values predicted by dynamical models, and provides a clear observational evidence in favor of such gradients. The shape of the observed proper-motion distribution is well fitted within the Poisson uncertainties. This implies that corrections to absolute proper motion (and, therefore, space velocities) for open clusters may be obtained using our model when no inertial reference frame is available. Using this approach, the derived tangential motions for NGC 188 and NGC 3680 are presented.

The results of speckle interferometric observations at the Southern Astrophysical Research Telescope (SOAR) telescope in 2014 are given. A total of 1641 observations were taken, yielding 1636 measurements of 1218 resolved binary and multiple stars and 577 non-resolutions of 441 targets. We resolved for the first time 56 pairs, including some nearby astrometric or spectroscopic binaries and ten new subsystems in previously known visual binaries. The calibration of the data is checked by linear fits to the positions of 41 wide binaries observed at SOAR over several seasons. The typical calibration accuracy is 0• . 1 in angle and 0.3% in pixel scale, while the measurement errors are on the order of 3 mas. The new data are used here to compute 194 binary star orbits, 148 of which are improvements on previous orbital solutions and 46 are first-time orbits.

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We present orbital elements and mass sums for eighteen visual binary stars of spectral types B to K (five of which are new orbits) with periods ranging from 20 to more than 500 yr. For two doubleline spectroscopic binaries with no previous orbits, the individual component masses, using combined astrometric and radial velocity data, have a formal uncertainty of ∼ 0.1M . Adopting published photometry, and trigonometric parallaxes, plus our own measurements, we place these objects on an H-R diagram, and discuss their evolutionary status. These objects are part of a survey to characterize the binary population of stars in the Southern Hemisphere, using the SOAR 4m telescope+HRCAM at CTIO. Orbital elements are computed using a newly developed Markov Chain Monte Carlo algorithm that delivers maximum likelihood estimates of the parameters, as well as posterior probability density functions that allow us to evaluate the uncertainty of our derived parameters in a robust way. For spectroscopic binaries, using our approach, it is possible to derive a self-consistent parallax for the system from the combined astrometric plus radial velocity data ("orbital parallax"), which compares well with the trigonometric parallaxes. We also present a mathematical formalism that allows a dimensionality reduction of the feature space from seven to three search parameters (or from ten to seven dimensions -including parallax -in the case of spectroscopic binaries with astrometric data), which makes it possible to explore a smaller number of parameters in each case, improving the computational efficiency of our Markov Chain Monte Carlo code.