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We present the results of a deep, wide-field search for transiting `Hot Jupiter (HJ)' planets in the globular cluster omega Centauri. As a result of a 25-night observing run with the ANU 40-inch telescope at Siding Spring Observatory, a total of 109,726 stellar time series composed of 787 independent data points were produced with differential photometry in a 52x52' (0.75 deg^2) field centered on the cluster core, but extending well beyond. Taking into account the size of transit signals as a function of stellar radius, 45,406 stars have suitable photometric accuracy (, Comment: 22 pages, 8 figures, accepted for publication in ApJ

We present a strong case for a transiting Hot Jupiter planet identified during a single-field transit survey towards the Lupus Galactic plane. The object, Lupus-TR-3b, transits a V=17.4 K1V host star every 3.91405d. Spectroscopy and stellar colors indicate a host star with effective temperature 5000 +/- 150K, with a stellar mass and radius of 0.87 +/- 0.04M_sun and 0.82 +/- 0.05R_sun, respectively. Limb-darkened transit fitting yields a companion radius of 0.89 +/- 0.07R_J and an orbital inclination of 88.3 +1.3/-0.8 deg. Magellan 6.5m MIKE radial velocity measurements reveal a 2.4 sigma K=114 +/- 25m/s sinusoidal variation in phase with the transit ephemeris. The resulting mass is 0.81 +/- 0.18M_J and density 1.4 +/- 0.4g/cm^3. Y-band PANIC image deconvolution reveal a V>=21 red neighbor 0.4'' away which, although highly unlikely, we cannot conclusively rule out as a blended binary with current data. However, blend simulations show that only the most unusual binary system can reproduce our observations. This object is very likely a planet, detected from a highly efficient observational strategy. Lupus-TR-3b constitutes the faintest ground-based detection to date, and one of the lowest mass Hot Jupiters known., 4 pages, 4 figures, accepted for publication in ApJL

We obtain high-precision limb-darkening measurements in five bands (V, V_E, I_E, I, and H) for the K3 III (Teff=4200 K, [Fe/H]=+0.3, log(g)=2.3) source of the Galactic bulge microlensing event EROS BLG-2000-5. These measurements are inconsistent with the predictions of atmospheric models at >10 sigma. While the disagreement is present in all bands, it is most apparent in I, I_E and V_E, in part because the data are better and in part because the intrinsic disagreement is stronger. We find that when limb-darkening profiles are normalized to have unit total flux, the I-band models for a broad range of temperatures all cross each other at a common point. The solar profile also passes through this point. However, the profile as measured by microlensing does not. We conjecture that the models have incorporated some aspect of solar physics that is not shared by giant atmospheres., Submitted to ApJ, 28 pages including 8 figures

We present photometric and spectroscopic data for the second microlensing event seen toward the Small Magellanic Cloud (SMC), MACHO 98-SMC-1. The lens is a binary. We resolve the caustic crossing and find that the source took 2 Δt=8.5 hr to transit the caustic. We measure the source temperature Teff=8000 K both spectroscopically and from the color, (V-I)0~0.22. We find two acceptable binary-lens models. In the first, the source crosses the caustic at =432 and the unmagnified source magnitude is Is=22.15. The angle implies that the lens crosses the source radius in time t*=Δt=2.92 hr. The magnitude (together with the temperature) implies that the angular radius of the source is θ*=0.089 μas. Hence, the proper motion is μ=θ*/t*=1.26 km s-1 kpc-1. For the second solution, the corresponding parameters are =306, Is=21.81, t*=2.15 hr, θ*=0.104 μas, and μ=θ*/t*=2.00 km s-1 kpc-1. Both proper-motion estimates are slower than 99.5% of the proper motions expected for halo lenses. Both are consistent with an ordinary binary lens moving at ~75-120 km s-1 within the SMC itself. We conclude that the lens is most likely in the SMC proper.

Microlensing is increasingly gaining recognition as a powerful method for the detection and characterization of extra-solar planetary systems. Naively, one might expect that the probability of detecting the influence of more than one planet on any single microlensing light curve would be small. Recently, however, Griest & Safizadeh (1998) have shown that, for a subset of events, those with minimum impact parameter $u_{min} \lsim 0.1$ (high magnification events), the detection probability is nearly 100% for Jovian mass planets with projected separations in the range 0.6--1.6 of the primary Einstein ring radius $R_E$, and remains substantial outside this zone. In this Letter, we point out that this result implies that, regardless of orientation, all Jovian mass planets with separations near 0.6--1.6$R_E$ dramatically affect the central region of the magnification pattern, and thus have a significant probability of being detected (or ruled out) in high magnification events. The probability, averaged over all orbital phases and inclination angles, of two planets having projected separations within 0.6--$1.6R_E$ is substantial: 1-15% for two planets with the intrinsic orbital separations of Jupiter and Saturn orbiting around 0.3--1.0$M_\odot$ parent stars. We illustrate by example the complicated magnification patterns and light curves that can result when two planets are present, and discuss possible implications of our result on detection efficiencies and the ability to discriminate between multiple and single planets in high magnification events., 14 pages, including 3 figures. Submitted to the Astrophysical Journal Letters

Spin vectors of 60 galaxies in the ``Ursa Major Filament'' are obtained from CCD images and spectroscopic determinations of the directions of rotation. These data are used to remove the four-fold degeneracy introduced by the project ed images of galaxies, making possible the complete reconstruction of the galaxy spin vectors. Several possible organizations of spin vectors are investigated by means of statistical analyses of the three-dimensional spin vector maps. The results indicate that there exists no significant alignment of galaxy spin vectors with respect to the supergalactic plane, the supergalactic axis, or the cylindrical axis of the filament itself. No tendency for linear alignment of spin vectors towards any specific direction was detected. We also obtain a statistically negative result for azimuthal, radial, and circul ar-helical orientation of spin vectors., Comment: 20 pages, 4 figures, request PostScript file to cheongho@payne.mps.ohio-state.edu, OSU-TA-14/94

If massive compact halo objects (\ms) are detected in ongoing searches, then \tsmctlmc, the ratio of the optical depth toward the Small and Large Magellanic Clouds, will be a robust indicator of the flattening of the Galactic dark matter halo. For a spherical halo, \tsmctlmc\ is about 1.45, independent of details of the shape of the Galactic rotation curve, the assumed mass of the Galactic disk and spheroid, and the truncation distance (if any) of the dark halo. For an E6 halo (axis ratio $c/a = 0.4$), the ratio of optical depths is \tsmctlmc\ $\sim 0.95$, again independent of assumptions about Galactic parameters. This ratio can be measured with a precision as good as $\sim 10\%$ depending on the typical mass of the MACHOs. If the halo is highly flattened (\eg E6) and closely truncated (\eg at twice the solar galactocentric radius), then the optical depth toward the LMC can be reduced by a factor of about two. For these extreme parameters, and the assumption of a heavy Galactic disk and spheroid, the upper limit of the \m\ mass range to which ongoing experiments are sensitive is reduced from ${\cal O}(10^6)\,M_\odot$ to ${\cal O}(10)\,M_\odot$., Comment: 30 pages, Phyzzx file, figures not included. For hardcopy with figures contact BEST@IASSNS.BITNET. Inst. for Advanced Study no. AST 93/23

By analyzing the rotation of its central disk and outer polar ring, limits are placed on the flattening of the unseen halo of the galaxy NGC 4650A. A model consisting of a bulge, disk, axisymmetric dark halo, and massive polar ring is fitted to both rotation curves, and it is shown that the observations are consistent with a range of halo flattening, from spherical to as flat as an E8 elliptical galaxy. The best fits are obtained for dark halo flattenings in the range E3-E7. The substantial mass of the ring is probably responsible for a characteristic wiggle in the polar rotation curve; fits to this feature suggest that there may be considerably more mass in the ring than has been reported from neutral hydrogen measurements. 30 refs.