[en] We present transit photometry of three exoplanets, TrES-4b, HAT-P-3b, and WASP-12b, allowing for refined estimates of the systems' parameters. TrES-4b and WASP-12b were confirmed to be 'bloated' planets, with radii of 1.706 ± 0.056R_Jup and 1.736 ± 0.092R_Jup, respectively. These planets are too large to be explained with standard models of gas giant planets. In contrast, HAT-P-3b has a radius of 0.827 ± 0.055R_Jup, smaller than a pure hydrogen-helium planet and indicative of a highly metal-enriched composition. Analyses of the transit timings revealed no significant departures from strict periodicity. For TrES-4, our relatively recent observations allow for improvement in the orbital ephemerides, which is useful for planning future observations.

[en] We present the spectroscopic orbit of LHS 1610A, a newly discovered single-lined spectroscopic binary with a trigonometric distance placing it at 9.9 ± 0.2 pc. We obtained spectra with the TRES instrument on the 1.5 m Tillinghast Reflector at the Fred Lawrence Whipple Observatory located on Mt. Hopkins in AZ. We demonstrate the use of the TiO molecular bands at 7065–7165 Å to measure radial velocities and achieve an average estimated velocity uncertainty of 28 m s⁻¹. We measure the orbital period to be 10.6 days and calculate a minimum mass of 44.8 ± 3.2 M _Jup for the secondary, indicating that it is likely a brown dwarf. We place an upper limit to 3σ of 2500 K on the effective temperature of the companion from infrared spectroscopic observations using IGRINS on the 4.3 m Discovery Channel Telescope. In addition, we present a new photometric rotation period of 84.3 days for the primary star using data from the MEarth-South Observatory, with which we show that the system does not eclipse.

[en] We present multi-band optical photometry of 94 spectroscopically confirmed Type Ia supernovae (SNe Ia) in the redshift range 0.0055-0.073, obtained between 2006 and 2011. There are a total of 5522 light-curve points. We show that our natural-system SN photometry has a precision of ∼< 0.03 mag in BVr'i', ∼< 0.06 mag in u', and ∼< 0.07 mag in U for points brighter than 17.5 mag and estimate that it has a systematic uncertainty of 0.014, 0.010, 0.012, 0.014, 0.046, and 0.073 mag in BVr'i'u'U, respectively. Comparisons of our standard-system photometry with published SN Ia light curves and comparison stars reveal mean agreement across samples in the range of ∼0.00-0.03 mag. We discuss the recent measurements of our telescope-plus-detector throughput by direct monochromatic illumination by Cramer et al. This technique measures the whole optical path through the telescope, auxiliary optics, filters, and detector under the same conditions used to make SN measurements. Extremely well characterized natural-system passbands (both in wavelength and over time) are crucial for the next generation of SN Ia photometry to reach the 0.01 mag accuracy level. The current sample of low-z SNe Ia is now sufficiently large to remove most of the statistical sampling error from the dark-energy error budget. But pursuing the dark-energy systematic errors by determining highly accurate detector passbands, combining optical and near-infrared (NIR) photometry and spectra, using the nearby sample to illuminate the population properties of SNe Ia, and measuring the local departures from the Hubble flow will benefit from larger, carefully measured nearby samples.

[en] We present photometric and spectroscopic observations of the 2009 February 2 transit of the exoplanet XO-3b. The new data show that the planetary orbital axis and stellar rotation axis are misaligned, as reported earlier by Hebrard and coworkers. We find the angle between the sky projections of the two axes to be 37.3 ± 3.7 deg., as compared to the previously reported value of 70 ± 15 deg. The significance of this discrepancy is unclear because there are indications of systematic effects. XO-3b is the first exoplanet known to have a highly inclined orbit relative to the equatorial plane of its parent star, and as such it may fulfill the predictions of some scenarios for the migration of massive planets into close-in orbits. We revisit the statistical analysis of spin-orbit alignment in hot-Jupiter systems. Assuming the stellar obliquities to be drawn from a single Rayleigh distribution, we find the mode of the distribution to be 13⁺⁵_-2 deg. However, it remains the case that a model representing two different migration channels-in which some planets are drawn from a perfectly aligned distribution and the rest are drawn from an isotropic distribution-is favored over a single Rayleigh distribution.