We demonstrate a path to hitherto unachievable differential photometric precisions from the ground, both in the optical and near-infrared (NIR), using custom-fabricated beam-shaping diffusers produced using specialized nanofabrication techniques. Such diffusers mold the focal plane image of a star into a broad and stable top-hat shape, minimizing photometric errors due to non-uniform pixel response, atmospheric seeing effects, imperfect guiding, and telescope-induced variable aberrations seen in defocusing. This PSF reshaping significantly increases the achievable dynamic range of our observations, increasing our observing efficiency and thus better averages over scintillation. Diffusers work in both collimated and converging beams. We present diffuser-assisted optical observations demonstrating -+ 62 16 26 ppm precision in 30minute bins on a nearby bright star 16 Cygni A (V = 5.95) using the ARC 3.5 m telescope-within a factor of ∼2 of Keplerʼs photometric precision on the same star. We also show a transit of WASP-85-Ab (V = 11.2) and TRES-3b (V = 12.4), where the residuals bin down to -+ 180 41 66 ppm in 30minute bins for WASP-85-Ab-a factor of ∼4 of the precision achieved by the K2 mission on this targetand to 101 ppm for TRES-3b. In the NIR, where diffusers may provide even more significant improvements over the current state of the art, our preliminary tests demonstrated -+ 3664 ppm precision for a K S =10.8 star on the 200 inchHale Telescope. These photometric precisions match or surpass the expected photometric precisions of TESS for the same magnitude range. This technology is inexpensive, scalable, easily adaptable, and can have an important and immediate impact on the observations of transits and secondary eclipses of exoplanets.

We report on the results of a spectroscopic survey of 130 comets that was conducted at McDonald observatory from 1980 through 2008. Some of the comets were observed on only one night, while others were observed repeatedly. For 20 of these comets, no molecules were detected. For the remaining 110 comets, some emission from CN, OH, NH, C 3 , C 2 , CH, and NH 2 molecules were observed on at least one occasion. We converted the observed molecular column densities to production rates using a Haser (1957) model. We defined a restricted data set of comets that had at least 3 nights of observations. The restricted data set consists of 59 comets. We used ratios of production rates to study the trends in the data. We find two classes of comets: typical and carbon-chain depleted comets. Using a very strict definition of depleted comets, requiring C 2 and C 3 to both be depleted, we find 9% of our restricted data set comets to be depleted. Using a more relaxed definition that requires only C 2 to be below a threshold (similar to other researchers), we find 25% of the comets are depleted. Two-thirds of the depleted comets are Jupiter Family comets, while one-third are Long Period comets. 37% of the Jupiter Family comets are depleted, while 18.5% of the Long Period comets are depleted. We compare our results with other studies and find good agreement. marked difference being the amount of continuum present. This simple observation leads to the question of whether all comets share the same composition or if there are comets with fundamentally different compositions. If differences are seen, then an additional question of the origin of the differences would be raised: are differences the result of different formational scenarios or different evolutionary scenarios? These

We conducted a VLA survey of nine magnetic cataclysmic variable stars (MCVs) at 8.436 GHz in 2003 October, to constrain models of radio emission. A follow-up study was conducted in 2004 September. We obtained the first radio detections of AR UMa, the MCV with the highest known magnetic field (230 MG), at flux densities of 0.422 AE 0.060 mJy (2003 October 16) and 0.734 AE 0.095 mJy (2004 September 4). We have completed the sample of radio observations of MCVs out to 100 pc. Surprisingly, the only radio-selected CV, FIRST J1023þ0038, was not detected. An upper limit of 0.20 mJy (4 ) was obtained. The original radio MCV, AM Her, was detected with a flux density of 0.586 AE 0.074 mJy (2003 October 17), consistent with previous observations. Typical (4 ) upper limits of 0.12 mJy were obtained for other targets. The lack of radio emission from isolated magnetic white dwarfs, as well as from nonmagnetic CVs (outside of outburst), places constraints on radio emission mechanisms for CVs. We suggest that accretion disks may preclude radio emission. Also, since we detect radio emission from AM Her in a low state and the pre-CV V471 Tau is a persistent radio source, accretion is not a necessary condition. A secondary with a kilogauss magnetic field might be necessary. We argue that the emission from AR UMa originates near the secondary. AR UMa joins AM Her and AE Aqr as the only confirmed persistent radio MCVs, and we suggest avenues of further study.

Prompted by peculiar spectroscopic variability observed in SDSS/APOGEE H-band spectra, we monitored the Be star HD 55606 using optical spectroscopy and found that it is an exotic double-lined spectroscopic binary (SB2) consisting of a Be star and a hot, compact companion that is probably an OB subdwarf (sdOB) star. Motion of the sdOB star is traced by its impact on the strong He i lines, observed as radial velocity (V r ) variable, double-peaked emission profiles with narrow central absorption cores. Weak He ii 4686Å absorption associated with the companion star is detected in most spectra. Use of the emission peaks of low-ionization emission lines to trace the Be star V r and the He i lines to trace the companion star V r yields a circular orbital solution with a 93.8-day period and masses of M Be = 6.2 M ⊙ and M sdOB = 0.9 M ⊙ in the case of i = 80 • . HD 55606 exhibits a variety of phase-locked variability, including the development of shell lines twice per orbit. The shell phases coincide with variation in the double emission peak separations, and both forms of variability are likely caused by a two-armed spiral density perturbation in the Be disk. The intensity ratios of the double emission peaks are also phase-locked, possibly indicating heating by the sdOB star of the side of the Be disk facing it. HD 55606 is a new member of the growing sample of Be+sdOB binaries, in which the Be star's rapid rotation and ability to form a disk can be attributed to past mass transfer. * Based on observations obtained with the Apache Point Observatory 3.5-meter telescope, which is owned and operated by the Astrophysical Research Consortium. Chojnowski