Identification and Removal of Noise Modes in Kepler Photometry

We present the Transiting Exoearth Robust Reduction Algorithm (TERRA) --- a novel framework for identifying and removing instrumental noise in Kepler photometry. We identify instrumental noise modes by finding common trends in a large ensemble of light curves drawn from the entire Kepler field of view. Strategically, these noise modes can be optimized to reveal transits having a specified range of timescales. For Kepler target stars of low photometric noise, TERRA produces ensemble-calibrated photometry having 33 ppm RMS scatter in 12-hour bins, rendering individual transits of earth-size planets around sun-like stars detectable as ~3 sigma signals.Comment: 18 pages, 7 figures, submitted to PAS

Further evidence for the planet around 51 Pegasi

The discovery of the planet around the solar-type star 51 Pegasi marked a watershed in the search for extrasolar planets. Since then seven other solar-type stars have been discovered, of which several have surprisingly short orbital periods, like the planet around 51 Peg. These planets were detected using the indirect technique of measuring variations in the Doppler shifts of lines in the spectra of the primary stars. But it is possible that oscillations of the stars themselves (or other effects) could mimic the signature of the planets, particularly around the short-period planets. The apparent lack of spectral and brightness variations, however, led to widespread acceptance that there is a planet around 51 Peg. This conclusion was challenged by the observation of systematic variations in the line profile shapes of 51 Peg, which suggested stellar oscillations. If these observations are correct, then there is no need to invoke a planet around 51 Peg to explain the data. Here we report observations of 51 Peg at a much higher spectral resolution than those in ref.9, in which we find no evidence for systematic changes in the line shapes. The data are most consistent with a planetary companion to 51 Peg.Comment: LaTeX, 6 pages, 2 figures. To appear in 8 January 1998 issue of Natur

Identification of Ancient Feather Fragments Found in Melting Alpine Ice Patches in Southern Yukon

Twelve ancient artifacts or fragmented feather samples recovered from melting alpine ice patches in southern Yukon were analyzed in order to identify the species of birds associated with the ice patches or used on weapons recovered from these sites. The identification of bird species used by ancient hunters as long ago as 4500 BP enhances our insight into the customs, culture, and sophistication of life at that time. Downy feather barbs were found on two samples and microscopically identified as duck (Anatidae) and falcon (Falconidae). Further examination and comparisons using museum specimens resulted in a total of six identifications: Anatidae, eagle (Aquila or Haliaeetus), gyrfalcon (Falco rusticolus), white-tailed ptarmigan (Lagopus leucurus), short-eared owl (Asio flammeus), and northern flicker (Colaptes auratus luteus). Three of the feather samples were complete enough to show apparent modification, or notching, along the feather shaft. The identification of non-game birds such as gyrfalcon and eagles, together with evidence of possible worked or notched feathers, indicates that as long as 4500 years ago, Subarctic hunters selected feathers not only for their utility in fletching, but also possibly for symbolic or decorative purposes.On a analysé 12 anciens artefacts ou échantillons de fragments de plumes découverts dans le sud du Yukon lors de la fonte de plaques de glace alpine, afin d’identifier les espèces aviaires associées à ces plaques de glace ou utilisées sur les armes provenant de ces sites. L’identification des espèces aviaires utilisées par les anciens chasseurs à une époque aussi reculée que 4500 BP nous permet de mieux comprendre les coutumes, la culture et le degré de sophistication de la vie à cette époque. On a trouvé des barbes duveteuses sur deux échantillons et l’analyse au microscope a révélé qu’elles appartenaient à un canard (anatidé) et à un faucon (falconidé). Un examen plus poussé et des comparaisons avec des spécimens présents dans des musées ont permis d’établir six provenances: anatidé, aigle (Aquila ou Haliaeetus), faucon gerfaut (Falco rusticolus), lagopède à queue blanche (Lagopus leucurus), hibou des marais (Asio flammeus) et pic flamboyant (Colaptes auratus luteus). Trois des échantillons de plumes étaient assez complets pour révéler des modifications apparentes ou encoches, le long de la tige de la plume. L’identification d’oiseaux non cynégétiques tels que le faucon gerfaut et les aigles, combinée avec la découverte de plumes encochées ou éventuellement travaillées, révèle qu’il y a 4500 ans, les chasseurs subarctiques sélectionnaient déjà les plumes non seulement dans un but utilitaire pour en faire des empennes de flèches, mais peut-être aussi à des fins symboliques ou d’ornementation

Star Spot Induced Radial Velocity Variability in LkCa 19

We describe a new radial velocity survey of T Tauri stars and present the first results. Our search is motivated by an interest in detecting massive young planets, as well as investigating the origin of the brown dwarf desert. As part of this survey, we discovered large-amplitude, periodic, radial velocity variations in the spectrum of the weak line T Tauri star LkCa 19. Using line bisector analysis and a new simulation of the effect of star spots on the photometric and radial velocity variability of T Tauri stars, we show that our measured radial velocities for LkCa19 are fully consistent with variations caused by the presence of large star spots on this rapidly rotating young star. These results illustrate the level of activity-induced radial velocity noise associated with at least some very young stars. This activity-induced noise will set lower limits on the mass of a companion detectable around LkCa 19, and similarly active young stars.Comment: ApJ accepted, 27 pages, 12 figures, aaste

“The Power of Self-Motion in Cavendish’s Nature”

Nature, according to Cavendish, has “an Infinite Natural power, that is, a power to produce infinite effects in her own self, by infinite changes of Motions.” While Cavendish mentions powers with respect to human beings, medicines, occasional causes, and other entities, these powers are really just the power of self-moving matter to cause changes in the world. This chapter examines why Cavendish attributes the power of self-motion to matter, what this power is, how it arose, how it is enacted, and its limitations. In doing so, it discusses her views on causation, perception, and motion, and argues that motion is not reducible to change in mereological facts

A Molecular Assessment of Speciation and Evolutionary History of the Globally Distributed Spotted Eagle Ray (Aetobatus narinari)

The spotted eagle ray (Aetobatus narinari), a species of conservation concern (Near Threatened IUCN category) is commonly associated with coral reef ecosystems worldwide where it is likely to play an important predatory role. Currently described as a single, circumglobally distributed species, geographic differences in parasite diversity have led to suggestions that A. narinari may constitute a species complex. There has been no systematic evidence to support this suggestion, however. If multiple species of spotted eagle ray exist, each will likely posses decreased geographic ranges and population sizes, altering the impacts of threats and requiring separate assessments of conservation needs. We assessed the validity of A. narinari as a single cosmopolitan species using 1570bp of sequence data from two mitochondrial genes (cytochrome b and COI) and the nuclear ribosomal ITS2 locus. Individuals from four major geographic regions were examined: western north Atlantic, and western, central, and eastern Pacific. Phylogenies for each locus concordantly described three distinct lineages (western north Atlantic, western/central Pacific, and eastern Pacific) with no genetic exchange among regions. Genetic distances among the most divergent lineages were comparable to taxonomically uncontroversial batoid and teleost congener pairs. Using combined genealogical concordance and genetic distance results, we recommend 1) that the western/central Pacific lineage be recognized as a distinct species from the western north Atlantic and eastern Pacific lineages, and 2) the western north Atlantic and eastern Pacific lineages, separated by the Isthmus of Panama, be given subspecies status. Dramatically higher nucleotide diversity and sequence divergence coupled with a basal position in multiple phylogenetic analyses support an Indo-West Pacific origin for the A. narinari species complex, with subsequent migration into the Atlantic. Evolutionary relationships among lineages suggest a westerly migration around the southern tip of Africa, with intensification of the Benguela coldwater upwelling system a possible vicariant mechanism underlying speciation

Ca II H and K Chromospheric Emission Lines in Late K and M Dwarfs

We have measured the profiles of the Ca II H and K chromospheric emission lines in 147 main sequence stars of spectral type M5-K7 (0.30-0.55 solar masses) using multiple high resolution spectra obtained during six years with the HIRES spectrometer on the Keck 1 telescope. Remarkably, the average FWHM, equivalent widths, and line luminosities of Ca II H and K increase by a factor of 3 with increasing stellar mass over this small range of stellar masses. We fit the H and K lines with a double Gaussian model to represent both the chromospheric emission and the non-LTE central absorption. Most of the sample stars display a central absorption that is typically redshifted by ~0.1 km/s relative to the emission, but the nature of this velocity gradient remains unknown. The FWHM of the H and K lines increase with stellar luminosity, reminiscent of the Wilson-Bappu effect in FGK-type stars. Both the equivalent widths and FWHM exhibit modest temporal variability in individual stars. At a given value of M_v, stars exhibit a spread in both the equivalent width and FWHM of Ca II H and K, due both to a spread in fundamental stellar parameters including rotation rate, age, and possibly metallicity, and to the spread in stellar mass at a given M_v. The K line is consistently wider than the H line, as expected, and its central absorption is more redshifted, indicating that the H and K lines form at slightly different heights in the chromosphere where the velocities are slightly different. The equivalent width of H-alpha correlates with Ca II H and K only for stars having Ca II equivalent widths above ~2 angstroms, suggesting the existence of a magnetic threshold above which the lower and upper chromospheres become thermally coupled.Comment: 40 pages including 12 figures and 17 pages of tables, accepted for publication in PAS