The unbiased frequency of planetary signatures around single and binary white dwarfs using Spitzer{\it Spitzer} and Hubble{\it Hubble}

This paper presents combined ${\it Spitzer}$ IRAC and ${\it Hubble}$ COS results for a double-blind survey of 195 single and 22 wide binary white dwarfs for infrared excesses and atmospheric metals. The selection criteria include cooling ages in the range 9 to 300 Myr, and hydrogen-rich atmospheres so that the presence of atmospheric metals can be confidently linked to ongoing accretion from a circumstellar disc. The entire sample has infrared photometry, whereas 168 targets have corresponding ultraviolet spectra. Three stars with infrared excesses due to debris discs are recovered, yielding a nominal frequency of $1.5_{-0.5}^{+1.5}$ per cent, while in stark contrast, the fraction of stars with atmospheric metals is $45\pm4$ per cent. Thus, only one out of 30 polluted white dwarfs exhibits an infrared excess at 3-4 $\mu$m in IRAC photometry, which reinforces the fact that atmospheric metal pollution is the most sensitive tracer of white dwarf planetary systems. The corresponding fraction of infrared excesses around white dwarfs with wide binary companions is consistent with zero, using both the infrared survey data and an independent assessment of potential binarity for well-established dusty and polluted stars. In contrast, the frequency of atmospheric pollution among the targets in wide binaries is indistinct from apparently single stars, and moreover the multiplicity of polluted white dwarfs in a complete and volume-limited sample is the same as for field stars. Therefore, it appears that the delivery of planetesimal material onto white dwarfs is ultimately not driven by stellar companions, but by the dynamics of planetary bodies.Comment: 15 pages, 6 figures, 3 tables; accepted for publication in MNRA

On The Formation, Evolution, And Destruction Of Minor Planetary Bodies

Minor planetary bodies can provide information on the history and future of planetary systems, from formation conditions in the Solar nebula to destruction processes of planets. Comets have long been heralded as pristine objects from the formation of the Solar System. Indeed, it is possible to infer the nature of the formation conditions of the Solar System by studying comets. In this thesis, an astrochemical model is used to derive potential initial Solar System conditions from Rosetta data. Importantly, there is a fundamental question not yet concretely answered: are the observed compositions indicative of formation conditions or evolutionary processes? Isomeric ratios can be useful as they may not vary since formation. However, recent results suggest that the water ortho-to-para ratio cannot be used to trace formation conditions, but may be used to probe cometary comae. This thesis presents Herschel observations of four comets and discusses how the observed non-typical water ortho-to-para ratios can help the understanding of evolutionary processes in comets. In addition to probing the Solar System, studying minor planetary bodies around white dwarfs can reveal the fate of these bodies. The evidence of white dwarf planetary systems have been known for a few decades and is inferred by atmospheric metals or circumstellar dust disks. By searching for destroyed planetesimals via these indicators, planetary system architectures, dynamics, and frequency can be inferred. A study of the largest, unbiased Spitzer and Hubble survey of white dwarfs to search for evidence of planetary systems is reported. Circumstellar disks have been thought of as static, however recent results have shown flux variations. In this thesis, a study of all white dwarfs debris disks using Spitzer and WISE data is detailed. Via observations over the longest baseline to date, it is possible to shed light on the destruction processes in these dynamical environments

Are there spurious temperature trends in the United States Climate Division database

The United States (U.S.) Climate Division data set is commonly used in applied climatic studies in the United States. The divisional averages are calculated by including all available stations within a division at any given time. The averages are therefore vulnerable to shifts in average station location or elevation over time, which may introduce spurious trends within these data. This paper examines temperature trends within the 15 climate divisions of New England, comparing the NCDC\u27s U.S. Divisional Data to the U.S. Historical Climate Network (USHCN) data. Correlation and multiple regression revealed that shifts in latitude, longitude, and elevation have affected the quality of the NCDC divisional data with respect to the USHCN. As a result, there may be issues with regard to their use in decadal- to century-scale climate change studies

Social media marketing in the hospitality industry : is it worth the effort?

This paper explores the impact of hotel social media activity on potential reservations and revenue generation. It does this by firstly exploring the perceptions of senior hotel executives towards the ROI of hotel social media activity. Secondly by data mining hotel reservation data to examine the extent of social media engagement being undertaken by guests with a hotel prior to and post a reservation being made. Thirdly through an experiment using social media advertising to examine its impact on the behaviour of fans and non-fans. The research suggests that social media engagement and advertising do have a positive impact on hotel reservations and revenue generation