2,252 research outputs found

    A Revised Exoplanet Yield from the Transiting Exoplanet Survey Satellite (TESS)

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    The Transiting Exoplanet Survey Satellite (TESS) has a goal of detecting small planets orbiting stars bright enough for mass determination via ground-based radial velocity observations. Here we present estimates of how many exoplanets the TESS mission will detect, physical properties of the detected planets, and the properties of the stars that those planets orbit. This work uses stars drawn from the TESS Input Catalog Candidate Target List and revises yields from prior studies that were based on Galactic models. We modeled the TESS observing strategy to select approximately 200,000 stars at 2-minute cadence, while the remaining stars are observed at 30-min cadence in full-frame image data. We placed zero or more planets in orbit around each star, with physical properties following measured exoplanet occurrence rates, and used the TESS noise model to predict the derived properties of the detected exoplanets. In the TESS 2-minute cadence mode we estimate that TESS will find 1250+/-70 exoplanets (90% confidence), including 250 smaller than 2 Earth-radii. Furthermore, we predict an additional 3100 planets will be found in full-frame image data orbiting bright dwarf stars and more than 10,000 around fainter stars. We predict that TESS will find 500 planets orbiting M-dwarfs, but the majority of planets will orbit stars larger than the Sun. Our simulated sample of planets contains hundreds of small planets amenable to radial velocity follow-up, potentially more than tripling the number of planets smaller than 4 Earth-radii with mass measurements. This sample of simulated planets is available for use in planning follow-up observations and analyses.Comment: Accepted for publication in ApJS. Table 2 is available in machine-readable format from https://doi.org/10.6084/m9.figshare.613767

    Searching for Variable Sources in the Rapid Temporal Survey

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    The Rapid Temporal Survey explores the faint, variable sky. I have led the development of the data reduction and analysis pipeline for this survey and have played a leading role in the observation and analysis of follow-up data. The survey and follow-up work is presented in this thesis. The strategy of the survey is to observe fields close to the Galactic plane at a cadence of ~1 min for around two hours down to a depth of g' = 23 The data presented in this thesis cover 31 square degrees of which 16 are within 10^o of the Galactic plane. This is the first dedicated survey to explore this parameter space and such I have had to develop new techniques when dealing with the data. The photometry was performed using a difference imaging technique and resulted in over 3 × 10^6 light curves. This work primarily deals with periodic variability and with this aim I have developed a method which combines two algorithms (Lomb-Scargle and Analysis of Variance) to produce a sub-set of variable sources which contains a very low number of false positives –around 600 out of 1.2 × 10^5 detected variables. For sources brighter than g' = 21 this technique is able to detect – at a confidence above 90 per cent – variability on time-scales of less than 10 min to tens of minutes in source with semi-amplitudes of less than 0.04 mag. Spectroscopic follow-up observations of a number of these targets have been performed and have resulted in the discovery of many different variables from several different classes. I highlight three populations to study in more detail: short-period, variable A-stars; SX Phe and /delta Scuti stars; and pulsating white dwarfs. Of particular interest are the SX Phe stars which I have found to be as far away as 30 kpc from us. I also provide a detailed examination of two variables sources: one is a dwarf nova which was discovered through quasi-periodic oscillations in quiescence, the other a pulsating white dwarf which appears to have a hot companion. I conclude by looking to the future of the project which will continue with a similar strategy but surveying the Kepler field of view

    Topics in perturbation theory

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    In providing a means of progressively improving an initial estimate, perturbation series have become a ubiquitous tool in modern physics. However, and mainly because this stepwise process of improvement rapidly becomes increasingly involved, surprisingly little is known about the formal properties of the series obtained. This thesis therefore investigates some aspects of these properties and how they effect the application of these techniques, with an emphasis on quantum field theory and the phenomenology of e+e(^-) colliders. One of the better understood examples of a perturbative series is the WKB one which is widely used to approximate the energy levels of quantum mechanical systems. Recently much interest has centred on a modification of this, the SWKB series. Apart from (possibly) offering an improvement on the original, this is intrinsically interesting in being related to the supersymmetry of field theory. Furthermore, as Chapter 1 explains, there is a close connection between the cases where the initial estimate requires no correction and an important set of quantum mechanical problems (the "shape invariant" ones) which can be solved elegantly and completely. The situation in field theory is more complicated, not least because the series for any particular problem is no longer unique. While this presents few theoretical difficulties, it has serious consequences when attempts are made to compare predictions with experiment. This obstacle is particularly severe in Quantum Chromodynamics and its fundamental constant (A(_QCD)) is therefore only roughly known at present. It will be argued that current responses to this are all imperfect, but that tests of the theory can be envisaged that circumvent the problem. This leads into questions concerning the origin of the divergences in the perturbation series - for although it may initially provide usefully improved estimates, the series probably breaks down eventually. Existing arguments about this topic are critically reviewed - and in one case substantially simplified - before an alternative one is proposed in some detail. By concentrating on a particularly restricted situation, the Common Effective Charge Approach simplifies matters to the extent that issues such as non-analyticity of functions and the potential accuracy of perturbative techniques in realistic applications can be conveniently investigated

    NASA/DoD Aerospace Knowledge Diffusion Research Project. Paper 29: The US government technical report and the transfer of federally funded aerospace R and D

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    This article discusses the U.S. government technical report and the transfer of federally funded aerospace research and development in a conceptual framework of the federal government as a producer of scientific and technical information. The article summarizes current literature and research and discusses U.S. government technical report use and the importance of using data obtained from the NASA/DoD Aerospace Knowledge Diffusion Research Project. The authors make a case for changing existing U.S. technology policy and present a research agenda for the U.S. government technical report
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