Single site observations of \textit{TESS} single transit detections

Context: TESS has been successfully launched and has begin data acquisition. To expedite the science that may be performed with the resulting data it is necessary to gain a good understanding of planetary yields. Given the observing strategy employed by TESS the probability of detecting single transits in long period systems is increased. These systems require careful consideration. Aims: To simulate the number of TESS transit detections during its 2 year mission with a particular emphasis on single transits. Additionally, to determine the feasibility of ground-based follow-up observations from a single site. Methods: A distribution of planets is simulated around the $\sim$ 4 million stars in the TESS Candidate Target List. These planets are tested for detectable transits and characterised. Based on simulated parameters the single transit detections are further analysed to determine which are amenable to ground-based follow-up. Results: TESS will discover an approximate lower bound of 4700 planets with around 460 being single transits. A large fraction of these will be observable from a single ground-based site. This paper finds that, in a single year, approximately 1000 transit events of around 320 unique TESS single transit detections are theoretically observable. Conclusions: As we consider longer period exoplanets the need for exploring single transit detections increases. For periods $\gtrsim45$ days the number of single transit detections outnumber multitransits by a factor of 3 (82$\pm$18 and 25$\pm$7 respectively) a factor which only grows as longer period detections are considered. Therefore, it is worth expending the extra effort required to follow-up these more challenging, but potentially very rewarding, discoveries. Additionally, we conclude that a large fraction of these targets can be theoretically observed from just a single ground-based site.Comment: 12 pages, 19 figures. To be published in Astronomy and Astrophysic

An examination of the effect of the TESS extended mission on southern hemisphere monotransits

Context: NASA recently announced an extended mission for TESS. As a result it is expected that the southern ecliptic hemisphere will be re-observed approximately two years after the initial survey. Aims: We aim to explore how TESS re-observing the southern ecliptic hemisphere will impact the number and distribution of mono-transits discovered during the first year of observations. This simulation will be able to be scaled to any future TESS re-observations. Methods: We carry out an updated simulation of TESS detections in the southern ecliptic hemisphere. This simulation includes realistic Sector window-functions based on the first 11 sectors of SPOC 2 min SAP lightcurves. We then extend this simulation to cover the expected Year 4 of the mission when TESS will re-observed the southern ecliptic fields. For recovered monotransits we also look at the possibility of predicting the period based on the coverage in the TESS data. Results: We find an updated prediction of 339 monotransits from the TESS Year 1 southern ecliptic hemisphere, and that approximately 80% of these systems (266/339) will transit again in the Year 4 observations. The Year 4 observations will also contribute new monotransits not seen in Year 1, resulting in a total of 149 monotransits from the combined Year 1 and Year 4 data sets. We find that 75% (189/266) of recovered Year 1 monotransits will only transit once in the Year 4 data set. For these systems we will be able to constrain possible periods, but period aliasing due to the large time gap between Year 1 and Year 4 observations means that the true period will remain unknown with further spectroscopic or photometric follow-up.Comment: 6 pages, 6 figures. Version to be published Astronomy and Astrophysic

Simulation, detection and characterisation of monotransits from the TESS mission

The discovery of exoplanets is a key astrophysics goal. I begin in Chapter 3 with details of two new planets from the WASP survey; WASP-150b, a 1.1RJ hot Jupiter on a 5.6 day orbit, and WASP-176b, a 1.5RJ hot Jupiter on a 3.9 day orbit. The exploration of longer period systems, such as those more similar to Earth, requires more effort. One method, explored extensively in this thesis is the use of monotransits. In Chapters 4 and 5 I describe simulations to predict the yield of monotransiting systems from TESS. The results indicate a significant number of detections, on the order of several hundred per hemisphere, with a key result being that monotransits outnumber multitransits for periods ≥ 30 days. The use of multiple instruments to characterise exoplanet systems is common practise and in Chapter 6 I explore using CHEOPS to follow-up monotransits identified in TESS. I show that CHEOPS could follow-up 90% of the monotransits and would observe additional transits for the majority. Monotransits, and exoplanets in general, are usually followed-up with a combination of photometry and spectroscopy. In Chapter 7 I examine the idea of using these two methods to follow-up poorly constrained exoplanet systems in a general manner. I show that photometry and spectroscopy are each preferred for different regions of exoplanet parameter space. Chapter 8 extends the TESS monotransit simulations and explores using follow-up on the recurring systems. I show that ∼400 planets will transit once in each of the primary and extended TESS missions but each has an average of 38 period aliases. I show that photometric and spectroscopic observations are both capable of resolving these aliases. Finally, Chapter 9, details the efforts of the NGTS monotransit working group to identify monotransits in the TESS data and characterise them using follow-up techniques. I describe the methods used and some of the key results including NGTS-11b

Simulated recovery of LEO objects using sCMOS blind stacking

We present the methodology and results of a simulation to determine the recoverability of LEO objects using a blind stacking technique. The method utilises sCMOS and GPU technology to inject and recover LEO objects in real observed data. We explore the target recovery fraction and pipeline run-time as a function of three optimisation parameters; number of frames per data-set, exposure time, and binning factor. Results are presented as a function of magnitude and velocity. We find that target recovery using blind stacking is significantly more complete, and can reach fainter magnitudes, than using individual frames alone. We present results showing that, depending on the combination of optimisation parameters, recovery fraction is up to 90% of detectable targets for magnitudes up to 13.5, and then falls off steadily up to a magnitude limit around 14.5. Run-time is shown to be a few multiples of the observing time for the best combinations of optimisation parameters, approaching real-time processing.Comment: 14 pages, 14 figures. Accepted for publication in Advances in Space Research (ASR

Simulated recovery of LEO objects using sCMOS blind stacking

We present the methodology and results of a simulation to determine the recoverability of LEO objects using a blind stacking technique. The method utilises sCMOS and GPU technology to inject and recover LEO objects in real observed data. We explore the target recovery fraction and pipeline run-time as a function of three optimisation parameters; number of frames per data-set, exposure time, and binning factor. Results are presented as a function of magnitude and velocity. We find that target recovery using blind stacking is significantly more complete, and can reach fainter magnitudes, than using individual frames alone. We present results showing that, depending on the combination of optimisation parameters, recovery fraction is up to 90% of detectable targets for magnitudes up to 13.5, and then falls off steadily up to a magnitude limit around 14.5. Run-time is shown to be a few multiples of the observing time for the best combinations of optimisation parameters, approaching real-time processing

Elicited preferences for components of ocean health in the California Current

As resource management efforts move towards more comprehensive approaches that spin multiple sectors and stakeholder groups, decision makers are faced with the challenge of deciding how important each group is, and how much weight their concerns should have, when making decisions. These decisions must be made transparently if they are to have credibility. This paper describes a systematic approach to eliciting such preferences, illustrated through a regional application of the Ocean Health Index in the California Current. The Index provides an ideal case study as it includes a comprehensive set of goals designed to-assess the benefits people derive from coasts and oceans. The approach leverages the strengths of two different methods for eliciting preferences, one based on random utility theory and the other on analytical deliberative methodologies. Results showed that the methods were accessible to individuals with diverse backgrounds and, in this case, revealed surprising consensus about fundamental values that may have been missed in deliberations around a specific action, rather than evaluating a spectrum of management priorities. Specifically, individuals, even extractive users, assigned higher weights to cultural and conservation goals compared to extractive ones. The approach offers a general procedure for eliciting explicit preferences through constructive deliberations among diverse stakeholders. (C) 2013 Elsevier-Ltd. All rights reserved.Keywords: Probabilistic inversion, Ecosystem-based management, Deliberative analytical, Marine spatial planning, Expert judgmen

The masses of retired A stars with asteroseismology::Kepler and K2 observations of exoplanet hosts

We investigate the masses of "retired A stars" using asteroseismic detections on seven low-luminosity red-giant and sub-giant stars observed by the NASA Kepler and K2 Missions. Our aim is to explore whether masses derived from spectroscopy and isochrone fitting may have been systematically overestimated. Our targets have all previously been subject to long term radial velocity observations to detect orbiting bodies, and satisfy the criteria used by Johnson et al. (2006) to select survey stars that may have had A-type (or early F-type) main-sequence progenitors. The sample actually spans a somewhat wider range in mass, from $\approx 1\,\rm M_{\odot}$ up to $\approx 1.7\,\rm M_{\odot}$. Whilst for five of the seven stars the reported discovery mass from spectroscopy exceeds the mass estimated using asteroseismology, there is no strong evidence for a significant, systematic bias across the sample. Moreover, comparisons with other masses from the literature show that the absolute scale of any differences is highly sensitive to the chosen reference literature mass, with the scatter between different literature masses significantly larger than reported error bars. We find that any mass difference can be explained through use of differing constraints during the recovery process. We also conclude that underestimated uncertainties on the input parameters can significantly bias the recovered stellar masses, which may have contributed to the controversy on the mass scale for retired A stars.Comment: Accepted MNRAS, 14 pages, 7 Figures, 3 Table