Utilising Galactic Archaeology Surveys for Exoplanetary Science

During the last decade, a wealth of new large-scale surveys have come online across the world. These huge spectral, astrometric and photometric surveys are providing astronomers with the richest datasets to date, to better characterise stars contained within the Milky Way like never before. Not only are these resources used to better understand the formation and evolution of our Galaxy and the stars contained within it, but these surveys can also be used to better understand the exoplanets found within the Milky Way. More planets are now being discovered in our galaxy, thanks largely to NASA’s new exoplanetary mission, the Transiting Exoplanet Survey Satellite (TESS). TESS has been operating since 2018, with an unprecedented number of stars being observed to monitor transit signals of exoplanets around nearby stars. My thesis firstly cross-matched spectroscopic, photometric, and astrometric data from GALAH Data Release 2, the TESS Input Catalog and Gaia Data Release 2, to create a curated, self-consistent catalog of physical and chemical properties for 47,285 stars, known as the GALAH-TESS catalog. Using these data, this thesis has derived isochrone masses and radii that are precise to within 5%. These masses and radii have then helped redetermine the physical properties of known and candidate exoplanets, casting doubt on the exoplanetary nature of at least three candidate systems discovered by TESS. The GALAH-TESS catalog contains abundances for up to 23 elements that specifically contains the abundance ratios for C/O, Mg/Si, Fe/Si and Fe/Mg, to assist in determining the composition and structure of planets with Rp < 4R⊕. From these ratios, 36 % fall within 2 sigma of the Sun/Earth values, suggesting that these stars may i host rocky exoplanets with geological compositions similar to planets found within our own Solar system. With GALAH releasing DR3, to include the K2 fields and the Southern TESS continuous viewing zone, and Gaia releasing EDR3, my thesis then focused on improving the characteristics of known and candidate exoplanets and their host stars. This thesis not only revises the physical properties for hundreds of confirmed and candidate exoplanets, but it has also decreased the uncertainties for some of these derived properties too. It was able to improve the parameters for five ultra-short period exoplanets, in particular, refining the radius and mass of three to their most precise values yet, to less than 2.3% and 8.5% uncertainty respectively. The radius estimate for CoRoT-7 b further suggests that it is large enough for an atmosphere to contribute to its overall radius. It also uncovered that Ultra-Hot Neptunes are more likely to be found around thick-disc stars rather than their thin-disc counterparts. Finally, my thesis presents the discovery of a hot-Jupiter orbiting a rapidly rotating (vsin (i) = 28 km s-1) early F dwarf HD 115447 (TOI-778). Combining the transit signal taken from Sector 10 of TESS’s initial detection of the exoplanet, this thesis also uses ground-based photometry, along with radial velocity measurements taken from Minerva-Australis, TRES, CORALIE and CHIRON to confirm and characterise TOI-778 b. A spectroscopic transit of TOI-778 b was taking to derive its spinorbit angle of 19.1±9.6 degrees, consistent with an aligned planetary system

Truly eccentric - I. Revisiting eight single-eccentric planetary systems

We examine eight known single-eccentric planetary systems in light of recently released large data archives and new analysis techniques. For four of these systems (HD 7449, HD 65216, HD 89744, HD 92788) we find evidence for additional long-period companions. HD 65216c is a Jupiter analogue, with a period of 14.7 yr, e = 0.18, and m sin i of 2MJup, while the remaining candidate companions move on as- yet-incomplete orbits. Our results highlight the importance of revisiting the analysis of known exoplanetary systems when new data become available, particularly given the possibility that poorly sampled data might previously have led to the detection of a `false-positive' single-eccentric planet, when the system in question actually contains two (or more) planets on near-circular orbits

Human language reveals a universal positivity bias

Using human evaluation of 100,000 words spread across 24 corpora in 10 languages diverse in origin and culture, we present evidence of a deep imprint of human sociality in language, observing that (i ) the words of natural human language possess a universal positivity bias, (ii ) the estimated emotional content of words is consistent between languages under translation, and (iii ) this positivity bias is strongly independent of frequency of word use. Alongside these general regularities, we describe interlanguage variations in the emotional spectrum of languages that allow us to rank corpora. We also show how our word evaluations can be used to construct physical-like instruments for both real-time and offline measurement of the emotional content of large-scale texts

Reply to Garcia et al.: Common mistakes in measuring frequency-dependent word characteristics

We demonstrate that the concerns expressed by Garcia et al. are misplaced, due to (1) a misreading of our findings in [1]; (2) a widespread failure to examine and present words in support of asserted summary quantities based on word usage frequencies; and (3) a range of misconceptions about word usage frequency, word rank, and expert-constructed word lists. In particular, we show that the English component of our study compares well statistically with two related surveys, that no survey design influence is apparent, and that estimates of measurement error do not explain the positivity biases reported in our work and that of others. We further demonstrate that for the frequency dependence of positivity---of which we explored the nuances in great detail in [1]---Garcia et al. did not perform a reanalysis of our data---they instead carried out an analysis of a different, statistically improper data set and introduced a nonlinearity before performing linear regression.Comment: 5 pages, 2 figures, 1 table. Expanded version of reply appearing in PNAS 201

Recreating the OSIRIS-REx Slingshot Manoeuvre from a Network of Ground-Based Sensors

Optical tracking systems typically trade-off between astrometric precision and field-of-view. In this work, we showcase a networked approach to optical tracking using very wide field-of-view imagers that have relatively low astrometric precision on the scheduled OSIRIS-REx slingshot manoeuvre around Earth on September 22nd, 2017. As part of a trajectory designed to get OSIRIS-REx to NEO 101955 Bennu, this flyby event was viewed from 13 remote sensors spread across Australia and New Zealand to promote triangulatable observations. Each observatory in this portable network was constructed to be as lightweight and portable as possible, with hardware based off the successful design of the Desert Fireball Network. Over a 4 hour collection window, we gathered 15,439 images of the night sky in the predicted direction of the OSIRIS-REx spacecraft. Using a specially developed streak detection and orbit determination data pipeline, we detected 2,090 line-of-sight observations. Our fitted orbit was determined to be within about 10~km of orbital telemetry along the observed 109,262~km length of OSIRIS-REx trajectory, and thus demonstrating the impressive capability of a networked approach to SSA

An analysis of baseline data from the PROUD study: an open-label randomised trial of pre-exposure prophylaxis

Background: Pre-exposure prophylaxis (PrEP) has proven biological efficacy to reduce the sexual acquisition of the human immunodeficiency virus (HIV). The PROUD study found that PrEP conferred higher protection than in placebo-controlled trials, reducing HIV incidence by 86 % in a population with seven-fold higher HIV incidence than expected. We present the baseline characteristics of the PROUD study population and place the findings in the context of national sexual health clinic data. Methods: The PROUD study was designed to explore the real-world effectiveness of PrEP (tenofovir-emtricitabine) by randomising HIV-negative gay and other men who have sex with men (GMSM) to receive open-label PrEP immediately or after a deferral period of 12 months. At enrolment, participants self-completed two baseline questionnaires collecting information on demographics, sexual behaviour and lifestyle in the last 30 and 90 days. These data were compared to data from HIV-negative GMSM attending sexual health clinics in 2013, collated by Public Health England using the genitourinary medicine clinic activity database (GUMCAD). Results: The median age of participants was 35 (IQR: 29–43). Typically participants were white (81 %), educated at a university level (61 %) and in full-time employment (72 %). Of all participants, 217 (40 %) were born outside the UK. A sexually transmitted infection (STI) was reported to have been diagnosed in the previous 12 months in 330/515 (64 %) and 473/544 (87 %) participants reported ever having being diagnosed with an STI. At enrolment, 47/280 (17 %) participants were diagnosed with an STI. Participants reported a median (IQR) of 10 (5–20) partners in the last 90 days, a median (IQR) of 2 (1–5) were condomless sex acts where the participant was receptive and 2 (1–6) were condomless where the participant was insertive. Post-exposure prophylaxis had been prescribed to 184 (34 %) participants in the past 12 months. The number of STI diagnoses was high compared to those reported in GUMCAD attendees. Conclusions: The PROUD study population are at substantially higher risk of acquiring HIV infection sexually than the overall population of GMSM attending sexual health clinics in England. These findings contribute to explaining the extraordinary HIV incidence rate during follow-up and demonstrate that, despite broad eligibility criteria, the population interested in PrEP was highly selective. Trial registration: Current Controlled TrialsISRCTN94465371. Date of registration: 28 February 2013

The GALAH Survey: Using galactic archaeology to refine our knowledge of TESS target stars

An unprecedented number of exoplanets are being discovered by the Transiting Exoplanet Survey Satellite (TESS). Determining the orbital parameters of these exoplanets, and especially their mass and radius, will depend heavily upon the measured physical characteristics of their host stars. We have cross-matched spectroscopic, photometric, and astrometric data from GALAH Data Release 2, the TESS Input Catalog and Gaia Data Release 2, to create a curated, self-consistent catalogue of physical and chemical properties for 47 285 stars. Using these data, we have derived isochrone masses and radii that are precise to within 5 per cent. We have revised the parameters of three confirmed, and twelve candidate, TESS planetary systems. These results cast doubt on whether CTOI-20125677 is indeed a planetary system, since the revised planetary radii are now comparable to stellar sizes. Our GALAH-TESS catalogue contains abundances for up to 23 elements. We have specifically analysed the molar ratios for C/O, Mg/Si, Fe/Si, and Fe/Mg, to assist in determining the composition and structure of planets with Rp < 4R⊕. From these ratios, 36 per cent fall within 2$\sigma$ sigma of the Sun/Earth values, suggesting that these stars may host rocky exoplanets with geological compositions similar to planets found within our own Solar system.JTC would like to thank SW, BC, and DN, and is supported by the Australian Government Research Training Program (RTP) Scholarship. JTC would also like to thank Vardan Adibekyan for their valuable comments which have significantly improved the science of this manuscript. JDS and SM acknowledges the support of the Australian Research Council through Discovery Project grant DP180101791. SB acknowledges funds from the Australian Research Council (grants DP150100250 and DP160103747). Parts of this research were supported by the Australian Research Council (ARC) Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D), through project number CE170100013. YST is grateful to be supported by the NASA Hubble Fellowship grant HSTHF2-51425.001 awarded by the Space Telescope Science Institute