Enshrouded Exoplanetary Systems

This thesis is based on the hypothesis that stars hosting short period planets can show anomalously low apparent stellar activity values caused by planetary mass-loss enshrouding the system. The resulting circumstellar absorption depresses the cores of the Ca II H&K lines, where the activity index log(R'HK) is measured. I searched for this effect in a sample of ∼2700 stars, identifying 39 objects with log(R'HK) below the main sequence basal limit, and 6 Hyades and Pleiades stars with activity levels well below the cluster distributions. I describe a radial velocity programme to search for short period planets orbiting these stars. Because nearby bright stars are targeted, their mass-losing companions will offer key opportunities to probe planetary composition through transmission spectroscopy. I present four planet candidates discovered through this programme orbiting HD11231 and HD38677. The former is a γ-Doradus pulsator hosting a Saturn-mass planet in a 6 day orbit, and the latter is a compact system containing planets with ∼18, 13 and 3 Earth masses and periods between 20 and 1.7 days. In addition, the Robert Stobie Spectrograph was calibrated to measure log(R'HK) values. The activity index of the known Hot Jupiter hosts WASP-43, WASP-51/HAT-P-30, WASP-72 & WASP-103 was measured to search for anomalous values caused by the companions. The activity level of WASP-43 is extremely high in absolute terms and relative to its age and X-ray emission. The activity of WASP-103 is marginally higher than expected from the system age. In both cases, star-planet interactions may enhance Ca II H & K emission. WASP-51/HAT-P-30 and WASP-72 show anomalously low activity; the latter falls below the basal envelopes of main sequence and evolved stars. I highlight that a quarter of transiting, short period planets hosts with published activity data exhibit anomalously low activity. These 22 systems include Hot Jupiters and low mass companions

СТАРИЙ ЗАВІТ ЯК ДЖЕРЕЛО ХРИСТИЯНСЬКИХ СИМВОЛІЧНИХ ТОПОСІВ

У статті досліджено старозавітна генеза християнської символіки. Проаналізовано вплив юдейських текстів на формування теологічної символіки таїнства хрещення. Розглянуто континуальність біблійної семіосфери жертвопринесень: від старозавітних жертв до новозавітної євхаристії. З’ясовано, що теологічна спадкоємність Старого й Нового Завітів передбачає успадкування християнством із юдаїзму образно-символічних топосів у парадигмі "традиція-новаторство", відповідно до новозавітної сотеріології. Зроблено висновок, що органічний взаємозв'язок двох частин Біблії прослідковується не тільки на теологічному рівні, але й на структурно-семіотичному рівні

P2_7 Close Encounters of the Unkind

 Possible effects on satellites in Earth orbit caused by the unusually close encounter between the asteroid 9942 Apophis and Earth in 2029 are assessed. A worst case scenario for GPS, the most important system at risk, showed that the gravitational perturbation of orbits is negligible. Furthermore, it was found that Apophis will remain intact during the encounter, as its closest possible approach occurs at approximately twice the Roche limit

P2_9 Superconducting vs. Overhead Lines

  High temperature (below liquid nitrogen boiling temps.) superconductors have potential applications in power transmission lines as they can carry currents with effectively no resistance. This report gives a first order estimate of losses in presently used overhead cables at around 15% of power output. To better this efficiency a superconductor would need to be clad in an insulator with an outer diameter of greater than 1.93 times that of its inner diameter, provided a liquid nitrogen refrigeration pump could work at 10% efficiency

A possible transit of a disintegrating exoplanet in the nearby multiplanet system DMPP-1

We analyse TESS photometry of DMPP-1 (HD 38677; TIC 66560666), a nearby F8V star hosting hot super-Earth planets and a warm Neptune. Using the Transit Least Squares algorithm and other methods we find a transit signal at $P=3.2854^{+0.0032}_{-0.0025}$ d with depth 87$^{+25}_{-30}$ ppm and false alarm probability 1.6%. This is shallower than hitherto published TESS discoveries. The 3.285 d signal is recovered for several, but not all, methods for detrending stellar astrophysical variability. Further observations are needed to improve the significance of the detection. If this transit were due to an Earth-like rocky planet it would have been detected in the RV data, but it is not. The TESS data cover seven individual transits, one of which is consistent with zero depth. The insolation of the putative planet is $990 {\rm S_{\oplus}}$, typical of fluxes experienced by the three known catastrophically disintegrating exoplanets (CDEs). The transits can be self-consistently attributed to a CDE with a mass below the RV detection threshold. We searched for transits of the known RV planets, finding null results and detection thresholds of < 100 ppm, which we quantify for each. The DMPP-1 planetary system was discovered as a consequence of circumstellar gas attributed to ablation of hot planets. The RV planets may have been ablated to near-pure iron cores. We place limits on the orbital inclinations of the RV planets where the expected transit depth exceeds the detection threshold. If the 3.2854 day transit detection is confirmed, e.g. with CHEOPS photometry, DMPP-1 would be a first-rate target for JWST spectroscopy

P2_5 Wiggle Your Washing Dry!

An investigation is conducted to determine what frequency one would need to wiggle a washing line at, in order for the wave to provide enough energy to dry a sheet. For a modelled line it is found that a frequency of around 324 Hz would be needed for 0.1m amplitude of oscillation. A more realistic frequency of 5Hz would require an amplitude of 6.47m

P2_8 The tide is high but I am still short

This work considers the acceleration due to tidal forces on Earth due to the Moon and due to Earth and the amount it would stretch a human’s cortical bones. It is found that a human’s change in height is negligible and therefore cannot be measured. It is estimated that in order for humans to feel tidal accelerations due to breaking bones, they would have to be at a distance of 151 km from a Neutron star of mass 3.98×1030 kg

P2_3 Like Looking for an Assassin in a Haystack

The “Leap of Faith†is an extraordinary and repeatable stunt, whereby people jump from buildings into haystacks, performed by characters in the popular computer game series Assassin’s Creed. By considering the elastic deformation of wheat straw it was found that if a person were to attempt this they would experience deceleration nearly 8000 times that of gravity, resulting in certain death

P2_1 James' Giant Peach Transport across the Atlantic

In Roald Dahl's children's classic James and the Giant Peacha magically enlarged fruit travels across the Atlantic Ocean, partly floated on the water and partly airlifted by a flock of seagulls. Through examining the buoyancy and modelling the seagulls as aerofoils it has been found that although the initial part of the journey is possible, given a sufficiently hollow peach, James would have to tether approximately two and a half million Common Gulls, rather than the 501 as described in the book