The evolution of the self-lensing binary KOI-3278: evidence of extra energy sources during CE evolution

Post-common-envelope binaries (PCEBs) have been frequently used to observationally constrain models of close-compact-binary evolution, in particular common-envelope (CE) evolution. However, recent surveys have detected PCEBs consisting of a white dwarf (WD) exclusively with an M dwarf companion. Thus, we have been essentially blind with respect to PCEBs with more massive companions. Recently, the second PCEB consisting of a WD and a G-type companion, the spectacularly self-lensing binary KOI-3278, has been identified. This system is different from typical PCEBs not only because of the G-type companion, but also because of its long orbital period. Here we investigate whether the existence of KOI-3278 provides new observational constraints on theories of CE evolution. We reconstruct its evolutionary history and predict its future using BSE, clarifying the proper use of the binding energy parameter in this code. We find that a small amount of recombination energy, or any other source of extra energy, is required to reconstruct the evolutionary history of KOI-3278. Using BSE we derive progenitor system parameters of M1,i = 2.450 Msun, M2,i = 1.034 Msun, and Porb,i ~ 1300 d. We also find that in ~9 Gyr the system will go through a second CE phase leaving behind a double WD, consisting of a C/O WD and a He WD with masses of 0.636 Msun and 0.332 Msun, respectively. After IK Peg, KOI-3278 is the second PCEB that clearly requires an extra source of energy, beyond that of orbital energy, to contribute to the CE ejection. Both systems are special in that they have long orbital periods and massive secondaries. This may also indicate that the CE efficiency increases with secondary mass.Comment: Accepted for publication in A&A Letters, 4 pages, 2 figure

Eclipsing white dwarf binaries

Recent years have seen an explosion in the number of eclipsing binaries containing white dwarfs. In the last few years the number of systems has increased from 7 to over 40, thanks mainly to large surveys such as the Sloan Digital Sky Survey and the Catalina Sky Survey. Many of these systems are survivors of the common envelope phase during which the two stars orbit within a single envelope which is rapidly thrown off through loss of energy and angular momentum. Detailed analysis of these systems can yield extremely precise physical parameters for both the white dwarf primary and its companion star. Stellar masses and radii are some of the most fundamental parameters in astronomy and can be used to test models of stellar structure and evolution. They can also be used to constrain the evolutionary history of the binary system offering us the chance to better understand the common envelope phase itself. In this thesis I present high-precision studies of several eclipsing post common envelope binaries. I use a combination of high-speed photometry and high-resolution spectroscopy to measure the masses and radii of both stars in each system. I compare these results to evolutionary models and theoretical mass-radius relations and find that, on the whole, the measured masses and radii agree well with models. However, the main-sequence companion stars are generally oversized compared to evolutionary models, although this deviation is much less severe at very low masses (< ∼ 0.1M⊙). I also find that the measured masses and radii of carbon-oxygen core white dwarfs are in excellent agreement with theoretical models. Conversely, the first ever precision mass-radius measurement of a low-mass helium core white dwarf appears undersized compared to models. Large scale surveys have also begun to identify double white dwarf eclipsing binaries. In this thesis I present a study of one of these systems and show the potential, as a double-lined spectroscopic binary, of measuring precise parameters for both stars in the future. Finally, I show that the mid-eclipse times of eclipsing binaries containing white dwarfs can be measured to a high enough precision that we can monitor them for evidence of period changes. I find that many systems show complex variations in their eclipse times and in many cases the only mechanism able to produce these changes is one or more sub-stellar objects in orbit around the binary. However, I show that care must be taken when attempting to detect planets in binary systems using eclipse timings

Self-reported pain severity is associated with a history of coronary heart disease

This study was funded by Arthritis Research UK (grant number: 17292).Peer reviewedPublisher PD

Intention and motor representation in purposive action

Are there distinct roles for intention and motor representation in explaining the purposiveness of action? Standard accounts of action assign a role to intention but are silent on motor representation. The temptation is to suppose that nothing need be said here because motor representation is either only an enabling condition for purposive action or else merely a variety of intention. This paper provides reasons for resisting that temptation. Some motor representations, like intentions, coordinate actions in virtue of representing outcomes; but, unlike intentions, motor representations cannot feature as premises or conclusions in practical reasoning. This implies that motor representation has a distinctive role in explaining the purposiveness of action. It also gives rise to a problem: were the roles of intention and motor representation entirely independent, this would impair effective action. It is therefore necessary to explain how intentions interlock with motor representations. The solution, we argue, is to recognise that the contents of intentions can be partially determined by the contents of motor representations. Understanding this content-determining relation enables better understanding how intentions relate to actions

Groundwater seepage landscapes from distant and local sources in experiments and on Mars

© 2014 Author(s). Valleys with theater-shaped heads can form due to the seepage of groundwater and as a result of knickpoint (waterfall) erosion generated by overland flow. This ambiguity in the mechanism of formation hampers the interpretation of such valleys on Mars, particularly since there is limited knowledge of material properties. Moreover, the hydrological implications of a groundwater or surface water origin are important for our understanding of the evolution of surface features on Mars, and a quantification of valley morphologies at the landscape scale may provide diagnostic insights on the formative hydrological conditions. However, flow patterns and the resulting landscapes produced by different sources of groundwater are poorly understood. We aim to improve the understanding of the formation of entire valley landscapes through seepage processes from different groundwater sources that will provide a framework of landscape metrics for the interpretation of such systems. We study groundwater seepage from a distant source of groundwater and from infiltration of local precipitation in a series of sandbox experiments and combine our results with previous experiments and observations of the Martian surface. Key results are that groundwater flow piracy acts on valleys fed by a distant groundwater source and results in a sparsely dissected landscape of many small and a few large valleys. In contrast, valleys fed by a local groundwater source, i.e., nearby infiltration, result in a densely dissected landscape. In addition, valleys fed by a distant groundwater source grow towards that source, while valleys with a local source grow in a broad range of directions and have a strong tendency to bifurcate, particularly on flatter surfaces. We consider these results with respect to two Martian cases: Louros Valles shows properties of seepage by a local source of groundwater and Nirgal Vallis shows evidence of a distant source, which we interpret as groundwater flow from Tharsis

A J-band detection of the donor star in the dwarf nova OY Carinae, and an optical detection of its `iron curtain'

Purely photometric models can be used to determine the binary parameters of eclipsing cataclysmic variables with a high degree of precision. However, the photometric method relies on a number of assumptions, and to date there have been very few independent checks of this method in the literature. We present time-resolved spectroscopy of the P=90.9 min eclipsing cataclysmic variable OY Carinae obtained with X-shooter on the VLT, in which we detect the donor star from K I lines in the J-band. We measure the radial velocity amplitude of the donor star K2 = 470.0 +/- 2.7 km/s, consistent with predictions based upon the photometric method (470 +/- 7 km/s). Additionally, the spectra obtained in the UVB arm of X-shooter show a series of Fe I and Fe II lines with a phase and velocity consistent with an origin in the accretion disc. This is the first unambiguous detection at optical wavelengths of the `iron curtain' of disc material which has been previously reported to veil the white dwarf in this system. The velocities of these lines do not track the white dwarf, reflecting a distortion of the outer disc that we see also in Doppler images. This is evidence for considerable radial motion in the outer disk, at up to 90 km/s towards and away from the white dwarf.Comment: MNRAS accepted. 11 pages with 10 figures and 2 table

The development of a new measure of quality of life for children with congenital cardiac disease

The purpose of the study was to develop a questionnaire measuring health-related R1 quality of life for children and adolescents with congenital heart disease, the ConQol, that would have both clinical and research applications. We describe here the process of construction of a questionnaire, the piloting and the development of a weighted scoring system, and data on the psychometric performance of the measure in a sample of 640 children and young people recruited via 6 regional centres for paediatric cardiology from across the United Kingdom. The ConQol has two versions, one designed for children aged from 8 to 11 years, and the other for young people aged from 12 to 16 years. Initial findings suggest that it is a valid and reliable instrument, is acceptable to respondents, and is simple to administer in both a research and clinical context

The role of parental and child physical and mental health on behavioural and emotional adjustment in mid-childhood: a comparison of two generations of British children born 30 years apart

Poor physical health and behavioural and emotional problems in childhood have a lasting impact on well-being in adolescence and adulthood. Here we address the relationship between poor parent and child physical and mental health in early childhood (age 5) and conduct, hyperactivity and emotional problems in mid-childhood (age 10/11). We compare results across two generations of British children born 30 years apart in 1970 (n = 15,856) and 2000/2 (16,628). We take advantage of rich longitudinal birth cohort data and establish that a child’s own poor health was associated with conduct, hyperactivity and emotional problems in mid-childhood in both generations, and that with the exception of conduct problems in the 1970 cohort these relationships remained when family socio-economic status and individual characteristics were accounted for. Poor maternal mental health was similarly associated with conduct, hyperactivity and emotional problems in both generations; poor parental physical health with a child having later hyperactivity and emotional problems in the younger generation. Results also indicated that earlier behaviour problems had more influence on later problems for children in the more recent cohort. Given the increasing proportion of children and adolescents with mental health problems and that socio-economic disadvantage increases physical and mental well-being concerns within families, policy solutions must consider the holistic nature of a child’s family environment to prevent some children experiencing a ‘double whammy’ of disadvantage. The early years provide the best opportunity to promote children’s resilience and well-being and minimise the development of entrenched negative behaviours and their subsequent costs to society

Relationships and events: towards a general theory of reification and truthmaking.

We propose a novel ontological analysis of relations and relationships based on a re-visitation of a classic problem in the practice of knowledge repre- sentation and conceptual modeling, namely relationship reification. Our idea is that a relation holds in virtue of a relationship's existence. Relationships are therefore truthmakers of relations. In this paper we present a general theory or reification and truthmaking, and discuss the interplay between events and rela- tionships, suggesting that relationships are the focus of events, which emerge from the context (the scene) they occur in

The evolutionary state of short-period magnetic white dwarf binaries

We present phase-resolved spectroscopy of two new short-period low accretion rate magnetic binaries, SDSS J125044.42+154957.3 (Porb= 86 min) and SDSS J151415.65+074446.5 (Porb= 89 min). Both systems were previously identified as magnetic white dwarfs from the Zeeman splitting of the Balmer absorption lines in their optical spectra. Their spectral energy distributions exhibit a large near-infrared excess, which we interpret as a combination of cyclotron emission and possibly a late-type companion star. No absorption features from the companion are seen in our optical spectra. We derive the orbital periods from a narrow, variable Hα emission line which we show to originate on the companion star. The high radial velocity amplitude measured in both systems suggests a high orbital inclination, but we find no evidence for eclipses in our data. The two new systems resemble the polar EF Eri in its prolonged low state and also SDSS J121209.31+013627.7, a known magnetic white dwarf plus possible brown dwarf binary, which was also recovered by our method