Circinus X-1: survivor of a highly asymmetric supernova

We have analyzed the kinematical parameters of Cir X-1 to constrain the nature of its companion star, the eccentricity of the binary and the pre-supernova parameter space. We argue that the companion is most likely to be a low-mass (< 2.0 M_sun) unevolved star and that the eccentricity of the orbit is 0.94 +/- 0.04. We have evaluated the dynamical effects of the supernova explosion and we find it must have been asymmetric. On average, we find that a kick of 740 km/s is needed to account for the recently measured radial velocity of +430 km/s (Johnston, Fender & Wu) for this extreme system. The corresponding minimum kick velocity is 500 km/s. This is the largest kick needed to explain the motion of any observed binary system. If Cir X-1 is associated with the supernova remnant G321.9-0.3 then we find a limiting minimum age of this remnant of 60000 yr. Furthermore, we predict that the companion star has lost 10% of its mass as a result of stripping and ablation from the impact of the supernova shell shortly after the explosion

Probing Electron-Capture Supernovae: X-Ray Binaries in Starbursts

Presenting population models of high-mass X-ray binaries (HMXBs) formed after bursts of star formation, we investigate the effect of electron-capture supernovae (ECS) of massive ONeMg white dwarfs and the hypothesis that ECS events are associated with typically low supernova kicks imparted to the nascent neutron stars. We identify an interesting ECS bump in the time evolution of HMXB numbers; this bump is caused by significantly increased production of wind-fed HMXBs 20-60 Myr post starburst. The amplitude and age extent of the ECS bump depend on the strength of ECS kicks and the mass range of ECS progenitors. We also find that ECS-HMXBs form through a specific evolutionary channel that is expected to lead to binaries with Be donors in wide orbits. These characteristics, along with their sensitivity to ECS properties, provide us with an intriguing opportunity to probe ECS physics and progenitors through studies of starbursts of different ages. Specifically, the case of the Small Magellanic Cloud, with a significant observed population of Be HMXBs and starburst activity 30-60 Myr ago, arises as a promising laboratory for understanding the role of electron-capture supernovae in neutron star formation.Comment: 5 pages, 3 figures, Published by ApJ in 07/0

Towards the development of the psychosocial impact of assistive devices scale for continence (C-PIADS)

BACKGROUND: Current outcome measures for continence management devices do not adequately address psychosocial impact. The PIADS is an assessment tool that has been shown to reliably predict the adoption and use of assistive technology devices, but it is not widely used for continence devices. OBJECTIVE: To explore whether the PIADS requires modification to address the particular needs of continence device users and to inform any subsequent item development. METHODS: The study used interpretive methods in which qualitative information from semi-structured interviews was combined with the findings from cognitive interviews for questionnaire pre-testing. A total of 40 participants in UK and Canada were interviewed. RESULTS: Few participants had difficulty in understanding or relating to the majority of PIADS items. Several items were not considered relevant to continence and some areas for potential new items were uncovered. Embarrassment and concealment of urinary incontinence from others were common topics. CONCLUSIONS: The PIADS appears to fundamentally address many, but not all, of the important psychosocial concerns of adults who have continence difficulties. A version for continence, the C-PIADS, will require modification of the PIADS and is likely to contain some new items

T Pyxidis: The First Cataclysmic Variable with a Collimated Jet

We present the first observational evidence for a collimated jet in a cataclysmic variable system; the recurrent nova T Pyxidis. Optical spectra show bipolar components of H$\alpha$ with velocities $\sim 1400 km/s$, very similar to those observed in the supersoft X-ray sources and in SS 433. We argue that a key ingredient of the formation of jets in the supersoft X-ray sources and T Pyx (in addition to an accretion disk threaded by a vertical magnetic field), is the presence of nuclear burning on the surface of the white dwarf.Comment: 10 pages 2 figures to appear in ApJ Letter

Tackling Ageing Continence through Theory, Tools & Technology

Originally presented at ‘Aging and Society: An Interdisciplinary Conference’, University of California, Berkeley (2011), this article was double-blind peer reviewed, receiving scores of 96% and 73%. It outlines the interdisciplinary research of the cross-Research-Council-funded New Dynamics of Ageing Tackling Ageing Continence through Theory Tools & Technology (TACT3) project (2008–12), which brought together designers, social scientists, bio-engineers, chemists and care-management services to understand the challenges faced by an ageing population in the management of continence. Bichard’s Work Package, ‘Challenging Environmental Barriers to Continence’, explored the need for public toilet provision as essential for quality of life, health and well-being. It developed a life-course methodology that considered ageing from birth through to advanced age (0–101 years), and involved inclusive design research with members of the public and providers of facilities to assess public expectations and provider limitations in service provision. As co-investigator on TACT3, this research built on Bichard’s previous work for the VivaCity2020 consortium (Bichard REF Output 2). Whereas the VivaCity2020 work focused on architectural barriers in toilet provision, the TACT3 project examined the problem in service provision, and how, through inclusive design research, service-design solutions might be explored and implemented. Bichard’s contribution to the TACT3 project produced The Great British Public Toilet Map (http://greatbritishpublictoiletmap.rca.ac.uk/), a public participation website that provides information and locations of public toilets, encouraging members of the public to contact relevant local authorities that have not released information in the format of Open Data. Secondary analysis of TACT3 data for references to issues of personal safety and community initiative in toilet provision was used for the ESRC-funded Robust Accessible Toilets (RATs) project (2011) and produced Publicly Accessible Toilets: An Inclusive Design Guide (2011). Related published conference papers include those in ‘Cumulus 2010’ (China) and ‘Include 2011’ (UK)

Properties of Deflagration Fronts and Models for Type Ia Supernovae

Detailed models of the explosion of a white dwarf, which include self-consistent calculations of the light curve and spectra, provide a link between observational quantities and the underlying explosion.These calculations assume spherical geometry and are based on parameterized descriptions of the burning front during the deflagration phase. Recently, first multi-dimensional calculations for nuclear burning fronts have been performed. Although a fully consistent treatment of the burning fronts is beyond the current state of the art, these calculations provided a new and better understanding of the physics, and new descriptions for the flame propagation have been proposed. Here, we have studied the influence on the results of previous analyses of Type Ia Supernovae, namely, the nucleosynthesis and structure of the expanding envelope. Our calculations are based on a set of delayed detonation models with parameters that give a good account of the optical and infrared light curves, and of the spectral evolution. In this scenario, the burning front propagates first in a deflagration mode and, subsequently, turns into a detonation. The explosions and light curves are calculated using a one-dimensional Lagrangian radiation-hydro code, including a detailed nuclear network.Comment: 9 pages, 4 figures, macros 'crckapb.sty'. The Astrophysical Journal (accepted

The Physics of Supernova Remnant Blast Waves. I. Kinematics of DEM L71 in the Large Magellanic Cloud

We present the results from Fabry-Perot imaging spectroscopy of the Balmer-dominated supernova remnant DEM L71 (0505-67.9) in the LMC. Spectra extracted from the entire circumference of the blast wave reveal the broad and narrow component H-alpha line emission characteristic of non-radiative shocks in partially neutral gas. The new spectra of DEM L71 include portions of the rim that have not been previously observed. We find that the broad component width varies azimuthally along the edge of DEM L71, ranging from 450+/-60 km/s along the eastern edge to values as high as 985 (+210)(-165) km/s along the faint western edge. In part of the faint northern rim the broad component is not detected, possibly indicating a lower density in these regions and/or a broad component width in excess of 1000 km/s. Between the limits of zero and full electron-ion temperature equilibration at the shock front, the allowed range of shock velocities is 430-560 km/s along the east rim and 700-1250 km/s along other parts of the blast wave. The H-alpha broad-to-narrow flux ratios vary considerably around the remnant, ranging from 0.4 to 0.8. These ratios lie below the values predicted by our shock models. We find that narrow component H-alpha emission from a cosmic ray precursor may be the cause of the discrepancy. The least decelerated portions of the blast wave (i.e., regions excluding the brightest filaments) are well characterized by Sedov models with a kinetic energy E_51= (0.37+/-0.06)*D_50**(5/2), where D_50 is the LMC distance in units of 50 kpc. The corresponding age for DEM L71 is (4360+/-290)*D_50 yr. This is the first time that velocity information from the entire blast wave has been utilized to study the global kinematics of a non-radiative SNR at a known distance.Comment: 21 pages, including 8 postscript figures and 4 tables, LaTeX, accepted to ApJ; see companion pape

Thermal Timescale Mass Transfer and the Evolution of White Dwarf Binaries

The evolution of binaries consisting of evolved main sequence stars (1 < M_d/Msun < 3.5) with white dwarf companions (0.7 < M_wd/Msun < 1.2) is investigated through the thermal mass transfer phase. Taking into account the stabilizing effect of a strong, optically thick wind from the accreting white dwarf surface, we have explored the formation of several evolutionary groups of systems for progenitors with initial orbital periods of 1 and 2 days. The numerical results show that CO white dwarfs can accrete sufficient mass to evolve to a Type Ia supernova and ONeMg white dwarfs can be built up to undergo accretion induced collapse for donors more massive than about 2 Msun. For donors less massive than ~2 Msun the system can evolve to form a He and CO or ONeMg white dwarf pair. In addition, sufficient helium can be accumulated (~0.1 Msun) in systems characterized by 1.6 < M_d/Msun < 1.9 and 0.8 < M_wd/Msun < 1 such that sub Chandrasekhar mass models for Type Ia supernovae, involving off center helium ignition, are possible for progenitor systems evolving via the Case A mass transfer phase. For systems characterized by mass ratios > 3 the system likely merges as a result of the occurrence of a delayed dynamical mass transfer instability. A semi-analytical model is developed to delineate these phases which can be easily incorporated in population synthesis studies of these systems.Comment: 9 pages, 6 figures, Latex, emulateapj style, ApJ accepte

Neutrino-Driven Jets and Rapid-Process Nucleosynthesis

We have studied whether the jet in a collapse-driven supernova can be a key process for the rapid-process (r-process) nucleosynthesis. We have examined the features of a steady, subsonic, and rigidly rotating jet in which the centrifugal force is balanced by the magnetic force. As for the models in which the magnetic field is weak and angular velocity is small, we found that the r-process does not occur because the final temperature is kept to be too high and the dynamical timescale becomes too long when the neutrino luminosities are set to be high. Even if the luminosities of the neutrinos are set to be low, which results in the low final temperature, we found that the models do not give a required condition to produce the r-process matter. Furthermore, the amount of the mass outflow seems to be too little to explain the solar-system abundance ratio in such low-luminosity models. As for the models in which the magnetic field is strong and angular velocity is large, we found that the entropy per baryon becomes too small and the dynamical timescale becomes too long. This tendency is, of course, a bad one for the production of the r-process nuclei. As a conclusion, we have to say that it is difficult to cause a successful r-process nucleosynthesis in the jet models in this study.Comment: 34 pages and 6 postscript figures. submitted to Astrophysical Journa

Supersoft X-ray sources in M31: II. ROSAT-detected supersoft sources in the ROSAT, Chandra and XMM eras

We have performed Chandra observations during the past 3 years of 5 of the M31 supersoft X-ray sources (SSS) discovered with ROSAT. Surprisingly, only one of these sources has been detected, despite a predicted detection of about 20-80 counts. This has motivated a thorough check of the ROSAT M31 survey I data, including a relaxation of the hardness ratio requirement used to select SSS. This increases the number of SSS identified in survey I by 7. We then carried out a comparison with the ROSAT M31 survey II dataset which had hitherto not been explicitly investigated for SSS. We find that most of the ROSAT survey I sources are not detected, and only two new SSS are identified. The low detection rate in the ROSAT survey II and our Chandra observations implies that the variability time scale of SSS is a few months. If the majority of these sources are close-binary SSS with shell hydrogen burning, it further implies that half of these sources predominantly experience large mass transfer rates.Comment: accepted for publ. in ApJ; 2 ps-figures; high-quality figures available at http://www.mpe.mpg.de/~jcg/publis.htm