Observations of Doppler Boosting in Kepler Lightcurves

Among the initial results from Kepler were two striking lightcurves, for KOI 74 and KOI 81, in which the relative depths of the primary and secondary eclipses showed that the more compact, less luminous object was hotter than its stellar host. That result became particularly intriguing because a substellar mass had been derived for the secondary in KOI 74, which would make the high temperature challenging to explain; in KOI 81, the mass range for the companion was also reported to be consistent with a substellar object. We re-analyze the Kepler data and demonstrate that both companions are likely to be white dwarfs. We also find that the photometric data for KOI 74 show a modulation in brightness as the more luminous star orbits, due to Doppler boosting. The magnitude of the effect is sufficiently large that we can use it to infer a radial velocity amplitude accurate to 1 km/s. As far as we are aware, this is the first time a radial-velocity curve has been measured photometrically. Combining our velocity amplitude with the inclination and primary mass derived from the eclipses and primary spectral type, we infer a secondary mass of 0.22+/-0.03 Msun. We use our estimates to consider the likely evolutionary paths and mass-transfer episodes of these binary systems.Comment: 8 pages, 4 figures, ApJ 715, 51 (v4 is updated to match the published version, including a note added in proof with measured projected rotational velocities)

Stability and correlations in dilute two-dimensional boson systems

The hyperspherical adiabatic expansion method is used to describe correlations in a symmetric boson system rigorously confined to two spatial dimensions. The hyperangular eigenvalue equation turns out to be almost independent of the hyperradius, whereas the solutions are strongly varying with the strength of the attractive two-body potentials. Instability is encountered in hyperangular, hyperradial, and mean-field equations for almost identical strengths inversely proportional to the particle number. The derived conditions for stability are similar to mean-field conditions and closely related to the possible occurrence of the Thomas and Efimov effects. Renormalization in mean-field calculations for two spatial dimensions is probably not needed.Comment: 5 pages, two figures, submitted to Phys. Rev. A, second version contains added discussion, especially of renormalizatio

Risk factors for COPD exacerbations in inhaled medication users: the COPDGene study biannual longitudinal follow-up prospective cohort.

BackgroundDespite inhaled medications that decrease exacerbation risk, some COPD patients experience frequent exacerbations. We determined prospective risk factors for exacerbations among subjects in the COPDGene Study taking inhaled medications.Methods2113 COPD subjects were categorized into four medication use patterns: triple therapy with tiotropium (TIO) plus long-acting beta-agonist/inhaled-corticosteroid (ICS ± LABA), tiotropium alone, ICS ± LABA, and short-acting bronchodilators. Self-reported exacerbations were recorded in telephone and web-based longitudinal follow-up surveys. Associations with exacerbations were determined within each medication group using four separate logistic regression models. A head-to-head analysis compared exacerbation risk among subjects using tiotropium vs. ICS ± LABA.ResultsIn separate logistic regression models, the presence of gastroesophageal reflux, female gender, and higher scores on the St. George's Respiratory Questionnaire were significant predictors of exacerbator status within multiple medication groups (reflux: OR 1.62-2.75; female gender: OR 1.53 - OR 1.90; SGRQ: OR 1.02-1.03). Subjects taking either ICS ± LABA or tiotropium had similar baseline characteristics, allowing comparison between these two groups. In the head-to-head comparison, tiotropium users showed a trend towards lower rates of exacerbations (OR = 0.69 [95 % CI 0.45, 1.06], p = 0.09) compared with ICS ± LABA users, especially in subjects without comorbid asthma (OR = 0.56 [95% CI 0.31, 1.00], p = 0.05).ConclusionsEach common COPD medication usage group showed unique risk factor patterns associated with increased risk of exacerbations, which may help clinicians identify subjects at risk. Compared to similar subjects using ICS ± LABA, those taking tiotropium showed a trend towards reduced exacerbation risk, especially in subjects without asthma.Trial registrationClinicalTrials.gov NCT00608764, first received 1/28/2008

Revealing charge-tunneling processes between a quantum dot and a superconducting island through gate sensing

We report direct detection of charge-tunneling between a quantum dot and a superconducting island through radio-frequency gate sensing. We are able to resolve spin-dependent quasiparticle tunneling as well as two-particle tunneling involving Cooper pairs. The quantum dot can act as an RF-only sensor to characterize the superconductor addition spectrum, enabling us to access subgap states without transport. Our results provide guidance for future dispersive parity measurements of Majorana modes, which can be realized by detecting the parity-dependent tunneling between dots and islands.Comment: 6 pages, 4 figures, supplemental material included as ancillary fil

Observations and asteroseismological analysis of the rapid subdwarf B pulsator EC 09582-1137

We made photometric and spectroscopic observations of the rapidly pulsating subdwarf B star EC 09582-1137 with the aim of determining the target's fundamental structural parameters from asteroseismology. The new data comprise ~ 30 hours of fast time-series photometry obtained with SUSI2 at the NTT on La Silla, Chile, as well as 1 hour of low-resolution spectroscopy gathered with EMMI, also mounted on the NTT. From the photometry we detected 5 independent harmonic oscillations in the 135-170 s period range with amplitudes up to 0.5% of the mean brightness of the star. In addition, we extracted two periodicities interpreted as components of a rotationally split multiplet that indicate a rotation period of the order of 2-5 days. We also recovered the first harmonic of the dominant pulsation, albeit at an amplitude below the imposed 4-sigma detection threshold. The spectroscopic observations led to the following estimates of the atmospheric parameters of EC 09582-1137: Teff = 34,806+-233 K, log g = 5.80+-0.04, and log[N(He)/N(H)] = - 1.68+-0.06. Using the observed oscillations as input, we searched in model parameter space for unique solutions that present a good fit to the data. Under the assumption that the two dominant observed periodicities correspond to radial or dipole modes, we were able to isolate a well-constrained optimal model that agrees with the atmospheric parameters derived from spectroscopy. The inferred structural parameters of EC 09582-1137 are Teff = 34,806 K (from spectroscopy), log g = 5.788+-0.004, M = 0.485+-0.011 M_solar, log(M_env/M_star) = - 4.39+-0.10, R = 0.147+-0.002 R_solar, and L = 28.6+-1.7 L_solar. We additionally derive the absolute magnitude M_V = 4.44+-0.05 and the distance d = 1460+-66 pc.Comment: accepted for publication in Astronomy and Astrophysic

Mode identification from monochromatic amplitude and phase variations for the rapidly pulsating subdwarf B star EC 20338-1925

We obtain time-series spectrophotometry observations at the VLT with the aim of partially identifying the dominant oscillation modes in the rapidly pulsating subdwarf B star EC 20338-1925 on the basis of monochromatic amplitude and phase variations. From the data gathered, we detect four previously known pulsations with periods near 147, 168, 126 and 140 s and amplitudes between 0.2 and 2.3 % of the star's mean brightness. We also determine the atmospheric parameters of EC 20338-1925 by fitting our non-LTE model atmospheres to an averaged combined spectrum. The inferred parameters are Teff = 34,153+-94 K, log g =5.966+-0.017 and log[N(He)/N(H)] = - 1.642+-0.022, where the uncertainty estimates quoted refer to the formal fitting errors. Finally, we calculate the observed monochromatic amplitudes and phases for the periodicities extracted using least-squares fitting to the light curves obtained for each wavelength bin. These observed quantities are then compared to the corresponding theoretical values computed on the basis of dedicated model atmosphere codes and also taking into account non-adiabatic effects. We find that the quality of the data is sufficient to identify the dominant pulsation at 146.9 s as a radial mode, while two of the lower amplitude periodicities must be low-degree modes with l=0-2. This is the first time that monochromatic amplitudes and phases have been used for mode identification in a subdwarf B star, and the results are highly encouraging.Comment: 11 pages. Accepted for publication in Astronomy & Astrophysic

Low and intermediate-mass close binary evolution and the initial - final mass relation

Using Eggleton's stellar evolution code, we carry out 150 runs of Pop I binary evolution calculations, with the initial primary mass between 1 and 8 solar masses the initial mass ratio between 1.1 and 4, and the onset of Roche lobe overflow (RLOF) at an early, middle, or late Hertzsprung-gap stage. We assume that RLOF is conservative in the calculations, and find that the remnant mass of the primary may change by more than 40 per cent over the range of initial mass ratio or orbital period, for a given primary mass. This is contrary to the often-held belief that the remnant mass depends only on the progenitor mass if mass transfer begins in the Hertzsprung gap. We fit a formula, with an error less than 3.6 per cent, for the remnant (white dwarf) mass as a function of the initial mass of the primary, the initial mass ratio, and the radius of the primary at the onset of RLOF. We also find that a carbon-oxygen white dwarf with mass as low as 0.33 solar masses may be formed if the primary's initial mass is around 2.5 solar masses.Comment: 7 pages for main text, 11 pages for appendix (table A1), 12 figure

Salt marsh accretion with and without deep soil subsidence as a proxy for sea-level rise

The relation between salt marsh accretion and flooding regime was quantified by statistical analysis of a unique dataset of accretion measurements using sedimentation-erosion bars, on three barrier islands in the Dutch Wadden Sea over a period of c. 15 years. On one of the islands, natural gas extraction caused deep soil subsidence, which resulted in gradually increasing flooding frequency, duration, and depth, and can thus be seen as a proxy for sea-level rise. Special attention was paid to effects of small-scale variation e.g., in distance to tidal creeks or marsh edges, elevation of the marsh surface, and presence of livestock. Overall mean accretion rate was 0.44 ± 0.0005 cm year−1, which significantly exceeded the local rate of sea-level rise of 0.25 ± 0.009 cm year−1. A multiple regression approach was used to detect the combined effect of flooding regime and the local environment. The most important flooding-related factors that enhance accretion are mean water depth during flooding and overall mean water depth, but local accretion strongly decreases with increasing distance to the nearest creek or to the salt marsh edge. Mean water depth during flooding can be seen as an indicator for storm intensity, while overall mean water depth is a better indicator for storm frequency. The regression parameters were used to run a simple model simulating the effect of various sea-level scenarios on accretion and show that, even under extreme scenarios of sea-level rise, these salt marshes can probably persist for the next 100 years, although the higher parts may experience more frequent inundation

Towards optimising distributed data streaming graphs using parallel streams

Modern scientific collaborations have opened up the op-portunity of solving complex problems that involve multi-disciplinary expertise and large-scale computational experi-ments. These experiments usually involve large amounts of data that are located in distributed data repositories running various software systems, and managed by different organi-sations. A common strategy to make the experiments more manageable is executing the processing steps as a work-flow. In this paper, we look into the implementation of fine-grained data-flow between computational elements in a scientific workflow as streams. We model the distributed computation as a directed acyclic graph where the nodes rep-resent the processing elements that incrementally implement specific subtasks. The processing elements are connected in a pipelined streaming manner, which allows task executions to overlap. We further optimise the execution by splitting pipelines across processes and by introducing extra parallel streams. We identify performance metrics and design a mea-surement tool to evaluate each enactment. We conducted ex-periments to evaluate our optimisation strategies with a real world problem in the Life Sciences—EURExpress-II. The paper presents our distributed data-handling model, the op-timisation and instrumentation strategies and the evaluation experiments. We demonstrate linear speed up and argue that this use of data-streaming to enable both overlapped pipeline and parallelised enactment is a generally applicable optimisation strategy