Extent of pollution in planet-bearing stars

(abridged) Search for planets around main-sequence (MS) stars more massive than the Sun is hindered by their hot and rapidly spinning atmospheres. This obstacle has been sidestepped by radial-velocity surveys of those stars on their post-MS evolutionary track (G sub-giant and giant stars). Preliminary observational findings suggest a deficiency of short-period hot Jupiters around the observed post MS stars, although the total fraction of them with known planets appears to increase with their mass. Here we consider the possibility that some very close- in gas giants or a population of rocky planets may have either undergone orbital decay or been engulfed by the expanding envelope of their intermediate-mass host stars. If such events occur during or shortly after those stars' main sequence evolution when their convection zone remains relatively shallow, their surface metallicity can be significantly enhanced by the consumption of one or more gas giants. We show that stars with enriched veneer and lower-metallicity interior follow slightly modified evolution tracks as those with the same high surface and interior metallicity. As an example, we consider HD149026, a marginal post MS 1.3 Msun star. We suggest that its observed high (nearly twice solar) metallicity may be confined to the surface layer as a consequence of pollution by the accretion of either a planet similar to its known 2.7-day-period Saturn-mass planet, which has a 70 Mearth compact core, or a population of smaller mass planets with a comparable total amount of heavy elements. It is shown that an enhancement in surface metallicity leads to a reduction in effective temperature, in increase in radius and a net decrease in luminosity. The effects of such an enhancement are not negligible in the determinations of the planet's radius based on the transit light curves.Comment: 25 pages, 8 figures, submitted to Ap

Planet Consumption and Stellar Metallicity Enhancements

The evolution of a giant planet within the stellar envelope of a main-sequence star is investigated as a possible mechanism for enhancing the stellar metallicities of the parent stars of extrasolar planetary systems. Three-dimensional hydrodynamical simulations of a planet subject to impacting stellar matter indicate that the envelope of a Jupiter-like giant planet can be completely stripped in the outer stellar convection zone of a solar-mass star. In contrast, Jupiter-like and less massive Saturn-like giant planets are able to survive through the base of the convection zone of a 1.22 solar-mass star. Although strongly dependent on details of planetary interior models, partial or total dissolution of giant planets can result in significant enhancements in the metallicity of host stars with masses between about 1.0 and 1.3 solar masses. The implications of these results with regard to planetary orbital migration are briefly discussed.Comment: 11 pages, 2 figures, accepted for ApJ Letter

A compact and reconfigurable silicon nitride time-bin entanglement circuit

Photonic chip based time-bin entanglement has attracted significant attention because of its potential for quantum communication and computation. Useful time-bin entanglement systems must be able to generate, manipulate and analyze entangled photons on a photonic chip for stable, scalable and reconfigurable operation. Here we report the first time-bin entanglement photonic chip that integrates time-bin generation, wavelength demultiplexing and entanglement analysis. A two-photon interference fringe with an 88.4% visibility is measured (without subtracting any noise), indicating the high performance of the chip. Our approach, based on a silicon nitride photonic circuit, which combines the low-loss characteristic of silica and tight integration features of silicon, paves the way for scalable real-world quantum information processors.Comment: 4 pages, 5 figure

Increased disease activity, severity and autoantibody positivity in rheumatoid arthritis patients with co-existent bronchiectasis.

PublishedArticleCopyright © 2015 Asia Pacific League of Associations for Rheumatology and Wiley Publishing Asia Pty LtdAim: Patients with rheumatoid arthritis (RA) and co-existent Bronchiectasis (BRRA) have a 5-fold increased mortality compared to rheumatoid arthritis alone. Yet previous studies have found no difference in clinical and serological markers of RA disease severity between BRRA patients and RA alone. RA disease activity measures such as DAS28-CRP and anti-cyclic citrullinated peptide antibodies (anti-CCP) however have not been studied, so we assessed these parameters in patients with BRRA and RA alone. Methods: BRRA patients (n = 53) had HRCT proven bronchiectasis without any interstitial lung disease and ≥2 respiratory infections/year. RA alone patients (n = 50) had no clinical or radiological evidence of lung disease. DAS28-CRP, rheumatoid factor (IgM) and anti-CCP were measured in all patients, together with detailed clinical and radiology records. Results: In BRRA, BR predated RA in 58% of patients. BRRA patients had higher DAS28 scores (3.51 vs. 2.59), higher levels of anti-CCP (89 vs. 46%) and RF (79 vs. 52%) (p = 0.003) compared to RA alone. Where hand and foot radiology findings were recorded, 29/37 BRRA (78%) and 13/30 (43%) RA alone had evidence of erosive change (p = 0.003). There were no significant differences between groups in smoking history or DMARD/biologic therapy. Conclusions: Increased levels of RA disease activity, severity and RA autoantibodies are demonstrated in patients with RA and co-existent bronchiectasis compared to patients with RA alone, despite lower tobacco exposure. This study demonstrates that BRRA is a more severe systemic disease than RA alone.Arthritis Research UKHEFCECornwall Arthritis TrustNorthcott Devon Medical FoundationDutchy Health CharityNIHR CLR

Slow-light optical bullets in arrays of nonlinear Bragg-grating waveguides

We demonstrate how to control independently both spatial and temporal dynamics of slow light. We reveal that specially designed nonlinear waveguide arrays with phase-shifted Bragg gratings demonstrate the frequency-independent spatial diffraction near the edge of the photonic bandgap, where the group velocity of light can be strongly reduced. We show in numerical simulations that such structures allow a great flexibility in designing and controlling dispersion characteristics, and open a way for efficient spatiotemporal self-trapping and the formation of slow-light optical bullets.Comment: 4 pages, 4 figures; available from http://link.aps.org/abstract/PRL/v97/e23390

Aspherical supernova explosions and formation of compact black hole low-mass X-ray binaries

It has been suggested that black-hole low-mass X-ray binaries (BHLMXBs) with short orbital periods may have evolved from BH binaries with an intermediate-mass secondary, but the donor star seems to always have higher effective temperatures than measured in BHLMXBs (Justham, Rappaport & Podsiadlowski 2006). Here we suggest that the secondary star is originally an intermediate-mass (\sim 2-5 M_{\sun}) star, which loses a large fraction of its mass due to the ejecta impact during the aspherical SN explosion that produced the BH. The resulted secondary star could be of low-mass (\la 1 M_{\sun}). Magnetic braking would shrink the binary orbit, drive mass transfer between the donor and the BH, producing a compact BHLMXB.Comment: 4 pages, accepted for publication in MNRAS Letter

Correlated photon-pair generation in a periodically poled MgO doped stoichiometric lithium tantalate reverse proton exchanged waveguide

We demonstrate photon-pair generation in a reverse proton exchanged waveguide fabricated on a periodically poled magnesium doped stoichiometric lithium tantalate substrate. Detected pairs are generated via a cascaded second order nonlinear process where a pump laser at wavelength of 1.55 $\mu$m is first doubled in frequency by second harmonic generation and subsequently downconverted around the same spectral region. Pairs are detected at a rate of 42 per second with a coincidence to accidental ratio of 0.7. This cascaded pair generation process is similar to four-wave-mixing where two pump photons annihilate and create a correlated photon pair

Cuspons, peakons and regular gap solitons between three dispersion curves

A general wave model with the cubic nonlinearity is introduced to describe a situation when the linear dispersion relation has three branches, which would intersect in the absence of linear couplings between the three waves. Actually, the system contains two waves with a strong linear coupling between them, to which a third wave is then coupled. This model has two gaps in its linear spectrum. Realizations of this model can be made in terms of temporal or spatial evolution of optical fields in, respectively, a planar waveguide or a bulk-layered medium resembling a photonic-crystal fiber. Another physical system described by the same model is a set of three internal wave modes in a density-stratified fluid. A nonlinear analysis is performed for solitons which have zero velocity in the reference frame in which the group velocity of the third wave vanishes. Disregarding the self-phase modulation (SPM) term in the equation for the third wave, we find two coexisting families of solitons: regular ones, which may be regarded as a smooth deformation of the usual gap solitons in a two-wave system, and cuspons with a singularity in the first derivative at their center. Even in the limit when the linear coupling of the third wave to the first two vanishes, the soliton family remains drastically different from that in the linearly uncoupled system; in this limit, regular solitons whose amplitude exceeds a certain critical value are replaced by peakons. While the regular solitons, cuspons, and peakons are found in an exact analytical form, their stability is tested numerically, which shows that they all may be stable. If the SPM terms are retained, we find that there again coexist two different families of generic stable soliton solutions, namely, regular ones and peakons.Comment: a latex file with the text and 10 pdf files with figures. Physical Review E, in pres

Uncertainties in models of stellar structure and evolution

Numerous physical aspects of stellar physics have been presented in Ses- sion 2 and the underlying uncertainties have been tentatively assessed. We try here to highlight some specific points raised after the talks and during the general discus- sion at the end of the session and eventually at the end of the workshop. A table of model uncertainties is then drawn with the help of the participants in order to give the state of the art in stellar modeling uncertainties as of July 2013.Comment: Proc. of the workshop "Asteroseismology of stellar populations in the Milky Way" (Sesto, 22-26 July 2013), Astrophysics and Space Science Proceedings, (eds. A. Miglio, L. Girardi, P. Eggenberger, J. Montalban

Detection of Solar-like Oscillations in the G7 Giant Star xi Hya

We report the firm discovery of solar-like oscillations in a giant star. We monitored the star xi Hya (G7III) continuously during one month with the CORALIE spectrograph attached to the 1.2m Swiss Euler telescope. The 433 high-precision radial-velocity measurements clearly reveal multiple oscillation frequencies in the range 50 - 130 uHz, corresponding to periods between 2.0 and 5.5 hours. The amplitudes of the strongest modes are slightly smaller than 2 m/s. Current model calculations are compatible with the detected modes.Comment: 4 pages, 4 figures, accepted for publication as a letter in A&