A purely geometric distance to the binary star Atlas, a member of the Pleiades

We present radial velocity and new interferometric measurements of the double star Atlas, which permit, with the addition of published interferometric data, to precisely derive the orbital parameters of the binary system and the masses of the components. The derived semi-major axis, compared with its measured angular size, allows to determine a distance to Atlas of 132+-4 pc in a purely geometrical way. Under the assumption that the location of Atlas is representative of the average distance of the cluster, we confirm the distance value generally obtained through main sequence fitting, in contradiction with the early Hipparcos result (118.3+-3.5 pc).Comment: 5 pages, 3 figures, accepted for publication in A&A Letter

Extrasolar planets and brown dwarfs around A-F type stars - VII. Theta Cygni radial velocity variations: planets or stellar phenomenon?

(abridged) In the frame of the search for extrasolar planets and brown dwarfs around early-type main-sequence stars, we present the results obtained on the early F-type star Theta Cygni. Elodie and Sophie at OHP were used to obtain the spectra. Our dedicated radial-velocity measurement method was used to monitor the star's radial velocities over five years. We also use complementary, high angular resolution and high-contrast images taken with PUEO at CFHT. We show that Theta Cygni radial velocities are quasi-periodically variable, with a ~150-day period. These variations are not due to the ~0.35-Msun stellar companion that we detected in imaging at more than 46 AU from the star. The absence of correlation between the bisector velocity span variations and the radial velocity variations for this 7 km/s vsini star, as well as other criteria indicate that the observed radial velocity variations are not due to stellar spots. The observed amplitude of the bisector velocity span variations also seems to rule out stellar pulsations. However, we observe a peak in the bisector velocity span periodogram at the same period as the one found in the radial velocity periodogram, which indicates a probable link between these radial velocity variations and the low amplitude lineshape variations which are of stellar origin. Long-period variations are not expected from this type of star to our knowledge. If a stellar origin (hence of new type) was to be confirmed for these long-period radial velocity variations, this would have several consequences on the search for planets around main-sequence stars, both in terms of observational strategy and data analysis. An alternative explanation for these variable radial velocities is the presence of at least one planet of a few Jupiter masses orbiting at less than 1 AU. (abridged)Comment: 9 pages, accepted in A

Nonlinear characterisation of a silicon integrated Bragg waveguide filter

Bragg waveguides are promising optical filters for pump suppression in spontaneous Four-Wave Mixing (FWM) photon sources. In this work, we investigate the generation of unwanted photon pairs in the filter itself. We do this by taking advantage of the relation between spontaneous and classical FWM, which allows for the precise characterisation of the nonlinear response of the device. The pair generation rate estimated from the classical measurement is compared with the theoretical value calculated by means of a full quantum model of the filter, which also allows to investigate the spectral properties of the generated pairs. We find a good agreement between theory and experiment, confirming that stimulated FWM is a valuable approach to characterise the nonlinear response of an integrated filter, and that the pairs generated in a Bragg waveguide are not a serious issue for the operation of a fully integrated nonclassical source

An integrated source of spectrally filtered correlated photons for large scale quantum photonic systems

We demonstrate the generation of quantum-correlated photon-pairs combined with the spectral filtering of the pump field by more than 95dB using Bragg reflectors and electrically tunable ring resonators. Moreover, we perform demultiplexing and routing of signal and idler photons after transferring them via a fiber to a second identical chip. Non-classical two-photon temporal correlations with a coincidence-to-accidental ratio of 50 are measured without further off-chip filtering. Our system, fabricated with high yield and reproducibility in a CMOS process, paves the way toward truly large-scale quantum photonic circuits by allowing sources and detectors of single photons to be integrated on the same chip.Comment: 4 figure

Energy correlations of photon pairs generated by a silicon microring resonator probed by Stimulated Four Wave Mixing

Compact silicon integrated devices, such as micro-ring resonators, have recently been demonstrated as efficient sources of quantum correlated photon pairs. The mass production of integrated devices demands the implementation of fast and reliable techniques to monitor the device performances. In the case of time-energy correlations, this is particularly challenging, as it requires high spectral resolution that is not currently achievable in coincidence measurements. Here we reconstruct the joint spectral density of photons pairs generated by spontaneous four-wave mixing in a silicon ring resonator by studying the corresponding stimulated process, namely stimulated four wave mixing. We show that this approach, featuring high spectral resolution and short measurement times, allows one to discriminate between nearly-uncorrelated and highly-correlated photon pairs.Comment: 7 pages, 4 figure

Sleep hygiene intervention for youth aged 10 to 18 years with problematic sleep: a before-after pilot study

BACKGROUND: The current study aimed to examine the changes following a sleep hygiene intervention on sleep hygiene practices, sleep quality, and daytime symptoms in youth. METHODS: Participants aged 10–18 years with self-identified sleep problems completed our age-appropriate F.E.R.R.E.T (an acronym for the categories of Food, Emotions, Routine, Restrict, Environment and Timing) sleep hygiene programme; each category has three simple rules to encourage good sleep. Participants (and parents as appropriate) completed the Adolescent Sleep Hygiene Scale (ASHS), Pittsburgh Sleep Quality Index (PSQI), Sleep Disturbance Scale for Children (SDSC), Pediatric Daytime Sleepiness Scale (PDSS), and wore Actical® monitors twice before (1 and 2 weeks) and three times after (6, 12 and 20 weeks) the intervention. Anthropometric data were collected two weeks before and 20 weeks post-intervention. RESULTS: Thirty-three youths (mean age 12.9 years; M/F = 0.8) enrolled, and retention was 100%. ASHS scores significantly improved (p = 0.005) from a baseline mean (SD) of 4.70 (0.41) to 4.95 (0.31) post-intervention, as did PSQI scores [7.47 (2.43) to 4.47 (2.37); p < 0.001] and SDSC scores [53.4 (9.0) to 39.2 (9.2); p < 0.001]. PDSS scores improved from a baseline of 16.5 (6.0) to 11.3 (6.0) post- intervention (p < 0.001). BMI z-scores with a baseline of 0.79 (1.18) decreased significantly (p = 0.001) post-intervention to 0.66 (1.19). Despite these improvements, sleep duration as estimated by Actical accelerometry did not change. There was however a significant decrease in daytime sedentary/light energy expenditure. CONCLUSIONS: Our findings suggest the F.E.R.R.E.T sleep hygiene education programme might be effective in improving sleep in children and adolescents. However because this was a before and after study and a pilot study with several limitations, the findings need to be addressed with caution, and would need to be replicated within a randomised controlled trial to prove efficacy. TRIAL REGISTRATION: Australian New Zealand Clinical Trials Registry: ACTRN1261200064981

Extrasolar planets and brown dwarfs around A--F type stars. VIII. A giant planet orbiting the young star HD113337

In the frame of the search for extrasolar planets and brown dwarfs around early-type main-sequence stars, we present the detection of a giant planet around the young F-type star HD113337. We estimated the age of the system to be 150 +100/-50 Myr. Interestingly, an IR excess attributed to a cold debris disk was previously detected on this star. The SOPHIE spectrograph on the 1.93m telescope at Observatoire de Haute-Provence was used to obtain ~300 spectra over 6 years. We used our SAFIR tool, dedicated to the spectra analysis of A and F stars, to derive the radial velocity variations. The data reveal a 324.0 +1.7/-3.3 days period that we attribute to a giant planet with a minimum mass of 2.83 +- 0.24 Mjup in an eccentric orbit with e=0.46 +- 0.04. A long-term quadratic drift, that we assign to be probably of stellar origin, is superimposed to the Keplerian solution.Comment: 7 pages, 4 figure

Component Separation for Spectral X-Ray Imaging Using the XPAD3 Hybrid Pixel Camera

The advent of hybrid pixel cameras in X-ray imaging opens the way to the acquisition of spectral measurements. These new devices for which photon counting replaces charge integration incorporate a dedicated readout electronic for each pixel including a capability of selecting energies via the setup of an energy threshold. This ability is of uppermost importance for the development of new polychromatic X-ray imaging approaches that will exploit spectral information on the detected X-rays. Spectral measurements in X-ray imaging pave the way to the separation of images in several components of physical and biological interest: the photoelectric and the Compton contributions can be separated while several contrast agents can be simultaneously localized. We investigate the capability to perform component separation by using the newly developed XPAD3 hybrid pixel camera incorporated in the micro-CT demonstrator PIXSCAN. Firstly, we propose an approach to configure the acquisition setup in order to optimize the component separation problem with respect to the robustness to the photon noise. The method is based on the Cramer-Rao Bound (CRB) that indicates the lowest reachable variance for the estimation of each component whatever the algorithm. Secondly, we investigate the separation problem with two components namely the photoelectric and the Compton ones. We show on noisy simulated data that such a separation with optimized setup i) enhances the contrast and the Contrast to Noise Ratio (CNR) between biological materials (adipose, soft tissues) and water; ii) cancels the artifacts of the beam-hardening effect that may strongly degrade the image quality. On going work involves two steps: first, dealing with Monte Carlo simulations and real data acquired with the PIXSCAN demonstrator; second, dealing with component separation with more than two components by adding several contrast agents, for which PIXSCAN has already proved its ability to separate them

Planets around evolved intermediate-mass stars. I. Two substellar companions in the open clusters NGC 2423 and NGC 4349

Context. Many efforts are being made to characterize extrasolar planetary systems and unveil the fundamental mechanisms of planet formation. An important aspect of the problem, which remains largely unknown, is to understand how the planet formation process depends on the mass of the parent star. In particular, as most planets discovered to date orbit a solar-mass primary, little is known about planet formation around more massive stars. Aims. To investigate this point, we present first results from a radial velocity planet search around red giants in the clump of intermediate-age open clusters. We choose clusters harbouring red giants with masses between 1.5 and 4 M_sun, using the well-known cluster parameters to accurately determine the stellar masses. We are therefore exploring a poorly-known domain of primary masses, which will bring new insights into the properties of extrasolar planetary systems. Methods. We are following a sample of about 115 red giants with the Coralie and HARPS spectrographs to obtain high-precision radial velocity (RV) measurements and detect giant planets around these stars. We use bisector and activity index diagnostics to distinguish between planetary-induced RV variations and stellar photospheric jitter. Results. We present the discoveries of a giant planet and a brown dwarf in the open clusters NGC 2423 and NGC 4349, orbiting the 2.4 M_sun-star NGC2423 No3 (TYC 5409-2156-1) and the 3.9 M_sun-star NGC4349 No127 (TYC 8975-2606-1). These low-mass companions have orbital periods of 714 and 678 days and minimum masses of 10.6 and 19.8 M_jup, respectively. Combined with the other known planetary systems, these detections indicate that the frequency of massive planets is higher around intermediate-mass stars, and therefore probably scales with the mass of the protoplanetary disk.Comment: 9 pages, 11 figures, accepted for publication in A&