Probing the internal magnetic field of slowly pulsating B-stars through g modes

We suggest that high-order g modes can be used as a probe of the internal magnetic field of SPB (slowly pulsating B) stars. The idea is based on earlier work by the authors which analytically investigated the effect of a vertical magnetic field on p and g modes in a plane-parallel isothermal stratified atmosphere. It was found that even a weak field can significantly shift the g-mode frequencies -- the effect increases with mode order. In the present study we adopt the classical perturbative approach to estimate the internal field of a 4 solar mass SPB star by looking at its effect on a low-degree ($l=1$) and high-order ($n=20$) g mode with a period of about 1.5 d. We find that a polar field strength of about 110 kG on the edge of the convective core is required to produce a frequency shift of 1%. Frequency splittings of that order have been observed in several SPB variables, in some cases clearly too small to be ascribed to rotation. We suggest that they may be due to a poloidal field with a strength of order 100 kG, buried in the deep interior of the star.Comment: 4 pages, 2 figures (to appear in Astronomy & Astrophysics

XMM-Newton and INTEGRAL analysis of the Supergiant Fast X-ray Transient IGR J17354-3255

We present the results of combined INTEGRAL and XMM-Newton observations of the supergiant fast X-ray transient (SFXT) IGR J17354$-$3255. Three XMM-Newton observations of lengths 33.4 ks, 32.5 ks and 21.9 ks were undertaken, the first an initial pointing to identify the correct source in the field of view and the latter two performed around periastron. Simultaneous INTEGRAL observations across $\sim66\%$ of the orbital cycle were analysed but the source was neither detected by IBIS/ISGRI nor by JEM-X. The XMM-Newton light curves display a range of moderately bright X-ray activity but there are no particularly strong flares or outbursts in any of the three observations. We show that the spectral shape measured by XMM-Newton can be fitted by a consistent model throughout the observation, suggesting that the observed flux variations are driven by obscuration from a wind of varying density rather than changes in accretion mode. The simultaneous INTEGRAL data rule out simple extrapolation of the simple powerlaw model beyond the XMM-Newton energy range.Comment: 13 pages, 9 figures, This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society Published by Oxford University Pres

Bounds on the Magnetic Fields in the Radiative Zone of the Sun

We discuss bounds on the strength of the magnetic fields that could be buried in the radiative zone of the Sun. The field profiles and decay times are computed for all axisymmetric toroidal Ohmic decay eigenmodes with lifetimes exceeding the age of the Sun. The measurements of the solar oblateness yield a bound <~ 7 MG on the strength of the field. A comparable bound is expected to come from the analysis of the splitting of the solar oscillation frequencies. The theoretical analysis of the double diffusive instability also yields a similar bound. The oblateness measurements at their present level of sensitivity are therefore not expected to measure a toroidal field contribution.Comment: 15 pages, 6 figure

New insights on accretion in Supergiant Fast X-ray Transients from XMM-Newton and INTEGRAL observations of IGR J17544−-2619

XMM-Newton observations of the supergiant fast X-ray transient IGR$~$J17544$-$2619 are reported and placed in the context of an analysis of archival INTEGRAL/IBIS data that provides a refined estimate of the orbital period at 4.9272$\pm$0.0004 days. A complete outburst history across the INTEGRAL mission is reported. Although the new XMM-Newton observations (each lasting $\sim$15 ks) targeted the peak flux in the phase-folded hard X-ray light curve of IGR$~$J17544$-$2619, no bright outbursts were observed, the source spending the majority of the exposure at intermediate luminosities of the order of several 10$^{33}\,$erg$\,$s$^{-1}$ (0.5$\,-\,$10$\,$keV) and displaying only low level flickering activity. For the final portion of the exposure, the luminosity of IGR$~$J17544$-$2619 dropped to $\sim$4$\times$10$^{32}\,$erg$\,$s$^{-1}$ (0.5 - 10 keV), comparable with the lowest luminosities ever detected from this source, despite the observations being taken near to periastron. We consider the possible orbital geometry of IGR$~$J17544$-$2619 and the implications for the nature of the mass transfer and accretion mechanisms for both IGR$~$J17544$-$2619 and the SFXT population. We conclude that accretion under the `quasi-spherical accretion' model provides a good description of the behaviour of IGR$~$J17544$-$2619, and suggest an additional mechanism for generating outbursts based upon the mass accumulation rate in the hot shell (atmosphere) that forms around the NS under the quasi-spherical formulation. Hence we hope to aid in explaining the varied outburst behaviours observed across the SFXT population with a consistent underlying physical model.Comment: 12 pages, 5 figures, accepted for publication in MNRA

New Analysis of Mercury Laser Altimeter Crossovers to Improve Geodetic Constraints by MESSENGER

No abstract availabl

Analysis of MERCATOR data Part I: variable B stars

We re-classified 31 variable B stars which were observed more than 50 times in the Geneva photometric system with the P7 photometer attached to the MERCATOR telescope (La Palma) during its first 3 years of scientific observations. HD89688 is a possible beta Cephei/slowly pulsating B star hybrid and the main mode of the COROT target HD180642 shows non-linear effects. The Maia candidates are re-classified as either ellipsoidal variables or spotted stars. Although the mode identification is still ongoing, all the well-identified modes so far have a degree l = 0, 1 or 2.Comment: 4 pages, 3 figures. To appear in: Proceedings of JENAM 2005 'Distant worlds', Communications in Asteroseismolog

Using a gamified monitoring app to change adolescents' snack intake : the development of the REWARD app and evaluation design

Background: As the snacking pattern of European adolescents is of great concern, effective interventions are necessary. Till now health promotion efforts in children and adolescents have had only limited success in changing adolescents' eating patterns and anthropometrics. Therefore, the present study proposes an innovative approach to influence dietary behaviors in youth based on new insights on effective behavior change strategies and attractive intervention channels to engage adolescents. This article describes the rationale, the development, and evaluation design of the 'Snack Track School' app. The aim of the app is to improve the snacking patterns of Flemish 14- to 16-year olds. Methods: The development of the app was informed by the systematic, stepwise, iterative, and collaborative principles of the Intervention Mapping protocol. A four week mHealth intervention was developed based on the dual-system model with behavioral change strategies targeting both the reflective (i.e., active learning, advance organizers, mere exposure, goal-setting, monitoring, and feedback) and automatic processes (i.e., rewards and positive reinforcement). This intervention will be evaluated via a controlled pre-post design in Flemish schools among 1400 adolescents. Discussion: When this intervention including strategies focused on both the reflective and automatic pathway proves to be effective, it will offer a new scientifically-based vision, guidelines and practical tools for public health and health promotion (i.e., incorporation of learning theories in intervention programs)

Psychometric properties of the Dutch version of the London Measure of Unplanned Pregnancy in women with pregnancies ending in birth

OBJECTIVE: To evaluate the psychometric properties of the Dutch version of the London Measure of Unplanned Pregnancy in women with pregnancies ending in birth. METHODS: A two-phase psychometric evaluation design was set-up. Phase I comprised the translation from English into Dutch and pretesting with 6 women using cognitive interviews. In phase II, the reliability and validity of the Dutch version of the LMUP was assessed in 517 women giving birth recently. Reliability (internal consistency) was assessed using Cronbach's alpha, inter-item correlations, and corrected item-total correlations. Construct validity was assessed using principal components analysis and hypothesis testing. Exploratory Mokken scale analysis was carried out. RESULTS: 517 women aged 15-45 completed the Dutch version of the LMUP. Reliability testing showed acceptable internal consistency (alpha = 0.74, positive inter-item correlations between all items, all corrected item-total correlations >0.20). Validity testing confirmed the unidimensional structure of the scale and all hypotheses were confirmed. The overall Loevinger's H coefficient was 0.57, representing a 'strong' scale. CONCLUSION: The Dutch version of the LMUP is a reliable and valid measure that can be used in the Dutch-speaking population in Belgium to assess pregnancy planning. Future research is necessary to assess the stability of the Dutch version of the LMUP, and to evaluate its psychometric properties in women with abortions