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See detailThe blue-edge problem of the V1093 Herculis instability strip revisited using evolutionary models with atomic diffusion
Bloemen, S.; Hu, H.; Aerts, C. et al

in Astronomy and Astrophysics (2014), 569

We have computed a new grid of evolutionary subdwarf B star (sdB) models from the start of central He burning, taking into account atomic diffusion due to radiative levitation, gravitational settling ... [more ▼]

We have computed a new grid of evolutionary subdwarf B star (sdB) models from the start of central He burning, taking into account atomic diffusion due to radiative levitation, gravitational settling, concentration diffusion, and thermal diffusion. We have computed the non-adiabatic pulsation properties of the models and present the predicted p-mode and g-mode instability strips. In previous studies of the sdB instability strips, artificial abundance enhancements of Fe and Ni were introduced in the pulsation driving layers. In our models, the abundance enhancements of Fe and Ni occur naturally, eradicating the need to use artificial enhancements. We find that the abundance increases of Fe and Ni were previously underestimated and show that the instability strip predicted by our simulations solves the so-called blue edge problem of the subdwarf B star g-mode instability strip. The hottest known g-mode pulsator, KIC 10139564, now resides well within the instability strip even when only modes with low spherical degrees (l ≤ 2) are considered. Appendix A is available in electronic form at <A href="http://www.aanda.org/10.1051/0004-6361/201323309/olm">http://www.aanda.org</A> [less ▲]

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See detailStrontiohurlbutite, SrBe2(PO4)2, a new mineral from Nanping no. 31 pegmatite, Fujian Province, Southeastern China
Rao, C; Wang, R; Hatert, Frédéric ULg et al

in American Mineralogist (2014), 99

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See detailA pulsation zoo in the hot subdwarf B star KIC 10139564 observed by Kepler
Baran, A.S.; Reed, M.D.; Stello, D. et al

in Monthly Notices of the Royal Astronomical Society (2012), 424

We present our analyses of 15 months of Kepler data on KIC 10139564. We detected 57 periodicities with a variety of properties not previously observed all together in one pulsating subdwarf B (sdB) star ... [more ▼]

We present our analyses of 15 months of Kepler data on KIC 10139564. We detected 57 periodicities with a variety of properties not previously observed all together in one pulsating subdwarf B (sdB) star. Ten of the periodicities were found in the low-frequency region, and we associate them with nonradial g modes. The other periodicities were found in the high-frequency region, which are likely p modes. We discovered that most of the periodicities are components of multiplets with a common spacing. Assuming that multiplets are caused by rotation, we derive a rotation period of 25.6 ± 1.8 d. The multiplets also allow us to identify the pulsations to an unprecedented extent for this class of pulsator. We also detect l ≥ 2 multiplets, which are sensitive to the pulsation inclination and can constrain limb darkening via geometric cancellation factors. While most periodicities are stable, we detected several regions that show complex patterns. Detailed analyses showed that these regions are complicated by several factors. Two are combination frequencies that originate in the super-Nyquist region and were found to be reflected below the Nyquist frequency. The Fourier peaks are clear in the super-Nyquist region, but the orbital motion of Kepler smears the Nyquist frequency in the barycentric reference frame and this effect is passed on to the sub-Nyquist reflections. Others are likely multiplets but unstable in amplitudes and/or frequencies. The density of periodicities also makes KIC 10139564 challenging to explain using published models. This menagerie of properties should provide tight constraints on structural models, making this sdB star the most promising for applying asteroseismology. To support our photometric analysis, we have obtained spectroscopic radial-velocity measurements of KIC 10139564 using low-resolution spectra in the Balmer-line region. We did not find any radial-velocity variation. We used our high signal-to-noise average spectrum to improve the atmospheric parameters of the sdB star, deriving Teff = 31 859 K and log g = 5.673 dex. Based also on observations made with the Nordic Optical Telescope, operated on the island of La Palma jointly by Denmark, Finland, Iceland, Norway and Sweden, in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias. [less ▲]

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