WASP-33: The first delta Scuti exoplanet host star

We report the discovery of photometric oscillations in the host star of the exoplanet WASP-33 b (HD 15082). The data were obtained in the R band in both transit and out-of-transit phases from the 0.3-m telescope and the Montcabrer Observatory and the 0.8-m telescope at the Montsec Astronomical Observatory. Proper fitting and subsequent removal of the transit signal reveals stellar photometric variations with a semi-amplitude of about 1 mmag. The detailed analysis of the periodogram yields a structure of significant signals around a frequency of 21 cyc per day, which is typical of delta Scuti-type variable stars. An accurate study of the power spectrum reveals a possible commensurability with the planet orbital motion with a factor of 26, but this remains to be confirmed with additional time-series data that will permit the identification of the significant frequencies. These findings make WASP-33 the first transiting exoplanet host star with delta Sct variability and a very interesting candidate to search for star-planet interactions.Comment: 5 pages, 6 figures. Revised version accepted for publication in A&A Letter

The effects of moderately fast shellular rotation on adiabatic oscillations

We investigate adiabatic oscillations for delta Scuti star models, taking into account a moderate rotation velocity ~100 \km/s. The resulting oscillation frequencies include corrections for rotation up to second order in the rotation rate including those of near degeneracy. Effects of either a uniform rotation or a rotation profile assuming local angular momentum conservation of the form Omega=Omega(r) on oscillation frequencies are compared. As expected, important differences (around 3 microHz) are obtained in the $g$ and mixed mode regions. For higher frequency p modes, differences range between 1 microHz and 3 microHz. Such differences are likely to be detectable with future space missions such as COROT, where precisions in frequency around 0.5 microHz will be reachable.Comment: A&A, in press (18 pag, 14 fig

Rotation and Convective Core Overshoot in theta Ophiuchi

(abridged) Recent work on several beta Cephei stars has succeeded in constraining both their interior rotation profile and their convective core overshoot. In particular, a recent study focusing on theta$ Oph has shown that a convective core overshoot parameter of alpha = 0.44 is required to model the observed pulsation frequencies, significantly higher than for other stars of this type. We investigate the effects of rotation and overshoot in early type main sequence pulsators, and attempt to use the low order pulsation frequencies to constrain these parameters. This will be applied to a few test models and theta Oph. We use a 2D stellar evolution code and a 2D linear adiabatic pulsation code to calculate pulsation frequencies for 9.5 Msun models. We calculate low order p-modes for models with a range of rotation rates and convective core overshoot parameters. Using these models, we find that the convective core overshoot has a larger effect on the pulsation frequencies than the rotation, except in the most rapidly rotating models considered. When the differences in radii are accounted for by scaling the frequencies, the effects of rotation diminish, but are not entirely accounted for. We find that increasing the convective core overshoot decreases the large separation, while producing a slight increase in the small separations. We created a model frequency grid which spanned several rotation rates and convective core overshoot values. Using a modified chi^2 statistic, we are able to recover the rotation velocity and core overshoot for a few test models. Finally, we discuss the case of the beta Cephei star theta Oph. Using the observed frequencies and a fixed mass and metallicity, we find a lower overshoot than previously determined, with alpha = 0.28 +/- 0.05. Our determination of the rotation rate agrees well with both previous work and observations, around 30 km/s.Comment: 10 pages, 14 figures. Accepted for publication in A&A

Discovery and analysis of p-mode and g-mode oscillations in the A-type primary of the eccentric binary HD 209295

We have discovered both intermediate-order gravity mode and low-order pressure mode pulsation in the same star, HD 209295. It is therefore both a Gamma Doradus and a Delta Scuti star, which makes it the first pulsating star to be a member of two classes. The star is a single-lined spectroscopic binary with an orbital period of 3.10575 d and an eccentricity of 0.352. Weak pulsational signals are found in both the radial velocity and line-profile variations, allowing us to show that the two highest-amplitude Gamma Doradus pulsation modes are consistent with l=1 and |m|=1. In our 280 h of BVI multi-site photometry we detected ten frequencies in the light variations, one in the Delta Scuti regime and nine in the Gamma Doradus domain. Five of the Gamma Doradus frequencies are exact integer multiples of the orbital frequency. This observation leads us to suspect they are tidally excited. Results of theoretical modeling (stability analysis, tidal excitation) were consistent with the observations. We could not detect the secondary component of the system in infrared photometry, suggesting that it may not be a main-sequence star. Archival data of HD 209295 show a strong ultraviolet excess, the origin of which is not known. The orbit of the primary is consistent with a secondary mass of M > 1.04 Msun indicative of a neutron star or a white dwarf companion.Comment: 18 pages, 18 figures, accepted for publication in MNRAS, shortened abstrac

Approximate Micromechanics Treatise of Composite Impact

A formalism is described for micromechanic impact of composites. The formalism consists of numerous equations which describe all aspects of impact from impactor and composite conditions to impact contact, damage progression, and penetration or containment. The formalism is based on through-the-thickness displacement increments simulation which makes it convenient to track local damage in terms of microfailure modes and their respective characteristics. A flow chart is provided to cast the formalism (numerous equations) into a computer code for embedment in composite mechanic codes and/or finite element composite structural analysis

A multisite photometric study of two unusual Beta Cep stars: the magnetic V2052 Oph and the massive rapid rotator V986 Oph

We report a multisite photometric campaign for the Beta Cep stars V2052 Oph and V986 Oph. 670 hours of high-quality differential photoelectric Stromgren, Johnson and Geneva time-series photometry were obtained with eight telescopes on five continents during 182 nights. Frequency analyses of the V2052 Oph data enabled the detection of three pulsation frequencies, the first harmonic of the strongest signal, and the rotation frequency with its first harmonic. Pulsational mode identification from analysing the colour amplitude ratios confirms the dominant mode as being radial, whereas the other two oscillations are most likely l=4. Combining seismic constraints on the inclination of the rotation axis with published magnetic field analyses we conclude that the radial mode must be the fundamental. The rotational light modulation is in phase with published spectroscopic variability, and consistent with an oblique rotator for which both magnetic poles pass through the line of sight. The inclination of the rotation axis is 54o <i< 58o and the magnetic obliquity 58o <beta< 66o. The possibility that V2052 Oph has a magnetically confined wind is discussed. The photometric amplitudes of the single oscillation of V986 Oph are most consistent with an l=3 mode, but this identification is uncertain. Additional intrinsic, apparently temporally incoherent, light variations of V986 Oph are reported. Different interpretations thereof cannot be distinguished at this point, but this kind of variability appears to be present in many OB stars. The prospects of obtaining asteroseismic information for more rapidly rotating Beta Cep stars, which appear to prefer modes of higher l, are briefly discussed.Comment: 12 pages, 8 figures, MNRAS, in pres

Predicting Properties of Unidirectional-Nanofiber Composites

A theory for predicting mechanical, thermal, electrical, and other properties of unidirectional-nanofiber/matrix composite materials is based on the prior theory of micromechanics of composite materials. In the development of the present theory, the prior theory of micromechanics was extended, through progressive substructuring, to the level of detail of a nanoscale slice of a nanofiber. All the governing equations were then formulated at this level. The substructuring and the equations have been programmed in the ICAN/JAVA computer code, which was reported in "ICAN/JAVA: Integrated Composite Analyzer Recoded in Java" (LEW-17247), NASA Tech Briefs, Vol. 26, No. 12 (December 2002), page 36. In a demonstration, the theory as embodied in the computer code was applied to a graphite-nanofiber/epoxy laminate and used to predict 25 properties. Most of the properties were found to be distributed along the through-the-thickness direction. Matrix-dependent properties were found to have bimodal through-the-thickness distributions with discontinuous changes from mode to mode