Yazar "Fuller, J." seçeneğine göre listele

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    The single-sided pulsator CO Camelopardalis
    (Oxford Univ Press, 2020) Kurtz, D. W.; Handler, G.; Rappaport, S. A.; Saio, H.; Fuller, J.; Jacobs, T.; Schmitt, A.
    CO Cam (TIC 160268882) is the second 'single-sided pulsator' to be discovered. These are stars where one hemisphere pulsates with a significantly higher amplitude than the other side of the star. CO Cam is a binary star comprised of an Am d Sct primary star with T-eff = 7070 +/- 150 K, and a spectroscopically undetected G main-sequence secondary star. The dominant pulsating side of the primary star is centred on the L1 point. We have modelled the spectral energy distribution combined with radial velocities, and independently the TESS light curve combined with radial velocities. Both of these give excellent agreement and robust system parameters for both stars. The d Sct star is an oblique pulsator with at least four low radial overtone (probably) f modes with the pulsation axis coinciding with the tidal axis of the star, the line of apsides. Preliminary theoretical modelling indicates that the modes must produce much larger flux perturbations near the L1 point, although this is difficult to understand because the pulsating star does not come near to filling its Roche lobe. More detailed models of distorted pulsating stars should be developed. These newly discovered single-sided pulsators offer new opportunities for astrophysical inference from stars that are oblique pulsators in close binary stars.
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    Tidally trapped pulsations in a close binary star system discovered by TESS
    (Nature Publishing Group, 2020) Handler, G.; Kurtz, D. W.; Rappaport, S. A.; Saio, H.; Fuller, J.; Jones, D.; Guo, Z.
    It has long been suspected that tidal forces in close binary stars could modify the orientation of the pulsation axis of the constituent stars. Such stars have been searched for, but until now never detected. Here we report the discovery of tidally trapped pulsations in the ellipsoidal variable HD 74423 in Transiting Exoplanet Survey Satellite (TESS) space photometry data. The system contains a delta Scuti pulsator in a 1.6 d orbit, whose pulsation mode amplitude is strongly modulated at the orbital frequency, which can be explained if the pulsations have a much larger amplitude in one hemisphere of the star. We interpret this as an obliquely pulsating distorted dipole oscillation with a pulsation axis aligned with the tidal axis. This is the first time that oblique pulsation along a tidal axis has been recognized. It is unclear whether the pulsations are trapped in the hemisphere directed towards the companion or in the side facing away from it, but future spectral measurements can provide the solution. In the meantime, the single-sided pulsator HD 74423 stands out as the prototype of a new class of obliquely pulsating stars in which the interactions of stellar pulsations and tidal distortion can be studied. HD 74423 is an unusual binary star system containing two lambda Bootis pulsators. TESS photometry reveals that one of the pair is pulsating along its tidal axis-but only in one hemisphere. Such an odd arrangement provides an interesting laboratory in which to study stellar pulsations and tidal distortion.