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See detailFirst Kepler results on compact pulsators - I. Survey target selection and the first pulsators
Ostensen, R. H.; Silvotti, R.; Charpinet, S. et al

in Monthly Notices of the Royal Astronomical Society (2010), 409

We present results from the first two quarters of a survey to search for pulsations in compact stellar objects with the Kepler spacecraft. The survey sample and the various methods applied in its ... [more ▼]

We present results from the first two quarters of a survey to search for pulsations in compact stellar objects with the Kepler spacecraft. The survey sample and the various methods applied in its compilation are described, and spectroscopic observations are presented to separate the objects into accurate classes. From the Kepler photometry we clearly identify nine compact pulsators and a number of interesting binary stars. Of the pulsators, one shows the strong, rapid pulsations typical of a V361 Hya-type sdB variable (sdBV); seven show long-period pulsation characteristics of V1093 Her-type sdBVs; and one shows low-amplitude pulsations with both short and long periods. We derive effective temperatures and surface gravities for all the subdwarf B stars in the sample and demonstrate that below the boundary region where hybrid sdB pulsators are found, all our targets are pulsating. For the stars hotter than this boundary temperature a low fraction of strong pulsators (<10 per cent) is confirmed. Interestingly, the short-period pulsator also shows a low-amplitude mode in the long-period region, and several of the V1093 Her pulsators show low-amplitude modes in the short-period region, indicating that hybrid behaviour may be common in these stars, also outside the boundary temperature region where hybrid pulsators have hitherto been found. [less ▲]

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See detailEclipse of the B3V companion and flaring of emission lines in V838 Monocerotis
Munari, U.; Corradi, R. L. M.; Henden, A. et al

in Astronomy and Astrophysics (2007), 474

After four years during which only the spectacular light echo was showing continuous and rapid evolution while the central star was nearly constant, in autumn 2006 V838 Mon began a sequence of events ... [more ▼]

After four years during which only the spectacular light echo was showing continuous and rapid evolution while the central star was nearly constant, in autumn 2006 V838 Mon began a sequence of events which profoundly altered its spectroscopic and photometric behavior: (a) an eclipse of the B3V companion, characterized by the disappearance and reappearance of the B3V companion from optical spectra, and an eclipse-like lightcurve of ~70 day duration and Δ B ˜ 1.15 mag, Δ V ˜ 0.55 mag, Δ R[SUB]C[/SUB] ˜ 0.10 mag maximum depth; (b) a large increase in intensity of the [FeII] and FeII emission lines, and the appearance in emission for the first time since the 2002 outburst of Hα and higher Balmer series lines. While the [FeII] and FeII lines maintained a very sharp and unresolved profile, the Hα developed into a wide and structured profile, characterized by a sharp central reversal at the same velocity as one of the CO radio emission components. The disappearance of the B3V companion is equally well explained by a grazing eclipse from the outbursting L-type supergiant or by an eclipse from a dust cloud characterized by E[SUB]B-V[/SUB]=0.55 and R[SUB]V[/SUB]=3.1. We believe the flaring of the emission lines occurred at a similar time as the B3V eclipse just by chance. Tables 2-4 are only available in electronic form at http://www.aanda.org Based on observations made with the Asiago 1.82 m of the INAF Astronomical Observatory of Padova, and with 4.2 m WHT and 2.5 m INT operated by the Isaac Newton Group of Telescopes, and with the 2.6 m NOT operated jointly by Denmark, Finland, Iceland, Norway, and Sweden, in the Spanish Observatorio del Roque de Los Muchachos of the Instituto de Astrofísica de Canarias. [less ▲]

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