2,356 research outputs found
Multiperiodicity in the large-amplitude rapidly-rotating Ceph ei star HD 203664
We perform a seismic study of the young massive Cephei star HD 203664
with the goal to constrain its interior structure. Our study is based on a time
series of 328 new Geneva 7-colour photometric data of the star spread over
496.8 days. The data confirm the frequency of the dominant mode of the star
which we refine to c d. The mode has a large amplitude of
37 mmag in V and is unambiguously identified as a dipole mode () from
its amplitude ratios and non-adiabatic computations. Besides , we discover
two additional new frequencies in the star with amplitudes above :
c d and c d or one of their daily
aliases. The amplitudes of these two modes are only between 3 and 4 mmag which
explains why they were not detected before. Their amplitude ratios are too
uncertain for mode identification. We show that the observed oscillation
spectrum of HD 203664 is compatible with standard stellar models but that we
have insufficient information for asteroseismic inferences. Among the
large-amplitude Cephei stars, HD 203664 stands out as the only one
rotating at a significant fraction of its critical rotation velocity ().Comment: 7 pages, 5 figures, accepted for publication in A&A (Astronomy &
Astrophysics
e^+ e^- -> 3 jets and event shapes at NNLO
We report on the calculation of NNLO corrections to the 3-jet cross section
and related event shape distributions in electron-positron annihilation. The
corrections are sizable for all variables, however the magnitude of the
corrections is substantially different for different observables. We observe
that inclusion of the NNLO corrections yields a considerably better agreement
between theory and experimental data both in shape and normalization of the
event shape distributions in the region where the perturbative result is
expected to hold. A new extraction of using the event shape
variables up to NNLO yields a considerably better consistency between the
observables indicating a stabilization of the perturbative corrections at this
order.Comment: Contribution to the Proceedings of the 9th DESY workshop on "Loops
and Legs in Quantum Field Theory", Sondershausen, April 200
- …