214 research outputs found
Bloch cavity solitons in nonlinear resonators with intracavity photonic crystals
We predict a novel type of cavity solitons, Bloch cavity solitons, existing in nonlinear resonators with
the refractive index modulated in both longitudinal and transverse directions and for both focusing (at
normal diffraction) and defocusing (at anomalous diffraction) nonlinearities. We develop a modified
mean-field theory and analyze the properties of these novel cavity solitons demonstrating, in particular,
their substantial narrowing in the zero-diffraction regime
Wind and nebula of the M33 variable GR290 (WR/LBV)
Context: GR290 (M33/V532=Romano's Star) is a suspected post-LBV star located
in M33 galaxy that shows a rare Wolf-Rayet spectrum during its minimum light
phase. In spite of many studies, its atmospheric structure, its circumstellar
environment and its place in the general context of massive stars evolution is
poorly known. Aims: Detailed study of its wind and mass loss, and study of the
circumstellar environment associated to the star. Methods: Long-slit spectra of
GR290 were obtained during its present minimum luminosity phase with the GTC
together with contemporaneous BVRI photometry. The data were compared with
non-LTE model atmosphere synthetic spectra computed with CMFGEN and with CLOUDY
models for ionized interstellar medium regions. Results: The current
mag, is the faintest at which this source has ever been observed. The non-LTE
models indicate effective temperature =27-30 kK at radius
=27-21 Rsun and mass loss rate Msun
yr. The terminal wind speed =620 is faster
than ever before recorded while the current luminosity Lsun is the lowest ever deduced. It is overabundant in He and N and
underabundant in C and O. It is surrounded by an unresolved compact HII region
with dimensions 4 pc, from where H-Balmer, HeI lines and [OIII] and [NII]
are detected. In addition, we find emission from a more extended interstellar
medium (ISM) region which appears to be asymmetric, with a larger extent to the
East (16-40 pc) than to the West. Conclusions: In the present long lasting
visual minimum, GR290 is in a lower bolometric luminosity state with higher
mass loss rate. The nearby nebular emission seems to suggest that the star has
undergone significant mass loss over the past years and is nearing
the end stages of its evolution.Comment: submitted to A&A, 12 pages, 9 figures, 7 table
Calculation of the water vapor line intensities for rotational transitions between high-excited energy levels
The intensities of water vapor in the range of pure rotational transitions were calculated up to high quantum numbers (Jmax ~ 30 and Ka max ~ 25). The diagonalization of the effective rotational Hamiltonian, approximated by Pade-Borel method, is applied to obtain the eigenvectors. The centrifugal distortion perturbations in line intensities were taken into account by the traditional equations for matrix elements of the transformed dipole moment, including eight parameters, and previously developed by authors Pade approximant. Moreover, to conduct the calculations, the rotational wavefunctions of the symmetric rotor molecule were applied. The results were compared with the known theoretical data. Β© (2015) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only
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