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تسجيل مستخدم جديدThe compact planetary nebula B[e] star Hen 2-90
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We present a study of the optical spectrum of the fascinating B[e] star Hen 2-90 based on new high-resolution observations taken with FEROS at the ESO 1.52m telescope in La Silla (Chile). The recent HST image of Hen 2-90 (Sahai et al. 2002) reveals a bipolar, highly ionized region, a neutral disk-like structure seen almost perfectly edge-on, and an intermediate region of moderate ionization. The slits of our observations cover the same innermost region of Hen 2-90 as the HST image, which allows us to combine the observations. Our spectra contain a huge amount of permitted and forbidden emission lines of atoms in different stages of ionization. In addition, the line wings deliver velocity information of the emitting region. We find correlation between the different ionization states of the elements and the velocities derived from the line profiles: the highly ionized atoms have the highest outflow velocity, while the neutral lines have the lowest. When combining the velocity information with the HST image of Hen 2-90, it seems that a non-spherical stellar wind model is a good option to explain the ionization and spatial distribution of the circumstellar material. Our modeling of the forbidden emission lines results in strong evidence for Hen 2-90 being a compact planetary nebulae that has undergone a superwind phase of high, non-spherical mass loss, most probably triggered by a central star that was rotating with about 80% of the critical velocity. We find a total mass loss rate during this superwind phase on the order of 3 x 10^(-5) M_sun/yr.
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The proto-planetary nebula Hen 3-1475 shows a remarkable highly collimated optical jet with an S-shaped string of three pairs of knots and extremely high velocities. We present here a detailed analysis of the overall morphology, kinematic structure a
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(abridged) We study the optical spectrum of the exciting B[e] star Hen 2-90 based on new high-resolution observations that cover the innermost 2. Our investigation is splitted in two parts, a qualitative study of the presence of the numerous emission
lines and the classification of their line profiles which indicate a circumstellar environment of high complexity, and a quantitative analysis of numerous forbidden lines, e.g. [OI], [OII], [OIII], [SII], [SIII], [ArIII], [ClII], [ClIII] and [NII]. We find a correlation between the different ionization states of the elements and the velocities derived from the line profiles: the highly ionized atoms have the highest outflow velocity while the neutral lines have the lowest outflow velocity. The recent HST image of Hen 2-90 reveals a bipolar, highly ionized region, a neutral disk-like structure and an intermediate region of moderate ionization. It seems that a non-spherical stellar wind model is a good option to explain the ionization and spatial distribution of the circumstellar material. We modelled the forbidden lines under the assumption of a non-spherically symmetric wind based on the HST image. We find that in order to fit the observed line luminosities, the mass flux, surface temperature, and terminal wind velocities need to be latitude dependent, which might be explained in terms of a rapidly rotating central star. A rotation speed of 75-80 % of the critical velocity has been derived. The total mass loss rate of the star was determined to be of order 3 10^{-5} M_sun/yr. Such a wind scenario and the fact that compared to solar abundances C, O, and N seem to be underabundant while S, Ar and Cl have solar abundances, might be explained in terms of a rapidly rotating post-AGB star.
We present BVRI CCD aperture polarization and near-infrared photometry of the proto-planetary nebula Hen 3-1475. Its intrinsic polarization is high and shows a strong spectral dependence. The position angles in all bands are perpendicular to the axis
of the observed bipolar structure. A Monte Carlo code is used to model the intrinsic polarization of hhe. Using disk dimensions and other constraints suggested by previous works, we are able to reproduce the observations with an optically thick disk composed by grains with a power-law size distribution ranging from 0.06 to 0.22 um. We also reliably estimate the foreground polarization from hundreds of stars contained in the CCD images. It is parallel to the intrinsic polarization of Hen 3-1475. Possible implications of this result are discussed. From IR observations, we estimate a interstellar reddening, A(V), of about 3.2.
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