644 research outputs found
The nature of the recent extreme outburst of the Herbig Be/FU Ori binary Z CMa
Z CMa is a binary system which consists of two young stars: A Herbig AeBe
component "Z CMa NW" embedded in a dust cocoon and a less massive component "Z
CMa SE", which is classified as a FU Orionis type star. Recently, the system
showed the largest outburst reported during the almost 90 years of available
observations. During the recent outburst we detect that the Z CMa system is
polarized by 2.6% in the continuum and emission line spectrum, with a position
angle still perpendicular to the jet. From the high level of polarization we
conclude that the outburst is associated with the dust embedded Herbig AeBe NW
component. The main result of our studies is that the bolometric luminosity of
Z CMa remained surprisingly constant during the recent "outburst". We conclude
that either the geometry of the cavity through which the light escapes from the
cocoon has opened a new path, or that the screen of dust, which reflects the
light toward the observer became more efficient causing the observed increase
of the visual brightness by about 2.5 magnitudes.Comment: letter to A&A, accepted 17/12/200
Magnetic field detection in the B2Vn star HR 7355
The B2Vn star HR 7355 is found to be a He-rich magnetic star.
Spectropolarimetric data were obtained with FORS1 at UT2 on Paranal observatory
to measure the disk-averaged longitudinal magnetic field at various phases of
the presumed 0.52 d cycle. A variable magnetic field with strengths between B_z
= -2200 and +3200G was found, with confidence limits of 100 to 130G. The field
topology is that of an oblique dipole, while the star itself is seen about
equator-on. In the intensity spectra the HeI-lines show the typical equivalent
width variability of He-strong stars, usually attributed to surface abundance
spots. The amplitudes of the equivalent width variability of the HeI lines are
extraordinarily strong compared to other cases. These results not only put HR
7355 unambiguously among the early-type magnetic stars, but confirm its
outstanding nature: With v sin i = 320 km/s the parameter space in which
He-strong stars are known to exist has doubled in terms of rotational velocity.Comment: 6 pages, 5 figures, 1 Table. Accepted for publication in MNRAS
Letter
All-inorganic core-shell silica-titania mesoporous colloidal nanoparticles showing orthogonal functionality
Colloidal mesoporous silica (CMS) nanoparticles with a thin titania-enriched outer shell showing a spatially resolved functionality were synthesized by a delayed co-condensation approach. The titaniashell can serve as a selective nucleation site for the growth of nanocrystalline anatase clusters. These fully inorganic pure silica-core titania-enriched shell mesoporous nanoparticles show orthogonal functionality, demonstrated through the selective adsorption of a carboxylate-containing ruthenium N3-dye. UV-Vis and fluorescence spectroscopy indicate the strong interaction of the N3-dye with the titania-phase at the outer shell of the CMS nanoparticles. In particular, this interaction and thus the selective functionalization are greatly enhanced when anatase nanocrystallites are nucleated at the titania-enriched shell surface
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