5,297 research outputs found
Four new HgMn stars: HD 18104, HD 30085, HD 32867, HD 53588
We have detected four new HgMn stars, while monitoring a sample of apparently
slowly rotating superficially normal bright late B and early A stars in the
northern hemisphere. Important classification lines of Hg II and Mn II are
found as conspicuous features in the high resolution SOPHIE spectra of these
stars (R = 75000). Several lines of Hg II, Mn II and Fe II have been
synthesized using model atmospheres and the spectrum synthesis code SYNSPEC48
including hyperfine structure of various isotopes when relevant. These
synthetic spectra have been compared to high resolution high signal-to-noise
observations of these stars in order to derive abundances of these key
elements. The four stars are found to have distinct enhancements of Hg and Mn
which show that these stars are not superficially normal B and A stars, but
actually are new HgMn stars and should reclassified as such.Comment: 4 pages, 3 figures, accepted in A&
A dedicated photometric system for the detection of Wolf-Rayet stars
We present here tests of a five-filter photometric system aimed at WR
classification. In addition to the well-known easy separation between the WN
and WC spectral types, these tests indicate interesting potentialities in the
discrimination of subgroups among the WN and the WC which look well related to
the classical subtypes. The proposed combinations of filters (or derived ones)
bear enough discriminating power to satisfy some evolutionary studies in
crowded fields where spectroscopic follow-up is not possible.Comment: 10 pages, 7 figures, uses l-aa.sty and psfig for figure inclusion.
Also available at http://vela.astro.ulg.ac.be/preprint/P10 Accepted for
publication in Astronomy & Astrophysics Supp
Ternary cluster decay within the liquid drop model
Longitudinal ternary and binary fission barriers of Ar, Ni and
Cf nuclei have been determined within a rotational liquid drop model
taking into account the nuclear proximity energy. For the light nuclei the
heights of the ternary fission barriers become competitive with the binary ones
at high angular momenta since the maximum lies at an outer position and has a
much higher moment of inertia.Comment: Talk presented at the 9th International Conference on Clustering
Aspects of Nuclear Structure and Dynamics (CLUSTERS'07
Compact star clusters of the LMC HII region N11C
Based on imaging and spectroscopy obtained at the ESO NTT telescope and using
an efficient image analysis algorithm, we study the core of the LMC OB
association LH13, particularly the two compact stellar clusters Sk-6641 and HNT
in the HII, region N11C. We resolve Sk-6641 into 15 components and for the
first time the HNT cluster into 70 stars, and derive photometry for the
members. Moreover, from medium resolution spectroscopy we determine the
spectral types for sixteen stars in N11C. We compare the color-magnitude
diagrams of the clusters with that of the field stars and discuss the cluster
ages. With an age of ~100 Myr, the HNT cluster appears significantly older than
the very young (< 5 Myr) Sk-6641 starburst. We suggest that most of the `field'
O-stars in the core of N11C have actually been ejected from Sk-6641 through
dynamical interactions in the compact cluster. The properties of the Sk-6641
and HNT clusters suggest that we are viewing different star formation regions
lying at different distances along the same line of sight.Comment: 12 pages, 8 figure
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