Zobrazeno 1 - 10
of 67
pro vyhledávání: '"Koeppen, J. A."'
Publikováno v:
In Nurse Education in Practice July 2024 78
Autor:
Miszalski, B., Boffin, H. M. J, Jones, D., Karakas, A. I., Köppen, J., Tyndall, A. A., Mohamed, S. S., Rodríguez-Gil, P., Santander-García, M.
Classical barium stars are binary systems which consist of a late-type giant enriched in carbon and slow neutron capture (s-process) elements and an evolved white dwarf (WD) that is invisible at optical wavelengths. The youngest observed barium stars
Externí odkaz:
http://arxiv.org/abs/1309.5239
Spectral analyses of hot, compact stars with NLTE (non-local thermodynamical equilibrium) model-atmosphere techniques allow the precise determination of photospheric parameters. The derived photospheric metal abundances are crucial constraints for st
Externí odkaz:
http://arxiv.org/abs/1210.7614
Autor:
Miszalski, B., Crowther, P. A., De Marco, O., Köppen, J., Moffat, A. F. J., Acker, A., Hillwig, T. C.
We report on the serendipitous discovery of the first central star of a planetary nebula (PN) that mimics the helium- and nitrogen-rich WN sequence of massive Wolf-Rayet (WR) stars. The central star of IC 4663 (PN G346.2-08.2) is dominated by broad H
Externí odkaz:
http://arxiv.org/abs/1203.3303
Autor:
Boffin, Henri M. J., Miszalski, B., Frew, D. J., Acker, A., Köppen, J., Moffat, A. F. J., Parker, Q. A.
We have found the central star of Abell 70 (PN G038.1-25.4, hereafter A 70) to be a binary consisting of a G8 IV-V secondary and a hot white dwarf. The secondary shows enhanced Ba II and Sr II features, firmly classifying it as a barium star. The neb
Externí odkaz:
http://arxiv.org/abs/1109.1519
Autor:
Miszalski, B., Boffin, H. M. J., Frew, D. J., Acker, A., Köppen, J., Moffat, A. F. J., Parker, Q. A.
Abell 70 (PN G038.1-25.4, hereafter A 70) is a planetary nebula (PN) known for its diamond ring appearance due a superposition with a background galaxy. The previously unstudied central star is found to be a binary consisting of a G8IV-V secondary at
Externí odkaz:
http://arxiv.org/abs/1108.3957
Autor:
Miszalski, B., Mikołajewska, J., Köppen, J., Rauch, T., Acker, A., Cohen, M., Frew, D. J., Moffat, A. F. J., Parker, Q. A., Jones, A. F., Udalski, A.
The central star of the planetary nebula (CSPN) M 2-29 shows an extraordinary R Coronae Borealis-like fading event in its optical lightcurve. The only other CSPN to show these events are CPD-568032 (Hen 3-1333) and V651 Mon (NGC 2346). Dust cloud for
Externí odkaz:
http://arxiv.org/abs/1101.4959
Publikováno v:
Mon.Not.Roy.Astron.Soc.375:673-684,2007
Observations show that galaxies follow a mass-metallicity relation over a wide range of masses. One currently favoured explanation is that less massive galaxies are less able to retain the gas and stellar ejecta and thus may lose the freshly produced
Externí odkaz:
http://arxiv.org/abs/astro-ph/0611723
Autor:
Köppen, J., Hensler, G.
The chemical evolution of galaxies that undergo an episode of massive and rapid accretion of metal-poor gas is investigated with models using both simplified and detailed nucleosynthesis recipes. The rapid decrease of the oxygen abundance during infa
Externí odkaz:
http://arxiv.org/abs/astro-ph/0501415
Publikováno v:
Astrophys.Space Sci. 277 (2001) 169-172
We employ analytical and numerical chemical evolution models to study observed trends in abundance ratios involving carbon, nitrogen, and oxygen. Several sets of published stellar yields for both intermediate-mass and massive stars are considered, an
Externí odkaz:
http://arxiv.org/abs/astro-ph/0101070