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Post Info TOPIC: HD65949
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HD 65949
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Title: HD 65949: Rosetta Stone or Red Herring
Authors: C. R. Cowley, S. Hubrig, P. Palmeri, P. Quinet, É. Biémont, G. M. Wahlgren, O. Schütz, J. F. González

HD 65949 is a late B star with exceptionally strong Hg II at 3984[A], but it is not a typical HgMn star. The Re II spectrum is of extraordinary strength. Abundances, or upper limits are derived here for 58 elements based on a model with Teff = 13100K, and log(g) = 4.0. Even-Z elements through nickel show minor deviations from solar abundances. Anomalies among the odd-Z elements through copper are mostly small. Beyond the iron peak, a huge scatter is found. The abundance pattern of the heaviest elements resembles the N=126 r-process peak of solar material, though not in detail. We find a significant correlation of the abundance excesses with second ionisation potentials for elements with Z > 30. This indicates the relevance of photospheric or near-photospheric processes. We explore a model with mass accretion of exotic material followed by the more commonly accepted differentiation by diffusion. That model leads to a number of predictions which challenge future work.
Likely primary and secondary masses are near 3.3 and 1.6 M(solar), with a separation of ca. 0.25 AU. New atomic structure calculations are presented in two appendices.

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RE: HD65949
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Title: Re II and Other Exotic Spectra in HD 65949
Authors: C. R. Cowley, S. Hubrig, G. M. Wahlgren

Powerful astronomical spectra reveal an urgent need for additional work on atomic lines, levels, and oscillator strengths. The star HD 65949 provides some excellent examples of species rarely identified in stellar spectra. For example, the Re II spectrum is well developed, with 17 lines between 3731 and 4904 [A], attributed wholly or partially to Re II. Classifications and oscillator strengths are lacking for a number of these lines. The spectrum of Os II is well identified. Of 14 lines attributed wholly or partially to Os II, only one has an entry in the VALD database. We find strong evidence that Te II is present. There are NO Te II lines in the VALD database. Ru II is clearly present, but oscillator strengths for lines in the visual are lacking. There is excellent to marginal evidence for a number of less commonly identified species, including Kr II, Nb II, Sb II, Xe II, Pr III, Ho III, Au II, and Pt II (probably Pt-198), to be present in the spectrum of HD 65949. The line Hg II at 3984 [A] is of outstanding strength, and all three lines of Multiplet 1 of Hg I are present, even though the surface temperature of HD 65949 is relatively high. Finally, we present the case of an unidentified, 24 [mA], line at 3859.63 [A], which could be the same feature seen in magnetic CP stars. It is typically blended with a putative U II line used in cosmochronology.

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Blobrana


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Title: HD 65949: The Highest Known Mercury Excess Of Any CP Star?
Authors: Charles R. Cowley, S. Hubrig, G. F. Gonzalez, N. Nunez

ESO spectra of HD 65949 show it to be unlike any of the well-known types within its temperature range ~ 13600K. It is neither a silicon, nor a mercury-manganese star, though it has a huge Hg II line at λ3984. We estimate log( Hg/H) + 12.0 ≈ 7.4. This is higher than any published stellar mercury abundance. HD 65949 is a member of a nearby open cluster, NGC 2516, which is only slightly older than the Pleiades, and has been of recent interest because of its numerous X-ray emission stars, including HD 65949 itself, or a close companion. A longitudinal magnetic field of the order of -290 Gauss at the 4.7σ level was very recently diagnosed from accurate circular spectropolarimetric observations with FORS 1 at the VLT.
The spectral lines are sharp, allowing a thorough identification study. Second spectra of Ti, Cr, and Fe are rich. Mn II is well identified but not unusually strong. Numerous lines of S II and P II are found, but not Ga II. The resonance lines of Sr II are strong. While many Y II lines are identified, and Nb II is very likely present, no Zr II lines were found. Xe II is well identified. Strong absorptions from the third spectra of the lanthanides Pr, Nd, and Ho are present, but lines from the second spectra of lanthanides are extremely weak or absent. Among lines from the heavier elements, those of Pt II are clearly present, and the heaviest isotope, ^198Pt, is indicated. The uncommon spectrum of Re II is certain, while Os II and Te II are highly probable. Several of the noted anomalies are unusual for a star as hot as HD 65949.

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