826 research outputs found
Discovery of a Close Substellar Companion to the Hot Subdwarf Star HD 149382-the Decisive Influence of Substellar Objects on Late Stellar Evolution
No full textSubstellar objects, like planets and brown dwarfs orbiting stars, are by-products of the star Formation process. The evolution of their host stars may have an enormous impact on these small companions. Vice versa a planet might also influence stellar evolution as has recently been argued. Here, we report the discovery of an 8-23 Jupiter-mass substellar object orbiting the hot subdwarf HD 149382 in 2.391 d at a distance of only about five solar radii. Obviously, the companion must have survived engulfment in the red giant envelope. Moreover, the substellar companion has triggered envelope ejection and enabled the sdB star to form. Hot subdwarf stars have been identified as the sources of the unexpected ultraviolet (UV) emission in elliptical galaxies, but the Formation of these stars is not fully understood. Being the brightest star of its class, HD 149382 offers the best conditions to detect the substellar companion. Hence, undisclosed substellar companions offer a natural solution for the long-standing Formation problem of apparently single hot subdwarf stars. Planets and brown dwarfs may therefore alter the evolution of old stellar populations and may also significantly affect the UV emission of elliptical galaxies.Deutsche Forschungsgemeinschaft He 1356/40-4McDonald Observator
Tidal Synchronisation Of The Subdwarf B Binary Pg 0101+039
No full textAims. Tidally locked rotation is a frequently applied assumption that helps to measure masses of invisible compact companions in close binaries. The calculations of synchronisation times are affected by large uncertainties, in particular for stars with radiative envelopes, calling for observational constraints. We aim to verify tidally locked rotation for the binary PG 0101+039, a subdwarf B star + white dwarf binary from its tiny (0.025%) light variations measured with the MOST satellite (Randall et al. 2005). Methods. Binary parameters were derived from the mass function, apparent rotation and surface gravity of PG 0101+039 assuming a canonical mass of 0.47 M-circle dot and tidally locked rotation. The light curve was then synthesised and was found to match the observed amplitude well. Results. We verified that the light variations are due to ellipsoidal deformation and that tidal synchronisation is established for PG 0101+039. Conclusions. We conclude that this assumption should hold for all sdB binaries with orbital periods of less than half a day. Hence the masses can be derived from systems that are too faint to measure tiny light variations.Deutsche Forschungsgemeinschaft He1354/40-3McDonald Observator
Simultaneous time-series spectroscopy and multi-band photometry of the sdBV PG 1605+072
No full textWe present time-series spectroscopy and multi-band photometry of the sdBV
PG 1605+072 carried out simultaneously at the Calar Alto 2.2-m and 3.5-m
telescopes. The periodogram analysis of the radial velocity curves reveals three
frequencies at 2.078, 2.756, and 1.985 mHz for and at 2.076,
2.753, and 1.978 mHz for . The corresponding radial velocity
amplitudes are 12.7, 8.0, and 7.9 km s-1 for and 14.3,
6.5, and 7.2 km s-1 for . Furthermore, we found five
frequencies that are present in all wavelength bands of the BUSCA photometer.
The frequencies detected in the radial velocity curves are recovered by the
photometric measurements. Moreover, additional frequencies were present in the
periodograms which could not be identified in all four bands simultaneously. The
comparison of the amplitudes presented here with previous results from radial
velocity and photometric observations of PG 1605+072 shows a significant
change or even switch in the power of the modes within short time scales, i.e.
about one year. No changes in frequency were registered and the phases of
the modes show no wavelength dependency within our multi-band photometry
Cyclooctatetraenyl complexes of the early transition metals and lanthanides. 13. The first organolanthanide complex of the tripod ligand [(C5H5)Co{P(O)(OEt)(2)}(3)](-)
No full textThe reaction of [(eta(8)-C8H8)Sm(mu-Cl)(THF)](2) (1) with Na[(C5H5)Co{P(O)(OEt)(2)}(3)] (2) in a molar ratio of 1:2 in THF solution affords orange, crystalline (eta(8)-C8H8)Sm[(C5H5)Co-{P(O)(OEt)(2)}(3)] (3) as the first organolanthanide complex containing Klaui's tripod ligand. The compound has been fully characterized by elemental analysis and spectroscopic methods
A Structurally Characterized Organometallic Plutonium(IV) Complex
No full textbibtex: ISI:000399384700030 bibtex\location:'POSTFACH 101161, 69451 WEINHEIM, GERMANY',publisher:'WILEY-V C H VERLAG GMBH',type:'Article',affiliation:'Walter, O (Reprint Author), European Commiss, Joint Res Ctr, Directorate Nucl Safety & Secur G, POB 2340, D-76125 Karlsruhe, Germany. Vogt, J; Edelmann, FT (Reprint Author), Otto von Guericke Univ, Inst Chem, Univ Pl 2, D-39106 Magdeburg, Germany. Maron, L (Reprint Author), Univ Toulouse, INSA, CNRS, Lab Phys & Chim Nanoobjets LPCNO,UMR5215, 135 Ave Rangueil, F-31077 Toulouse 4, France. Apostolidis, Christos; Walter, Olaf, European Commiss, Joint Res Ctr, Directorate Nucl Safety & Secur G, POB 2340, D-76125 Karlsruhe, Germany. Vogt, Jochen; Liebing, Phil; Edelmann, Frank T., Otto von Guericke Univ, Inst Chem, Univ Pl 2, D-39106 Magdeburg, Germany. Maron, Laurent, Univ Toulouse, INSA, CNRS, Lab Phys & Chim Nanoobjets LPCNO,UMR5215, 135 Ave Rangueil, F-31077 Toulouse 4, France.','author-email':'[email protected] [email protected] [email protected] [email protected]',da:'2018-12-05','doc-delivery-number':'ES2UZ',eissn:'1521-3773','funding-acknowledgement':'Otto-von-Guericke-Universitat Magdeburg','funding-text':'We thank the Otto-von-Guericke-Universitat Magdeburg for general financial support.','journal-iso':'Angew. Chem.-Int. Edit.','keywords-plus':'TRIS(ETA-5-CYCLOPENTADIENYL) ACTINIDE COMPLEXES; FOCK PERTURBATION-THEORY; BUILDING-BLOCK APPROACH; F-ORBITAL COVALENCY; SANDWICH COMPLEXES; ELECTRONIC-STRUCTURE; CRYSTAL-STRUCTURE; CYCLOOCTATETRAENYL COMPLEXES; TH-PU; ACTINOCENES','number-of-cited-references':'69',oa:'Other Gold, Green Published','orcid-numbers':'Edelmann, Frank T./0000-0001-5209-0018 walter, olaf/0000-0002-2679-1715 Liebing, Phil/0000-0002-4660-1691','research-areas':'Chemistry','times-cited':'8','unique-id':'ISI:000399384700030','usage-count-last-180-days':'2','usage-count-since-2013':'23','web-of-science-categories':'Chemistry, Multidisciplinary'\International audienceThe blood-red plutonocene complex Pu(1,3-COT `')(1,4-COT `') (4; COT `' = eta(8)-bis(trimethylsilyl) cyclooctatetraenyl) has been synthesized by oxidation of the anionic sandwich complex Li[Pu(1,4-COT `')(2)] (3) with anhydrous cobalt(II) chloride. The first crystal structure determination of an organoplutonium(IV) complex revealed an asymmetric sandwich structure for 4 where one COT `' ring is 1,3-substituted while the other retains the original 1,4-substitution pattern. The electronic structure of 4 has been elucidated by a computational study, revealing a probable cause for the unexpected silyl group migration
Cryofixation and Cryosubstitution for Routine Work in Transmission Electron Microscopy
No full textAfter a brief review of the present state of the theory of cryofixation, methods and instruments as well as criteria for the application of cryofixation and cryosubstitution in daily routine work in cell biology and medicine are described. Good results are obtainable using liquid nitrogen for impact freezing on highly polished copper surfaces or by plunging into liquefied propane. Based on these results a versatile and safe system for routine plunging and impact freezing for the majority of biomedical objects has been developed. In order to enable ultramicrotomy at ambient temperature a cryosubstitution system according to the Edelmann principle has been de signed and applied
Preparation and structural characterization of dioxane-coordinated alkali metal bis(trimethylsilyl)amides
No full textUnsolvated RbN(SiMe3)z (1) and CsN(SiMe3)z (2) have been prepared from rubidium and cesium metal respectively and excess hexamethyldisilazane. The molecular structures of the polymeric dioxane adducts NaN(SiMes) .C4HsO2 (3) and [MN(S~M~~)~~.~C~H~(4O, M~ ]=. ROb; .5, ~MC =~ CHs)~ haOveZ been determined by low-temperature single-crystal X-ray diffraction
Dichloro(dimethylsulfoximino)phosphane
No full textThe title compound, C2H6Cl2NOPS, crystallizes as dimers via C - H center dot center dot center dot O hydrogen bonds. S - N [ 1.5446 ( 16) angstrom] is shorter than P - N [ 1.618 ( 2) angstrom], although the latter is a short phosphorus - nitrogen single bond
Solid-state and solution structures of three lithiumsulfinimidamides: Identification of two distinct structural types
No full textThe bidentate sulfinimidamide ligand has almost the same bulk as the cyclopentadienyl l&and. Two distinct structural types of highly reactive lithium sulfinimidamides, commonly used reagents, have been identified by X-ray diffraction and solution NMR studies. In the crystalline state the diethyl ether adducts [(Me,SiN),S(C,H,)Li],.Et,O and [(Me,S~X’BuN)S(C,H,)Lil,.EtzO adopt a twisted tricyclic structure with both a four coordinate and a three coordinate lithium atom in the same aggregate. The ‘H NMR spectra at various temperatures and the low temperature phase-sensitive 6Li, ‘H HOEp. NMR experiment show that this structure is essentially retained in solution. The smaller bulk and higher polarity of tetrahydrofuran compared with diethyl ether results in the coordination of two solvent molecules to give [(Me,S~) S(C,H,)Li.THF],, which has a centrosymmetric stair-shaped tricyclic structure consisting of three fused four-membered rings
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