Direct Observation of the Fourth Star in the Zeta Cancri System

Direct imaging of the zeta Cnc system has resolved the fourth star in the system, which is in orbit around zeta Cnc C. The presence of the fourth star has been inferred for many years from irregularities in the motion of star C, and recently from C's spectroscopic orbit. However, its mass is close to that of C, making its non-detection puzzling. Observing at wavelengths of 1.2, 1.7, and 2.2 microns with the adaptive-optics system of the CFHT, we have obtained images which very clearly reveal star D and show it to have the color of an M2 star. Its brightness is consonant with its being two M stars, which are not resolved in our observations but are likely to be in a short-period orbit, thereby accounting for the large mass and the difficulty of detection at optical wavelengths, where the magnitude difference is much larger. The positions and colors of all four stars in the system are reported and are consistent with the most recent astrometric observations.Comment: 7 pages including 3 tables, 1 figure; To appear in PAS

A New Linear Inductive Voltage Adder Driver for the Saturn Accelerator

Saturn is a dual-purpose accelerator. It can be operated as a large-area flash x-ray source for simulation testing or as a Z-pinch driver especially for K-line x-ray production. In the first mode, the accelerator is fitted with three concentric-ring 2-MV electron diodes, while in the Z-pinch mode the current of all the modules is combined via a post-hole convolute arrangement and driven through a cylindrical array of very fine wires. We present here a point design for a new Saturn class driver based on a number of linear inductive voltage adders connected in parallel. A technology recently implemented at the Institute of High Current Electronics in Tomsk (Russia) is being utilized[1]. In the present design we eliminate Marx generators and pulse-forming networks. Each inductive voltage adder cavity is directly fed by a number of fast 100-kV small-size capacitors arranged in a circular array around each accelerating gap. The number of capacitors connected in parallel to each cavity defines the total maximum current. By selecting low inductance switches, voltage pulses as short as 30-50-ns FWHM can be directly achieved.Comment: 3 pages, 4 figures. This paper is submitted for the 20th Linear Accelerator Conference LINAC2000, Monterey, C

New ground-based observational methods and instrumentation for asteroseismology

Space instrumentation like SOHO, MOST, CoRoT and Kepler has been and is being built to attain very high precision data to be used for asteroseismic analysis. Nonetheless, there is a very strong need for providing additional information, especially on mode identification. With this contribution I will review the efforts been put on new ground-based instrumentation and the methodology that can be used to achieve this aim.Comment: 6 pages. Review contribution to be published in Astrophysics and Space Science Proceedings series (ASSP), in the proceedings of "20th Stellar Pulsation Conference Series: Impact of new instrumentation and new insights in stellar pulsations", 5-9 September 2011, Granada, Spai

Sub-chronic inhalation of high concentrations of manganese sulfate induces lower airway pathology in rhesus monkeys

BACKGROUND: Neurotoxicity and pulmonary dysfunction are well-recognized problems associated with prolonged human exposure to high concentrations of airborne manganese. Surprisingly, histological characterization of pulmonary responses induced by manganese remains incomplete. The primary objective of this study was to characterize histologic changes in the monkey respiratory tract following manganese inhalation. METHODS: Subchronic (6 hr/day, 5 days/week) inhalation exposure of young male rhesus monkeys to manganese sulfate was performed. One cohort of monkeys (n = 4–6 animals/exposure concentration) was exposed to air or manganese sulfate at 0.06, 0.3, or 1.5 mg Mn/m(3 )for 65 exposure days. Another eight monkeys were exposed to manganese sulfate at 1.5 mg Mn/m(3 )for 65 exposure days and held for 45 or 90 days before evaluation. A second cohort (n = 4 monkeys per time point) was exposed to manganese sulfate at 1.5 mg Mn/m(3 )and evaluated after 15 or 33 exposure days. Evaluations included measurement of lung manganese concentrations and evaluation of respiratory histologic changes. Tissue manganese concentrations were compared for the exposure and control groups by tests for homogeneity of variance, analysis of variance, followed by Dunnett's multiple comparison. Histopathological findings were evaluated using a Pearson's Chi-Square test. RESULTS: Animals exposed to manganese sulfate at ≥0.3 mg Mn/m(3 )for 65 days had increased lung manganese concentrations. Exposure to manganese sulfate at 1.5 mg Mn/m(3 )for ≥15 exposure days resulted in increased lung manganese concentrations, mild subacute bronchiolitis, alveolar duct inflammation, and proliferation of bronchus-associated lymphoid tissue. Bronchiolitis and alveolar duct inflammatory changes were absent 45 days post-exposure, suggesting that these lesions are reversible upon cessation of subchronic high-dose manganese exposure. CONCLUSION: High-dose subchronic manganese sulfate inhalation is associated with increased lung manganese concentrations and small airway inflammatory changes in the absence of observable clinical signs. Subchronic exposure to manganese sulfate at exposure concentrations (≤0.3 mg Mn/m(3)) similar to the current 8-hr occupational threshold limit value established for inhaled manganese was not associated with pulmonary pathology

A deep Tasman outflow of Pacific waters during the last glacial period

© The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Struve, T., Wilson, D., Hines, S., Adkins, J., & van de Flierdt, T. A deep Tasman outflow of Pacific waters during the last glacial period. Nature Communications, 13(1), (2022): 3763, https://doi.org/10.1038/s41467-022-31116-7.The interoceanic exchange of water masses is modulated by flow through key oceanic choke points in the Drake Passage, the Indonesian Seas, south of Africa, and south of Tasmania. Here, we use the neodymium isotope signature (εNd) of cold-water coral skeletons from intermediate depths (1460‒1689 m) to trace circulation changes south of Tasmania during the last glacial period. The key feature of our dataset is a long-term trend towards radiogenic εNd values of ~−4.6 during the Last Glacial Maximum and Heinrich Stadial 1, which are clearly distinct from contemporaneous Southern Ocean εNd of ~−7. When combined with previously published radiocarbon data from the same corals, our results indicate that a unique radiogenic and young water mass was present during this time. This scenario can be explained by a more vigorous Pacific overturning circulation that supported a deeper outflow of Pacific waters, including North Pacific Intermediate Water, through the Tasman Sea.The authors acknowledge financial support from the Grantham Institute of Climate Change and the Environment (T.v.d.F. and T.S.), the Ministry for Science and Culture of the State of Lower Saxony (T.S.), Marie Curie Reintegration grant IRG 230828 (T.v.d.F.), Leverhulme Trust grant RPG-398 (T.v.d.F.), Natural Environment Research Council grants NE/F016751/1 (T.v.d.F.), NE/N001141/1 (T.v.d.F. and D.J.W.), and NE/T011440/1 (D.J.W.), and National Science Foundation grant OCE-1503129 (J.F.A. and S.K.V.H.). Open Access funding is enabled by the DFG open access publication fund and the Carl von Ossietzky University Oldenburg

The statistics of the photometric accuracy based on MASS data and the evaluation of high-altitude wind

The effect of stellar scintillation on the accuracy of photometric measurements is analyzed. We obtain a convenient form of estimaton of this effect in the long exposure regime, when the turbulence shift produced by the wind is much larger than the aperture of the telescope. A simple method is proposed to determine index $S_3$ introduced by perture of the Kenyon et al. (2006), directly from the measurements with the Multi Aperture Scintillation Sensor (MASS) without information on vertical profile of the wind. The statistics $S_3$ resulting from our campaign of 2005 -- 2007 at Maidanak observatory is presented. It is shown that these data can be used to estimate high-altitude winds at pressure level 70 -- 100 mbar. Comparison with the wind speed retrieved from the NCEP/NCAR global models shows a good agreement. Some prospects for retrieval of the wind speed profile from the MASS measurements are outlined.Comment: 11 pages, 9 figures, accepted for publication in Astronomy Letter

Sea-ice control on deglacial lower cell circulation changes recorded by Drake Passage deep-sea corals

Financial support to DJW, TS, and TvdF was provided by the Natural Environment Research Council (NE/N001141/1), the Leverhulme Trust (RPG-398), the Grantham Institute for Climate Change and the Environment, and a Marie Curie Reintegration grant (IRG 230828). LFR acknowledges support from the Natural Environment Research Council (NE/N003861/1) and the European Research Council (278705).The sequence of deep ocean circulation changes between the Last Glacial Maximum and the Holocene provides important insights for understanding deglacial climate change and the role of the deep ocean in the global carbon cycle. Although it is known that significant amounts of carbon were sequestered in a deep overturning cell during glacial periods and released during deglaciation, the driving mechanisms for these changes remain unresolved. Southern Ocean sea-ice has recently been proposed to play a critical role in setting the global deep ocean stratification and circulation, and hence carbon storage, but testing such conceptual and modelling studies requires data constraining past circulation changes. To this end, we present the first deglacial dataset of neodymium (Nd) isotopes measured on absolute-dated deep-sea corals from modern Lower Circumpolar Deep Water depths in the Drake Passage. Our record demonstrates deglacial variability of 2.5 εNd units, with radiogenic values of up to during the Last Glacial Maximum providing evidence for a stratified glacial circulation mode with restricted incorporation of Nd from North Atlantic Deep Water in the lower cell. During the deglaciation, a renewed Atlantic influence in the deep Southern Ocean is recorded early in Heinrich Stadial 1, coincident with Antarctic sea-ice retreat, and is followed by a brief return to more Pacific-like values during the Antarctic Cold Reversal. These changes demonstrate a strong influence of Southern Ocean processes in setting deep ocean circulation and support the proposed sea-ice control on deep ocean structure. Furthermore, by constraining the Nd isotopic composition of Lower Circumpolar Deep Water in the Southern Ocean, our new data are important for interpreting deglacial circulation changes in other ocean basins and support a spatially asynchronous return of North Atlantic Deep Water to the deep southeast and southwest Atlantic Ocean.PostprintPostprintPeer reviewe

A Method for the Detection of Planetary Transits in Large Time-Series Datasets

We present a fast, efficient and easy to apply computational method for the detection of planetary transits in large photometric datasets. The code has been specifically produced to analyse an ensemble of 21,950 stars in the globular cluster 47 Tucanae, the results of which are the subject of a separate paper. Using cross correlation techniques and Monte Carlo tested detection criteria, each time-series is compared with a large database of appropriate transit models. The algorithm recovers transit signatures with high efficiency while maintaining a low false detection probability, even in noisy data. This is illustrated by describing its application to our 47 Tuc dataset, for which the algorithm produced a weighted mean transit recoverabilty spanning 85% to 25% for orbital periods of 1-16 days despite gaps in the time series caused by weather and observing duty cycle. The code is easily adaptable and is currently designed to accept time-series produced using Difference Imaging Analysis.Comment: 28 pages, 12 figures. Accepted and 'in press' for ApJ. Higher resolution versions for both this paper and astro-ph/0411233 are available at http://www.mso.anu.edu.au/~dtf

Neutral material around the B[e] supergiant star LHA 115-S 65: An outflowing disk or a detached Keplerian rotating disk?

B[e] supergiants are surrounded by large amounts of hydrogen neutral material, traced by the emission in the optical [OI] lines. This neutral material is most plausibly located within their dense, cool circumstellar disks, which are formed from the (probably non-spherically symmetric) wind material released by the star. Neither the formation mechanism nor the resulting structure and internal kinematics of these disks (or disk-like outflows) are well known. However, rapid rotation, lifting the material from the equatorial surface region, seems to play a fundamental role. The B[e] supergiant LHA 115-S 65 (S65) in the SMC is one of the two most rapidly rotating B[e] stars known. Its almost edge-on orientation allows a detailed kinematical study of its optically thin forbidden emission lines. With a focus on the [OI] lines, we test the two plausible disk scenarios: the outflowing and the Keplerian rotating disk. Based on high- and low-resolution optical spectra, we investigate the density and temperature structure in those disk regions that are traced by the [OI] emission to constrain the disk sizes and mass fluxes needed to explain the observed [OI] line luminosities. In addition, we compute the emerging line profiles expected for either an outflowing disk or a Keplerian rotating disk, which can directly be compared to the observed profiles. Both disk scenarios deliver reasonably good fits to the line luminosities and profiles of the [OI] lines. Nevertheless, the Keplerian disk model seems to be the more realistic one, because it also agrees with the kinematics derived from the large number of additional lines in the spectrum. As additional support for the presence of a high-density, gaseous disk, the spectrum shows two very intense and clearly double-peaked [CaII] lines. We discuss a possible disk-formation mechanism, and similarities between S65 and the group of LBVs.Comment: 13 pages, 12 figures, accepted for publication in A&

Neodymium isotope analyses after combined extraction of actinide and lanthanide elements from seawater and deep-sea coral aragonite

Author Posting. © American Geophysical Union, 2016. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry, Geophysics, Geosystems 17 (2016): 232–240, doi:10.1002/2015GC006130.Isotopes of the actinide elements protactinium (Pa), thorium (Th), and uranium (U), and the lanthanide element neodymium (Nd) are often used as complementary tracers of modern and past oceanic processes. The extraction of such elements from low abundance matrices, such as seawater and carbonate, is however labor-intensive and requires significant amounts of sample material. We here present a combined method for the extraction of Pa, Th, and Nd from 5 to 10 L seawater samples, and of U, Th, and Nd from <1 g carbonate samples. Neodymium is collected in the respective wash fractions of Pa-Th and U-Th anion exchange chromatographies. Regardless of the original sample matrix, Nd is extracted during a two-stage ion chromatography, followed by thermal ionization mass spectrometry (TIMS) analysis as NdO+. Using this combined procedure, we obtained results for Nd isotopic compositions on two GEOTRACES consensus samples from Bermuda Atlantic Time Series (BATS), which are within error identical to results for separately sampled and processed dedicated Nd samples (εNd = −9.20 ± 0.21 and −13.11 ± 0.21 for 15 and 2000 m water depths, respectively; intercalibration results from 14 laboratories: εNd = −9.19 ± 0.57 and −13.14 ± 0.57). Furthermore, Nd isotope results for an in-house coral reference material are identical within analytical uncertainty for dedicated Nd chemistry and after collection of Nd from U-Th anion exchange chromatography. Our procedure does not require major adaptations to independently used ion exchange chromatographies for U-Pa-Th and Nd, and can hence be readily implemented for a wide range of applications.Funding that supported this work was received from the National Science Foundation (NSF 0752402), the Leverhulme Trust (RPG-398), the Natural Environmental Research Council (NE/J021636/1 and NE/N003861/1), the European Research Council (278705), and the Grantham Institute for Climate Change.2016-07-0