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- Groh, J. H., et al.
(författare)
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Detection of high-velocity material from the wind-wind collision zone of Eta Carinae across the 2009.0 periastron passage
- 2010
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Ingår i: Astronomy & Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 517
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Tidskriftsartikel (refereegranskat)abstract
- We report near-infrared spectroscopic observations of the Eta Carinae massive binary system during 2008-2009 using the CRIRES spectrograph mounted on the 8m UT 1 Very Large Telescope (VLT Antu). We detect a strong, broad absorption wing in He I lambda 10833 extending up to -1900 km s(-1) across the 2009.0 spectroscopic event. Analysis of archival Hubble Space Telescope/Space Telescope Imaging Spectrograph ultraviolet and optical data identifies a similar high-velocity absorption (up to -2100 km s(-1)) in the ultraviolet resonance lines of Si IV lambda lambda 1394, 1403 across the 2003.5 event. Ultraviolet resonance lines from low-ionization species, such as Si II lambda lambda 1527, 1533 and CII lambda lambda 1334, 1335, show absorption only up to -1200 km s(-1), indicating that the absorption with velocities -1200 to -2100 km s(-1) originates in a region markedly more rapidly moving and more ionized than the nominal wind of the primary star. Seeing-limited observations obtained at the 1.6m OPD/LNA telescope during the last four spectroscopic cycles of Eta Carinae (1989-2009) also show high-velocity absorption in He I lambda 10833 during periastron. Based on the large OPD/LNA dataset, we determine that material with velocities more negative than -900 km s(-1) is present in the phase range 0.976 <= phi <= 1.023 of the spectroscopic cycle, but absent in spectra taken at phi <= 0.947 and phi >= 1.049. Therefore, we constrain the duration of the high-velocity absorption to be 95 to 206 days (or 0.047 to 0.102 in phase). We propose that the high-velocity absorption component originates in shocked gas in the wind-wind collision zone, at distances of 15 to 45 AU in the line-of-sight to the primary star. With the aid of three-dimensional hydrodynamical simulations of the wind-wind collision zone, we find that the dense high-velocity gas is along the line-of-sight to the primary star only if the binary system is oriented in the sky such that the companion is behind the primary star during periastron, corresponding to a longitude of periastron of omega similar to 240 degrees-270 degrees. We study a possible tilt of the orbital plane relative to the Homunculus equatorial plane and conclude that our data are broadly consistent with orbital inclinations in the range i = 40 degrees-60 degrees.
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| 4. |
- Zethson, T., et al.
(författare)
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eta Carinae: linelist for the emission spectrum of the Weigelt blobs in the 1700 to 10 400 angstrom wavelength region
- 2012
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Ingår i: Astronomy & Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 540
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Tidskriftsartikel (refereegranskat)abstract
- Aims. We present line identifications in the 1700 to 10 400 angstrom region for the Weigelt blobs B and D, located 0.'' 1 to 0 ''.3 NNW of Eta Carinae. The aim of this work is to characterize the behavior of these luminous, dense gas blobs in response to the broad highstate and the short low-state of. Carinae during its 5.54-year spectroscopic period. Methods. The spectra were recorded in a low state (March 1998) and an early high state (February 1999) with the Hubble Space Telescope/Space Telescope Imaging Spectrograph (HST/STIS) from 1640 to 10 400 angstrom using the 52 '' x 0.1 aperture centered on Eta Carinae at position angle, PA = 332 degrees. Extractions of the reduced spectrum including both Weigelt B and D, 0.'' 28 in length along the slit, were used to identify the narrow, nebular emission lines, measure their wavelengths and estimate their fluxes. Results. A linelist of 2500 lines is presented for the high and low states of the combined Weigelt blobs B and D. The spectra are dominated by emission lines from the iron-group elements, but include lines from lighter elements including parity-permitted and forbidden lines. A number of lines are fluorescent lines pumped by H Ly alpha. Other lines show anomalous excitation.
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| 5. |
- Bautista, M. A., et al.
(författare)
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The abundance of iron-peak elements and the dust composition in eta Carinae: manganese
- 2011
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Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 1365-2966 .- 0035-8711. ; 410:4, s. 2643-2652
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Tidskriftsartikel (refereegranskat)abstract
- We study the chemical abundances of the strontium filament found in the ejecta of eta Carinae. In particular, we derive the abundances of iron-peak elements from the spectra of their singly ionized ions present in the optical/infrared (IR) spectra. In this paper we analyse the spectrum of Mn II using a new non-local thermodynamic equilibrium (non-LTE) model for this system. In constructing this models we carried out theoretical calculations of radiative transition rates and electron impact excitation rate coefficients. We find that relative to Ni the gas-phase abundance ratio of Mn is roughly solar, similar to the Cr abundance but in contrast to the large enhancements in the abundances of Sc and Ti. We interpret this result as an indication of non-equilibrium condensation in the ejecta of eta Carinae.
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| 6. |
- Hertel, Jens K., et al.
(författare)
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FTO, Type 2 Diabetes, and Weight Gain Throughout Adult Life A Meta-Analysis of 41,504 Subjects From the Scandinavian HUNT, MDC, and MPP Studies
- 2011
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Ingår i: Diabetes. - : American Diabetes Association. - 1939-327X .- 0012-1797. ; 60:5, s. 1637-1644
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE-FTO is the most important polygene identified for obesity. We aimed to investigate whether a variant in FTO affects type 2 diabetes risk entirely through its effect on BMI and how FTO) influences BMI across adult life span. RESEARCH DESIGN AND METHODS-Through regression models, we assessed the relationship between the FTO single nucleotide polymorphisms rs9939609, type 2 diabetes, and BMI across life span in subjects from the Norwegian population-based HUNT study using cross-sectional and longitudinal perspectives. For replication and meta-analysis, we used data from the Malmo Diet and Cancer (MDC) and Malmo Preventive Project (MPP) cohorts, comprising a total sample of 41,504 Scandinavians. RESULTS-The meta-analysis revealed a highly significant association for rs9939609 with both type 2 diabetes (OR 1.13; P = 4.5 x 10(-8)) and the risk to develop incident type 2 diabetes (OR 1.16; P = 3.2 x 10(-8)). The associations remained also after correction for BMI and other anthropometric measures. Furthermore, we confirmed the strong effect on BMI (0.28 kg/m(2) per risk allele; P = 2.0 x 10(-26), with no heterogeneity between different age-groups. We found no differences in change of BMI over time according to rs9939609 risk alleles, neither overall (Delta BMI = 0.0 [-0.05, 0.05]) nor in any individual age stratum, indicating no further weight gain attributable to FTO genotype in adults. CONCLUSIONS-We have identified that a variant in FTO alters type 2 diabetes risk partly independent of its observed effect on BMI. The additional weight gain as a result of the FTO risk variant seems to occur before adulthood, and the BMI difference remains stable thereafter. Diabetes 60:1637-1644, 2011
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