| 1. |
- Ramstedt, Sofia, et al.
(författare)
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The wonderful complexity of the Mira AB system
- 2014
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 570, s. Art. no. L14-
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Tidskriftsartikel (refereegranskat)abstract
- We have mapped the (CO)-C-12(3-2) line emission around the Mira AB system at 0 ''.5 resolution using the Atacama Large Millimeter/submillimeter Array (ALMA). The CO map shows amazing complexity. The circumstellar gas has been shaped by different dynamical actors during the evolution of the system, and several morphological components can be identified. The companion is marginally resolved in continuum emission and is currently at 0 ''.487 +/- 0 ''.006 separation. In the main line component, centered on the stellar velocity, spiral arcs around Mira A are found. The spiral appears to be relatively flat and oriented in the orbital plane. An accretion wake behind the companion is clearly visible, and the projected arc separation is about 5 ''. In the blue wing of the line emission, offset from the main line, several large (similar to 5-10 '') opposing arcs are found. We tentatively suggest that this structure is created by the wind of Mira B blowing a bubble in the expanding envelope of Mira A.
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| 2. |
- Van Holsbeke, C., et al.
(författare)
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Endometriomas: their ultrasound characteristics
- 2010
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Ingår i: Ultrasound in Obstetrics & Gynecology. - : Wiley. - 1469-0705 .- 0960-7692. ; 35:6, s. 730-740
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Tidskriftsartikel (refereegranskat)abstract
- Objectives To describe the ultrasound characteristics of endometriomas in pre- and postmenopausal patients and to develop rules that characterize endometriomas. Methods All patients included in the International Ovarian Tumor Analysis (IOTA) studies were used in our analysis. Patients with an adnexal mass were scanned by experienced sonologists using a standardized research protocol. The gold standard was the histology of the surgically removed adnexal mass. The gray-scale and Doppler ultrasound characteristics of the endometriomas were compared with those of other benign and malignant masses. Based on decision-tree analysis, the existing literature and clinical experience, ultrasound rules for the detection of endometriomas were created and evaluated. Results Of all 3511 patients included in the IOTA studies, 713 (20%) had endometriomas. Fifty-one per cent of the endometriomas were unilocular cysts with ground glass echogenicity of the cyst fluid. These characteristics were found less often among other benign tumors or malignancies, or among the small set of endometriomas (4%) that were found in postmenopausal patients. Based on the decision-tree analysis, the optimal rule to detect endometriomas was an adnexal mass in a premenopausal patient with ground glass echogenicity of the cyst fluid, one to four locules and no papillations with detectable blood flow'. Based on clinical considerations, the following rule: 'premenopausal status, ground glass echogenicity of the cyst fluid, one to four locules and no solid parts' seems preferable. Conclusions Several rules had a good ability to characterize endometriomas. The ultrasound characteristics of endometriomas differ between pre- and postmenopausal patients. Masses in postmenopausal women whose cystic contents have a ground glass appearance have a high risk of malignancy. Copyright (C) 2010 ISUOG. Published by John Wiley & Sons, Ltd.
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| 3. |
- Ameye, L., et al.
(författare)
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Clinically oriented three-step strategy for assessment of adnexal pathology
- 2012
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Ingår i: Ultrasound in Obstetrics & Gynecology. - : Wiley. - 1469-0705 .- 0960-7692. ; 40:5, s. 582-591
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Tidskriftsartikel (refereegranskat)abstract
- Objective To determine the diagnostic performance of ultrasound-based simple rules, risk of malignancy index (RMI), two logistic regression models (LR1 and LR2) and real-time subjective assessment by experienced ultrasound examiners following the exclusion of masses likely to be judged as easy and 'instant' to diagnose by an ultrasound examiner, and to develop a new strategy for the assessment of adnexal pathology based on this. Methods 3511 patients with at least one persistent adnexal mass preoperatively underwent transvaginal ultrasonography to assess tumor morphology and vascularity. They were included in two consecutive prospective studies by the International Ovarian Tumor Analysis (IOTA) group: Phase 1 (1999-2005), development of the simple rules and logistic regression models LR1 and LR2, and Phase 2, a validation study (2005-2007). Results Almost half of the cases (43%) were identified as 'instant' to diagnose on the basis of descriptors applied to the database. To assess diagnostic performance in the more difficult 'non-instant' masses, we used only Phase 2 data (n = 1036). The sensitivity of LR2 was 88%, of RMI it was 41% and of subjective assessment it was 87%. The specificity of LR2 was 67%, of RMI it was 90% and of subjective assessment it was 86%. The simple rules yielded a conclusive result in almost 2/3 of the masses, where they resulted in sensitivity and specificity similar to those of real-time subjective assessment by experienced ultrasound examiners: sensitivity 89 vs 89% (P = 0.76), specificity 91 vs 91% (P = 0.65). When a three-step strategy was appliedwith easy 'instant' diagnoses as Step 1, simple rules where conclusive as Step 2 and subjective assessment by an experienced ultrasound examiner in the remaining masses as Step 3, we obtained a sensitivity of 92% and specificity of 92% compared with sensitivity 90% (P = 0.03) and specificity 93% (P = 0.44) when using real-time subjective assessment by experts in all tumors. Conclusion A diagnostic strategy using simple descriptors and ultrasound rules when applied to the variables contained in the IOTA database obtains results that are at least as good as those obtained by subjective assessment of a mass by an expert. Copyright. (C) 2012 ISUOG. Published by John Wiley & Sons, Ltd.
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| 4. |
- Cruzalebes, P., et al.
(författare)
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Measuring deviation from centrosymmetry for a source brightness distribution observed by spectro-interferometry
- 2014
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 443:4, s. 3550-3563
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Tidskriftsartikel (refereegranskat)abstract
- We report on the testing of the centrosymmetry parameter (CSP), an indicator of deviation from centrosymmetry of a source brightness distribution. This indicator is derived from the spectral distribution of the triple product measured over three baselines of an optical interferometer. Numerical simulations using parametric toy-models (separated or transiting binary, one-spot model), generated with the SPIDAST software, are applied to the VLTI/AMBER facility in the K band (2.2 mu m). The simulations show that, in case of centrosymmetry, the CSP parameter is in agreement with the usual phase of the spectral mean of the triple product (called GCP, global closure phase). To justify the preferential use of CSP rather than GCP, we show situations with asymmetric geometries for which GCP diagnoses centrosymmetry, while CSP does not. Using realistic Roche lobe-filling binary and hydrodynamic convective models, we show that CSP can also be used as an indicator for geometric similarity between physical and toy-models. Thus, dealing with real data, the toy-model parameters can be fitted on the measured CSP values, in order to assess the input-parameter values of the most suitable complex physical model that will be used to interpret the data.
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| 5. |
- Paladini, C., et al.
(författare)
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To be or not to be asymmetric? VLTI and the mass loss geometry of red giants
- 2012
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Ingår i: Proceedings of SPIE - The International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. - 9780819491466 ; 8445, s. Art. no. 84451R-
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Konferensbidrag (refereegranskat)abstract
- The mass-loss process is a key ingredient for our understanding in many fields of astrophysics, including stellar evolution and the enrichment of the interstellar medium (ISM) via stellar yields. We combined the capability of the VLTI/MIDI and VLT/VISIR instruments with very recent Herschel/PACS observations to characterize the geometry of mass loss from evolved red giants on the Asymptotic Giant Branch (AGB) at various scales. This paper describes the sample of objects, the observing strategy, the tool for the interpretation, and preliminary MIDI results for two targets: U Ant and θ Aps.
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| 6. |
- Van Holsbeke, C., et al.
(författare)
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Acoustic streaming cannot discriminate reliably between endometriomas and other types of adnexal lesion: a multicenter study of 633 adnexal masses
- 2010
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Ingår i: Ultrasound in Obstetrics & Gynecology. - : Wiley. - 1469-0705 .- 0960-7692. ; 35:3, s. 349-353
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Tidskriftsartikel (refereegranskat)abstract
- Objective To determine the ability of acoustic streaming to discriminate between endometriomas and other adnexal masses. Methods We used data from 1938 patients with an adnexal mass included in Phase 2 of the International Ovarian Tumor Analysis (IOTA) study. All patients had been examined by transvaginal gray-scale and Doppler ultrasound following a standardized research protocol. Assessment of acoustic streaming was voluntary and was carried out only in lesions containing echogenic cyst fluid. Acoustic streaming was defined as movement of particles inside the cyst fluid during gray-scale and/or color Doppler examination provided that the probe had been held still for two seconds to ensure that the movement of the particles was not caused by movement of the probe or the patient. Only centers where acoustic streaming had been evaluated in > 90% of cases were included. Sensitivity, specificity, positive and negative likelihood ratios (LR+, LR-), and positive and negative predictive values (PPV and NPV) of acoustic streaming with regard to endometrioma were calculated. Results 460 (24%) masses were excluded because they were examined in centers where <= 90% of the masses with echogenic cyst fluid had been evaluated for the presence of acoustic streaming. Acoustic streaming was evaluated in 633 of 646 lesions containing echogenic cyst fluid. It was present in 19 (9%) of 209 endometriomas and in 55 (13%) of 424 other lesions. This corresponds to a sensitivity of absent acoustic streaming with regard to endometrioma of 91% (190/209), a specificity of 13% (55/424), LR+ of 1.04, LR- of 0.69, PPV of 34% (190/559) and NPV of 74% (55/74). Conclusions Acoustic streaming cannot discriminate reliably between endometrioinas and other adnexal lesions, and the presence of acoustic streaming does not exclude an endometrioma. Copyright (C) 2009 ISUOG. Published by John Wiley & Sons, Ltd.
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| 7. |
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| 8. |
- Fossati, L., et al.
(författare)
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A detailed spectroscopic analysis of the open cluster NGC 5460
- 2011
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 413:2, s. 1132-1144
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Tidskriftsartikel (refereegranskat)abstract
- Within the context of a large project aimed at studying early F-, A- and late B-type stars, we present the abundance analysis of the photospheres of 21 members of the open cluster NGC 5460, an intermediate-age cluster (log t similar to 8.2) previously not studied with spectroscopy. Our study is based on medium- and high-resolution spectra obtained with the Fibre Large Array Multi Element Spectrograph (FLAMES) instrument of the European Southern Observatory/Very Large Telescope. We show that cluster members have a nearly solar metallicity and that there is evidence that the abundances of magnesium and iron are correlated with the effective temperature, exhibiting a maximum around T-eff = 10 500 K. No correlations are found between abundances and projected equatorial velocity, except for marginal evidence of barium being more abundant in slower than in faster rotating stars. We discovered two He-weak stars and a binary system where the hotter component is an HgMn star. We provide new estimates for the cluster distance (720 +/- 50 pc), age (log t = 8.2 +/- 0.1) and mean radial velocity (-17.9 +/- 5.2 km s-1).
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| 9. |
- Maercker, Matthias, 1979, et al.
(författare)
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Unexpectedly large mass loss during the thermal pulse cycle of the red giant star R Sculptoris
- 2012
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 490:7419, s. 232-234
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Tidskriftsartikel (refereegranskat)abstract
- The asymptotic giant branch star R Sculptoris is surrounded by a detached shell of dust and gas. The shell originates from a thermal pulse during which the star undergoes a brief period of increased mass loss. It has hitherto been impossible to constrain observationally the timescales and mass-loss properties during and after a thermal pulse - parameters that determine the lifetime on the asymptotic giant branch and the amount of elements returned by the star. Here we report observations of CO emission from the circumstellar envelope and shell around R Sculptoris with an angular resolution of 1.3 arcsec. What was hitherto thought to be only a thin, spherical shell with a clumpy structure, is revealed to contain a spiral structure. Spiral structures associated with circumstellar envelopes have been seen previously, from which it was concluded that the systems must be binaries. Using the data, combined with hydrodynamic simulations, we conclude that R Sculptoris is a binary system that underwent a thermal pulse approximately 1800 years ago, lasting approximately 200 years. About 0.003 Msun of mass was ejected at a velocity of 14.3 km s-1 and at a rate approximately 30 times higher than the prepulse mass-loss rate. This shows that approximately 3 times more mass is returned to the interstellar medium during and immediately after a pulse than previously thought.
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| 10. |
- Paladini, C., et al.
(författare)
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Detection of an asymmetry in the envelope of the carbon Mira R Fornacis using VLTI/MIDI
- 2012
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 544, s. L5-
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Tidskriftsartikel (refereegranskat)abstract
- Aims. We present a study of the envelope morphology of the carbon Mira R For with VLTI/MIDI. This object is one of the few asymptotic giant branch (AGB) stars that underwent a dust-obscuration event. The cause of such events is still a matter of discussion. Several symmetric and asymmetric scenarios have been suggested in the literature.Methods. Mid-infrared interferometric observations were obtained separated by two years. The observations probe different depths of the atmosphere and cover different pulsation phases. The visibilities and the differential phases were interpreted using GEM-FIND, a tool for fitting spectrally dispersed interferometric observations with the help of wavelength-dependent geometric models.Results. We report the detection of an asymmetric structure revealed through the MIDI differential phase. This asymmetry is observed at the same baseline and position angle two years later. The observations are best simulated with a model that includes a uniform-disc plus a Gaussian envelope plus a point-source. The geometric model can reproduce both the visibilities and the differential phase signatures.Conclusions. Our MIDI data favour explanations of the R For obscuration event that are based on an asymmetric geometry. We clearly detect a photocentre shift between the star and the strongly resolved dust component. This might be caused by a dust clump or a substellar companion. However, the available observations do not allow us to distinguish between the two options. The finding has strong implications for future studies of the geometry of the envelope of AGB stars: if this is a binary, are all AGB stars that show an obscuration event binaries as well? Or are we looking at asymmetric mass-loss processes (i.e. dusty clumps) in the inner part of a carbon-rich Mira?
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