We present the analysis performed on spectropolarimetric data of 97 O-type targets included in the framework of the Magnetism in Massive Stars (MiMeS) Survey. Mean least-squares deconvolved Stokes I ...and V line profiles were extracted for each observation, from which we measured the radial velocity, rotational and non-rotational broadening velocities, and longitudinal magnetic field B sub( l). The investigation of the Stokes I profiles led to the discovery of two new multiline spectroscopic systems (HD 46106, HD 204827) and confirmed the presence of a suspected companion in HD 37041. We present a modified strategy of the least-squares deconvolution technique aimed at optimizing the detection of magnetic signatures while minimizing the detection of spurious signatures in Stokes V. Using this analysis, we confirm the detection of a magnetic field in six targets previously reported as magnetic by the MiMeS collaboration (HD 108, HD 47129A2, HD 57682, HD 148937, CPD-28 2561, and NGC 1624-2), as well as report the presence of signal in Stokes V in three new magnetic candidates (HD 36486, HD 162978, and HD 199579). Overall, we find a magnetic incidence rate of 7 plus or minus 3 per cent, for 108 individual O stars (including all O-type components part of multiline systems), with a median uncertainty of the B sub( l) measurements of about 50 G. An inspection of the data reveals no obvious biases affecting the incidence rate or the preference for detecting magnetic signatures in the magnetic stars. Similar to A- and B-type stars, we find no link between the stars' physical properties (e.g. T sub( eff), mass, and age) and the presence of a magnetic field. However, the Of?p stars represent a distinct class of magnetic O-type stars.
Sleep disorders are common in the general population and even more so in clinical practice, yet are relatively poorly understood by doctors and other health care practitioners. These British ...Association for Psychopharmacology guidelines are designed to address this problem by providing an accessible up-to-date and evidence-based outline of the major issues, especially those relating to reliable diagnosis and appropriate treatment. A consensus meeting was held in London in May 2009. Those invited to attend included BAP members, representative clinicians with a strong interest in sleep disorders and recognized experts and advocates in the field, including a representative from mainland Europe and the USA. Presenters were asked to provide a review of the literature and identification of the standard of evidence in their area, with an emphasis on meta-analyses, systematic reviews and randomized controlled trials where available, plus updates on current clinical practice. Each presentation was followed by discussion, aimed to reach consensus where the evidence and/or clinical experience was considered adequate or otherwise to flag the area as a direction for future research. A draft of the proceedings was then circulated to all participants for comment. Key subsequent publications were added by the writer and speakers at draft stage. All comments were incorporated as far as possible in the final document, which represents the views of all participants although the authors take final responsibility for the document.
Summary Background Previous studies of patients with chronic lymphocytic leukaemia reported high response rates to fludarabine combined with cyclophosphamide. We aimed to establish whether this ...treatment combination provided greater survival benefit than did chlorambucil or fludarabine. Methods 777 patients with chronic lymphocytic leukaemia requiring treatment were randomly assigned to fludarabine (n=194) or fludarabine plus cyclophosphamide (196) for six courses, or chlorambucil (387) for 12 courses. The primary endpoint was overall survival, with secondary endpoints of response rates, progression-free survival, toxic effects, and quality of life. Analysis was by intention to treat. This study is registered as an International Standard Randomised Controlled Trial, number NCT 58585610. Findings There was no significant difference in overall survival between patients given fludarabine plus cyclophosphamide, fludarabine, or chlorambucil. Complete and overall response rates were better with fludarabine plus cyclophosphamide than with fludarabine (complete response rate 38% vs 15%, respectively; overall response rate 94% vs 80%, respectively; p<0·0001 for both comparisons), which were in turn better than with chlorambucil (complete response rate 7%, overall response rate 72%; p=0·006 and 0·04, respectively). Progression-free survival at 5 years was significantly better with fludarabine plus cyclophosphamide (36%) than with fludarabine (10%) or chlorambucil (10%; p<0·00005). Fludarabine plus cyclophosphamide was the best combination for all ages, including patients older than 70 years, and in prognostic groups defined by immunoglobulin heavy chain gene (VH ) mutation status and cytogenetics, which were tested in 533 and 579 cases, respectively. Patients had more neutropenia and days in hospital with fludarabine plus cyclophosphamide, or fludarabine, than with chlorambucil. There was less haemolytic anaemia with fludarabine plus cyclophosphamide (5%) than with fludarabine (11%) or chlorambucil (12%). Quality of life was better for responders, but preliminary analyses showed no significant difference between treatments. A meta-analysis of these data and those of two published phase III trials showed a consistent benefit for the fludarabine plus cyclophosphamide regimen in terms of progression-free survival. Interpretation Fludarabine plus cyclophosphamide should now become the standard treatment for chronic lymphocytic leukaemia and the basis for new protocols that incorporate monoclonal antibodies.
Various surveys focusing on the magnetic properties of intermediate-mass main-sequence (MS) stars have been previously carried out. One particularly puzzling outcome of these surveys is the ...identification of a dichotomy between the strong ({≳ }100 G), organized fields hosted by magnetic chemically peculiar (mCP) stars and the ultraweak ({≲ }1 G) fields associated with a small number of non-mCP MS stars. Despite attempts to detect intermediate strength fields (i.e. those with strengths ≳10 and {≲ }100 G), remarkably few examples have been found. Whether this so-called magnetic desert, separating the stars hosting ultraweak fields from the mCP stars truly exists has not been definitively answered. In 2007, a volume-limited spectropolarimetric survey of mCP stars using the MuSiCoS spectropolarimeter was initiated to test the existence of the magnetic desert by attempting to reduce the biases inherent in previous surveys. Since then, we have obtained a large number of ESPaDOnS and NARVAL Stokes V measurements allowing this survey to be completed. Here, we present the results of our homogeneous analysis of the rotational periods (inferred from photometric and magnetic variabilities) and magnetic properties (dipole field strengths and obliquity angles) of the 52 confirmed mCP stars located within a heliocentric distance of 100 pc. No mCP stars exhibiting field strengths {≲ }300 G are found within the sample, which is consistent with the notion that the magnetic desert is a real property and not the result of an observational bias. Additionally, we find evidence of magnetic field decay, which confirms the results of previous studies.
We present the first results of a volume-limited survey of main-sequence (MS) magnetic chemically peculiar (mCP) stars. The sample consists of all identified intermediate-mass MS stars (mCP and ...non-mCP) within a heliocentric distance of 100 pc as determined using Hipparcos parallaxes. The two populations are compared in order to determine the unique properties that allow a small fraction of MS stars with masses {≳ }1.4 M_⊙ to host strong, large-scale magnetic fields. A total of 52 confirmed mCP stars are identified using published magnetic, spectroscopic, and photometric observations along with archived and newly obtained spectropolarimetric (Stokes V) observations. We derive the fundamental parameters (effective temperatures, luminosities, masses, and evolutionary states) of the mCP and non-mCP populations using homogeneous analyses. A detailed analysis of the mCP stars is performed using the LLMODELS code, which allows observed spectral energy distributions to be modelled while incorporating chemical peculiarities and magnetic fields. The surface gravities and mean chemical abundances are derived by modelling averaged spectra using the GSSP and ZEEMAN spectral synthesis codes. Masses and stellar ages are derived using modern, densely calculated evolutionary model grids. We confirm a number of previously reported evolutionary properties associated with mCP stars including a conspicuously high incidence of middle-aged MS stars with respect to the non-mCP subsample; the incidence of mCP stars is found to sharply increase with mass from 0.3 per cent at 1.5 M_⊙ to ≈11 per cent at 3.8 M_⊙. Finally, we identify clear trends in the mean photospheric chemical abundances with stellar age.
Isolated cool white dwarf stars more often have strong magnetic fields than young, hotter white dwarfs, which has been a puzzle because magnetic fields are expected to decay with time but a cool ...surface suggests that the star is old. In addition, some white dwarfs with strong fields vary in brightness as they rotate, which has been variously attributed to surface brightness inhomogeneities similar to sunspots, chemical inhomogeneities and other magneto-optical effects. Here we describe optical observations of the brightness and magnetic field of the cool white dwarf WD 1953-011 taken over about eight years, and the results of an analysis of its surface temperature and magnetic field distribution. We find that the magnetic field suppresses atmospheric convection, leading to dark spots in the most magnetized areas. We also find that strong fields are sufficient to suppress convection over the entire surface in cool magnetic white dwarfs, which inhibits their cooling evolution relative to weakly magnetic and non-magnetic white dwarfs, making them appear younger than they truly are. This explains the long-standing mystery of why magnetic fields are more common amongst cool white dwarfs, and implies that the currently accepted ages of strongly magnetic white dwarfs are systematically too young.
Abstract
Surface magnetic fields have a strong impact on stellar mass loss and rotation and, as a consequence, on the evolution of massive stars. In this work, we study the influence of an evolving ...dipolar surface fossil magnetic field with an initial field strength of 4 kG on the characteristics of 15 M⊙ solar metallicity models using the Geneva stellar evolution code. Non-rotating and rotating models considering two different scenarios for internal angular momentum transport are computed, including magnetic field evolution, mass-loss quenching, and magnetic braking. Magnetic field evolution results in weakening the initially strong magnetic field; however, in our models, an observable magnetic field is still maintained as the star evolves towards the red supergiant phase. At the given initial mass of the models, mass-loss quenching is modest. Magnetic braking greatly enhances chemical element mixing if radial differential rotation is allowed for; on the other hand, the inclusion of surface magnetic fields yields a lower surface enrichment in the case of near solid-body rotation. Models including surface magnetic fields show notably different trends on the Hunter diagram (plotting nitrogen abundance versus vsin i) compared to those that do not. The magnetic models agree qualitatively with the anomalous ‘Group 2 stars’, showing slow surface rotation and high surface nitrogen enhancement on the main sequence.
The groundbreaking detection of gravitational waves produced by the inspiralling and coalescence of the black hole (BH) binary GW150914 confirms the existence of ‘heavy’ stellar-mass BHs with masses ...>25 M⊙. Initial characterization of the system by Abbott et al. supposes that the formation of BHs with such large masses from the evolution of single massive stars is only feasible if the wind mass-loss rates of the progenitors were greatly reduced relative to the mass-loss rates of massive stars in the Galaxy, concluding that heavy BHs must form in low-metallicity (Z ≲ 0.25-0.5 Z⊙) environments. However, strong surface magnetic fields also provide a powerful mechanism for modifying mass-loss and rotation of massive stars, independent of environmental metallicity. In this paper, we explore the hypothesis that some heavy BHs, with masses >25 M⊙ such as those inferred to compose GW150914, could be the natural end-point of evolution of magnetic massive stars in a solar-metallicity environment. Using the mesa code, we developed a new grid of single, non-rotating, solar-metallicity evolutionary models for initial zero-age main sequence masses from 40 to 80 M⊙ that include, for the first time, the quenching of the mass-loss due to a realistic dipolar surface magnetic field. The new models predict terminal-age main-sequence (TAMS) masses that are significantly greater than those from equivalent non-magnetic models, reducing the total mass lost by a strongly magnetized 80 M⊙ star during its main-sequence evolution by 20 M⊙. This corresponds approximately to the mass-loss reduction expected from an environment with metallicity Z = 1/30 Z⊙.
Abstract
ρ Pup is a δ Scuti F2 pulsator, known to host a main radial mode as well as non-radial pulsations, with chemical peculiarities typical of evolved Am stars. We present a high-precision ...spectropolarimetric observations of this star, obtained with ESPaDOnS at the Canada–France–Hawaii Telescope in the frame of the BRITE spectropolarimetric survey. A magnetic field is clearly detected in ρ Pup, with a longitudinal field strength below 1 G. This makes ρ Pup the second known magnetic δ Scuti discovered, after HD 188774, and a possible cool evolved counterpart of the recently discovered ultraweakly magnetic Am family.
The cycling and fate of polycyclic aromatic hydrocarbons (PAHs) is not well understood in estuarine systems. It is critical now more than ever given the increased ecosystem pressures on these ...critical coastal habitats. A budget of PAHs and cycling has been created for Galveston Bay (Texas) in the northwestern Gulf of Mexico, an estuary surrounded by 30-50% of the US capacity of oil refineries and chemical industry. We estimate that approximately 3 to 4 mt per year of pyrogenic PAHs are introduced to Galveston Bay via gaseous exchange from the atmosphere (ca. 2 mt/year) in addition to numerous spills of petrogenic PAHs from oil and gas operations (ca. 1.0 to 1.9 mt/year). PAHs are cycled through and stored in the biota, and ca. 20 to 30% of the total (0.8 to 1.5 mt per year) are estimated to be buried in the sediments. Oysters concentrate PAHs to levels above their surroundings (water and sediments) and contain substantially greater concentrations than other fish catch (shrimp, blue crabs and fin fish). Smaller organisms (infaunal invertebrates, phytoplankton and zooplankton) might also retain a significant fraction of the total, but direct evidence for this is lacking. The amount of PAHs delivered to humans in seafood, based on reported landings, is trivially small compared to the total inputs, sediment accumulation and other possible fates (metabolic remineralization, export in tides, etc.), which remain poorly known. The generally higher concentrations in biota from Galveston Bay compared to other coastal habitats can be attributed to both intermittent spills of gas and oil and the bay's close proximity to high production of pyrogenic PAHs within the urban industrial complex of the city of Houston as well as periodic flood events that transport PAHs from land surfaces to the Bay.
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