Aims: We investigate the magnetic dichotomy between Ap/Bp and other A-type stars by carrying out a deep spectropolarimetric study of Am and HgMn stars. Methods: Using the NARVAL spectropolarimeter at the T�lescope Bernard Lyot (Observatoire du Pic du Midi, France), we obtained high-resolution circular ...

A common explanation for the observed X-ray emission of A-type stars is the presence of a hidden late-type companion. While this assumption can be shown to be correct in some cases, a number of lines of evidence suggests that low-mass companions cannot be the correct cause for the observed activity in all cases. A model explains the X-ray emission for ...

A-type stars have both a shallow near-surface zone of fast convection that can excite acoustic modes and a deep zone of core convection whose properties may be studied through asteroseismology. Many A stars also exhibit large magnetic spots as they rotate. We have explored the properties of core convection in ...

We have decided to address the problem of how abundances and peculiarities change during main sequence evolution. We have setup a program to measure the atmospheric abundance patterns from tens of A-type star members of clusters of different ages, and compare the results with theory predictions. In this paper we present the overall project and we focus on the results obtained ...

We present the results of 3--D simulations of core convection dynamos within A-type stars of 2 solar masses, at a range of rotation rates. The inner 30% by radius of such stars are considered in our calculations, with the spherical domain thereby encompassing the convective core and some of the surrounding radiative envelope. We ...

We present the results of 3-D nonlinear simulations of magnetic dynamo action by core convection within A-type stars of 2 M? with a range of rotation rates. We consider the inner 30% by radius of such stars, with the spherical domain thereby encompassing the convective core and a portion of the surrounding ...

Aims:We aim to provide observational constraints on diffusion models that predict peculiar chemical abundances in the atmospheres of Am stars. We also intend to check if chemical peculiarities and slow rotation can be explained by the presence of a weak magnetic field. Methods: We have obtained high resolution, high signal-to-noise ratio spectra of eight ...

We have carried out 3-D simulations of core convection and dynamo activity within A-type stars of two solar masses at a range of rotation rates. Our models consider the inner 30% by radius of such stars, thus capturing the entire convective core and a portion of the surrounding radiative envelope within the spherical computational ...

The sun as a magnetic star is described on the basis of recent work on solar magnetism. Observations

A common explanation for the observed X-ray emission of A-type stars is the presence of a hidden late-type companion. While this hypothesis can be shown to be correct in some cases, there is also evidence suggesting that low-mass companions cannot be the proper cause for the observed X-ray activity in all cases. Babel and Montmerle (1997) presented a theoretical framework to ...

Massive stars are crucial building blocks of galaxies and the universe, as production sites of heavy elements and as stirring agents and energy providers through stellar winds and supernovae. The field of magnetic massive stars has seen tremendous progress in recent years. Different perspectives�ranging from direct field measurements ...

Massive stars are crucial building blocks of galaxies and the universe, as production sites of heavy elements and as stirring agents and energy providers through stellar winds and supernovae. The field of magnetic massive stars has seen tremendous progress in recent years. Different perspectives - ranging from direct field measurements ...

Core convection and dynamo activity deep within rotating A-type stars of 2 Msolar are studied with three-dimensional nonlinear simulations. Our modeling considers the inner 30% by radius of such stars, thus capturing within a spherical domain the convective core and a modest portion of the surrounding radiative envelope. The ...

Jun 6, 2007 ... Artist's rendering of the planet orbiting the star Gliese 436 (Lynette ... "A" type stars - ones that have nearly completed their life cycle ...

We present the results of nonlinear 3--D simulations of magnetic dynamo action by core convection within A-type stars of 2 solar masses, at a range of rotation rates. We consider the inner 30% by radius of such stars, with the spherical domain thereby encompassing the convective core and a portion of the ...

A model for disk accretion by a rotating magnetic neutron star is proposed which includes a detailed

Although Am stars have been assumed to be nonmagnetic stars, we found recently that the hot Am stars

Aims: We aim at a highly sensitive search for weak magnetic fields in main sequence stars of intermediate mass, by scanning classes of stars with no previously reported magnetic members. After detecting a weak magnetic field on the normal, rapidly rotating A-type ...

... Title : Magnetic Fields in Stars and Galaxies. Radiation Processes and Interaction with Ionized Material in Magnetic Fields. ...

The vigorous magnetic dynamo action achieved within the convective cores of A-type stars may be influenced by fossil magnetic fields within their radiative envelopes. We study such effects through three-dimensional simulations that model the inner 30% by radius of a 2 M sun A-type star, ...

The vigorous magnetic dynamo action achieved within the convective cores of A-type stars may be influenced by fossil magnetic fields within their radiative envelopes. We study such effects through three-dimensional simulations that model the inner 30% by radius of a 2 M {sub sun} A-type star, ...

The evolution of neutron stars is determined by the evolution of their magnetic fields. The observational evidence for field evolution is presented. Recent observations suggest that the magnetic field of a neutron star initially decays with a timescale of...

The equations of structure for rotating stars in general relativity are presented and put in a form suitable for computer calculations. The results of equilibrium calculations for supermassive stars, neutron stars, and magnetically supported stars are reported, as are calculations of ...

The statistical properties of magnetic fields and magnetic fluxes of OB stars were investigated. The mean magnetic fluxes of massive OB stars appear to be 3 order larger than those for neutron stars.

... STAR Technology for Real Time Localization of Unexploded Ordnance ... II. STAR SENSOR: THEORY AND CONSTRUCTION ...

The consequences of magnetic fields for the atmospheres of cool stars are addressed based on IUE and

The ultraviolet spectrum obtained with the IUE satellite of the magnetic degenerate white dwarf star

Three mechanisms that promote the loss of magnetic flux from an isolated neutron star - Ohmic decay,

Extensive H? spectroscopy of the cool, helium-strong star ?OriC obtained over two decades has enabled a detailed analysis of the variable H? emission observed in this sharp-lined and strongly magnetic B3V star. Radial velocity measurements from these and other spectra have also confirmed the binary nature of the ...

Normal A type stars, nonradiative heating in A type stars, magnetic Ap stars. The Am stars, the delta Scu stars, A supergiants, peculiar B type stars, and model atmospheres are addressed.

Model neutron star atmospheres are calculated for typical cooling stars with a strong magnetic field

Page 1. Improved Magnetic STAR Methods for ... The prototype STAR Sensor comprises: a) A cubic array of eight fluxgate magnetometers. ...

A search for Lambda Bootis stars in two OB associations, Orion OB1 and Lacerta OB1, has been carried out. One Lambda Bootis star has been discovered in the Orion OB1 association. In addition, nine A-type stars which appear to be slightly metal weak have been found in the two associations. The Lambda Bootis ...

Four-color (uvby) photoelectric observations have yielded provisional periods for three peculiar A-type stars. For 108 Aquarii, the period is 3.73d. For HD 184905, the period is either 1.84d or 2.17d, and for theta 1 Microscopii the most probable periods ...

... Accession Number : AD0266323. Title : ON THE THERMAL GENERATION OF TOROIDAL MAGNETIC FIELDS IN ROTATING STARS. ...

Under certain simplifying assumptions the influence of a magnetic field on the pulsational stability

... (Author). Descriptors : (*STARS, THERMAL RADIATION), MAGNETIC FIELDS, NEUTRINOS, FIELD THEORY, MAGNETIC PROPERTIES. ...

The presence of magnetic fields at the surfaces of many massive stars has been suspected for decades, to explain the observed properties and activity of OB stars. However, very few genuine high-mass stars had been identified as magnetic before the advent of a new generation of powerful ...

In this paper we introduce an extension to the MK system of spectral classification that allows the precise classification of pre-main-sequence (PMS) A-type stars, including most Herbig Ae stars. This classification scheme characterizes the star by a standard MK type, the presence and strength of emission and/or ...

Algol-type binary star systems contain a cool Sun-like star and a hotter blue star. The cool star has a magnetic field many times more powerful than that of our Sun, with starspots that are similar to sunspots. The magnetic fields of Algol binaries are po...

-Newton observation of Altair and study the coronal X-ray properties of a late A-type star for the first time that resembles those of low activity stars of later spectral type. Cool plasma at low density produces weak X-ray, Stars: activity, Stars: coronae, X-rays: stars ...