994 research outputs found
Orbital parameters, chemical composition, and magnetic field of the Ap binary HD 98088
HD 98088 is a synchronised, double-lined spectroscopic binary system with a
magnetic Ap primary component and an Am secondary component. We study this rare
system using high-resolution MuSiCoS spectropolarimetric data, to gain insight
into the effect of binarity on the origin of stellar magnetism and the
formation of chemical peculiarities in A-type stars. Using a new collection of
29 high-resolution Stokes VQU spectra we re-derive the orbital and stellar
physical parameters and conduct the first disentangling of spectroscopic
observations of the system to conduct spectral analysis of the individual
stellar components. From this analysis we determine the projected rotational
velocities of the stars and conduct a detailed chemical abundance analysis of
each component using both the SYNTH3 and ZEEMAN spectrum synthesis codes. The
surface abundances of the primary component are typical of a cool Ap star,
while those of the secondary component are typical of an Am star. We present
the first magnetic analysis of both components using modern data. Using
Least-Squares Deconvolution, we extract the longitudinal magnetic field
strength of the primary component, which is observed to vary between +1170 and
-920 G with a period consistent with the orbital period. There is no field
detected in the secondary component. The magnetic field in the primary is
predominantly dipolar, with the positive pole oriented approximately towards
the secondary.Comment: Accepted for publication by MNRAS, 17 pages, 12 figure
The solar wind in time â II. 3D stellar wind structure and radio emission
In this work, we simulate the evolution of the solar wind along its main-sequence lifetime and compute its thermal radio emission. To study the evolution of the solar wind, we use a sample of solar mass stars at different ages. All these stars have observationally reconstructed magnetic maps, which are incorporated in our 3D magnetohydrodynamic simulations of their winds. We show that angular-momentum loss and mass-loss rates decrease steadily on evolutionary time-scales, although they can vary in a magnetic cycle time-scale. Stellar winds are known to emit radiation in the form of thermal bremsstrahlung in the radio spectrum. To calculate the expected radio fluxes from these winds, we solve the radiative transfer equation numerically from first principles. We compute continuum spectra across the frequency range 100 MHz to 100 GHz and find maximum radio flux densities ranging from 0.05 to 2.2 ÎŒJy. At a frequency of 1 GHz and a normalized distance of d = 10 pc, the radio flux density follows 0.24 (Ω/Ωâ)0.9 (d/[10pc])-2ÎŒJy, where Ω is the rotation rate. This means that the best candidates for stellar wind observations in the radio regime are faster rotators within distances of 10 pc, such as Îș1 Ceti (0.73 ÎŒJy) and Ï1 Ori (2.2 ÎŒJy). These flux predictions provide a guide to observing solar-type stars across the frequency range 0.1-100 GHz in the future using the next generation of radio telescopes, such as ngVLA and Square Kilometre Array
Erratum: The solar wind in time II: 3D stellar wind structure and radio emission
This is an erratum to the paper âThe solar wind in time - II: 3D stellar wind structure and radio emissionâ, which was published in MNRAS, 483(1), 873, 2019 (Ă FionnagĂĄin et al. 2019)
Investigating the pre-main sequence magnetic chemically peculiar system HD 72106
The origin of the strong magnetic fields observed in chemically peculiar Ap
and Bp stars stars has long been debated. The recent discovery of magnetic
fields in the intermediate mass pre-main sequence Herbig Ae and Be stars links
them to Ap and Bp stars, providing vital clues about Ap and Bp stars and the
origin and evolution of magnetic fields in intermediate and high mass stars. A
detailed study of one young magnetic B star, HD 72106A, is presented. This star
appears to be in a binary system with an apparently normal Herbig Ae star. A
maximum longitudinal magnetic field strength of +391 +/- 65 G is found in HD
72106A, as are strong chemical peculiarities, with photospheric abundances of
some elements ranging up to 100x above solar.Comment: 8 pages, 6 figures. Proceeding of the 2006 conference of the Special
Astrophysical Observatory of the Russian Academy of Science
- âŠ