Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userMagnetic field and element surface distribution of the CP2 star alpha^2 CVn
74
0
0.0
(
0
)
Authors
Yu.V. Glagolevskij
Ask ChatGPT about the research
No Arabic abstract
We investigate the radial velocity and the magnetic field of the CP star alpha^2 CVn. The observed variation of the magnetic field is compared with that of our model. We search for a relation between the magnetic field and the distribution of the chemical elements. The period in the radial velocities is constant over a time interval of about 100 years.
rate research
Read More
We search for a relation between the published distributions of different elements and the calculated magnetic field structure, following from a dipole-quadrupole configuration, of the CP2 star CU Vir. The highest concentration of individual chemical elements on the stellar surface coincides obviously with the regions of the highest values of the magnetic field strength.
New high-precision measurements of the longitudinal magnetic field of Ap stars suggest the existence of secular intrinsic variations of the global magnetic field in some stars. We argue that such changes are apparent in the Ap star $alpha^2$ CVn in the time scale of $sim$ 10 years, which results from the analysis of literature data. Therefore, such an observation implies, that the rate of magnetic field evolution of Ap stars is much higher than was previously thought.
In atmospheres of magnetic main-sequence stars, the diffusion of chemical elements leads to a number of observed anomalies, such as abundance spots across the stellar surface. The aim of this study was to derive a detailed picture of the surface abundance distribution of the magnetic chemically peculiar star HD 3980. Based on high-resolution, phase-resolved spectroscopic observations of the magnetic A-type star HD 3980, the inhomogeneous surface distribution of 13 chemical elements (Li, O, Si, Ca, Cr, Mn, Fe, La, Ce, Pr, Nd, Eu, and Gd) has been reconstructed. The INVERS12 code was used to invert the rotational variability in line profiles to elemental surface distributions. Assuming a centered, dominantly dipolar magnetic field configuration, we find that Li, O, Mg, Pr, and Nd are mainly concentrated in the area of the magnetic poles and depleted in the regions around the magnetic equator. The high abundance spots of Si, La, Ce, Eu, and Gd are located between the magnetic poles and the magnetic equator. Except for La, which is clearly depleted in the area of the magnetic poles, no obvious correlation with the magnetic field has been found for these elements otherwise. Ca, Cr, and Fe appear enhanced along the rotational equator and the area around the magnetic poles. The intersection between the magnetic and the rotational equator constitutes an exception, especially for Ca and Cr, which are depleted in that region. No obvious correlation between the theoretically predicted abundance patterns and those determined in this study could be found. This can be attributed to a lack of up-to-date theoretical models, especially for rare earth elements.
This work is a continuation of the studies of the ultrafast variability of line profiles in the spectra of early-type stars. Line profile variations (LPVs) in the spectrum a chemically peculiar A0Vp star $alpha^2,$CVn are investigated using the January 6, 2020 observations carried out with the 6-meter BTA telescope at Special Astrophysical observatory (SAO) of the Russian Academy of Sciences (RAS) equipped with the MSS spectrograph. Regular short-term periodic variations of the H$_beta$, Fe,II, and Cr,II lines were detected with periods ranging from $sim!$4 to $sim!$140 minutes. The magnetic field of the star was determined for all observations. The average measured longitudinal magnetic field component over the entire duration of observations is about $approx$600,G, which is close to the value expected from the well-known magnetic field phase curve.
High-field magnetization of the spin-$1/2$ antiferromagnet $alpha$-Cu$_2$V$_2$O$_7$ was measured in pulsed magnetic fields of up to 56 T in order to study its magnetic phase diagram. When the field was applied along the easy axis (the $a$-axis), two distinct transitions were observed at $H_{c1}=6.5$~T and $H_{c2}=18.0$~T. The former is a spin-flop transition typical for a collinear antiferromagnet and the latter is believed to be a spin-flip transition of canted moments. The canted moments, which are induced by the Dzyaloshinskii-Moriya interactions, anti-align for $H_{c1}<H<H_{c2}$ due to the anisotropic exchange interaction that favors the antiferromagnetic arrangement along the $a$-axis. Above $H_{c2}$, the Zeeman energy of the applied field overcomes the antiferromagnetic anisotropic interaction and the canted moments are aligned along the field direction. Density functional theory was employed to compute the exchange interactions, which were used as inputs for quantum Monte Carlo calculations and then further refined by fitting to the magnetic susceptibility data. Contrary to our previous report in Phys. Rev. B {bf 92}, 024423, the dominant exchange interaction is between the third nearest-neighbor spins, which form zigzag spin-chains that are coupled with one another through an intertwining network of the nonnegligible nearest and second nearest-neighbor interactions. In addition, elastic neutron scattering under the applied magnetic fields of up to 10 T reveals the incommensurate helical spin structure in the spin-flop state.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
