Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p> <jats:italic>γ</jats:italic> Draconis, a K5III star, showed radial velocity (RV) variations consistent with a 10.7 Jupiter mass planet from 2003 to 2011. After 2011, the periodic signal decayed, then reappeared with a phase shift. Hatzes et al. suggested that <jats:italic>γ</jats:italic> Dra’s RV variations could come from oscillatory convective modes, but did not fit a mathematical model. Here we assess whether a quasi-periodic Gaussian process—appropriate when spots with finite lifetimes trace underlying periodicity—can explain the RVs. We find that a model with only one quasiperiodic signal is not adequate: we require a second component to fit the data. The best-fit model has quasi-periodic oscillations with <jats:italic>P</jats:italic> <jats:sub>1</jats:sub> = 705 days and <jats:italic>P</jats:italic> <jats:sub>2</jats:sub> = 15 days. The 705 day signal may be caused by magnetic activity. The 15 day period requires further investigation.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Silicate dust particles are part of many astronomical objects such as comets and circumstellar discs. In the spectrum, silicates exhibit a number of characteristic emission features. In this paper, we studied the contribution of quartz (SiO<jats:sub>2</jats:sub>) particles to these features. Using the Mie theory, calculations were made of the intensity of light scattered by such particles. Two spectral features were found in the spectrum—near 9 <jats:italic>μ</jats:italic>m and near 20.5 <jats:italic>μ</jats:italic>m. The main properties of these features are investigated. It is established, that the 9 <jats:italic>μ</jats:italic>m feature is much narrower than the 20.5 <jats:italic>μ</jats:italic>m; with an increase in the size of the scattering particle from very small values the position of spectral features (both 9 <jats:italic>μ</jats:italic>m and 20.5 <jats:italic>μ</jats:italic>m) shifts toward longer wavelengths; the 9 <jats:italic>μ</jats:italic>m feature cannot be clearly seen with particle sizes greater than 18 <jats:italic>μ</jats:italic>m, while the 20.5 <jats:italic>μ</jats:italic>m feature is apparent even at particle radius 60 <jats:italic>μ</jats:italic>m.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The tangent point method (TPM) is commonly used to calculate the rotation curve of the inner portion of the Milky Way, relying on the assumption that along one line of sight, the point tangent to the Galactic center is the point where the observed radial velocity is an extremum. This work compares rotation curves derived from the TPM, using neutral hydrogen gas data, and direct measurements of stellar positions and velocities from the Gaia Satellite. The Gaia data indicate that the rotation curve based upon stellar kinematics is much shallower than that previously reported based on the TPM, especially in the inner regions of the Galaxy. Additionally, based on stellar kinematics, the locations of the extremum radial velocities and tangent points often differ. While these results are consistent with previously published simulations, future data from the Gaia satellite will allow for further confidence in determining an accurate rotation curve.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present the results of deep narrowband imaging of two nested shells around the blue supergiant ALS 19653, which confirm that the outer shell is physically associated with the star.</jats:p>