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The importance of nucleus rotation in determining the largest grains ejected from comets
Molina, A.
The maximum diameter of large boulders ejected from the cometary nuclei is investigated using the classical model of dust grain as dragged out by radially expanding cometary gases. The importance of the inertial forces, and particularly those due to the rotation of the comet is shown. Although a larger dust grain can be lifted from the nucleus sur…
On the origin of the tailward velocity of O+ ions over the magnetic poles of Mars
Pérez-de-Tejada, H.; Reyes-Ruiz, M.; Aceves, H.
We numerically simulate the dynamics of a population of O+ ions of ionospheric origin picked-up by the solar wind in the dayside ionosheath of Mars. Their average velocity as they reach the magnetic polar regions of the planet is compared with in situ measurements of the Mars Express spacecraft. We find that the velocity of O+ ions measured over t…
The 3D velocity structure of the planetary nebula NGC 7009
Steffen, W.; Koning, N.; Espíndola, M. +1 more
In search for deviations from homologous expansion in planetary nebulae we present a 3D morphokinematical model of NGC 7009. The model has been constructed with Shape based on PV diagrams from the literature and HST images. We find that the data are consistent with a radial velocity field with increased gradient at high latitudes compared to the e…
Radio Proper Motions of Wolf-Rayet Stars
Rodríguez, L. F.; Dzib, S.
We present the analysis of observations taken from the Very Large Array archive of six Wolf-Rayet stars with radio emission, with the purpose of determining their proper motions. Typically, these observations cover periods of 10 to 20 years. To verify the method, we included WR 140 in the sample, and found that the proper motions determined by us …
Kinematics and Velocity Ellipsoid of the K Giants
Branham, R. L., Jr.
To study the kinematics of the K giant stars (luminosity class III) use is made of proper motions taken from van Leeuwen's new reduction of the Hipparcos catalog. 11,372 stars, of which 880 have radial velocities, were used in the final study. Semi-definite programming solves for the kinematical parameters such as the Oort constants and simultaneo…
Kinematics and Velocity Ellipsoid of M Giants
Branham, R. L., Jr.
To study the kinematics of M giant stars (luminosity class III) use is made of 1,532 stars with proper motions taken from the Hipparcos catalog, of which 480 have radial velocities. Stars farther off than 700 pc were excluded because they induce a noticeable tilt in the distribution of the stars. Various solutions were performed, and the one calcu…
Determination of the IMF in the LMC Stellar Cluster NGC 2156
Silva-Villa, E.; Sirianni, M.; Zuluaga, J.
We present a study on the IMF of the stellar cluster NGC 2156 in the LMC from deep HST-WFPC2 images in the bands F555W and F814W. The study is part of a larger program to investigate whether the IMF at low stellar masses is dependent on local conditions by observing young globular clusters in the LMC and the SMC. We detected stars down to a limiti…
Radio Continuum Sources Associated with AB Aur
Rodríguez, L. F.; Ho, P. T. P.; Zapata, L.
We present high angular resolution, high-sensitivity Very Large Array observations at 3.6 cm of the Herbig Ae star AB Aur. This star is of interest since its circumstellar disk exhibits characteristics that have been attributed to the presence of an undetected low mass companion or giant gas planet. Our image confirms the continuum emission known …
Orbit, Masses and Spectral Analysis of the Visual Binary A 2329
Andrade, M.
A revised orbit for the visual binary A 2329, calculated taking into account a set of interferometric measures distributed over one orbital revolution, is presented. On the basis of new orbital elements and the Hipparcos parallax, a dynamical mass of the system of 1.25+/-0.14 M_⊙ is obtained. By considering new spectral data, we confirm its MK spe…
Formation of a Two-Dense-Rings-Pattern Disk from the Collapse of a Cloud
Nagel, E.
In this paper, the formation of a disk resulting from the collapse of a rigidly-rotating cloud is studied. The plane perpendicular to the angular velocity axis that contains the star is the locus where materials falling from both sides face each other with the consequent formation of a double layer shock structure. The shocked material that moves …