Search Publications
The inverse problem of the theory of degenerate dwarfs
Vavrukh, M. V.; Smerechynskyi, S. V.; Tyshko, N. L.
Based on the radii and masses of degenerate dwarfs derived from HIPPARCOS and other observations, we estimate the microscopic parameters of a Chandrasekhar model (the relativistic parameter at the stellar center x 0, and the chemical-composition parameter µ e = A/Z, where A is the mass number and Z is the nuclear charge). We…
Statistics of interacting galaxies at z ∼ 0.7
Reshetnikov, V. P.; Mohamed, Y. H.
We present the results of our analysis of the frequencies of galaxies with tidal tails and M51-type galaxies in several deep fields of the Hubble Space Telescope (HDF-N, HDF-S, HUDF, GOODS, GEMS). In total, we have found about seven hundred interacting galaxies at redshifts z ≤ 1.5 in these fields. At z ≤ 0.7, the observed space densities of galax…
Filaments and the magnetic configuration. I. Observation of the solar case
Meunier, N.; Delfosse, X.
Context. The emission of Ca and Hα is correlated for the Sun, but this does not seem to be true for other stars. We previously demonstrated that this lack of correlation could be due to the presence of filaments.
Aims: We aim to establish a link between the activity level, the magnetic configuration, and the number of filaments, and therefore…
Strong Gravitational Lens Modeling with Spatially Variant Point-spread Functions
Rogers, Adam; Fiege, Jason D.
Astronomical instruments generally possess spatially variant point-spread functions, which determine the amount by which an image pixel is blurred as a function of position. Several techniques have been devised to handle this variability in the context of the standard image deconvolution problem. We have developed an iterative gravitational lens m…
Mars reconnaissance lander: Vehicle and mission design
Ambrosi, R. M.; Bridges, J. C.; Bannister, N. P. +7 more
There is enormous potential for more mobile planetary surface science. This is especially true in the case of Mars because the ability to cross challenge terrain, access areas of higher elevation, visit diverse geological features and perform long traverses of up to 200 km supports the search for past water and life. Vehicles capable of a ballisti…
Atmospheric parameters of the B-supergiant HD 198478 from the UV spectra
Jurkić, Tomislav; Sarta Deković, Mariza; Dominis Prester, Dijana +1 more
We determined atmospheric parameters of the Galactic early B-supergiant HD 198478 (55 Cyg) from the UV silicon lines taken from the high-resolution 1150–1980 Å IUE spectra. TLUSTY numerical code was used to model the stellar atmosphere and to determine the temperature and surface gravity assuming a non-LTE plane parallel hydrostatic stellar atmosp…
Evidence for the nearby F4V star λ Ara as a binary system
Stahl, O.; Chini, R.; Fuhrmann, K. +1 more
We report on the spectroscopic evidence for the nearby, bright and supposedly single F4V star λ Ara as a binary system. The basic observational tracer is a discrepancy with the Hipparcos-based astrometric surface gravity as opposed to the spectroscopically derived value from the pressure-dependent Mg Ib triplet lines. We demonstrate how this discr…
The Need for Physics-based Inversions of Sunspot Structure and Flows
Birch, A. C.; Braun, D. C.; Crouch, A. D. +1 more
Current controversy exists in the interpretation and modeling of helioseismic signals in and around magnetic regions like sunspots. Unresolved issues include the dependence of the sign of both the inferred flows and wave speed on the type of filtering used, and the discrepancy between the relatively deep two-layer wave-speed models derived from st…
Spatial scales of the magnetic ramp at the Venusian bow shock
Zhang, T. L.; Walker, S. N.; Pope, S. A. +1 more
Typically multi-spacecraft missions are ideally suited to the study of shock spatial scales due to the separation of temporal and spatial variations. These missions are not possible at all locations and therefore in-situ multi-spacecraft measurements are not available beyond the Earth. The present paper presents a study of shock spatial scales usi…
Effects of the guard electrode on the photoelectron distribution around an electric field sensor
Miyake, Y.; Usui, H.; Kojima, H.
We have developed a numerical model of a double-probe electric field sensor equipped with a photoelectron guard electrode for the particle-in-cell simulation. The model includes typical elements of modern double-probe sensors on, e.g., BepiColombo/MMO, Cluster, and THEMIS spacecraft, such as a conducting boom and a preamplifier housing called a pu…