Search Publications
Global parameters of the totally-eclipsing W UMa stars NSVS 6673994, NSVS 4316778, PP Lac and NSVS 1926064
Popov, Velimir A.; Petrov, Nikola I.; Kjurkchieva, Diana P.
Photometric observations of four totally-eclipsing W UMa binaries, NSVS 6673994, NSVS 4316778, PP Lac and NSVS 1926064, are presented. Their global parameters were determined from the light curve solutions and GAIA distances. The main results are as follows: (i) NSVS 6673994, NSVS 4316778 and PP Lac are of W subtype while NSVS 1926064 is of A subt…
X-Ray Emission and Disk Irradiation of HL Tau and HD 100546
Skinner, Stephen L.; Güdel, Manuel
We present new X-ray observations of the optically obscured protostar HL Tau and the intermediate-mass Herbig Be star HD 100546. Both objects are surrounded by spectacular disks showing complex morphology, including rings and gaps that may have been sculpted by protoplanets. HL Tau was detected as a variable hard X-ray source by Chandra, typical o…
Driving solar coronal MHD simulations on high-performance computers
Bourdin, Philippe-A.
The quality of today's research is often tightly limited to the available computing power and scalability of codes to many processors. For example, tackling the problem of heating the solar corona requires a most realistic description of the plasma dynamics and the magnetic field. Numerically solving such a magneto-hydrodynamical (MHD) description…
Illuminating a tadpole's metamorphosis III: quantifying past and present environmental impact
Reiter, Megan; Garay, Guido; McLeod, Anna F. +3 more
We combine Multi-Unit Spectroscopic Explorer and Atacama Large Millimeter/sub-millimeter Array observations with theoretical models to evaluate how a tadpole-shaped globule located in the Carina Nebula has been influenced by its environment. This globule is now relatively small (radius ~2500 au), hosts a protostellar jet+outflow (HH 900), and, wit…
The Solar Origin of Particle Events Measured by Parker Solar Probe
Vourlidas, Angelos; Poirier, Nicolas; Kouloumvakos, Athanasios +4 more
During the second solar encounter phase of Parker Solar Probe (PSP), two small solar energetic particle (SEP) events were observed by the Integrated Science Investigation of the Sun, on 2019 April 2 and 4. At the time, PSP was approaching its second perihelion at a distance of ∼24.8 million kilometers from the solar center, it was in near-radial a…
CS Depletion in Prestellar Cores
Soam, Archana; Kim, Shinyoung; Kim, Gwanjeong +6 more
The CS molecule is known to be adsorbed onto dust in cold and dense conditions, causing it to be significantly depleted in the central region of cores. This study is aimed to investigate the depletion of the CS molecule using the optically thin {C}34{S} molecular line observations. We mapped five prestellar cores, L1544, L1552, L1689B, …
Extrapolation of Three-dimensional Magnetic Field Structure in Flare-productive Active Regions with Different Initial Conditions
Shimizu, T.; Inoue, S.; Kawabata, Y.
Nonlinear force-free field (NLFFF) modeling has been extensively used as a tool to infer three-dimensional (3D) magnetic field structure. In this study, the dependency of the NLFFF calculation with respect to the initial guess of the 3D magnetic field is investigated. While major parts of the previous studies used the potential field as the initia…
Magnetohydrodynamic Modeling of the Solar Wind Key Parameters and Current Sheets in the Heliosphere: Radial and Solar Cycle Evolution
Malova, H. V.; Popov, V. Yu.; Petrukovich, A. A. +4 more
We develop an axisymmetric numerical MHD model that allows us to investigate the spatial characteristics of the interplanetary magnetic field (IMF) and key solar wind plasma parameters from 20 to 400 solar radii over all heliolatitudes. The study is aimed at an analysis of the evolution of the spatial structure of the heliosphere through the solar…
Turbulence Near the Venusian Bow Shock: Venus Express Observations
Zhang, T. L.; Vörös, Z.; Chen, Y. Q. +3 more
In terms of composition and size, Venus is an Earth-like planet without a global intrinsic magnetic field. The Venusian bow shock and magnetosheath, reaching only 10% of the size of the Earth, are formed from the interaction of the solar wind with the Venusian ionosphere. Energy injection from the solar wind to the Venusian space environment can b…
Automated detection of block falls in the north polar region of Mars
Oberst, J.; Hauber, E.; Gwinner, K. +1 more
We developed a change detection method for the identification of ice block falls using NASA's HiRISE images of the north polar scarps on Mars. Our method is based on a Support Vector Machine (SVM), trained using Histograms of Oriented Gradients (HOG), and blob detection. The SVM detects potential new blocks between a set of images; the blob detect…