Search Publications
On the Origin of Metal-poor Stars in the Solar Neighborhood
Bilir, Selçuk; Şahin, Timur
We determined the ages, kinematic parameters, and Galactic orbital parameters of six metal-poor (-2.4 < [Fe/H] < -1.0 dex), F-type, high-proper-motion (HPM) stars to investigate their HPM nature and origin. For the kinematical procedure, the astrometric data from the Gaia DR2 were used. High-resolution ELODIE spectra of the six dwarfs were a…
Oxygen Atom Escape from the Martian Atmosphere during Proton Auroral Events
Shematovich, V. I.; Kalinicheva, E. S.
We present the model calculation results of the atomic oxygen loss rate from the Martian atmosphere induced by precipitation of high-energy protons and hydrogen atoms (H/H+) from the solar wind plasma. Penetration of energetic protons and hydrogen atoms from the solar wind plasma to the upper atmosphere of Mars at altitudes of 100-250 k…
Chromospheric Magnetic Field: A Comparison of He I 10830 Å Observations with Nonlinear Force-free Field Extrapolation
Shimizu, Toshifumi; Asensio Ramos, Andrés; Inoue, Satoshi +1 more
The nonlinear force-free field (NLFFF) modeling has been extensively used to infer the three-dimensional magnetic field in the solar corona. One of the assumptions in the NLFFF extrapolation is that the plasma beta is low, but this condition is considered to be incorrect in the photosphere. We examine direct measurements of the chromospheric magne…
New observations of DW Cnc: where is the 38 min signal?
Ramírez, S. H.; Echevarría, J.; Segura Montero, O.
We present extensive radial velocity observations of the intermediate polar DW Cnc during its 2018-2019 low state. We show that the 86 min signal associated with the orbital period is strong in our radial velocity analysis, power spectrum search, and in our Doppler tomography. However, we find that the velocity modulation associated with the 70 mi…
On the Nature of the T Tauri Triple System
Chapillon, E.; Schaefer, G. H.; Guilloteau, S. +4 more
We present a multiwavelength analysis to reveal the nature of the enigmatic T Tauri triple star system. New optical and infrared measurements are coupled with archival X-ray, UV, and millimeter data sets to show the morphologies of disk material and outflow kinematics. A dark lane of obscuring material is seen in silhouette in several emission lin…
Discovery of a retrogradely rotating neutron star in the X-ray pulsar GX 301-2
Doroshenko, Victor; Tsygankov, Sergey S.; Poutanen, Juri +3 more
We report on the analysis of the spin evolution of a slow X-ray pulsar GX 301-2 along the orbit using long-term monitoring by Fermi/Gamma-ray Burst Monitor. Based on the observationally confirmed accretion scenario and an analytical model for the accretion of angular momentum, we demonstrate that in this system, the neutron star spins retrogradely…
Ultraviolet and X-ray properties of Coma's ultra-diffuse galaxies
Gallo, Elena; Hodges-Kluck, Edmund; Lee, Chris H.
Many ultra-diffuse galaxies (UDGs) have been discovered in the Coma cluster, and there is evidence that some, notably Dragonfly 44, have Milky Way-like dynamical masses despite dwarf-like stellar masses. We used X-ray, ultraviolet (UV), and optical data to investigate the star formation and nuclear activity in the Coma UDGs, and we obtained deep U…
The historical record of massive star formation in Cygnus
Comerón, F.; Schneider, N.; Pasquali, A. +1 more
Context. The Cygnus region, which dominates the local spiral arm of the Galaxy, is one of the nearest complexes of massive star formation, extending over several hundred parsecs. Its massive stellar content, regions of ongoing star formation, and molecular gas have been studied in detail at virtually all wavelengths. However, little is known of th…
A Non-Linear Magnetic Field Calibration Method for Filter-Based Magnetographs by Multilayer Perceptron
Ji, Kaifan; Su, Jiangtao; Deng, Yuanyong +5 more
For filter-based magnetographs, the linear calibration method under the weak-field assumption is usually adopted; this leads to magnetic saturation effect in the regions with strong magnetic field. This article explores a new method to overcome the above disadvantage using a multilayer perceptron network, which we call MagMLP, based on a back-prop…
Mapping and spatial statistical analysis of Mars Yardangs
Di, Kaichang; Liu, Bin; Liu, Jia +4 more
Mars yardang fields were mapped using the newly available high-resolution Context Camera (CTX) mosaics (30°N to 30°S) through visual interpretation and manual digitization. We classified the Martian yardangs into three types according to their shapes: long ridge, inverted hull and curvilinear shapes, and found that the number of long ridge yardang…