Search Publications
Machine learning applied to multifrequency data in astrophysics: blazar classification
Arsioli, B.; Dedin, P.
The study of machine learning (ML) techniques for the autonomous classification of astrophysical sources is of great interest, and we explore its applications in the context of a multifrequency data-frame. We test the use of supervised ML to classify blazars according to its synchrotron peak frequency, either lower or higher than 1015 H…
Extremely precise age and metallicity of the open cluster NGC 2506 using detached eclipsing binaries
Grundahl, F.; Knudstrup, E.; Lund, M. N. +10 more
Accurate stellar parameters of stars in open clusters can help constrain models of stellar structure and evolution. Here, we wish to determine the age and metallicity content of the open cluster NGC 2506. To this end, we investigated three detached eclipsing binaries (DEBs; V2032, V4, and V5) for which we determined their masses and radii, as well…
Kinematics of coronal mass ejections in the LASCO field of view
Yashiro, Seiji; Ravishankar, Anitha; Michałek, Grzegorz
In this paper we present a statistical study of the kinematics of 28894 coronal mass ejections (CMEs) recorded by the Large Angle and Spectrometric Coronagraph (LASCO) on board the Solar and Heliospheric Observatory spacecraft from 1996 until mid-2017. The initial acceleration phase is characterized by a rapid increase in CME velocity just after e…
The Electron Proton Helium INstrument as an example for a Space Weather Radiation Instrument
Heber, Bernd; Malandraki, Olga; Posner, Arik +3 more
The near-Earth energetic particle environment has been monitored since the 1970's. With the increasing importance of quantifying the radiation risk for, e.g. for the human exploration of the Moon and Mars, it is essential to continue and further improve these measurements. The Electron Proton Helium INstrument (EPHIN) on-board SOHO continually pro…
Convection in the Magnetosphere-Ionosphere System: A Multimission Survey of Its Response to IMF <span type="mathematics">By Reversals
Fear, R. C.; Haaland, S.; Case, N. A. +2 more
Past studies have demonstrated that the interplanetary magnetic field (IMF) By component introduces asymmetries in the magnetosphere-ionosphere (M-I) system, though the exact timings involved are still unclear with two distinct mechanisms proposed. In this study, we statistically analyze convective flows from three regions of the M-I sy…
Compiling Magnetosheath Statistical Data Sets Under Specific Solar Wind Conditions: Lessons Learnt From the Dayside Kinetic Southward IMF GEM Challenge
Dimmock, A. P.; Hietala, H.; Zou, Y.
The Geospace Environmental Modelling (GEM) community offers a framework for collaborations between modelers, observers, and theoreticians in the form of regular challenges. In many cases, these challenges involve model-data comparisons to provide wider context to observations or validate model results. To perform meaningful comparisons, a statisti…
High-precision calculation of the light curve and its interpretation
Abubekerov, M. K.; Gostev, N. Yu.
We present a highly precise calculation of the theoretical light curve and its derivatives for a binary star-planet system in an elliptical orbit. We also describe an analytical fitting by limb-darkening coefficients to reduce the number of parameters for nonlinear fitting. We demonstrate the practical importance of the precision computation of th…
Chandra Imaging of the Western Hotspot in the Radio Galaxy Pictor A: Image Deconvolution and Variability Analysis
Cheung, C. C.; Stawarz, Ł.; Siemiginowska, A. +3 more
Here we present an analysis of the X-ray morphology and flux variability of the particularly bright and extended western hotspot in the nearest powerful (FR II-type) radio galaxy, Pictor A, based on data obtained with the Chandra X-ray Observatory. The hotspot marks the position where the relativistic jet, which originates in the active nucleus of…
Wolf-Rayet stars in M 81 using GTC/OSIRIS: seven new detections, analysis, and classification of the full sample
Alvarez, C.; Toalá, J. A.; Gómez-González, V. M. A. +3 more
We report the detection of seven new Wolf-Rayet (WR) star locations in M 81 using the Multi-Object Spectrograph of the OSIRIS instrument at Gran Telescopio Canarias. These detections are the result of a follow-up of an earlier study using the same instrumental set-up that resulted in the detection of 14 WR locations. We analyse the entire sample o…
An XMM-Newton X-Ray View of Supernova Remnant W49B: Revisiting Its Recombining Plasmas and Progenitor Type
Chen, Yang; Sun, Lei
We present a comprehensive X-ray spectroscopy and imaging study of supernova remnant W49B using archival XMM-Newton observations. The overionization state of the shocked ejecta in W49B is clearly indicated by the radiative recombination continua of Si XIV, S XV, and Fe XXV, combined with the Lyα lines of Ca and Fe. The line flux images of W49B ind…