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Discovery of a White Dwarf Companion to HD 159062
Fulton, Benjamin J.; Hirsch, Lea A.; Howard, Andrew W. +11 more
We report on the discovery of a white dwarf companion to the nearby late G dwarf star, HD 159062. The companion is detected in 14 years of precise radial velocity (RV) data, and in high-resolution imaging observations. RVs of HD 159062 from 2003 to 2018 reveal an acceleration of -13.3 ± 0.12 {{m}} {{{s}}}-1 {yr}}-1, indicatin…
The GALAH Survey: lithium-strong KM dwarfs
Zwitter, T.; Buder, S.; Casagrande, L. +10 more
Identifying and characterizing young stars in the Solar neighbourhood is essential to find and describe planets in the early stages of their evolution. This work seeks to identify nearby young stars showing a lithium 6708 Å absorption line in the GALAH survey. A robust, data-driven approach is used to search for corresponding templates in the pool…
Statistical Study of Chromospheric Evaporation in Impulsive Phase of Solar Flares
Kerr, Graham S.; Kosovichev, Alexander G.; Sadykov, Viacheslav M. +1 more
We present a statistical study of chromospheric evaporation in solar flares using simultaneous observations by the RHESSI X-ray telescope and the Interface Region Imaging Spectrograph UV spectrograph. The results are compared with radiation hydrodynamic flare models from the F-CHROMA RADYN database. For each event, we study spatially resolved Dopp…
Deriving star cluster parameters with convolutional neural networks. I. Age, mass, and size
Narbutis, D.; Vansevičius, V.; Bialopetravičius, J.
Context. Convolutional neural networks (CNNs) have been proven to perform fast classification and detection on natural images and have the potential to infer astrophysical parameters on the exponentially increasing amount of sky-survey imaging data. The inference pipeline can be trained either from real human-annotated data or simulated mock obser…
The Origin of [C II] 158 µm Emission toward the H II Region Complex S235
Schneider, N.; Tremblin, P.; Zavagno, A. +9 more
Although the {}2{{{P}}}3/2-{}2{{{P}}}1/2 transition of [C II] at λ ≃ 158 µ {{m}} is known to be an excellent tracer of active star formation, we still do not have a complete understanding of where within star formation regions the emission originates. Here, we use SOFIA upGREAT observations of [C I…
The spectacular cluster chain Abell 781 as observed with LOFAR, GMRT, and XMM-Newton
Brunetti, G.; Shimwell, T. W.; Gastaldello, F. +20 more
Context. A number of merging galaxy clusters show the presence of large-scale radio emission associated with the intra-cluster medium (ICM). These synchrotron sources are generally classified as radio haloes and radio relics.
Aims: Whilst it is commonly accepted that mergers play a crucial role in the formation of radio haloes and relics, not…
Scattering, absorption, and thermal emission by large cometary dust particles: Synoptic numerical solution
Agarwal, Jessica; Markkanen, Johannes
Context. Remote light scattering and thermal infrared observations provide clues about the physical properties of cometary and interplanetary dust particles. Identifying these properties will lead to a better understanding of the formation and evolution of the Solar System.
Aims: We present a numerical solution for the radiative and conductiv…
Coordinated UV and X-Ray Spectroscopic Observations of the O-type Giant ξ Per: The Connection between X-Rays and Large-scale Wind Structure
Ignace, Richard; Massa, Derck; Oskinova, Lida +1 more
We present new, contemporaneous Hubble Space Telescope STIS and XMM-Newton observations of the O7 III(n)((f)) star ξ Per. We supplement the new data with archival IUE spectra, to analyze the variability of the wind lines and X-ray flux of ξ Per. The variable wind of this star is known to have a 2.086-day periodicity. We use a simple, heuristic spo…
Modeling of the Sunspot-Associated Microwave Emission Using a New Method of DEM Inversion
Patsourakos, S.; Alissandrakis, C. E.; Bogod, V. M. +2 more
We develope a method to compute the temperature and density structure along the line of sight by inversion of the differential emission measure (DEM), under the assumptions of stratification and hydrostatic equilibrium. We apply this method to the DEM obtained from the Atmospheric Imaging Assembly (AIA) observations and use the results, together w…
Spectral Magnetic Helicity of Solar Active Regions between 2006 and 2017
Gosain, Sanjay; Brandenburg, Axel
We compute magnetic helicity and energy spectra from about 2485 patches of about 100 Mm side length on the solar surface using data from Hinode during 2006-2017. An extensive database is assembled where we list the magnetic energy and helicity, large- and small-scale magnetic helicity, mean current helicity density, fractional magnetic helicity, a…