Search Publications
Selection of Compton-thick AGN from a hard photometric sample using XMM-Newton observations
Guainazzi, Matteo; Mostafa, Reham; Ibrahim, Alaa
We present a selection technique to detect Compton-thick (CT) active galactic nuclei (AGNs) in the 3XMM/SDSS-DR7 cross-correlation. A subsample of 3481 X-ray sources that are detected in the hard band (2-8 keV) and have photometric redshifts constitute our parent sample. We first applied an automated spectral-fitting procedure to select highly abs…
Study of the X-ray properties of radio sources, based on NVSS catalogue
Mickaelian, A. M.; Abrahamyan, H. V.; Paronyan, G. M. +4 more
An identification of radio sources from the NVSS list with ROSAT X-ray sources was made as well as also with optical objects from SDSS DR 16. We have tried to find the connection between the fluxes of different wave ranges, for different types of objects. We also have tried to find the relationship between the sizes and polarization angles of sour…
HST proper motions on the far side of the Galactic bar-data
Clarkson, William I.; Rich, R. Michael; Kunder, Andrea +10 more
This is the third paper in a series that attempts to observe a clear signature of the Galactic bar/bulge using kinematic observations of the bulge stellar populations in low foreground extinction windows. We report on the detection of ~100 000 new proper motions in four fields covering the far side of the Galactic bar/bulge, at negative longitudes…
Restoration of T80-S telescope's images using neural networks
Roth, Martin M.; Bernardi, Rafael L.; Berdja, Amokrane +2 more
Convolutional neural networks (CNNs) have been used for a wide range of applications in astronomy, including for the restoration of degraded images using a spatially invariant point spread function (PSF) across the field of view. Most existing development techniques use a single PSF in the deconvolution process, which is unrealistic when spatially…
Updated Elements of Variable Stars in Sagittarius
Lemke, W.
High-precision Mg abundances in the metal-rich Galactic disc: chemodynamical relations and comparison with chemical evolution models
Recio-Blanco, A.; Kordopatis, G.; Palla, M. +2 more
The [Mg/Fe] abundance ratios are a fundamental fossil signature in Galactic archaeology for tracing the chemical evolution of disc stellar populations. High-precision chemical abundances, accurate stellar ages, distances, and dynamical data, together with their direct comparison with theoretical models, are crucial to infer the Milky Way formation…
A Comparison of Co-temporal Vector Magnetograms Obtained with HMI/SDO and SP/Hinode
Zhang, Mei; Zhang, Haocheng; Jiang, Chengqing
Accurate measurement of magnetic fields is very important for understanding the formation and evolution of solar magnetic fields. Currently, there are two types of solar magnetic field measurement instruments: filter-based magnetographs and Stokes polarimeters. The former gives high temporal resolution magnetograms and the latter provides more acc…
Model-independent periodogram for scanning astrometry
Zucker, S.; Binnenfeld, A.; Shahaf, S.
We present a new periodogram for the periodicity detection in one-dimensional time-series data from scanning astrometry space missions such as HIPPARCOS or Gaia. The periodogram is non-parametric and does not rely on a full or approximate orbital solution. Since no specific properties of the periodic signal are assumed, the method is expected to b…
Photometric calibration of M-dwarf metallicity using Bayesian inference
Caballero, J. A.; Montes, D.; Duque-Arribas, C. +3 more
Metallicity has remained as a challenging parameter when characterizing M-type dwarf stars due to difficulties in the analysis of their spectra, dominated by molecular features, but it is required in multiple areas of astrophysics, for example to constrain theoretical stellar models or guide exoplanet searches. In order to estimate the metallicity…
Multifilter Time-series Observations of Eleven Blue Short-period ATLAS Variable Stars
Kniazev, A.; Schaffenroth, V.; Koen, C.
Eleven periodic variable stars were observed photometrically through two to four filters from the set UBVR C I C . Phase-folded data for each star cover full cycles of variation. Spectral energy distributions, based on absolute photometry extracted from the literature, are used to inform models of the stars. The stars incl…