Search Publications
Soft X-Ray Excess from Shocked Black Hole Accretion
Fukumura, Keigo; Przybylek, Jeff
A certain class of luminous galaxies hosting supermassive black holes (BHs) is known to exhibit an excess of "soft X-rays" in their X-ray spectra. However, its physical identity and origin are yet to be understood. In this work, we systematically study a sample of 9 well-documented narrow-line Seyfert 1 active galactic nuclei by utilizing the arch…
Multipoint Observations of the Dynamics at an ICME Sheath-Ejecta Boundary
Pulkkinen, Tuija I.; Kilpua, Emilia K. J.; Good, Simon W. +3 more
The radial evolution of interplanetary coronal mass ejections (ICMEs) is dependent on their interaction with the ambient medium, which causes ICME erosion and affects their geoefficiency. Here, an ICME front boundary, which separates the confined ejecta from the mixed, interacted sheath-ejecta plasma upstream, is analyzed in a multipoint study exa…
Kinematic structure of the stellar population of the solar neighborhood by Gaia DR3
Vereshchagin, S. V.; Chupina, N. V.; Postnikova, E. S. +1 more
The data of modern catalogs allow us to consider in detail the issue of the spatial velocity distribution. The stars in the solar vicinity make it possible to avoid errors and draw detailed conclusions about their kinematics. For a corrected study, we took a sample of stars from the Gaia DR3 within 300 pc. This area contains a number of star clust…
Statistical analysis of microflares as observed by the 4–8 GHz spectropolarimeter
Altyntsev, Alexander; Meshalkina, Nataliya; Zhdanov, Dmitriy +1 more
Radio observations of weak events are one of the promising methods for studying energy release and non-thermal processes in the solar corona. The development of instrumental capabilities allows for radio observations of weak transient coronal events, such as quasi-stationary brightenings and weak flares of X-ray class B and below, which were previ…
The Cluster Virtual Observatory for ULF Waves
Richter, I.; Glassmeier, K. H.; Plaschke, F. +3 more
Since its launch in 2000, the Cluster fleet visited a vast domain of the circum-terrestrial environment, from the upstream solar wind and the distant tail, down to the plasmasphere, scanning in detail all magnetospheric regions during over two solar cycles. This led to an unprecedentedly rich data collection of multi-point measurements which will …
M51 ULX-4 ve NGC 1316 ULX X7'nin X-ışın ve Optik Özellikleri
Allak, Sinan; Soydugan, Faruk; Akyüz, Aysun
Bu çalışmada, gökada NGC 1316'da ULX X7 ve M51'de geçici ULX-4 kaynaklarının X-ışın tayfsal, zamansal ve optik özellikleri {\it Chandra}, {\it XMM-Newton}, {\it Swift-XRT} ve {\it HST} arşiv verileri kullanılarak kapsamlı bir şekilde araştırıldı. Bir X-ışın kaynağı olan X7'nin, ilk defa bu çalışmada 2019 {\it Chandra} gözlemleri kullanılarak bir U…
Comparison of Gaia BP/RP spectra with LDS (Low Dispersion Spectroscopy) photographic sky surveys
Hudec, R.
Blue (BP) and Red (RP) Photometer low-resolution spectral data is one of the exciting new products in the third data release of ESA satellite Gaia (Gaia DR3) https://gaia.aip.de/cms/services/spectra-access/. The Gaia "photometric mode" RP/BP generates ultra-low-dispersion prism spectra of celestial sources. The LDS (Low-Dispersion Spectroscopy) as…
Gaia-based comparative study of protoplanetary disk frequencies in young stellar clusters
Mendigutía, I.; Huélamo, N.; Solano, E. +4 more
This poster presents the results of a recent work (https://www.aanda.org/articles/aa/full_html/2022/08/aa43146-22/aa43146-22.html {Mendigutía et al. 2022, A&A, 664, A66}), where we have compared protoplanetary disk frequencies inferred from 2 widely different regions corresponding to 2 pc and 20 pc from the centers of a representative sample o…
Magnetohydrodynamic Shocks Revisited: Magnetically Constraining the Upstream Solar Wind Condition
Narita, Yasuhito; Schmid, Daniel
Magnetohydrodynamic (MHD) shocks are commonly found in various space and astrophysical systems. One often encounters the problem that only the magnetic field data are available when studying interplanetary shocks and planetary bow shocks in the solar system, and not the plasma data due to instrumental and/or telemetry limitations. We aim to reveal…
Feige 86: Gaia confirms its Horizontal Branch nature
Bonifacio, P.; Monaco, L.
The halo star Feige 86 was considered in the 1960's and 1970's a solar metallicity chemically peculiar, He-weak B type star. Margherita Hack was the first to study its UV spectrum acquired with the IUE satellite. Later studies of this star by Hack and collaborators suggested that, in spite of the fact its iron abundance is slightly above solar, th…