Search Publications
Near-ultraviolet detections of four dwarf nova candidates in the globular cluster 47 Tucanae
Wijnands, Rudy; Modiano, David; Parikh, Aastha S.
We investigate near-ultraviolet variability in the Galactic globular cluster (GC) 47 Tucanae (47 Tuc). This work was undertaken within the GC sub-project of the Transient UV Objects project, a programme which aims to find and study transient and strongly variable UV sources. Globular clusters are ideal targets for transient searches because of the…
Dependence of Dayside Electron Densities at Venus on Solar Irradiance
Pätzold, M.; Häusler, B.; Tellmann, S. +3 more
The ionosphere of Venus is a weakly ionized plasma layer embedded in the planet's upper atmosphere. Planetary ionospheres provide an excellent opportunity to study how our variable Sun affects the planets in our solar system. Because ionospheres are reservoirs from which atmospheric species can be lost to space, studying how ionospheres respond to…
KKH 22, the first dwarf spheroidal satellite of IC 342
Anand, Gagandeep S.; Shaya, Edward J.; Karachentsev, Igor D. +4 more
Aims: We present observations with the Advanced Camera for Surveys on the Hubble Space Telescope of the nearby dwarf spheroidal galaxy KKH 22 = LEDA 2807114 in the vicinity of the massive spiral galaxy IC 342.
Methods: We derived its distance of 3.12 ± 0.19 Mpc using the tip of red giant branch (TRGB) method. We also used the 6 m BTA spe…
Solar Total Eclipse of 21 August 2017: Study of the Inner Corona Dynamical Events Leading to a CME
Filippov, Boris; Koutchmy, Serge; Lefaudeux, Nicolas
Total solar eclipse (TSE) coronal large- and small-scale events were reported in the historical literature but a definite synoptic coverage was missing for studying a relationship with the more general magnetic context of the solar-disk. We here analyze temporal changes in the solar corona before, during, and after the total solar eclipse on 21 Au…
Ages of Dwarfs in the Solar Neighborhood: Considering C and O Enhancements
Wu, Yaqian; Chen, Yuqin; Bi, Shaolan +7 more
Precise stellar ages of stars are necessary to study the evolution of the Milky Way. The age determination is significantly affected by C and O abundances of stars due to their contribution to the overall metallicity and opacity. On the basis of C and O abundances derived from high-resolution observations, we determine the ages of 148 FGK-type dwa…
Ultradiffuse Galaxies in the Coma Cluster: Probing Their Origin and AGN Occupation Fraction
Bogdán, Ákos; Canning, Rebecca E. A.; Kovács, Orsolya E.
Ultradiffuse galaxies (UDGs) exhibit low surface brightness, but their optical extent is comparable to that of Milky Way-type galaxies. In this work, we utilize Chandra X-ray observations of 404 UDGs in the Coma cluster and address two crucial goals. First, we constrain the formation scenario of UDGs by probing the X-ray emission originating from …
Recombining plasma in supernova remnants: Discovery and progress in the last decade
Yamaguchi, Hiroya
Presence of recombining (overionized) plasma in several supernova remnants (SNRs), first suggested by ASCA observations, was anchored by the detection of enhanced radiative recombination continua in Suzaku spectra of the SNRs IC 443 and W49B. This discovery was surprising, because X‑ray‑emitting SNRs were thought to have ionizing plasmas in genera…
Kinematics of main-sequence stars from the Gaia DR2 and PMA proper motions
Akhmetov, V. S.; Fedorov, P. N.; Velichko, Anna B.
We aim at analysis of kinematics of main-sequence stars from the GaiaDR2 and PMA catalogues as well as comparison of kinematic parameters derived from their proper motions. We decompose the stellar velocity field on to a set of vector spherical harmonics (VSH), and, using the relations between the decomposition coefficients and the Ogorodnikov-Mil…
AStroLens: automatic strong-lens modelling of X-ray selected galaxy clusters
Ebeling, Harald; Zalesky, Lukas
We use AStroLens, a newly developed gravitational lens-modelling code that relies only on geometric and photometric information of cluster galaxies as input, to map the strong-lensing regions and estimate the lensing strength of 96 galaxy clusters at z = 0.5-0.9. All clusters were identified during the extended Massive Cluster Survey (eMACS) based…
A Swift view of X-ray and UV radiation in the planet-forming T Tauri system PDS 70
Güdel, Manuel; Pye, John P.; Page, Kim L. +4 more
PDS 70 is a ∼5-Myr-old star with a gas and dust disc in which several protoplanets have been discovered. We present the first ultraviolet (UV) detection of the system along with X-ray observations taken with the Neil Gehrels Swift Observatory satellite. PDS 70 has an X-ray flux of 3.4 × 10-13 erg cm-2 s-1 in the 0.…