Search Publications
Changes in the Period of V420 Cen, a W Vir-Type Cepheid
Berdnikov, L. N.
The reduction of all the available photometry for the Cepheid V420 Cen has allowed its $O-C$ diagram spanning a time interval of 131 years to be constructed. The data obtained provide evidence for the existence of large random fluctuations in the period ($\varepsilon/P≈ 0.021$). Fitting the $O-C$ residuals by a cubic parabola has made it possible …
Search for Evolutionary Changes in the Periods of the Cepheids CEa Cas and CEb Cas
Berdnikov, L. N.; Pastukhova, E. N.; Ikonnikova, N. P. +4 more
For two classical Cepheids, CEa Cas and CEb Cas, members of the open cluster NGC 7790, we have constructed $O-C$ diagrams spanning a time interval of 125 years. The $O-C$ diagrams have the shape of parabolas, which has allowed us for the first time to determine the quadratic light elements and to calculate the rates of evolutionary changes in thei…
Runaway Stars as Possible Sources of the Elliptical Ring Structures in NGC 7538
Fenske, Josephine; Arakawa, Jason; Fallscheer, Cassandra +1 more
Two large, ∼500 M⊙ elliptical ring structures have been identified in the high-mass star-forming region NGC 7538. The origin of these ring structures is unknown, so we investigate the possibility that a runaway O- or B-type star may have originated in or passed through the region and created either or both of the ring structures via ste…
Virtual Moon Atlas 7 Freeware
Legrand, C.; Chevalley, P.
Virtual Moon Atlas version 7 is a mapping freeware linking topographic, geologic, chemical and historical maps with databases, documents, and pictures libraries. It uses datas from NASA, USGS, JPL, Smart-1, LP, Kaguya, Chandrayann, and Chang'E probes.
Early Kyiv Observations of Asteroids: Analysis and New Reduction with Tycho-2 and Gaia Catalogs
Shatokhina, S. V.; Kazantseva, L. V.
For more than 50 years, the continuous photographic observations of asteroids have been carried outwith telescopes of the Astronomical Observatory of the Taras Shevchenko National University of Kyiv and the Main Astronomical Observatory of the National Academy of Sciences of Ukraine. About 3,000 photographic plates were obtained, some of which wer…
Four New Variable Stars in the Field of KELT-16
Brossard, D. J.; Kaitchuck, R. H.
We present three new variable stars in the field around the star KELT-16, and new period estimates for four previously known contact binary systems in this field, ASASSN-V J205658.12+314215.9, ASASSN-V J205552.88+314615.9, ZTF J205733.78+314612.6, and ZTF J205627.42+315322.4. Due to the short periods of these three new variable stars, and the shap…
NGC 2660: Gaia DR2, ASteCA and the end of controversies?
Perren, G. I.; Pera, M. S.; Vázquez, R. A. +4 more
NGC 2660, an old and very compact open cluster placed at about 3 kpc from the Sun in a region of moderate absorption, has been subject of several photometric and spectroscopic studies in the past. Controversies arise in terms of its distance, age and metal content. Previous comparisons with cluster synthetic models carried out did not resolve them…
The Unusual Weak-line Quasar PG1407+265 and Its Foreground z 0.7 X-Ray Cluster
McDowell, Jonathan C.; Gallo, Luigi C.; Siemiginowska, Aneta +2 more
We present new observations of the odd z = 0.96 weak-line quasar PG1407+265, and report the discovery of CXOU J140927.9+261813, a z = 0.68 X-ray cluster. Archival X-ray photometry spanning nearly four decades reveals that PG1407+265 is variable at the 1 dex level on a timescale of years. V-band variability is observed with an amplitude less than 0…
Orbital eccentricities as indicators of stellar populations. II. Vertical velocity distribution from the Gaia DR2 catalogue
Cubarsi, R.; Stojanović, M.; Ninković, S.
Context. In previous work, we showed how the planar and vertical eccentricities of disc stars, e and e′, could be used as indicators of the stars' kinematic populations. For a local stellar sample drawn from the Gaia DR2 catalogue, these populations were represented geometrically in the eccentricity diagram, e′2 vs. e2, appro…
Impact of the Solar Wind Dynamic Pressure on the Field-Aligned Currents in the Magnetotail: Cluster Observation
Dandouras, I.; Dunlop, M. W.; Rème, H. +6 more
We statistically investigate the influence of the solar wind dynamic pressure (SW Pdyn) on the field-aligned currents (FACs) in the magnetotail with 1,492 FAC cases from July to October in 2001 and 2004, which covers 74 Cluster crossings of the plasma sheet boundary layer (PSBL) in both storm time and non-storm time. The FAC density in …