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UV photometry of spotted stars in the horizontal branch of the globular cluster NGC 2808 using AstroSat
Sahu, Snehalata; Subramaniam, Annapurni; Prabhu, Deepthi S.
A recent study of hot (20,000 to 30,000 K) extreme horizontal branch (EHB) stars in globular clusters (GCs) has led to the discovery of their variability. It is suggested that this variability is driven by the projected rotation of magnetic spots on the stellar surfaces and is expected to have higher amplitudes at shorter wavelengths. Here, we pre…
Trigonometric Parallaxes of Two T Dwarfs With Keck and ShaneAO Astrometry
Lu, Jessica R.; Ammons, S. Mark; Nguyen, Jayke +4 more
We present trigonometric parallax and proper motion measurements for two T-type brown dwarfs. We derive our measurements from infrared laser guide star adaptive optics observations spanning five years from the ShaneAO/SHARCS and NIRC2/medium-cam instruments on the Shane and Keck telescopes, respectively. To improve our astrometric precision, we me…
Determinación de los parámetros H y G para 4000 asteroides del catálogo Gaia DR2
Duffard, R.; Colazo, M.; Weidmann, W.
The Gaia mission will provide the scientific community with high- quality observations of ∼ 300,000 asteroids of all categories. The purpose of this work is to obtain a catalog of phase function parameters (H and G) for all the asteroids that are observed by the Gaia mission and which were published in the DR2 catalogue. For this purpose, we intro…
UVIT observation of Milky Way satellite galaxy Reticulum II
Thirupathi, Sivarani; Divakar, Devika K.; Doddamani, Vijayakumar H.
We present the UV photometry of one of the Ultra-Faint Dwarf (UFD) Milky Way (MW) satellite galaxies, Reticulum II, using images acquired with the Ultra-Violet Imaging Telescope (UVIT) onboard AstroSat. Reticulum II is a dark matter dominated, one of the most metal-poor and old (13.5 Gyr) satellite galaxies. High resolution spectroscopy of red gia…
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…