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Transient Spiral Arms from Far Out-of-equilibrium Gravitational Evolution
Sylos Labini, Francesco; Benhaiem, David; Joyce, Michael
We describe how a simple class of out-of-equilibrium, rotating, and asymmetrical mass distributions evolve under their self-gravity to produce a quasi-planar spiral structure surrounding a virialized core, qualitatively resembling a spiral galaxy. The spiral structure is transient, but can survive tens of dynamical times, and further reproduces qu…
Evidence for Binarity and Possible Disk Obscuration in Kepler Observations of the Pulsating RV Tau Variable DF Cygni
Stassun, Keivan G.; Somers, Garrett; Vega, Laura D. +2 more
The Kepler light curve of DF Cyg is unparalleled in precision and cadence for any RV Tau star to date, spanning a baseline of ∼4 years and clearly displaying the signature pulsating behavior of alternating deep and shallow minima as well as the long-term trend indicative of an RVb-type variable. We measure DF Cyg’s formal period (the time interval…
Spontaneous hot flow anomalies at Mars and Venus
Zhang, Tielong; Futaana, Yoshifumi; Persson, Moa +8 more
We report the first observations of Spontaneous Hot Flow Anomalies (SHFAs) at Venus and Mars, demonstrating their existence in the foreshocks of other planets beyond Earth. Using data from the ESA Venus Express and the NASA Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft, we present magnetic and plasma observations from events at both pl…
Stars with fast Galactic rotation observed in Gaia TGAS: a signature driven by the Perseus arm?
Grand, Robert J. J.; Siebert, Arnaud; Famaey, Benoit +3 more
We report on the detection of a small overdensity of stars in velocity space with systematically higher Galactocentric rotation velocity than the Sun by about 20 km s-1 in the Gaia Data Release 1 Tycho-Gaia astrometric solution data. We find these fast Galactic rotators more clearly outside of the Solar radius, compared to inside of the…
Variability survey of brightest stars in selected OB associations
Tuvikene, Taavi; Eenmäe, Tõnis; Kolka, Indrek +2 more
Context. The stellar evolution theory of massive stars remains uncalibrated with high-precision photometric observational data mainly due to a small number of luminous stars that are monitored from space. Automated all-sky surveys have revealed numerous variable stars but most of the luminous stars are often overexposed. Targeted campaigns can imp…
Semi-empirical seismic relations of A-F stars from COROT and Kepler legacy data
Moya, A.; Suárez, J. C.; García Hernández, A. +1 more
Asteroseismology is witnessing a revolution, thanks to high-precise asteroseismic space data (MOST, COROT, Kepler, BRITE) and their large ground-based follow-up programs. Those instruments have provided an unprecedented large amount of information, which allows us to scrutinize its statistical properties in the quest for hidden relations among pul…
The structure of Andromeda II dwarf spheroidal galaxy
del Pino, Andrés; Hidalgo, Sebastian L.; Łokas, Ewa L. +1 more
We analyse in detail the spatial distribution and kinematic properties of two different stellar populations in Andromeda II dwarf spheroidal galaxy. We obtained their detailed surface density maps together with their radial density profiles. The two populations differ not only in age and metallicity, but also in their spatial distribution and kine…
An XMM-Newton and NuSTAR Study of IGR J18214-1318: A Non-pulsating High-mass X-Ray Binary with a Neutron Star
Fürst, Felix; Pottschmidt, Katja; Wilms, Jörn +5 more
IGR J18214-1318, a Galactic source discovered by the International Gamma-Ray Astrophysics Laboratory, is a high-mass X-ray binary (HMXB) with a supergiant O-type stellar donor. We report on the XMM-Newton and NuSTAR observations that were undertaken to determine the nature of the compact object in this system. This source exhibits high levels of a…
Orion revisited. III. The Orion Belt population
Bouy, H.; Burkert, A.; Sarro, L. M. +11 more
Aims: This paper continues our study of the foreground population to the Orion molecular clouds. The goal is to characterize the foreground population north of NGC 1981 and to investigate the star formation history in the large Orion star-forming region. We focus on a region covering about 25 square degrees, centered on the ɛ Orionis supergia…
Temporal and spatial variations of the absolute reflectivity of Jupiter and Saturn from 0.38 to 1.7 µm with PlanetCam-UPV/EHU
Hueso, R.; Sánchez-Lavega, A.; Rojas, J. F. +3 more
Aims: We provide measurements of the absolute reflectivity of Jupiter and Saturn along their central meridians in filters covering a wide range of visible and near-infrared wavelengths (from 0.38 to 1.7 µm) that are not often presented in the literature. We also give measurements of the geometric albedo of both planets and discuss the l…