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V2551 Cyg: a pulsating star with enigmatic peculiarities
Popov, Velimir A.; Petrov, Nikola I.; Kjurkchieva, Diana P. +2 more
Intensive photometric and spectral observations of the variable star V2551 Cyg are presented. The light curve shape reveals that the target is a pulsating star, contrary to its previous classification as an eclipsing binary. The period and amplitude of the light curve, the amplitudes of color changes and the radial velocity curve of V2551 Cyg are …
OB Stars and Cepheids From the Gaia TGAS Catalogue: Test of their Distances and Proper Motions
Bobylev, Vadim V.; Bajkova, Anisa T.
We consider young distant stars from the Gaia TGAS catalog. These are 250 classical Cepheids and 244 OB stars located at distances up to 4 kpc from the Sun. These stars are used to determine the Galactic rotation parameters using both trigonometric parallaxes and proper motions of the TGAS stars. In this case the considered stars have relative par…
The highly ionized, high-velocity gas in NGC 6231
Massa, Derck
It is well known that clusters of massive stars are influenced by the presence of strong winds, that they are sources of diffuse X-rays from shocked gas, and that this gas can be vented into the surrounding region or the halo through the champagne effect. However, the details of how these different environments interact and evolve are far from com…
Relationship between electron field-aligned anisotropy and dawn-dusk magnetic field: Nine years of Cluster observations in the Earth magnetotail
Nakamura, R.; Artemyev, A.; Petrukovich, A. +1 more
We investigate the distribution and possible origins of thermal anisotropic electrons in the Earth's magnetotail, using 9 years of Cluster observations. We mainly focus on relation between electron anisotropy and Bz and By magnetic field components (in GSM coordinates). The anisotropy of electron population is characterized b…
Leveraging high‑resolution spectra to understand black hole spectra
Nowak, M. A.
For the past 17 years, both XMM-Newton and Chandra have brought the powerful combination of high spatial and spectral resolution to the study of black hole systems. Each of these attributes requires special consideration--- in comparison to lower spatial resolution, CCD quality spectra--- when modeling observations obtained by these spacecraft. A …
Discovery of H2O megamasers in obscured active galactic nuclei
Terashima, Yuichi; Salak, Dragan; Nakai, Naomasa +9 more
A new method to discover obscured active galactic nuclei (AGNs) by utilizing X-ray and infrared data has recently been developed. We carried out a survey of H2O maser emission toward 10 obscured AGNs with the Nobeyama 45 m telescope. We newly detected the maser emission with a signal-noise-ratio (SNR) of above 4 from two AGNs; NGC 1402 …
Morphology and temporal variation of the polar oval of Venus revealed by VMC/Venus express visible and UV images
Imamura, Takeshi; Muto, Keishiro
The morphology of the dark polar oval seen at the Venus cloud top in visible and ultraviolet wavelengths has been unclear because the portion of the oval on the nightside is invisible. We analyzed in detail the variability of the whole shape of the oval by connecting VMC/Venus Express visible images taken on different days after shifting the image…
Surface roughness of Saturn's rings and ring particles inferred from thermal phase curves
Spilker, Linda; Morishima, Ryuji; Turner, Neal
We analyze thermal phase curves of all the main rings of Saturn (the A, B, C rings, and the Cassini division) measured by both the far-IR and mid-IR detectors of the Cassini Composite InfraRed Spectrometer (CIRS). All the rings show temperature increases toward zero phase angle, known as an opposition effect or thermal beaming. For the C ring and …
Absolute Nuv magnitudes of Gaia DR1 astrometric stars and a search for hot companions in nearby systems
Makarov, V. V.
Accurate parallaxes from Gaia DR1 (TGAS) are combined with GALEX visual Nuv magnitudes to produce absolute Mnuv magnitudes and an ultraviolet HR diagram for a large sample of astrometric stars. A functional fit is derived of the lower envelope main sequence of the nearest 1403 stars (distance <40 pc), which should be reddening-free. Using this …
Dawn-Dusk Asymmetries in the Near-Earth Plasma Sheet
Daly, P. W.; Haaland, S. E.; Grigorenko, E. E. +4 more