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Dependence of Galactic Halo Kinematics on the Adopted Galactic Potential
Beers, Timothy C.; Lee, Young Sun; Kim, Young Kwang
We explore differences in Galactic halo kinematic properties derived from two commonly employed Galactic potentials: the Stäckel potential and the default Milky Way-like potential used in the “Galpy” package (MWPotential2014), making use of stars with available metallicities, radial velocities, and proper motions from Sloan Digital Sky Survey Data…
A remarkable change of the spectrum of the magnetic Of?p star HD 148937 reveals evidence of an eccentric, high-mass binary
Howarth, I. D.; Wade, G. A.; Gamen, R. +10 more
We report new spectroscopic observations of the magnetic Of?p star HD 148937 obtained since 2015 that differ qualitatively from its extensive historical record of weak, periodic spectral variations. This remarkable behaviour represents clear evidence for an unprecedented change in the character of variability of the star. In this paper, we describ…
Effect of the non-uniform solar chromospheric Lyα radiation on determining the coronal H I outflow velocity
Sasso, C.; Romoli, M.; Andretta, V. +13 more
We derived maps of the solar wind outflow velocity of coronal neutral hydrogen atoms at solar minimum in the altitude range 1.5-4.0 R⊙. We applied the Doppler dimming technique to coronagraphic observations in the UV H I Lyα line at 121.6 nm. The technique exploits the intensity reduction in the coronal line with increasing velocities o…
A deep X-ray view of the bare AGN Ark 120. VI. Geometry of the hot corona from spectroscopic and polarization signatures
Bianchi, S.; Porquet, D.; Matt, G. +9 more
Context. The spectral shape of the hard X-ray continuum of Active Galactic Nuclei (AGN) can be ascribed to inverse Compton scattering of optical/UV seed photons from the accretion disc by a hot corona of electrons. This physical process produces a polarization signal which is strongly sensitive to the geometry of the scattering medium (i.e. the ho…
The Two Most Recent Thermonuclear Supernovae in the Local Group: Radio Constraints on their Progenitors and Evolution
Chomiuk, Laura; Badenes, Carles; Tremou, Evangelia +3 more
Young supernova remnants (SNRs) provide a unique perspective on supernova (SN) progenitors and connect the late evolution of SNe with the onset of the SNR phase. Here we study SN 1885A and G1.9+0.3, the most recent thermonuclear SNe in the Local Group (with ages ∼100 yr) with radio data, which provide a sensitive probe of the SN environment and en…
New Spatially Resolved Imaging of the SR 21 Transition Disk and Constraints on the Small-grain Disk Geometry
van der Marel, N.; Ireland, M. J.; Puglisi, A. +9 more
We present new 0.6-4 µm imaging of the SR 21 transition disk from Keck/NIRC2 and Magellan/MagAO. The protoplanetary disk around SR 21 has a large (∼30-40 au) clearing first inferred from its spectral energy distribution and later detected in submillimeter imaging. Both the gas and small dust grains are known to have a different morphology, w…
Disentangling the Arcturus stream
Kushniruk, Iryna; Bensby, Thomas
Context. The Arcturus stream is an over-density of stars in velocity space and its origin has been much debated recently without any clear conclusion. The (classical) dissolved open cluster origin is essentially refuted; instead the discussions try to distinguish between an accretion, a resonant, or an external-perturbation origin for the stream. …
The GAPS Programme with HARPS-N at TNG. XVIII. Two new giant planets around the metal-poor stars HD 220197 and HD 233832
Scandariato, G.; Pagano, I.; Poretti, E. +40 more
Context. Statistical studies of exoplanets have shown that giant planets are more commonly hosted by metal-rich dwarf stars than low-metallicity stars, while no such correlation is evident for lower mass planets. The search for giant planets around metal-poor stars and the estimate of their occurrence fp is an important element in provi…
Four Metal-poor Stars in the Sagittarius Dwarf Spheroidal Galaxy
Frebel, Anna; Chiti, Anirudh
We present the metallicities and carbon abundances of four newly discovered metal-poor stars with -2.2 < [Fe/H] < -1.6 in the Sagittarius dwarf spheroidal galaxy. These stars were selected as metal-poor member candidates using a combination of public photometry from the SkyMapper Southern Sky Survey and proper-motion data from the second dat…
Multi-scale analysis of the Monoceros OB 1 star-forming region. I. The dense core population
Sanhueza, Patricio; Soam, Archana; Doi, Yasuo +24 more
Context. Current theories and models attempt to explain star formation globally, from core scales to giant molecular cloud scales. A multi-scale observational characterisation of an entire molecular complex is necessary to constrain them. We investigate star formation in G202.3+2.5, a ∼10 × 3 pc sub-region of the Monoceros OB1 cloud with a complex…