Search Publications
First stellar occultation by the Galilean moon Europa and upcoming events between 2019 and 2021
Maury, A.; Cacella, P.; Lainey, V. +21 more
Context. Bright stellar positions are now known with an uncertainty below 1 mas thanks to Gaia DR2. Between 2019-2020, the Galactic plane will be the background of Jupiter. The dense stellar background will lead to an increase in the number of occultations, while the Gaia DR2 catalogue will reduce the prediction uncertainties for the shadow path. …
Variations on a theme: the puzzling behaviour of Schulte 12
Nazé, Yaël; Mahy, Laurent; Rauw, Gregor +2 more
One of the first massive stars detected in X-rays, Schulte 12 has remained a puzzle in several aspects. In particular, its extreme brightness both in the visible and X-ray ranges is intriguing. Thanks to Swift and XMM-Newton observations covering ∼5000 d, we report the discovery of a regular 108 d modulation in X-ray flux of unknown origin. The mi…
A MUSE study of the inner bulge globular cluster Terzan 9: a fossil record in the Galaxy
Bica, E.; Barbuy, B.; Kamann, S. +5 more
Context. Moderately metal-poor inner bulge globular clusters are relics of a generation of long-lived stars that formed in the early Galaxy. Terzan 9, projected at 4°.12 from the Galactic center, is among the most central globular clusters in the Milky Way, showing an orbit which remains confined to the inner 1 kpc.
Aims…
Resolving the distance controversy for Sharpless 269. A possible kink in the outer arm
Immer, K.; Reid, M. J.; Quiroga-Nuñez, L. H. +2 more
Context. Sharpless 269 (S 269) is one of a few HII regions in the outer spiral arm of the Milky Way with strong water maser emission. Based on data from the Very Long Baseline Interferometry (VLBI) Exploration of Radio Astrometry (VERA) array, two parallax measurements have been published, which differ by nearly 2σ. Each distance estimate supports…
Multi-line Herschel/HIFI observations of water reveal infall motions and chemical segregation around high-mass protostars
Shipman, R. F.; Braine, J.; van der Tak, F. F. S. +3 more
Context. The physical conditions during high-mass star formation are poorly understood. Outflow and infall motions have been detected around massive protostellar objects, but their dependence on mass, luminosity, and age is unclear. In addition, physical conditions and molecular abundances are often estimated using simple assumptions such as spher…
A NuSTAR view of powerful γ-ray loud blazars
Tagliaferri, G.; Ghirlanda, G.; Ghisellini, G. +6 more
We observed three blazars at z > 2 with the NuSTAR satellite. These were detected in the γ-rays by Fermi/LAT and in the soft X-rays, but have not yet been observed above 10 keV. The flux and slope of their X-ray continuum, together with Fermi/LAT data allows us to estimate their total electromagnetic output and peak frequency. For some of them …
Broadband spectral analysis of MXB 1659-298 in its soft and hard state
Sanna, A.; Di Salvo, T.; Burderi, L. +7 more
Context. The X-ray transient eclipsing source MXB 1659-298 went into outburst in 1999 and 2015. During these two outbursts the source was observed by XMM-Newton, NuSTAR, and Swift/XRT.
Aims: Using these observations, we studied the broadband spectrum of the source to constrain the continuum components and to verify whether it had a reflection…
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…
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. …