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The most luminous blue quasars at 3.0 < z < 3.3. I. A tale of two X-ray populations
Marconi, A.; Vignali, C.; Gilli, R. +8 more
We present the X-ray analysis of 30 luminous quasars at z ≃ 3.0 - 3.3 with pointed XMM-Newton observations (28-48 ks) originally obtained by our group to test the suitability of active galactic nuclei as standard candles for cosmological studies. The sample was selected in the optical from the Sloan Digital Sky Survey Data Release 7 to be represen…
Massive galaxies on the road to quenching: ALMA observations of powerful high redshift radio galaxies
Lehnert, Matthew D.; De Breuck, Carlos; Wylezalek, Dominika +10 more
We present 0.″3 (band 6) and 1.″5 (band 3) ALMA observations of the (sub)millimeter dust continuum emission for 25 radio galaxies at 1 < z < 5.2. Our survey reaches a rms flux density of ∼50 µJy in band 6 (200-250 GHz) and ∼20 µJy in band 3 (100-130 GHz). This is an order of magnitude deeper than single-dish 850 µm observat…
Discriminating among theories of spiral structure using Gaia DR2
Rix, Hans-Walter; Carlberg, R. G.; Coronado, Johanna +2 more
We compare the distribution in position and velocity of nearby stars from the Gaia DR2 radial velocity sample with predictions of current theories for spirals in disc galaxies. Although the rich substructure in velocity space contains the same information, we find it more revealing to reproject the data into action-angle variables, and we describe…
ACR Proton Acceleration Associated with Reconnection Processes beyond the Heliospheric Termination Shock
Chen, Y.; Burlaga, L. F.; Zank, G. P. +6 more
One of the curious observations from the Voyagers is that the intensity of anomalous cosmic rays (ACRs) did not peak at the heliospheric termination shock (HTS) but instead a short distance (within ∼1 au) downstream of the HTS. One possible explanation is that the interaction of the wavy heliospheric current sheet with the HTS enhances magnetic re…
Gaia Data Release 2. All-sky classification of high-amplitude pulsating stars
Szabados, L.; Audard, M.; Plachy, E. +23 more
Context. More than half a million of the 1.69 billion sources in Gaia Data Release 2 (DR2) are published with photometric time series that exhibit light variations during the 22 months of observation.
Aims: An all-sky classification of common high-amplitude pulsators (Cepheids, long-period variables, δ Scuti/SX Phoenicis, and RR Lyrae stars) …
Abundances and kinematics of carbon-enhanced metal-poor stars in the Galactic halo. A new classification scheme based on Sr and Ba
Hansen, C. J.; Nordström, B.; Andersen, J. +4 more
Carbon-enhanced metal-poor (CEMP) stars span a wide range of stellar populations, from bona fide second-generation stars to later-forming stars that provide excellent probes of binary mass transfer and stellar evolution. Here we analyse 11 metal-poor stars (8 of which are new to the literature), and demonstrate that 10 are CEMP stars. Based on hig…
Neutron star radius measurement from the ultraviolet and soft X-ray thermal emission of PSR J0437-4715
Guillot, Sebastien; González-Caniulef, Denis; Reisenegger, Andreas
We analysed the thermal emission from the entire surface of the millisecond pulsar PSR J0437-4715 observed in the ultraviolet and soft X-ray bands. For this, we calculated non-magnetized, partially ionized atmosphere models of hydrogen, helium, and iron compositions and included plasma frequency effects that may affect the emergent spectrum. This …
Massive Stars in the Tarantula Nebula: A Rosetta Stone for Extragalactic Supergiant HII Regions
Crowther, Paul A.
A review of the properties of the Tarantula Nebula (30 Doradus) in the Large Magellanic Cloud is presented, primarily from the perspective of its massive star content. The proximity of the Tarantula and its accessibility to X-ray through radio observations permit it to serve as a Rosetta Stone amongst extragalactic supergiant HII regions since one…
MADE: a spectroscopic mass, age, and distance estimator for red giant stars with Bayesian machine learning
Sanders, Jason L.; Das, Payel
We present a new approach (MADE) that generates mass, age, and distance estimates of red giant stars from a combination of astrometric, photometric, and spectroscopic data. The core of the approach is a Bayesian artificial neural network (ANN) that learns from and completely replaces stellar isochrones. The ANN is trained using a sample of red gia…
Heliospheric Evolution of Magnetic Clouds
Möstl, C.; Farrugia, C. J.; Temmer, M. +7 more
The interplanetary evolution of 11 magnetic clouds (MCs) recorded by at least two radially aligned spacecraft is studied. The in situ magnetic field measurements are fitted to a cylindrically symmetric Gold-Hoyle force-free uniform-twist flux-rope configuration. The analysis reveals that in a statistical sense, the expansion of the studied MCs is …