Search Publications
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 …
The Sloan Digital Sky Survey Reverberation Mapping Project: Accretion and Broad Emission Line Physics from a Hypervariable Quasar
Trump, Jonathan R.; Green, Paul J.; Brandt, W. N. +18 more
We analyze extensive spectroscopic and photometric data of the hypervariable quasar SDSS J141324+530527 (RMID 017) at z = 0.456, an optical “changing-look” quasar from the Sloan Digital Sky Survey Reverberation Mapping project that increased in optical luminosity by a factor ≃10 between 2014 and 2017. The observed broad emission lines all respond …
A Giant Intragroup Nebula Hosting a Damped {Ly}\alpha Absorber at z = 0.313
Johnson, Sean D.; Zahedy, Fakhri S.; Chen, Hsiao-Wen +5 more
This Letter reports the discovery of spatially extended line-emitting nebula, reaching to ≈100 physical kpc (pkpc) from a damped {Ly}α absorber (DLA) at z DLA = 0.313 along the sightline toward quasi-stellar object (QSO) PKS 1127-145 (z QSO = 1.188). This DLA was known to be associated with a galaxy group of dynamical mass M …
A solution to the proplyd lifetime problem
Hacar, Alvaro; Rosotti, Giovanni P.; Clarke, Cathie J. +2 more
Protoplanetary discs (PPDs) in the Orion Nebula Cluster (ONC) are irradiated by UV fields from the massive star θ1C. This drives thermal winds, inducing mass-loss rates of up to \dot{M}_wind∼ 10^{-7} M_⊙ yr-1 in the `proplyds' (ionized PPDs) close to the centre. For the mean age of the ONC and reasonable initial PPD masses, s…
Chronostar: a novel Bayesian method for kinematic age determination - I. Derivation and application to the β Pictoris moving group
Federrath, Christoph; Žerjal, Maruša; Ireland, Michael J. +3 more
Gaia DR2 provides an unprecedented sample of stars with full 6D phase-space measurements, creating the need for a self-consistent means of discovering and characterizing the phase-space overdensities known as moving groups or associations. Here we present Chronostar, a new Bayesian analysis tool that meets this need. Chronostar uses the Expectatio…
Intermittency in Solar Wind Turbulence From Fluid to Kinetic Scales
Bruno, Roberto
Solar wind is a highly turbulent medium exhibiting fluctuations ranging from the solar sidereal rotation period to proton and electron gyroperiods. Their amplitudes show remarkable scalings with frequency across more than seven decades, suggesting a self-similar nature for these fluctuations. However, these fluctuations are not globally scale inva…