Search Publications
A gap in HD 92945's broad planetesimal disc revealed by ALMA
Wyatt, M. C.; Marino, S.; Kennedy, G. M. +4 more
In the last few years, multiwavelength observations have revealed the ubiquity of gaps/rings in circumstellar discs. Here we report the first ALMA observations of HD 92945 at 0.86 mm, which reveal a gap at about 73 ± 3 au within a broad disc of planetesimals that extends from 50 to 140 au. We find that the gap is 20^{+10}_{-8} au wide. If cleared …
Rejuvenated galaxies with very old bulges at the origin of the bending of the main sequence and of the `green valley'
Daddi, Emanuele; Juneau, Stéphanie; Liu, Daizhong +11 more
We investigate the nature of star-forming galaxies with reduced specific star formation rate (sSFR) and high stellar masses, those `green valley' objects that seemingly cause a reported bending, or flattening, of the star-forming main sequence. The fact that such objects host large bulges recently led some to suggest that the internal formation of…
Constraints on the chemical enrichment history of the Perseus Cluster of galaxies from high-resolution X-ray spectroscopy
Yamaguchi, H.; Simionescu, A.; Kaastra, J. S. +32 more
High-resolution spectroscopy of the core of the Perseus Cluster of galaxies, using the Hitomi satellite above 2 keV and the XMM-Newton Reflection Grating Spectrometer at lower energies, provides reliable constraints on the abundances of O, Ne, Mg, Si, S, Ar, Ca, Cr, Mn, Fe, and Ni. Accounting for all known systematic uncertainties, the Ar/Fe, Ca/F…
The outer halo globular cluster system of M31 - III. Relationship to the stellar halo
Côté, P.; Mackey, A. D.; Martin, N. F. +10 more
We utilize the final catalogue from the Pan-Andromeda Archaeological Survey to investigate the links between the globular cluster system and field halo in M31 at projected radii Rproj = 25-150 kpc. In this region the cluster radial density profile exhibits a power-law decline with index Γ = -2.37 ± 0.17, matching that for the stellar ha…
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…
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 …
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…
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…
The Galactic spiral structure as revealed by O- and early B-type stars
Wang, H. -F.; Huang, Y.; Chen, B. -Q. +7 more
We investigate the morphology and kinematics of the Galactic spiral structure based on a new sample of O- and early B-type stars. We select 6858 highly confident OB star candidates from the combined data of the VST Photometric H α Survey Data Release 2 (VPHAS+ DR2) and the Gaia Data Release 2 (Gaia DR2). Together with the O-B2 stars from the liter…