Search Publications
Stellar collisions in globular clusters: Constraints on the initial mass function of the first generation of stars
Dib, Sami; Haghi, Hosein; Zonoozi, Akram Hasani +2 more
Globular clusters display an anticorrelation between the fraction of the first generation of stars (N(G1)/N(tot)) and the slope of the present-day mass function of the clusters (αpd), which is particularly significant for massive clusters. In the framework of the binary-mediated collision scenario for the formation of the second-generat…
Radio properties of the OH megamaser galaxy IIZw 096
Chen, Xi; Zhang, Bo; Wu, Hong +9 more
Based on the two-epoch European Very Long Baseline Interferometry (VLBI) Network (EVN) archive data from OH line observations of IIZw 096, we confirm that the high-resolution OH emission in this source mainly comes from two spots (OH1 and OH2) of component (comp) D1 of this merging system. We found no significant variations in the OH 1667 MHz line…
Radio observations of massive stars in the Galactic centre: The Quintuplet cluster
Alberdi, A.; Najarro, F.; Yusef-Zadeh, F. +4 more
We present high-angular-resolution radio continuum observations of the Quintuplet cluster, one of the most emblematic massive clusters in the Galactic centre. Data were acquired in two epochs and at 6 and 10 GHz with the Karl G. Jansky Very Large Array. With this work we have quadrupled the number of known radio stars in the cluster. Even though t…
Fundamental stellar parameters of benchmark stars from CHARA interferometry. III. Giant and subgiant stars
White, T. R.; Casagrande, L.; Nordlander, T. +3 more
Context. Large spectroscopic surveys of the Milky Way must be calibrated against a sample of benchmark stars to ensure the reliable determination of atmospheric parameters.
Aims: Here, we present new fundamental stellar parameters of seven giant and subgiant stars that will serve as benchmark stars for large surveys. The aim is to reach a pre…
Radio detection of chemically peculiar stars with LOFAR
White, Glenn J.; Haverkorn, Marijke; Vedantham, Harish +5 more
Context. Chemically peculiar stars are upper main sequence stars that show anomalies in their optical spectra. These anomalies suggest peculiar chemical abundances of certain elements. Some chemically peculiar stars possess strong magnetic fields. Electrons originating from the ionising stellar wind travel in the magnetosphere of the star and beco…
Peculiar hydrogen-deficient carbon stars: strontium-rich stars and the s-process
Clayton, Geoffrey C.; Tisserand, Patrick; Crawford, Courtney L. +1 more
Context. R Coronae Borealis (RCB) variables and their non-variable counterparts, the dustless Hydrogen-deficient Carbon (dLHdC) stars have been known to exhibit enhanced s-processed material on their surfaces, especially Sr, Y, and Ba. No comprehensive work has been done to explore the s-process in these types of stars, however one particular RCB …
Upstream solar wind speed at comet 67P. Reconstruction method, model comparison, and results
Holmström, M.; Gunell, H.; Futaana, Y. +7 more
Context. Rosetta followed comet 67P at heliocentric distances from 1.25 to 3.6 au. The solar wind was observed for much of this time, but was significantly deflected and to some extent slowed down by the interaction with the coma.
Aims: We use the different changes in the speed of H+ and He2+ when they interact with the …
Short-timescale X-ray spectral variability in the Seyfert 1 galaxy NGC 3783
Kaastra, J. S.; Kriss, G. A.; Bianchi, S. +9 more
Aims: We report on the X-ray time-resolved spectral analysis of XMM-Newton observations of NGC 3783. Our main goal is to detect transient features in the Fe K line complex in order to study the dynamics of the innermost accretion flow.
Methods: We reanalyse archival observations of NGC 3783, a bright local active galactic nucleus, for wh…
Precision measurement of a brown dwarf mass in a binary system in the microlensing event. OGLE-2019-BLG-0033/MOA-2019-BLG-035
Bennett, D. P.; Bryden, G.; Soszyński, I. +94 more
Context. Brown dwarfs are transition objects between stars and planets that are still poorly understood, for which several competing mechanisms have been proposed to describe their formation. Mass measurements are generally difficult to carry out for isolated objects as well as for brown dwarfs orbiting low-mass stars, which are often too faint fo…
Quantification of O2 formation during UV photolysis of water ice: H2O and H2O:CO2 ices
Linnartz, H.; Chuang, K. -J.; Fedoseev, G. +4 more
Context. The Rosetta and Giotto missions investigated the composition of the cometary comae of 67P/Churyumov-Gerasimenko and 1P/Halley, respectively. In both cases, a surprisingly large amount of molecular oxygen (O2) was detected and was well correlated with the observed abundances of H2O. Laboratory experiments simulating c…