Search Publications
New constraints on the minimum mass for thermonuclear lithium burning in brown dwarfs
del Burgo, C.; Martín, E. L.; Lodieu, N.
The theory of substellar evolution predicts that there is a sharp mass boundary between lithium and non-lithium brown dwarfs, not far below the substellar-mass limit. The imprint of thermonuclear burning is carved on the surface lithium abundance of substellar-mass objects during the first few hundred million years of their evolution, leading to a…
Statistics of BY Draconis chromospheric variable stars
de Grijs, Richard; Kamath, Devika; Chen, Xiaodian +1 more
We present an extensive catalogue of BY Draconis (BY Dra)-type variables and their stellar parameters. BY Dra are main-sequence FGKM-type stars. They exhibit inhomogeneous starspots and bright faculae in their photospheres. These features are caused by stellar magnetic fields, which are carried along with the stellar disc through rotation and whic…
High-contrast, high-angular resolution view of the GJ 367 exoplanet system
Brandner, Wolfgang; Calissendorff, Per; Cantalloube, Faustine +1 more
We search for additional companions in the GJ 367 exoplanet system and aim to better constrain its age and evolutionary status. We analyse high-contrast direct imaging observations obtained with HST/NICMOS, VLT/NACO, and VLT/SPHERE. We investigate and critically discuss conflicting age indicators based on theoretical isochrones and models for Gala…
Evidence of globular cluster abundance anomalies in the SMC intermediate-age cluster Kron 3
Da Costa, G. S.; Milone, A. P.; Marino, A. F. +5 more
Using spectra obtained with the VLT/FORS2 and Gemini-S/GMOS-S instruments, we have investigated carbon, nitrogen, and sodium abundances in a sample of red giant members of the Small Magellanic Cloud star cluster Kron 3. The metallicity and luminosity of the cluster are comparable to those of Galactic globular clusters but it is notably younger (ag…
The K2 Galactic Archaeology Program: Overview, target selection, and survey properties
Bland-Hawthorn, Joss; Sharma, Sanjib; Stello, Dennis +3 more
K2 was a community-driven NASA mission where all targets were proposed through guest observer programmes. Here we provide an overview of one of the largest of these endeavours, the K2 Galactic Archaeology Programme (K2GAP), with about 25 per cent of the observed targets being allocated to this programme. K2GAP provides asteroseismic parameters for…
The alignment between brightest cluster galaxies and host clusters
Yuan, Z. S.; Wen, Z. L.
The alignment between the brightest cluster galaxies (BCGs) and host clusters can reveal the mystery of the formation and evolution of galaxy clusters. We measure cluster orientations in optical based on the projected distribution of member galaxies and in X-ray by fitting the morphology of intracluster medium (ICM). Cluster orientations determine…
A holistic approach to understand helium enrichment in interplanetary coronal mass ejections: new insights
Yogesh; Chakrabarty, D.; Srivastava, N.
Despite helium abundance [AHe = (nH/nHe) × 100] being ~8 per cent at the solar photospheric/chromospheric heights, AHe can be found to exceed 8 per cent in interplanetary coronal mass ejections (ICMEs) on many occasions. Although various factors like interplanetary shocks, chromospheric evaporation, and …
Exploring the connection between ultraviolet/optical variations and radio emission in radio-quiet quasars: clues about the origin of radio emission
Liao, Mai; Wang, Junxian; Zhou, Minhua +1 more
Radio emission in radio-quiet quasars (RQQs) has long been a mystery and its physical origin remains unclear. In previous work, we have found that quasars that are more variable in ultraviolet (UV)/optical have stronger X-ray emission, indicating a link between disc turbulence and X-ray corona heating. In this work, for the first time, we investig…
A cautionary tale of Ly C escape fraction estimates from high-redshift galaxies
Ryan-Weber, E. V.; Arnouts, S.; Sawicki, M. +7 more
Measuring the escape fraction, fesc, of ionizing, Lyman continuum (Ly C) radiation is key to our understanding of the process of cosmic reionization. In this paper, we provide a methodology for recovering the posterior probability distribution of the Ly C escape fraction, $f_{\rm esc}^{\rm PDF}$, considering both the observational uncer…
V410 Puppis: A useful laboratory for early stellar evolution
Erdem, Ahmet; Sürgit, Derya; Blackford, Mark G. +6 more
New spectrometric (HERCULES) and ground-based multicolour photometric data on the multiple star V410 Puppis are combined with satellite photometry (HIPPARCOS and TESS), as well as historic astrometric observations. Absolute parameters for V410 Pup Aab are derived: MAa = 3.15 ± 0.10, MAb = 1.83 ± 0.08 (M⊙); RAa…