On the origin of the ultramassive white dwarf GD50
We argue on the basis of astrometric and spectroscopic data that the ultramassive white dwarf GD50 is associated with the star formation event that created the...
On the origin of the γ-ray emission from the flaring blazar PKS 1222+216
The flat-spectrum radio quasar PKS 1222+216 (4C+21.35, z = 0.432) was detected in the very high energy γ-ray band by MAGIC during a highly active γ-ray phase...
We are all familiar with the fact that a linear flow of water in a tube can be obtained only for velocities below a certain critical limit and that, when the...
On the outburst amplitude of the soft X-ray transients
We find a strong correlation between the optical outburst amplitude and orbital period for the soft X-ray transient sources with orbital periods less than 1 d...
On the Pair-instability Supernova Origin of J1010+2358
The first (Population III) stars formed only out of H and He and were likely more massive than present-day stars. Massive Population III stars in the range 140...
On the parallax of WD 0346++246: a halo white dwarf candidate
We present a parallax measurement for the very cool degenerate WD 0346+246, the serendipitous discovery of which was reported by Hambly et al. We find an...
On The Parent Population of Radio Galaxies and the FR I-FR II Dichotomy
We test the hypothesis that radio galaxies are a random subset of otherwise normal elliptical galaxies. Starting with the observed optical luminosity functions...
On the period ratio P1/2P2 in the oscillations of coronal loops
Aims.With strong evidence of fast and slow magnetoacoustic modes arising in the solar atmosphere there is scope for improved determinations of coronal...
On the Period-Luminosity-Colour-Metallicity relation and the pulsational characteristics of lambda Bootis type stars
Generally, chemical peculiarity found for stars on the upper main sequence excludes delta Scuti type pulsation (e.g. Ap and Am stars), but for the group of...