Type-Ia supernovae are thought to occur when a white dwarf made of carbon and oxygen accretes sufficient mass to trigger a thermonuclear explosion. The accretion could be slow, from an unevolved (main-sequence) or evolved (subgiant or giant) star (the single-degenerate channel), or rapid, as the primary star breaks up a smaller orbiting white dwarf (the double-degenerate channel). A companion star will survive the explosion only in the single-degenerate channel. Both channels might contribute to the production of type-Ia supernovae, but the relative proportions of their contributions remain

Fullerenes and fullerene-related molecules have been proposed as explanations for unidentified astronomical features such as the intense UV absorption band at 217 nm and the enigmatic diffuse interstellar bands (DIBs), In order to shed light on the a long-standing DIB’s problem, we search high-resolution and high-quality VLT/UVES optical spectra of the hot R Coronae Borealis (RCB) star DY Cen for electronic transitions of the neutral C 60 fullerene molecule and DIBs. We report the non-detection of the strongest C 60 electronic transitions (e.g., those at ∼376, 398, and 402 nm). DIBs towards

We present observations and an interpretative model of the dust environment of the Main-Belt Comet P/2010 F5 (Gibbs). The narrow dust trails observed can be interpreted unequivocally as an impulsive event that took place around 2011 July 1 with an uncertainty of ±10 days, and a duration of less than a day, possibly of the order of a few hours. The best Monte Carlo dust model fits to the observed trail brightness imply ejection velocities in the range 8-10 cm s –1 for particle sizes between 30 cm and 130 μm. This weak dependence of velocity on size contrasts with that expected from ice

We report the detection of an orbital period decay of (dP/dt)= -1.83+-0.66 ms yr–1  in the black hole X-ray binary XTE J1118+480. This corresponds to a period change of –0.85 ± 0.30 μs per orbital cycle, which is ~150 times larger than expected from the emission of gravitational waves. These observations cannot be reproduced by conventional models of magnetic braking even when including significant mass loss from the system. The spiral-in of the star is either driven by magnetic braking under extremely high magnetic fields in the secondary star or by a currently unknown process, which will

Recent near-infrared data have contributed to the discovery of new (obscured) massive stellar clusters and massive stellar populations in previously known clusters in our Galaxy. These discoveries lead us to view the Milky Way as an active star-forming machine. Aims: The main purpose of this work is to  determine physically the main parameters (distance, size, total mass and age) of Masgomas-1, the first massive cluster discovered by our systematic search programme. Methods: Using near-infrared ( J, H, and K S) photometry we selected 23 OB-type and five red supergiant candidates for multi

Stars are generally spherical, yet their gaseous envelopes oftenappear non-spherical when ejected near the end of their lives. Thisquirk is most notable during the planetary nebula phase when theseenvelopes become ionized. The most popular explanation is that theasymmetry, and in particular the formation of highly collimatedstructures such as the precessing jets observed in a number ofnebulae, is caused by interactions in a binary system. The study ofthe prototypical planetary nebula Fleming 1 with the VLT telescopedemonstrates for the first time that the hypothesis iscorrect. Indeed, it is