Related papers: iPTF14hls as a variable hyper-wind from a very mas…

Supernovae arise from progenitor stars occupying the upper end of the initial mass function. Their extreme brightness allows individual massive stars to be detected at cosmic distances, lending supernovae great potential as tracers of the…

Observations of the type II SN 1996L reveal the presence of a slowly expanding (V~700$ km/s) shell at ~ 10^(16) cm from the exploding star. Narrow emission features are visible in the early spectra superposed on the normal SN spectrum.…

Extreme helium stars are very rare low-mass supergiants in a late stage of evolution. They are probably contracting to become white dwarfs following a violent phase of evolution which caused them to become hydrogen-deficient giants,…

We found the first direct evidence that the Cepheid class namesake, delta Cephei, is currently losing mass. These observations are based on data obtained with the Spitzer Space Telescope in the infrared, and with the Very Large Array in the…

Spectroscopic monitoring with Mercator-HERMES over the past two years reveals that MWC 314 is a massive binary system composed of an early B-type primary LBV star and a less-luminous supergiant companion. We determine an orbital period Porb…

The current status of both the observational evidence and the theory of the stellar initial mass function (IMF) is reviewed, with particular attention to the two basic, apparently universal features shown by all observations of nearby…

GRB 141221A was observed from infrared to soft gamma-ray bands. Here, we investigate its properties, in light of the standard model. We find that the optical light curve of the afterglow of this burst presents an unusual steep/quick rise.…

Performing the photometric observations of the cataclysmic variable IPHAS J051814.33+294113.0, we discovered very deep eclipses. The observations were obtained over 14 nights, had a total duration of 56 hours and covered one year. The large…

We investigate the line-profile variability (lpv) of H-alpha for a large sample of O-type supergiants. We used the Temporal Variance Spectrum (TVS) analysis, developed by Fullerton et al 1996 and modified by us to take into account the…

We present photometry and spectroscopy of PS1-14bj, a hydrogen-poor superluminous supernova (SLSN) at redshift $z=0.5215$ discovered in the last months of the Pan-STARRS1 Medium Deep Survey. PS1-14bj stands out by its extremely slow…

Calcium rich gap transients represent an intriguing new class of faint and fast evolving supernovae that exhibit strong [Ca II] emission in their nebular phase spectra. In this paper, we present the discovery and follow-up observations of…

The stellar winds of massive stars show large changes in mass-loss rates and terminal velocities during their evolution from O-star through the Luminous Blue Variable phase to the Wolf-Rayet phase. The luminosity remains approximately…

Hydrogen-poor superluminous supernovae (SLSN-I) are a class of rare and energetic explosions discovered in untargeted transient surveys in the past decade. The progenitor stars and the physical mechanism behind their large radiated energies…

Extensive photometric and spectroscopic observations of SN1994aj until 540d after maximum light have been obtained. The photometry around maximum suggests that the SN belongs to the Type II Linear class, with a peak absolute magnitude of Mv…

Searches for supernovae (SNe) progenitors have relied on a direct detection of the star in fortuitous pre-explosion images. We propose an alternative method, using a combination of photometric stellar population fitting alongside…

Observed variations in the slope of the initial stellar mass function are shown to be consistent with a model in which the protostellar gas is randomly sampled from hierarchical clouds at a rate proportional to the square root of the local…

We present high-speed, three-colour photometry of the eclipsing dwarf nova PHL 1445, which, with an orbital period of 76.3 min, lies just below the period minimum of ~82 min for cataclysmic variable stars. Averaging four eclipses reveals…

We present visual-wavelength photometry and spectroscopy of supernova SN2008S. Based on the low peak luminosity for a SN of M_R = -13.9 mag, photometric and spectral evolution unlike that of low-luminosity SNe, a late-time decline rate…

Eta Carinae is the nearest example of a supermassive, superluminous, unstable star. Mass loss from the system is critical in shaping its circumstellar medium and in determining its ultimate fate. Eta Car currently loses mass via a dense,…

Stars with masses in excess of 100 Msun are observed in the Local Universe, but they remain rare objects. Because of the shape of the mass function, they are expected to be present only in the most massive and youngest clusters. They may…