Related papers: How common is LBV S Dor variability at low metalli…
The progenitors of Type IIP supernovae have an apparent upper limit to their initial masses of about 20 solar masses, suggesting that the most massive red supergiants evolve to warmer temperatures before their terminal explosion. But very…
V348 Sgr is simultaneously an active hot R Coronae Borealis (RCB) variable, a peculiar extreme helium star, and the hydrogen-deficient central star of a planetary nebula. Explaining the RCB-type variability has been difficult since the star…
We use the eight year light-curve database from the MACHO (MAssive Compact Halo Objects) project together with infrared colors and magnitudes from 2MASS (the Two Micron All Sky Survey) to identify a sample of 22,000 long period variables in…
We have studied the optical spectra of a sample of 31 O- and early B-type stars in the Small Magellanic Cloud, 21 of which are associated with the young massive cluster NGC 346. Stellar parameters are determined using an automated fitting…
We search for effects of metallicity on B and Be stars in the Small and Large Magellanic Clouds (SMC and LMC) and in the Milky Way (MW). We extend our previous analysis of B and Be stars populations in the LMC to the SMC. The rotational…
The characterisation of the multiplicity of high-mass stars is of fundamental importance to understand their evolution, the diversity of observed core-collapse supernovae and the formation of gravitational wave progenitor systems. Despite…
Complete samples of 2MASS stars in 3 fields of differing metallicities (and possibly differing age distributions) have been extracted and cross-correlated with MACHO and ISO data to determine their variability and mass-loss properties. In…
In the past decade, several rapidly-evolving transients have been discovered whose timescales and luminosities are not easily explained by traditional supernovae (SN) models. The sample size of these objects has remained small due, at least…
Mass loss is a crucial process that affects the observational properties, evolution path and fate of highly evolved stars. However, the mechanism of mass loss is still unclear, and the mass-loss rate (MLR) of red supergiant stars (RSGs)…
The heavy mass loss observed in evolved asymptotic giant branch (AGB) stars is usually attributed to a two-stage process: atmospheric levitation by pulsation-induced shock waves, followed by radiative acceleration of newly formed dust…
Luminous Blue Variable (LBV) stars are evolved massive objects, previous to core-collapse supernova. LBVs are characterized by photometric and spectroscopic variability, produced by strong and dense winds, mass-loss events and very intense…
By cross-correlating the results of two recent large-scale surveys, the general properties of a well defined sample of semi-regular variable stars have been determined. ISOGAL mid-infrared photometry and MACHO lightcurves are assembled for…
Despite their importance to a number of astrophysical fields, the lifecycles of very massive stars are still poorly defined. In order to address this shortcoming, we present a detailed quantitative study of the physical properties of four…
We present ultraviolet spectra from the Space Telescope Imaging Spectrograph (STIS) of 12 early B-type stars in the Small Magellanic Cloud (SMC), comprising 9 supergiants and 3 giants. A morphological comparison with Galactic analogues is…
Despite the important advances in space asteroseismology during the last decade, the early phases of evolution of stars with masses above $\sim$15 M$_{\odot}$ have been only vaguely explored up to now. Our goal is to detect, analyze and…
Dust formation in the winds of hot stars is inextricably linked to the classic eruptive state of luminous blue variables (LBVs) because it requires very high mass loss rates, Mdot>10^(-2.5) Msun/year, for grains to grow and for the non-dust…
Very massive stars occasionally expel material in colossal eruptions, driven by continuum radiation pressure rather than blast waves. Some of them rival supernovae in total radiative output, and the mass loss is crucial for subsequent…
The Luminous Blue Variable stars exhibit behavior ranging from light curve `microvariations' on timescales of tens of days, to `outbursts' accompanied by mass loss of up to 10e-03 solar masses per year, occurring decades apart, to `giant…
We use the analysis of the heavy element abundances (C, N, O, S) in circumstellar nebulae around Luminous Blue Variables to infer the evolutionary phase in which the material has been ejected. (1) We discuss the different effects that may…
The LMC star BI 108 is photometrically variable with the unique light curve: Two strong periods are present in a strict 3:2 resonance, staying coherent over several observing seasons. A spectroscopic data collected at VLT/UVES reveals…