The open cluster Pismis 11 and the very luminous blue supergiant HD 80077

(Abridged) The very luminous blue supergiant HD 80077 has been claimed to be a member of the young open cluster Pismis 11, and hence a hypergiant. We obtained UBVRI photometry of the cluster field and low-resolution spectroscopy of a number of putative members. We derive spectral types from the spectra and determine that the reddening in this direction is standard. We then carry out a careful photometric analysis that allows us to determine individual reddening values, deriving unreddened parameters that are used for the main sequence fit. We identify 43 likely members of Pismis 11. We study the variation of extinction across the face of the cluster and find some dispersion, with a trend to higher values in the immediate neighbourhood of HD 80077. We estimate a distance of 3.6 kpc for the cluster. If HD 80077 is a member, it has M_bol<-10.5 and it is one of the three visually brightest stars in the Galaxy. Several early type stars in the vicinity of Pismis~11 fit well the cluster sequence and are likely to represent an extended population at the same distance. About 18 arcmin to the North of Pismis 11, we find a small concentration of stars, which form a clear sequence. We identify this group as a previously uncatalogued open cluster, which we provisionally call Alicante 5. The distance to Alicante 5 is also 3.6 kpc, suggesting that these two clusters and neighbouring early-type stars form a small association. Based on its proper motion, HD 80077 is not a runaway star and may be a member of the cluster. If this is the case, it would be one of the brightest stars in the Galaxy.Comment: 25 pages. It contains many figures and tables. Accepted for publication in Astronomy and Astrophysic

High-mass stars in clusters and associations

High-mass stars are major players in the chemical and dynamical evolution of galaxies. Open clusters and associations represent the natural laboratories to study their evolution. In this review, I will present a personal selection of current research topics that highlight the use of open clusters to constrain different properties of high-mass stars, such as the possible existence of an upper limit for the mass of a star, the evolutionary stage of blue supergiants or the characterisation of supernova progenitors.Comment: Invited review presented at "Stellar Clusters and Associations - A RIA workshop on GAIA", 23-27 May 2011, Granada, Spai

A WN4 companion to BD +62 2296 in Cas OB5

I report observations of the triple system BD +62 2296 showing that all its components are early-type stars, most likely physically related. The faintest component BD +62 2296B is a hitherto uncatalogued Wolf-Rayet star. The brightest component, star A, is shown to be a seemingly normal B2.5Ia supergiant. Long-slit spectroscopy of BD +62 2296B shows it to be a narrow-lined WN4 star. Given the spatial separation, the two objects are unlikely to form a physical binary. Spectra of the third visual component, BD +62 2296C, allow its classification as a B0III star. Such concentration of massive stars strongly suggests that BD +62 2296 is in reality a very compact young open cluster in the area of the OB association Cas OB5.Comment: Research Note accepted for publication in Astronomy & Astrophysics. 5 pages, 4 figures; uses new A&A style (included