Context. Several clusters of red supergiants have been discovered in a small region of the Milky Way close to the base of the Scutum-Crux Arm and the tip of the Long Bar. Population synthesis models indicate that they must be very massive to harbour so many supergiants. Amongst these clusters, Stephenson 2, with a core grouping of 26 red

We present new medium-band uvby Strömgren and broadband VI photometry for the central regions of the globular cluster ω Cen. From this photometry we have obtained differential reddening estimates relative to two other globular clusters (M13 and NGC 288) using a metallicity-independent, reddening-free temperature index, [c]≡(u-v)-(v-b)-0.2(b-y), for

An analysis of 50 optical spectra of the interstellar methylidyne ion in the direction of HD26676 and HD149038 derived very similar interstellar isotopic ratios for the two lines-of-sight. A lack of a Galactic gradient in isotopic ratios is noted which is consistent with the location in the solar vicinity of the gas in front of HD149038. The

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We use Gaia Data Release 2 proper motions of field OB stars from the Runaways and Isolated O-Type Star Spectroscopic Survey of the Small Magellanic Cloud (SMC) to study the kinematics of runaway stars. The data reveal that the SMC Wing has a systemic peculiar motion relative to the SMC Bar of ({v}α ,{v}δ ) =(62+/- 7,-18+/- 5) {km} {{{s}}}-1 and

We have studied the core morphology of the ultraluminous infrared galaxy Mrk 273 by combining a high-resolution adaptive optics near-infrared image with an optical image from the Hubble Space Telescope and interferometric radio continuum data, all at spatial resolutions of 150 mas or better. The near-infrared image reveals that the nucleus has two