Related papers: The Distances to Open Clusters from Main-Sequence …
We continue our series of papers on open cluster distances by comparing multicolor photometry of single stars in the Hyades to theoretical isochrones constructed with various color-temperature relations. After verifying that the isochrone…
Parallax data from the Hipparcos mission allow the direct distance to open clusters to be compared with the distance inferred from main sequence (MS) fitting. There are surprising differences between the two distance measurements, which…
In the first of a new series of papers on open cluster distances, we use updated stellar evolution models to construct an isochrone appropriate for the Hyades, and compare it with the Hyades eclipsing binary system vB 22. We find that the…
We present new BVRI photometry for a sample of 54 local G and K stars with accurate Hipparcos parallaxes in the metallicity range -0.4 < [Fe/H] < +0.3. We use this sample to develop a completely model-independent main sequence (MS) fitting…
We extend our effort to calibrate stellar isochrones in the Johnson-Cousins ($BVI_C$) and the 2MASS ($JHK_s$) filter systems based on observations of well-studied open clusters. Using cool main-sequence (MS) stars in Praesepe, we define…
Hipparcos parallax measurements of stars in the Pleiades notoriously result in a cluster distance of 118 pc; ~10% shorter than the `classical' results of MS-fitting. In an earlier paper we developed a purely empirical MS-fitting method to…
Metallicity is one of four free parameters typically considered when fitting isochrones to the cluster sequence. Unfortunately, this parameter is often ignored or assumed to be solar in most papers. Hence an unknown bias is introduced in…
The discrepancy between the Pleiades cluster distance based on Hipparcos parallaxes and main sequence fitting is investigated on the basis of Stromgren photometry of F-type stars. Field stars with the same metallicity as the Pleiades have…
An improved method for estimating distances to open clusters is presented and applied to Hipparcos data for the Pleiades and the Hyades. The method is applied in the context of the historic Pleiades distance problem, with a discussion of…
An extensive grid of metal-rich isochrones utilizing the latest available input physics has been calculated for comparison with the old, metal-rich open cluster NGC 6791. The isochrones have been simultaneously fit to BV and VI color…
We aim to investigate the feasibility of accurately determining the helium-to-metal enrichment ratio $\Delta Y/\Delta Z$ for open clusters using Gaia DR3 photometry. To test the reliability of this calibration, we performed a theoretical…
We derive the basic properties of seven Galactic open clusters containing Cepheids and construct their period-luminosity (P-L) relations. For our cluster main-sequence fitting we extend previous Hyades-based empirical color-temperature…
We present a reanalysis of the light curves of HD 23642, a detached eclipsing binary star in the Pleiades open cluster, with emphasis on a detailed error analysis. We compare the masses and radii of the two stars to predictions of stellar…
We present new isochrone fits to colour-magnitude diagrams of the Galactic globular cluster NGC\,6205 (M13). We utilise 34 photometric bands from the ultraviolet to mid-infrared by use of data from the {\it HST}, {\it Gaia} DR2, SDSS,…
We have combined existing optical magnitudes for stars in seven open clusters and 54 field stars with the corresponding JHKs photometry from the Two Micron All Sky Survey (2MASS). Combining optical with near-IR photometry broadens the color…
We present absolute trigonometric parallaxes and relative proper motions for three members of the Pleiades star cluster, obtained with HST's Fine Guidance Sensor 1r, a white-light interferometer. We estimate spectral types and luminosity…
We show that the errors in the Hipparcos parallaxes towards the Pleiades and the Hyades open clusters are spatially correlated over angular scales of 2 to 3 deg, with an amplitude of up to 2 mas. This correlation is stronger than expected…
We present a homogeneous catalogue of fundamental astrophysical parameters -- age, metallicity ([Fe/H]), heliocentric distance, and colour excess $E(G_{\mathrm{BP}}-G_{\mathrm{RP}})$ -- for 5,056 open star clusters drawn from the Unified…
We investigate the reddening and Main Sequence fitted distances to eleven young, Galactic open clusters that contain Cepheids. Each cluster contains or is associated with at least one Cepheid variable star. Reddening to the clusters is…
We apply the new distance measuring technique of Hendry, O'Dell and Collier- Cameron, 1993, to the Pleiades and $\alpha$ Persei clusters. The method relies on knowledge of the periods, rotation velocities and angular diameters of a sample…