Color anomalies and starspots in Hyades dwarfs

Hyades dwarfs later than about F7 show color anomalies which are found to correlate well with various indicators of chromospheric activity. It is proposed that the color anomalies are due to starspots, which apparently also cause the low level photometric variations seen in some stars. That some stars with small color anomaly are variable, plus the finding that Hyades dwarfs show a mean color anomaly relative to field stars, implies that virtually all late-type Hyades are spotted. Intermediate band photometry of spotted stars could give an apparent overestimate of the metallicity. This may explain why many Hyades abundance estimates from photometry are larger than from spectroscopic analyses. Similarly, starspots could explain the 'Hyades anomaly', the c1 excess of unevolved Hyades dwarfs relative to field stars. Starspots could lead to a displacement of the Hyades from the standard main sequence in the color-magnitude diagram, but detailed models of spotted stars are required to test this. Tentative evidence is found that Hyades dwarfs are roughly 0.1 mag brighter in V than field stars of the same B - V and metallicity. A new value of the solar B - V color is derived in the Appendix.