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Figure 11.7. H-R diagram for the nearby stars; main sequence stars with planetary mass companions are plotted as solid points, while evolved systems are plotted as solid triangles.

Figure 11.7. H-R diagram for the nearby stars; main sequence stars with planetary mass companions are plotted as solid points, while evolved systems are plotted as solid triangles.

stars are solar-like, spectral types F, G and K, and predominantly on the main sequence (see Figure 11.7). This is expected, since the vast majority (^120 systems) were discovered in radial velocity surveys, which preferentially target those stars. However, planetary companions have been detected around two M dwarfs: Gl 876, which has two companions on resonant orbits (P = 30.1 and 61.0 days); and Gl 836, which has one of the lowest mass companions identified so far, with m2 sin(i') = 0.067 Mj, or ~21 Earth masses. Planetary companions have been detected in stellar binary systems (e.g., 16 Cygni B); in stellar/brown dwarf systems (e.g., HD 41004AB, which includes a K0V dwarf, an M3 dwarf, a brown dwarf and at least one planet); around giant stars (e.g., HD 47536); and multiple planets have been found in more than 20 systems, including 4 companions to 55 Cnc. Almost all of the host stars lie within 50 parsecs of the Sun, but with the addition of transit and

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