New Photometric Investigation of the Solar-Type Shallow-Contact Binary HH Bootis

Figure 5

diagram of the short-period close binary HH Boo based on all the primary and secondary available photoelectric and CCD times of light minimum. The black solid line showed a cyclic period variation with a period of 6.58 yr. Residuals after the cyclic change was removed are shown in the lower panel. The black solid dots refer to the data collected by Grol et al. [31], the blue solid dots refer to the data by WASP database, the red solid dots refer to the data obtained by Nelson [21], Hubscher Lehmann [22] or Hubscher [23], and green solid dots refer to the data obtained by us.