The O--C Diagram of the Subdwarf B Pulsating Star HS 2201+2610: Detection of a Giant Planet?

In this article we present the O-C diagram of the hot subdwarf B pulsating star HS 2201+2610 after seven years of observations. A secular increase of the main pulsation period, dot{P}= (1.3± 0.1) × 10^-12, is inferred from the data. Moreover, a further sinusoidal pattern suggests the presence of a low-mass companion (M sin i ≃ 3.5 M_Jup), orbiting the hot star at a distance of about 1.7 AU with a period near 1140 days.