Hidden Companions to Nearby Intermediate-mass Stars. II. Discovery of a 0.80 M ⊙, 10.5 au Companion to the λ Boötis Star HIP 83650

HIP 83650 is a nearby intermediate mass star that shows the rare λ Boötis phenomenon of still uncertain origin. Here we report the discovery of a companion to this star with a K band flux ratio of 5.9% based on an archival VLTI/GRAVITY observation. This 0.80M⊙ companion at a projected separation 149.8 mas ↔ 10.5au confirms that the system is rather old as there is no detected X-ray emission from it. We therefore argue that the λ Boötis character of this star is not caused by a circumstellar debris disk (for which there is also no evidence in the near-infrared interferometry) but potentially by accretion from the ablated wind of a hot Jupiter. This can be tested with AO-assisted spectroscopy of the newly discovered companion.