Companion stars of type Ia supernovae and hypervelocity stars

Context. Recent investigations of the white dwarf (WD) + He star channel of Type Ia supernovae (SNe Ia) imply that this channel can produce SNe Ia with short delay times. The companion stars in this channel would survive and potentially be identifiable. Aims. In this Letter, we study the properties of the companion stars of this channel at the moment of SN explosion, which can be verified by future observations. Methods. According to SN Ia production regions of the WD + He star channel and three formation channels of WD + He star systems, we performed a detailed binary population synthesis study to obtain the properties of the surviving companions. Results. We obtained the distributions of many properties of the companion stars of this channel at the moment of SN explosion. We find that the surviving companion stars have a high spatial velocity (>400 km s-1) after SN explosion, which could be an alternative origin for hypervelocity stars (HVSs), especially for HVSs such as US 708