Velocity monitoring of γ Cas stars reveals their binarity status

The binary status of gamma Cas stars has been discussed while theoretically examining the origin of their peculiar X-ray emission. However, except in two cases, no systematic radial velocity monitoring of these stars had been undertaken yet to clarify their status. We now fill this gap using TIGRE, CARMENES, and LIVES high-resolution spectroscopy. Velocities were determined for 16 stars, revealing shifts and/or changes in line profiles. The orbit of six new binaries could be determined: the long periods (80-120 d) and small velocity amplitudes (5-7 km s(-1)) suggest low mass companions (0.6-1(circle dot)). The properties of the known gamma Cas binaries appear similar to those of other Be systems, with no clear-cut separation between them. One of the new systems is a candidate for a rare case of quadruple system involving a Be star. Five additional gamma Cas stars display velocity variations compatible with the presence of companions, but no orbital solution could yet be formally established for them hence they only receive the status of 'binary candidate'.

Automated summary

The binary status of gamma Cas stars has been discussed theoretically, but systematic radial velocity monitoring has not been conducted until now. This study used high-resolution spectroscopy to determine velocities for 16 stars and identified six new binary systems, one of which is a potential quadruple system. Five additional gamma Cas stars were classified as "binary candidates" due to velocity variations.