7_Vul
7 Vulpeculae
Star in the constellation Vulpecula
7 Vulpeculae is a binary star system approximately 910[5] light years away in the slightly northern constellation of Vulpecula.[6] It is a challenge to view with the naked eye, having an apparent visual magnitude of 6.3.[2] The system currently has a heliocentric radial velocity of −38 km/s.[4]
This is a single-lined spectroscopic binary star system with an orbital period of 69.3 days and an eccentricity of 0.16.[3] The visible component is a Be star with a stellar classification of B4–5 III–IVe that appears to be nearing the end of its main sequence lifetime. The system shows a rapid projected rotational velocity of 300 km/s, which is just below the estimated critical velocity for a binary of 367 km/s.[3]
There is a small variability in the magnitude over a 0.559-day cycle;[2] this is likely the rotation period of the primary star.[2]
The nature of the companion is unknown, but based upon its mass it may be a K- or M-type star. It could be a white dwarf that has undergone a mass transfer to the primary. Because of the lack of X-ray emission from the system, a third possibility is that the companion is a naked He star that has been stripped of its hydrogen envelope.[3]