T_Vulpeculae
T Vulpeculae
Variable star in the constellation Vulpecula
T Vulpeculae is a possible binary star system in the northern constellation of Vulpecula, near the star Zeta Cygni, close to the pair 31 Vulpeculae and 32 Vulpeculae.[11] It is visible to the naked eye with an apparent visual magnitude that ranges around 5.75.[3] The distance to this system is around 1,900 light years, as determined from its annual parallax shift of 1.67 mas.[2]
A well-studied Classical Cepheid variable and one of the brightest known,[12] the apparent magnitude of T Vulpeculae ranges from 5.41 to 6.09[4] over a period of 4.435 days.[3] It is a yellow-white hued supergiant of spectral type F5 Ib.[5] The variability of T Vul was discovered in 1885 by Edwin Sawyer.[13] Observations between 1885 and 2003 shows a small but continuous decrease in the period of variability amounting to 0.25 seconds per year.[14]
The companion star was detected in 1992;[12] it is an A-type main-sequence star with a class of A0.8 V and 2.1 times the Sun's mass.[5] Orbital periods of 738 and 1,745 days have been proposed for the pair, although, as of 2015, there remains doubt as to whether this is an actual binary system.[15]