T Vulpeculae
Variable star in the constellation Vulpecula
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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]
| Observation data Epoch J2000 Equinox ICRS | |
|---|---|
| Constellation | Vulpecula |
| Right ascension | 20h 51m 28.23825s[2] |
| Declination | +28° 15′ 01.8166″[2] |
| Apparent magnitude (V) | 5.754[3] (5.41 – 6.09)[4] |
| Characteristics | |
| Spectral type | F5 Ib + A0.8 V[5] |
| B−V color index | +0.616±0.049[6] |
| Variable type | δ Cep[4] |
| Astrometry | |
| Radial velocity (Rv) | −2.6±0.6[6] km/s |
| Proper motion (μ) | RA: +3.496[2] mas/yr Dec.: −15.087[2] mas/yr |
| Parallax (π) | 1.6738±0.0891 mas[2] |
| Distance | 1,900 ± 100 ly (600 ± 30 pc) |
| Absolute magnitude (MV) | −3.19[5] |
| Details | |
| T Vul A | |
| Mass | 4.9[5] M☉ |
| Radius | 35.6±4.4[7] R☉ |
| Luminosity | 1,620[5] L☉ |
| Surface gravity (log g) | 1.75[8] cgs |
| Temperature | 6,220[8] K |
| Metallicity [Fe/H] | 0.01[9] dex |
| Age | 120[9] Myr |
| T Vul B | |
| Mass | 2.1[5] M☉ |
| Other designations | |
| T Vul, AAVSO 2047+27, BD+27° 3890, HD 198726, HIP 102949, HR 7988, SAO 89216[10] | |
| Database references | |
| SIMBAD | data |
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]