T Vulpeculae

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.[10] It is visible to the naked eye with an apparent visual magnitude that ranges around 5.75.[2] The distance to this system is around 1,900 light years, as determined from its annual parallax shift of 1.67 mas.[1]

T Vulpeculae
Observation data
Epoch J2000      Equinox J2000
Constellation Vulpecula
Right ascension  20h 51m 28.23825s[1]
Declination +28° 15′ 01.8166″[1]
Apparent magnitude (V) 5.754[2] (5.41 – 6.09)[3]
Characteristics
Spectral type F5 Ib + A0.8 V[4]
B−V color index +0.616±0.049[5]
Variable type δ Cep[3]
Astrometry
Radial velocity (Rv)−2.6±0.6[5] km/s
Proper motion (μ) RA: +3.496[1] mas/yr
Dec.: −15.087[1] mas/yr
Parallax (π)1.6738 ± 0.0891[1] mas
Distance1,900 ± 100 ly
(600 ± 30 pc)
Absolute magnitude (MV)−3.19[4]
Details
T Vul A
Mass4.9[4] M☉
Radius35.6±4.4[6] R☉
Luminosity1,620[4] L☉
Surface gravity (log g)1.75[7] cgs
Temperature6,220[7] K
Metallicity [Fe/H]0.01[8] dex
Age120[8] Myr
T Vul B
Mass2.1[4] M☉
Other designations
T Vul, BD+27° 3890, HD 198726, HIP 102949, HR 7988, SAO 89216[9]
Database references
SIMBADdata

A well-studied Classical Cepheid variable and one of the brightest known,[11] the apparent magnitude of T Vulpeculae ranges from 5.41 to 6.09[3] over a period of 4.435 days.[2] It is a yellow-white hued supergiant of spectral type F5 Ib.[4] The variability of T Vul was discovered in 1885 by Edwin Sawyer.[12] Observations between 1885 and 2003 shows a small but continuous decrease in the period of variability amounting to 0.25 seconds per year.[13]

The companion star was detected in 1992;[11] it is an A-type main-sequence star with a class of A0.8 V and 2.1 times the Sun's mass.[4] 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.[14]

References
  1. Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051.
  2. Evans, Nancy Remage; et al. (July 2015). "Binary Properties from Cepheid Radial Velocities (CRaV)". The Astronomical Journal. 150 (1): 18. arXiv:1505.05823. Bibcode:2015AJ....150...13E. doi:10.1088/0004-6256/150/1/13. 13.
  3. BSJ (4 January 2010). "T Vulpeculae". AAVSO Website. American Association of Variable Star Observers. Retrieved 24 January 2014.
  4. Evans, Nancy Remage; Bond, Howard E.; Schaefer, Gail H.; Mason, Brian D.; et al. (2013). "Binary Cepheids: Separations and Mass Ratios in 5M ⊙ Binaries". Astronomical Journal. 146 (4): 93, 10. arXiv:1307.7123v1. Bibcode:2013AJ....146...93E. doi:10.1088/0004-6256/146/4/93.
  5. Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015.
  6. Gallenne, A.; et al. (May 2012). "Mean angular diameters, distances, and pulsation modes of the classical Cepheids FF Aquilae and T Vulpeculae. CHARA/FLUOR near-infrared interferometric observations". Astronomy & Astrophysics. 541: 5. arXiv:1203.6682. Bibcode:2012A&A...541A..87G. doi:10.1051/0004-6361/201219102. A87.
  7. Gray, R. O.; et al. (2001). "The Physical Basis of Luminosity Classification in the Late A-, F-, and Early G-Type Stars. II. Basic Parameters of Program Stars and the Role of Microturbulence". The Astronomical Journal. 121 (4): 2159. Bibcode:2001AJ....121.2159G. doi:10.1086/319957.
  8. Marsakov, V. A.; Koval', V. V.; Kovtyukh, V. V.; Mishenina, T. V. (2013). "Properties of the population of classical Cepheids in the Galaxy". Astronomy Letters. 39 (12): 851. Bibcode:2013AstL...39..851M. doi:10.1134/S1063773713120050.
  9. "HD 198726". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 18 August 2018.
  10. Moore, Patrick (2000), Exploring the Night Sky with Binoculars, Cambridge University Press, p. 147, ISBN 978-0521793902
  11. Evans, Nancy R. (July 1992). "The luminosity of the classical Cepheid T VUL". Astronomical Journal. 104 (1): 216–219. Bibcode:1992AJ....104..216E. doi:10.1086/116232.
  12. Sawyer, E. F. (1886). "On a new variable star in the Constellation Vulpecula" (PDF). Astronomische Nachrichten. 113 (16): 265. Bibcode:1886AN....113..265S. doi:10.1002/asna.18861131608.
  13. Meyer, Ralf (August 2006). "T Vulpeculae: Maximum Times Covering 120 Years Show a Slight, Continuous Period Decrease". Open European Journal on Variable Stars. 46: 1. Bibcode:2006OEJV...46....1M.
  14. Gallenne, A.; et al. (July 2015). "Robust high-contrast companion detection from interferometric observations. The CANDID algorithm and an application to six binary Cepheids". Astronomy & Astrophysics. 579: 12. Bibcode:2015A&A...579A..68G. doi:10.1051/0004-6361/201525917. A68.
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