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. S2CID 54943097. 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. S2CID 34133110.
  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, S2CID 119257644.
  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. S2CID 2424989. 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. S2CID 119788977.
  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". 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. arXiv:1505.02715. Bibcode:2015A&A...579A..68G. doi:10.1051/0004-6361/201525917. A68.
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