HR 7484

HR 7484 (V1143 Cyg) is a binary star system in the northern constellation of Cygnus. It is dimly visible to the naked eye under good viewing conditions, having an apparent visual magnitude of 5.89.[2] Based upon an annual parallax shift of 24.71,[1] it is located 132 light years away. The system is moving closer with a heliocentric radial velocity of −14 km/s.[4]

HR 7484
Observation data
Epoch J2000      Equinox J2000
Constellation Cygnus
Right ascension  19h 38m 41.18316s[1]
Declination +54° 58′ 25.6420″[1]
Apparent magnitude (V) 5.889±0.015[2] - 6.37[3]
Characteristics
Spectral type F6V[4] (F5 V + F5 V)[2]
B−V color index 0.482±0.004[4]
Variable type Algol[3]
Astrometry
Radial velocity (Rv)−13.9±0.2[4] km/s
Proper motion (μ) RA: +34.885[1] mas/yr
Dec.: +162.839[1] mas/yr
Parallax (π)24.7090 ± 0.0422[1] mas
Distance132.0 ± 0.2 ly
(40.47 ± 0.07 pc)
Absolute magnitude (MV)2.83[4]
Orbit[2]
Period (P)7.64075217±0.00000051 d[5]
Semi-major axis (a)22.6950 AU
Eccentricity (e)0.5378±0.0003
Inclination (i)87.0±1.0°
Argument of periastron (ω)
(secondary)		0.860±0.001°
Semi-amplitude (K1)
(primary)		88.02±0.05 km/s
Semi-amplitude (K2)
(secondary)		89.97±0.10 km/s
Details[2]
V1143 Cyg A
Mass1.356±0.003 M☉
Radius1.339±0.023 R☉
Luminosity2.83±0.2[6] L☉
Surface gravity (log g)4.317±0.015 cgs
Temperature6,450±100 K
Metallicity [Fe/H]0.08 dex
Rotational velocity (v sin i)18±3[6] km/s
V1143 Cyg B
Mass1.328±0.002 M☉
Radius1.316±0.023 R☉
Luminosity2.65±0.2[6] L☉
Surface gravity (log g)4.323±0.015 cgs
Temperature6,400±100 K
Rotational velocity (v sin i)28±3[6] km/s
Other designations
V1143 Cyg, HD 185912, HIP 96620, HR 7484, SAO 31850[7]
Database references
SIMBADdata

Radial velocity measurements taken at the Dominion Astrophysical Observatory in Victoria, British Columbia Canada in 1919 led to the determination by William Edmund Harper that HR 7484 is a double-lined spectroscopic binary.[8] It is a detached eclipsing binary, which means the orbital plane is aligned close to the line-of-sight from the Earth, causing the components to eclipse twice per orbit.[9] The system is undergoing apsidal motion, with a rate greater than that predicted by general relativity.[9] Both components are ordinary F-type main-sequence stars with similar physical properties.[2]

The star normally has an apparent magnitude of 5.89, but every 7.64 days (7 days, 15 hours, and 22 minutes) its brightness decreases to magnitude 6.37, approximately two thirds as bright. Five days and 17 hours after each primary eclipse, there is a secondary eclipse when the brightness drops to magnitude 6.06, about 85% of the normal brightness. Each eclipse lasts for 220 minutes.[3] Both eclipses are partial.[6]

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. Graczyk, Dariusz; et al. (March 2017). "The Surface Brightness-color Relations Based on Eclipsing Binary Stars: Toward Precision Better than 1% in Angular Diameter Predictions". The Astrophysical Journal. 837 (1): 19. arXiv:1611.09976. Bibcode:2017ApJ...837....7G. doi:10.3847/1538-4357/aa5d56. 7.
  3. Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/gcvs. Originally Published in: 2009yCat....102025S. 1. Bibcode:2009yCat....102025S.
  4. 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.
  5. Gimenez, A.; Margrave, T. E. (1984). "Relativistic apsidal motion in the eclipsing binary systems V1143 Cygni and EK Cephei". Astronomical Journal. 90 (2): 358–363. arXiv:astro-ph/0411788. Bibcode:1985AJ.....90..358G. doi:10.1086/113740.
  6. Anderson, J.; Garcia, J.; Gimenez, A.; Nordstrom, B. (1987). "Absolute dimensions of eclipsing binaries. X - V1143 Cygni". Astronomy & Astrophysics. 174: 107–115. Bibcode:1987A&A...174..107A.
  7. "HD 185912". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2018-07-14.
  8. Plaskett, J. S.; et al. (1919). "Fourth list of spectroscopic binaries". Journal of the Royal Astronomical Society of Canada. 13: 372–378. Bibcode:1919JRASC..13..372P.
  9. Dariush, A.; et al. (April 2005). "Photometric Observations and Apsidal Motion Study of V1143 Cyg". Astrophysics and Space Science. 296 (1–4): 141–144. arXiv:astro-ph/0411788. Bibcode:2005Ap&SS.296..141D. doi:10.1007/s10509-005-4416-0.
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