HD 5789/5788

HD 5789 and HD 5788 is a pair of stars comprising a binary star[12] system in the northern constellation of Andromeda. Located approximately 151 parsecs (490 ly) away, the primary is a hot, massive blue star with an apparent magnitude of 6.06 while the secondary is slightly smaller and cooler, with an apparent magnitude of 6.76. Both stars are main-sequence stars, meaning that they are currently fusing hydrogen into helium in their cores. As of 2016, the pair had an angular separation of 7.90″ along a position angle of 195°.[13] While both have a similar proper motion and parallax, there's still no proof that the pair is gravitationally bound.

HD 5789/5788
Observation data
Epoch J2000      Equinox J2000
Constellation Andromeda
HD 5789
Right ascension 01h 00m 03.55767s[1]
Declination +44° 42′ 47.6898″[1]
Apparent magnitude (V) 6.06[2]
HD 5788
Right ascension 01h 00m 03.38277s[1]
Declination +44° 42′ 40.0515″[1]
Apparent magnitude (V) 6.763[3]
Characteristics
HD 5789
Spectral type B9.5Vnn (λ Boo)[4]
B−V color index −0.031[5]
HD 5788
Spectral type A2 Vn[6]
B−V color index −0.010[5]
Astrometry
Radial velocity (Rv)+4.4±3.3[7] km/s
Proper motion (μ) RA: +13.85[8] mas/yr
Dec.: −23.83[8] mas/yr
Parallax (π)6.6432 ± 0.0809[1] mas
Distance491 ± 6 ly
(151 ± 2 pc)
Proper motion (μ) RA: +11.582[1] mas/yr
Dec.: −24.369[1] mas/yr
Parallax (π)6.5625 ± 0.0688[1] mas
Distance497 ± 5 ly
(152 ± 2 pc)
Details
HD 5789
Mass2.74±0.12[9] M☉
Luminosity85.6+19.2
−15.6[9] L☉
Temperature9,977[5] K
Rotational velocity (v sin i)249[9] km/s
HD 5788
Mass2.67±0.12[9] M☉
Luminosity73.3+18.4
−14.7[9] L☉
Temperature9,840[5] K
Rotational velocity (v sin i)270[9] km/s
Other designations
BD+43°193, HIP 4675, ADS 824, WDS J01001+4443
HD 5789: HR 283, SAO 36833[10]
HD 5788: HR 282, SAO 36832[11]
Database references
HD 5789
SIMBADdata
HD 5788
SIMBADdata

The primary component is HD 5789, a B-type main-sequence star with a stellar classification of B9.5Vnn (λ Boo), where the 'n' indicates "nebulous" lines due to rapid rotation. Abt and Morrell (1995) listed it as a Lambda Boötis star,[4] although this is disputed.[14] It has 2.7 times the mass of the Sun and is spinning rapidly with a projected rotational velocity of 249 km/s.[9] The star is radiating 86[9] times the Sun's luminosity from its photosphere at an effective temperature of 9,977 K.[5]

The fainter secondary component is an A-type main-sequence star with a class of A2 Vn.[6] It shows a projected rotational velocity of 270 km/s and has 2.7 times the Sun's mass. The star shines with 73[9] times the Sun's luminosity at an effective temperature of 9,840 K.[5]

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. 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.
  3. Høg, E.; et al. (2000). "The Tycho-2 catalogue of the 2.5 million brightest stars". Astronomy and Astrophysics. 355: L27. Bibcode:2000A&A...355L..27H. doi:10.1888/0333750888/2862.
  4. Abt, Helmut A.; Morrell, Nidia I. (July 1995), "The Relation between Rotational Velocities and Spectral Peculiarities among A-Type Stars", Astrophysical Journal Supplement, 99: 135, Bibcode:1995ApJS...99..135A, doi:10.1086/192182.
  5. Soubiran, Caroline; et al. (2016). "The PASTEL catalogue: 2016 version". Astronomy & Astrophysics. 591: A118. arXiv:1605.07384. Bibcode:2016A&A...591A.118S. doi:10.1051/0004-6361/201628497. S2CID 119258214.
  6. Cowley, A.; et al. (April 1969). "A study of the bright A stars. I. A catalogue of spectral classifications". Astronomical Journal. 74: 375–406. Bibcode:1969AJ.....74..375C. doi:10.1086/110819.
  7. Gontcharov, G. A. (November 2006), "Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system", Astronomy Letters, 32 (11): 759–771, arXiv:1606.08053, Bibcode:2006AstL...32..759G, doi:10.1134/S1063773706110065, S2CID 119231169.
  8. van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. S2CID 18759600.
  9. Zorec, J.; Royer, F. (2012). "Rotational velocities of A-type stars. IV. Evolution of rotational velocities". Astronomy & Astrophysics. 537: A120. arXiv:1201.2052. Bibcode:2012A&A...537A.120Z. doi:10.1051/0004-6361/201117691. S2CID 55586789.
  10. "HD 5789". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved October 10, 2018.
  11. "HD 5788". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved October 10, 2018.
  12. Eggleton, P. P.; Tokovinin, A. A. (2008). "A catalogue of multiplicity among bright stellar systems". Monthly Notices of the Royal Astronomical Society. 389 (2): 869. arXiv:0806.2878. Bibcode:2008MNRAS.389..869E. doi:10.1111/j.1365-2966.2008.13596.x. S2CID 14878976.
  13. Mason, B. D.; et al. (2014), "The Washington Visual Double Star Catalog", The Astronomical Journal, 122 (6): 3466, Bibcode:2001AJ....122.3466M, doi:10.1086/323920
  14. Murphy, Simon J.; et al. (October 2015), "An Evaluation of the Membership Probability of 212 λ Boo Stars. I. A Catalogue", Publications of the Astronomical Society of Australia, 32: 43, arXiv:1508.03633, Bibcode:2015PASA...32...36M, doi:10.1017/pasa.2015.34, S2CID 59405545, e036.
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