HD 91312
Observation data
Epoch J2000      Equinox J2000
Constellation Ursa Major
Right ascension 10h 33m 13.88880s[1]
Declination 40° 25′ 32.0172″[1]
Apparent magnitude (V) 4.72[2] (4.750 + 11.60)[3]
Characteristics
Spectral type A7IV-V[4] + M[5]
B−V color index 0.222±0.013[2]
Astrometry
Radial velocity (Rv)9.0±4.2[2] km/s
Proper motion (μ) RA: −138.103[1] mas/yr
Dec.: 3.172[1] mas/yr
Parallax (π)29.8168 ± 0.2283 mas[1]
Distance109.4 ± 0.8 ly
(33.5 ± 0.3 pc)
Absolute magnitude (MV)2.02[2]
Orbit[6]
Period (P)292.56 d
Semi-major axis (a)≥1.56×107 km
Eccentricity (e)0.30
Periastron epoch (T)2,419,108 JD
Argument of periastron (ω)
(secondary)		311°
Semi-amplitude (K1)
(primary)		14.5 km/s
Details
A
Mass1.83[7] M☉
Radius1.97+0.07
−0.02[1] R☉
Luminosity11.965+0.107
−0.088[1] L☉
Surface gravity (log g)4.0[8] cgs
Temperature7,648+34
−472[1] K
Rotational velocity (v sin i)119[8] km/s
Age~200[7] Myr
B
Mass0.337+0.042
−0.044[5] M☉
Other designations
BD+41°2101, HD 91312, HIP 51658, HR 4132, SAO 43379, ADS 7826 A, WDS J10332+4026A, TYC 3005-1206-1, 2MASS J10331388+4025316[9]
Database references
SIMBADdata

HD 91312 is a multiple star system in the northern circumpolar constellation Ursa Major. Faintly visible to the naked eye, it is the brightest star of Ursa Major without Flamsteed designation with a combined apparent visual magnitude of 4.72.[2] The system is located at a distance of 109 light-years from the Sun based on parallax. The radial velocity is poorly constrained, but it appears to be drifting further away at a rate of ~9 km/s.[2]

This was identified as a visual binary by John Herschel in 1831.[3] The pair have an angular separation of 23″, equivalent to a linear projected separation of ~796 AU. Variations in the radial velocity as well as direct imaging, indicate the presence of a low-mass stellar companion. This companion is an early-to-mid red dwarf, and orbits the primary on an edge-on orbit with a semi-major axis of 9.7 au.[5] This is a young system with an age of around 200 million years.[7] It display an infrared excess from a circumstellar disk of dusty debris.[10] It has a mean temperature of 35 K and is orbiting 218.1 AU from the inner pair.[11]

This star is relatively bright, but it was rarely included in old catalogues. Catalogues and atlases it was not included in are, for example, those by Ptolemy and all its derivatives and translations (by as-Sufi, al-Biruni, Ulugh Beg, Copernicus, Clavius, etc.), Tycho Brahe, de Houtman, Bayer, Kepler, Schiller, Halley, Flamsteed (as well as published by Carolina Herschel in 1798 catalogue of stars, observed by Flamsteed, but not inserted in his British Catalogue) and Bradley. Catalogues and atlases it was included in are those by Hevelius (1690) (65th in Ursa Major, designated In Ungula sinistri Pedis poster. trium sequens) and Bode (1801) (number 157 of Ursa Major). Bode used extended Bayer designations for some stars, and HD 91312 also was assigned designation "w", whereas original Bayer designations for Ursa Major stars are all Greek letters and Latin letters from "A" to "h".

References

  1. 1 2 3 4 5 6 7 8 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. Gaia DR2 record for this source at VizieR.
  2. 1 2 3 4 5 6 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. 1 2 Mason, B. D.; et al. (2014), "The Washington Visual Double Star Catalog", The Astronomical Journal, 122 (6): 3466–3471, Bibcode:2001AJ....122.3466M, doi:10.1086/323920.
  4. ↑ Gray, R. O.; Garrison, R. F. (1989), "The Late A-Type Stars: Refined MK Classification, Confrontation with Stroemgren Photometry, and the Effects of Rotation", The Astrophysical Journal Supplement Series, 70: 623, Bibcode:1989ApJS...70..623G, doi:10.1086/191349.
  5. 1 2 3 Chilcote, Jeffrey; Tobin, Taylor; Currie, Thayne; Brandt, Timothy D.; Groff, Tyler D.; Kuzuhara, Masayuki; Guyon, Olivier; Lozi, Julien; Jovanovic, Nemanja; Sahoo, Ananya; Deo, Vincent; Akiyama, Eiji; Janson, Markus; Knapp, Jill; Kwon, Jungmi; McElwain, Michael W.; Nishikawa, Jun; Wagner, Kevin; Hełminiak, Krzysztof; Skaf, Nour; Tamura, Motohide (2021). "SCExAO/CHARIS Direct Imaging of a Low-mass Companion at a Saturn-like Separation from an Accelerating Young A7 Star". The Astronomical Journal. 162 (6): 251. arXiv:2109.12124. Bibcode:2021AJ....162..251C. doi:10.3847/1538-3881/ac29ba. S2CID 237940421.
  6. ↑ Batten, A. H.; et al. (1978), "Seventh catalogue of the orbital elements of spectroscopic binary systems.", Publications of the Dominion Astrophysical Observatory Victoria, 15: 121−295, Bibcode:1978PDAO...15..121B. See No. 431
  7. 1 2 3 Borgniet, Simon; Lagrange, Anne-Marie; Meunier, Nadège; Galland, Franck; Arnold, Luc; Astudillo-Defru, Nicola; Beuzit, Jean-Luc; Boisse, Isabelle; Bonfils, Xavier; Bouchy, François; Debondt, Katrien; Deleuil, Magali; Delfosse, Xavier; Desort, Morgan; Díaz, Rodrigo F.; Eggenberger, Anne; Ehrenreich, David; Forveille, Thierry; Hébrard, Guillaume; Loeillet, Benoit; Lovis, Christophe; Montagnier, Guillaume; Moutou, Claire; Pepe, Francesco; Perrier, Christian; Pont, Frédéric; Queloz, Didier; Santerne, Alexandre; Santos, Nuno C.; Ségransan, Damien; da Silva, Ronaldo; Sivan, Jean-Pierre; Udry, Stéphane; Vidal-Madjar, Alfred (2019), "Extrasolar planets and brown dwarfs around AF-type stars. X. The SOPHIE northern sample. Combining the SOPHIE and HARPS surveys to compute the close giant planet mass-period distribution around AF-type stars", Astronomy & Astrophysics, 621: A87, arXiv:1809.09914, doi:10.1051/0004-6361/201833431, S2CID 67773783
  8. 1 2 Draper, Zachary H.; et al. (April 2018), "A-type Stellar Abundances: A Corollary to Herschel Observations of Debris Disks", The Astrophysical Journal, 857 (2): 16, Bibcode:2018ApJ...857...93D, doi:10.3847/1538-4357/aab1fd, S2CID 125197321, 93.
  9. ↑ "HD 91312". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-10-14.
  10. ↑ Sadakane, K.; Nishida, M. (July 1986), "Twelve additional "Vega-like" stars", Publications of the Astronomical Society of the Pacific, 98: 685–689, Bibcode:1986PASP...98..685S, doi:10.1086/131813.
  11. ↑ Cotten, Tara H.; Song, Inseok (July 2016), "A Comprehensive Census of Nearby Infrared Excess Stars", The Astrophysical Journal Supplement Series, 225 (1): 24, arXiv:1606.01134, Bibcode:2016ApJS..225...15C, doi:10.3847/0067-0049/225/1/15, S2CID 118438871, 15.
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