Alruba

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Alruba
Draco constellation map.svg
Red circle.svg
Location of Alruba (circled)
Observation data
Epoch J2000.0        Equinox J2000.0
Constellation Draco [1]
Pronunciation /ælˈruːbə/
Right ascension 17h 43m 59.17049s [2]
Declination +54° 48′ 06.1637″ [2]
Apparent magnitude  (V)5.76 [3]
Characteristics
Evolutionary stage Main sequence [4]
Spectral type A0V [5]
Astrometry
Radial velocity (Rv)−2.0 [6] km/s
Proper motion (μ)RA: 17.450 [2] mas/yr
Dec.: −18.125 [2] mas/yr
Parallax (π)7.1436±0.0605  mas [2]
Distance 457 ± 4  ly
(140 ± 1  pc)
Absolute magnitude  (MV)−0.3 [1]
Details
Mass 2.97±0.07 [4]   M☉
Luminosity 146.7+29.6
−24.7 [4]   L☉
Surface gravity (log g)3.80±0.10 [7]   cgs
Temperature 9,226+107
−106 [4]   K
Metallicity [Fe/H]−0.40±0.11 [7]   dex
Rotational velocity (v sin i)170 [4]  km/s
Age 58 [8]   Myr
Other designations
Alruba, BD+53°1978, CPD–51°9815, HD 161693, HIP 86782, HR 6618, SAO 30538 [9]
Database references
SIMBAD data

Alruba, [10] a name derived from Arabic for "the foal", is a suspected astrometric binary [11] star system in the northern circumpolar constellation of Draco. It is just barely visible to the naked eye as a dim point of light with an apparent visual magnitude of 5.76. [3] Based on parallax measurements obtained during the Gaia mission, it is located at a distance of about 457 light-years (140 parsecs ) from the Sun. The system is drifting closer with a radial velocity of −2 km/s. [6]

The visible component is an A-type main-sequence star with a stellar classification of A0 V. [5] It is about 58 million years old [8] with three times the mass of the Sun [4] and has a high rate of spin, showing a projected rotational velocity of 170 km/s. [4] The star is radiating 147 times the luminosity of the Sun [4] from its photosphere at an effective temperature of 9,226 K. [4] The system is a source for X-ray emission, which is most likely coming from the unseen companion. [12]

Nomenclature

In the Henry Draper catalogue this system has the designation HD 161693, while it has the identifier HR 6618 in the Bright Star Catalogue . [9]

It bore the traditional Arabic name الربع Al Rubaʽ "the foal" (specifically a young camel born in the spring), a member of the Mother Camels asterism in early Arabic astronomy. [13] [14]

In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) [15] to catalogue and standardize proper names for stars. The WGSN approved the name Alruba for this star on 1 June 2018 and it is now so entered on the List of IAU-approved Star Names. [10]

References

  1. 1 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. XHIP record for this object at VizieR.
  2. 1 2 3 4 5 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.
  3. 1 2 Oja, T. (March 1985), "UBV photometry of stars whose positions are accurately known. II", Astronomy and Astrophysics Supplement Series, 59: 461–464, Bibcode:1985A&AS...59..461O.
  4. 1 2 3 4 5 6 7 8 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.
  5. 1 2 Abt, Helmut A.; Morrell, Nidia I. (1995), "The Relation between Rotational Velocities and Spectral Peculiarities among A-Type Stars", The Astrophysical Journal Supplement Series, 99: 135, Bibcode:1995ApJS...99..135A, doi: 10.1086/192182 .
  6. 1 2 Gontcharov, G. A. (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.
  7. 1 2 Wu, Yue; et al. (2010), "Coudé-feed stellar spectral library – atmospheric parameters", Astronomy & Astrophysics, 525: A71, arXiv: 1009.1491 , Bibcode:2011A&A...525A..71W, doi:10.1051/0004-6361/201015014, S2CID   53480665.
  8. 1 2 Gullikson, Kevin; et al. (2016), "The Close Companion Mass-Ratio Distribution of Intermediate-Mass Stars", The Astronomical Journal, 152 (2): 40, arXiv: 1604.06456 , Bibcode:2016AJ....152...40G, doi: 10.3847/0004-6256/152/2/40 , S2CID   119179065.
  9. 1 2 "HD 161693 -- Star", SIMBAD Astronomical Database, Centre de Données astronomiques de Strasbourg , retrieved 2018-07-01.
  10. 1 2 Naming Stars, IAU.org, retrieved 2018-07-01.
  11. ↑ Eggleton, P. P.; Tokovinin, A. A. (September 2008), "A catalogue of multiplicity among bright stellar systems", Monthly Notices of the Royal Astronomical Society, 389 (2): 869–879, arXiv: 0806.2878 , Bibcode:2008MNRAS.389..869E, doi: 10.1111/j.1365-2966.2008.13596.x , S2CID   14878976.
  12. ↑ Schröder, C.; Schmitt, J. H. M. M. (November 2007), "X-ray emission from A-type stars", Astronomy and Astrophysics, 475 (2): 677–684, Bibcode:2007A&A...475..677S, doi: 10.1051/0004-6361:20077429 .
  13. ↑ Allen, R. H. (1963), Star Names: Their Lore and Meaning (rep. ed.), New York, NY: Dover Publications Inc., pp. 207–212, ISBN   0-486-21079-0 , retrieved 2020-01-07.{{citation}}: ISBN / Date incompatibility (help)
  14. ↑ Garfinkle, Robert A. (2008), Star-Hopping: Your Visa to Viewing the Universe (2nd ed.), Cambridge University Press, p. 183, ISBN   978-0521598897.
  15. ↑ "International Astronomical Union | IAU", www.iau.org, retrieved 2018-07-01.
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