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

Alruba,^[9] a name derived from Arabic for "the foal", is a suspected astrometric binary^[10] 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.^[2] 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.^[5]

The visible component is an A-type main-sequence star with a stellar classification of A0 V.^[4] It is about 58^[7] million years old with three^[3] times the mass of the Sun and has a high rate of spin, showing a projected rotational velocity of 170 km/s.^[3] The star is radiating 147^[3] times the luminosity of the Sun from its photosphere at an effective temperature of 9,226 K.^[3] The system is a source for X-ray emission, which is most likely coming from the unseen companion.^[11]

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.^[8]

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.^[12]^[13]

In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)^[14] 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.^[9]

References

^ ^a ^b ^c ^d ^e 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.
^ ^a ^b 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.
^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ 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.
^ ^a ^b 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.
^ ^a ^b 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.
^ ^a ^b 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.
^ ^a ^b 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.
^ ^a ^b "HD 161693 -- Star", SIMBAD Astronomical Database, Centre de Données astronomiques de Strasbourg, retrieved 2018-07-01.
^ ^a ^b Naming Stars, IAU.org, retrieved 2018-07-01.
^ 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.
^ 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.
^ 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.
^ Garfinkle, Robert A. (2008), Star-Hopping: Your Visa to Viewing the Universe (2nd ed.), Cambridge University Press, p. 183, ISBN 978-0521598897.
^ "International Astronomical Union | IAU", www.iau.org, retrieved 2018-07-01.