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

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References

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