Delta Corvi

Delta Corvi (δ Corvi, abbreviated Delta Crv, δ Crv), also named Algorab /ˈælɡəræb/,^[9] is a third magnitude star at a distance of 86.9 light-years (26.6 parsecs) from the Sun^[1] in the southern constellation of Corvus.

δ Corvi

Location of δ Corvi (circled)
Observation data Epoch J2000      Equinox J2000
Constellation	Corvus
Right ascension	12h 29m 51.85517s[1]
Declination	−16° 30′ 55.5525″[1]
Apparent magnitude (V)	+2.962[2]
Characteristics
Spectral type	A0 IV(n) kB9[3]
U−B color index	−0.050[2]
B−V color index	−0.045[2]
Astrometry
Radial velocity (Rv)	+9[4] km/s
Proper motion (μ)	RA: −210.49[1] mas/yr Dec.: −138.74[1] mas/yr
Parallax (π)	37.55±0.16 mas[1]
Distance	86.9 ± 0.4 ly (26.6 ± 0.1 pc)
Absolute magnitude (MV)	+0.2[5]
Details
Mass	2.74+0.07 −0.06[6] M☉
Radius	2.56[6][a] R☉
Luminosity	69.0+9.7 −8.9[6] L☉
Surface gravity (log g)	4.06±0.05[6] cgs
Temperature	10,400[6] K
Rotational velocity (v sin i)	236[7] km/s
Age	260+14 −24 or 3.2+0.1 −0.1[6] Myr
Other designations
7 Crv, BD−15 3482, FK5 465, HD 108767, HIP 60965, HR 4757, SAO 157323[8]
Database references
SIMBAD	data

Nomenclature

δ Corvi (Latinised to Delta Corvi) is the star's Bayer designation.

It bore the traditional name Algorab derived from Arabic الغراب al-ghuraab, meaning 'the crow'. In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)^[10] to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016^[11] included a table of the first two batches of names approved by the WGSN; which included Algorab for this star.

In Chinese, 軫宿 (Zhěn Sù), meaning Chariot, refers to an asterism consisting of Delta Corvi, Gamma Corvi, Epsilon Corvi and Beta Corvi.^[12] Consequently, Delta Corvi itself is known as 軫宿三 (Zhěn Sù sān, English: the Third Star of Chariot).^[13]

Stellar properties

Delta Corvi has more than 2.7 times the mass of the Sun, which is causing it to radiate a much higher energy output—roughly 69 times the Sun's luminosity. The effective temperature of the outer atmosphere is 10,400 K,^[6] giving it the white hue of an A-type star.^[14] The spectrum matches a stellar classification of A0 IV(n) kB9.^[3] However, it is more luminous—65 to 70 times that of the Sun—than it would be if it were on the main sequence. Hence it is either a subgiant star around 260 million years old that has nearly exhausted the supply of hydrogen at its core and is in the process of evolving away from the main sequence of stars like the Sun, or a pre-main-sequence star around 3.2 million years old that has not completely condensed and settled on the main sequence.^[6]

In 1823, Delta Corvi was found to be a wide double star by British astronomers James South and John Herschel. Since that time, the position of the two stars with respect to each other has not changed.^[15] The magnitude 9.3 companion, HR 4757 B, with a classification of K2Ve, is at an angular separation of 24.2 arcseconds along a position angle of 214°.^[15][16] Although the two stars share a common proper motion,^[16] the significant differences in their estimated ages suggests that they may not be physically connected.^[6]

A 2006 study found that Delta Corvi displayed no excess infrared emission that would otherwise suggest the presence of circumstellar matter;^[17] however, warm interstellar dust was detected in a 2014 study.^[18]

Delta Corvi may be a binary star system. There is a star that shares a similar proper motion and thus is believed to be gravitationally bound. This possible companion has a projected separation of 640 astronomical units and around 0.7 times the mass and 0.8 times the radius of the Sun.^[19]

In culture

USS Algorab (AKA-8) was a United States Navy ship named after the star.

Algorab is one of the Behenian fixed stars.

Notes

1. Calculated, using the Stefan-Boltzmann law and the star's effective temperature and luminosity, with respect to the solar nominal effective temperature of 5,772 K:$${\displaystyle {\sqrt {{\biggl (}{\frac {5,772}{10,400}}{\biggr )}^{4}\cdot 69.0}}=2.56\ R_{\odot }.}$$