δ Andromedae

Location of δ Andromedae (circled)
Observation data Epoch J2000.0       Equinox J2000.0 ( ICRS)
Constellation	Andromeda
Right ascension	00h 39m 19.67518s [1]
Declination	+30° 51′ 39.6783″ [1]
Apparent magnitude (V)	3.28 [2]
Characteristics
Spectral type	K3 III [3] + K4 ± 2 [4]
U−B color index	+1.48 [2]
B−V color index	+1.28 [2]
R−I color index	+0.66 [5]
Astrometry
Radial velocity (Rv)	−9.88±0.15 [6] km/s
Proper motion (μ)	RA: +114.45 [1]  mas/ yr Dec.: −84.02 [1]  mas/ yr
Parallax (π)	30.91 ± 0.15  mas [1]
Distance	105.5 ± 0.5  ly (32.4 ± 0.2  pc)
Absolute magnitude (MV)	+0.8 [7]
Orbit [8]
Period (P)	15,000 d
Eccentricity (e)	0.34±0.14
Periastron epoch (T)	2415568 JD
Argument of periastron (ω) (primary)	356.1±5.2°
Semi-amplitude (K1) (primary)	4.0±2.7 km/s
Details [4]
δ And Aa
Mass	~1.3 [9]  M☉
Radius	13.6±0.3  R☉
Luminosity	68±4  L☉
Surface gravity (log g)	2.0±0.3 [3]  cgs
Temperature	4,315±9  K
Metallicity [Fe/H]	0.04  dex
Rotational velocity (v sin i)	6.5 [6] km/s
Age	3.2  Gyr
δ And Ab
Mass	0.6–0.8  M☉
Other designations
δ And, Delta Andromedae, Delta And, 31 Andromedae, 31 And, NSV 15142, BD+30 91, FK5 20, HD 3627, HIP 3092, HR 165, SAO 54058, PPM 65514, WDS 00393+3052A [10] [11]
Database references
SIMBAD	data

Delta Andromedae, Latinized from δ Andromedae, is a triple star ^[12] system in the northern constellation of Andromeda. The system is visible to the naked eye as a point of light with a combined apparent visual magnitude of 3.28. ^[2] Based upon parallax measurements, it is located at a distance of approximately 105.5 light-years (32.3 parsecs) from the Sun. ^[1] The system is drifting closer with a radial velocity of −10 km/s. ^[6]

In Chinese, 奎宿 (Kuí Sù), meaning Legs (asterism), refers to an asterism consisting of δ Andromedae, η Andromedae, 65 Piscium, ζ Andromedae, ι Piscium, ε Andromedae, π Andromedae, ν Andromedae, μ Andromedae, β Andromedae, σ Piscium, τ Piscium, 91 Piscium, υ Piscium, φ Piscium, χ Piscium and ψ¹ Piscium. Consequently, the Chinese name for δ Andromedae itself is 奎宿五 (Kuí Sù wǔ, English: the Fifth Star of Legs.) ^[13] Apart from its Bayer designation, it was also given the title Delta by Elijah H. Burritt in his star atlas. ^[14]

This is a long-period spectroscopic binary with an orbital period of approximately 15,000 days (41 years). The primary of the spectroscopic binary, component Aa, has a stellar classification of K3 III, indicating that it is an aging giant star. ^{[3] [8]} It most likely evolved from a F-type main sequence star after consuming the hydrogen at its core. ^[15] The secondary, component Ab, is a relatively faint K-type dwarf, which has been imaged using a stellar coronagraph. The pair have a physical separation of 11.55±0.13  AU. ^[4] The system has two companions, the closest of which is most likely an orbiting red dwarf of class M3 with a separation of at least 900  astronomical units. ^[16]

An excess of infrared emission from δ Andromedae suggested that it may be surrounded by a shell of dust. ^{[3] [17]} In 2003 it was determined that this is more likely a circumstellar debris disk. ^[15]

References

External links

• The Constellation Andromeda: The Chained Maiden Archived 2021-02-13 at the Wayback Machine, web page, European Southern Observatory outreach.
• Image Delta Andromedae