Delta Delphini

Delta Delphini, Latinized from δ Delphini, is a binary star^[9] in the northern constellation of Delphinus. It is visible to the naked eye with an apparent visual magnitude of 4.43.^[2] Based upon an annual parallax shift of 14.61 mas as seen from the Earth,^[1] the system is located about 223 light years from the Sun.

A light curve for Delta Delphini, plotted from Hipparcos data^[10]

Delta Delphini

A star chart of the Delphinus constellation showing the position of δ Delphinus (circled)
Observation data Epoch J2000.0      Equinox J2000.0
Constellation	Delphinus
Right ascension	20h 43m 27.53338s[1]
Declination	+15° 04′ 28.4773″[1]
Apparent magnitude (V)	4.43[2] (4.38 - 4.49)[3]
Characteristics
Spectral type	kA7hF1VmF1pSrEuCr:[4]
B−V color index	+0.302[2]
Variable type	δ Sct[3]
Astrometry
Radial velocity (Rv)	9.48±0.07[5] km/s
Proper motion (μ)	RA: −20.44[1] mas/yr Dec.: −43.33[1] mas/yr
Parallax (π)	14.61±0.20 mas[1]
Distance	223 ± 3 ly (68.4 ± 0.9 pc)
Absolute magnitude (MV)	+0.25[6]
Orbit[5]
Period (P)	40.60505±0.00014 d
Semi-major axis (a)	5.4676±0.0037
Eccentricity (e)	0.64008±0.00018
Inclination (i)	13.92±0.18°
Longitude of the node (Ω)	63.73±0.33°
Periastron epoch (T)	56823.5019±0.0028 MJD
Argument of periastron (ω) (secondary)	65.07±0.32°
Semi-amplitude (K1) (primary)	13.88±0.14 km/s
Semi-amplitude (K2) (secondary)	15.27±0.07 km/s
Details
δ Del A
Mass	1.78[5] M☉
Radius	3.43[5] R☉
Luminosity	32.4[5] L☉
Surface gravity (log g)	3.71[7] cgs
Temperature	7,440±210[5] K
Metallicity [Fe/H]	−0.5[5] dex
Rotational velocity (v sin i)	17[5] km/s
Age	945[7] Myr
δ Del B
Mass	1.62[5] M☉
Radius	3.48[5] R☉
Luminosity	28.8[5] L☉
Temperature	7,110±180[5] K
Rotational velocity (v sin i)	12[5] km/s
Other designations
δ Del, 11 Del, BD+14°4403, HD 197461, HIP 102281, HR 7928, SAO 106425[8]
Database references
SIMBAD	data

This is a double-lined spectroscopic binary^[9] system with an orbital period of 40.58 days.^[9] The two components are nearly identical chemically peculiar stars, having a combined stellar classification of kA7hF1VmF1pSrEuCr:. This notation indicates the calcium K line matches an A7 star, the hydrogen lines an F1 star, and the metal lines an F1 star, with particularly strong lines of strontium, europium, and chromium. Each of the stars is a Delta Scuti variable, with the system having a dominant period of 0.1568 days and an amplitude of 0.0700 in magnitude.^[2] Delta Delphini forms the prototype of a class of metal-lined δ Scuti subgiant or giant stars.^[11]