Delta Delphini
Star in the constellation Delphinus
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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.
| 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]