1 Delphini
Star in the constellation Delphinus
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1 Delphini (1 Del) is the Flamsteed designation for a close binary star in the northern constellation of Delphinus. With a combined apparent magnitude of 6.08, it is barely visible to the naked eye, even under ideal conditions. Parallax measurements put the components at a distance 703 and 780 light years respectively. However, its approaching the Solar System with a radial velocity of 15 km/s.
 | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Delphinus |
| A | |
| Right ascension | 20h 30m 17.9623s[1] |
| Declination | +10° 53′ 45.335″[1] |
| Apparent magnitude (V) | 6.20±0.01[2] |
| B | |
| Right ascension | 20h 30m 17.9505s[3] |
| Declination | +10° 53′ 46.244″[3] |
| Apparent magnitude (V) | 8.00±0.01[2] |
| Characteristics | |
| Spectral type | A1:III shell[4] (A0e + A0)[5] |
| U−B color index | −0.11[6] |
| B−V color index | −0.03[6] |
| Astrometry | |
| Radial velocity (Rv) | −15.5 ± 2[7] km/s |
| Absolute magnitude (MV) | −0.69[8] |
| A | |
| Proper motion (μ) | RA: +19.320 mas/yr[1] Dec.: +4.645 mas/yr[1] |
| Parallax (π) | 4.6400±0.0616 mas[1] |
| Distance | 703 ± 9 ly (216 ± 3 pc) |
| B | |
| Proper motion (μ) | RA: +19.545[3] mas/yr Dec.: +4.710[3] mas/yr |
| Parallax (π) | 4.1851±0.1421 mas[3] |
| Distance | 780 ± 30 ly (239 ± 8 pc) |
| Details | |
| A | |
| Mass | 3.1±0.3[9] M☉ |
| Surface gravity (log g) | 3.66±0.77[9] cgs |
| Temperature | 10,651+932 −1156[9] K |
| Metallicity [Fe/H] | 0.00[10] dex |
| Rotational velocity (v sin i) | 217[11] km/s |
| Age | 246[10] Myr |
| B | |
| Surface gravity (log g) | 4.14+0.19 −0.47[9] cgs |
| Rotational velocity (v sin i) | 370[11] km/s |
| Other designations | |
| 1 Delphini, BD+10°4303, HD 195325, HIP 101160, HR 7836, SAO 106172, WDS J20303+1054AB | |
| Database references | |
| SIMBAD | data |
1 Del consists of three components. The brightest of them has a magnitude of 6.1; a companion located around 0.9 arcseconds from the primary has an apparent magnitude of 8.1; and a third star, located much farther away at around 17 arcseconds from component A, is the faintest with a magnitude of around 14 and is an unrelated background object.[12]
The entire system has a stellar classification of A1: III sh, indicating that it is a white giant and a shell star. However, there is some uncertainty about the temperature class. When resolved, the secondary has a class of B9. 1 Del A has 3 times the mass of the Sun and an effective temperature of 10,651 K,[9] giving it a bluish white glow. It is estimated to be almost 250 million years old and has a solar metallicity.[10] Both components spin rapidly, with projected rotational velocities of 217 and 370 km/s respectively.[11] As for the peculiarities, the shell star is a primary component; the spectrum of the secondary shows broad absorption lines.[11]
Due to the stability of the emission lines data from 1 Delphini has been used for developing models of shell stars and Be stars.[11]