Delta Pictoris
Variable star in the constellation Pictor
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Delta Pictoris, Latinized from δ Pictoris, is a binary star system in the southern constellation Pictor. It is visible to the naked with a combined apparent visual magnitude of 4.72.[2] The system is located at a distance of approximately 1,300 light years from the Sun based on parallax measurements,[1] and is drifting further away with a radial velocity of ~31 km/s.[9] It is a runaway star system that is generating a bow shock as it moves through the interstellar medium.[13]
  | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Pictor |
| Right ascension | 06h 10m 17.908s[1] |
| Declination | −54° 58′ 07.11″[1] |
| Apparent magnitude (V) | 4.72[2] |
| Characteristics | |
| Evolutionary stage | Main sequence[3] |
| Spectral type | B1/2(III)n[4] (B0.5:III?np + B0.5/3:)[5] |
| U−B color index | −1.00[6] |
| B−V color index | −0.229±0.008[2] |
| Variable type | β Lyr[7] + β Cep[8] |
| Astrometry | |
| Radial velocity (Rv) | +30.6±2.8[9] km/s |
| Proper motion (μ) | RA: −4.90 mas/yr[1] Dec.: +7.41 mas/yr[1] |
| Parallax (π) | 2.51±0.15 mas[1] |
| Distance | 1,300 ± 80 ly (400 ± 20 pc) |
| Absolute magnitude (MV) | −3.27[2] |
| Orbit[10] | |
| Period (P) | 1.67254 d |
| Semi-major axis (a) | ≥ 3.83 Gm (0.0256 AU) |
| Eccentricity (e) | 0.050±0.17 |
| Periastron epoch (T) | 2,438,500.79±0.09 JD |
| Argument of periastron (ω) (secondary) | 90±18° |
| Semi-amplitude (K1) (primary) | 167.0±2.8 km/s |
| Details | |
| Primary | |
| Mass | 16.3[11] M☉ |
| Radius | 7.62[11] R☉ |
| Luminosity | 20,900[11] L☉ |
| Temperature | 25,200[11] K |
| Rotational velocity (v sin i) | 170[8] km/s |
| Secondary | |
| Mass | 8.6[11] M☉ |
| Radius | 5.05[11] R☉ |
| Luminosity | 4,790[11] L☉ |
| Temperature | 21,400[11] K |
| Other designations | |
| δ Pic, del Pic, FK5 235, GC 7898, HD 42933, HIP 29276, HR 2212, SAO 234359[12] | |
| Database references | |
| SIMBAD | data |
The binary nature of this system was discovered by R. E. Wilson in 1914,[10] then it was found to be variable by A. W. J. Cousins in 1951.[15] A. D. A. Thackeray published orbital elements for the pair in 1966, showing they form an eclipsing double-lined spectroscopic binary with an orbital period of 1.67 days in essentially a circular orbit.[10] The low inclination of the orbital plane results in shallow eclipses.[3] The system is classified as a likely Beta Lyrae-type eclipsing binary with a peak magnitude of 4.65, which drops to 4.90 during the primary eclipse and 4.83 in the secondary eclipse.[7] It is probably a detached binary system with no circumstellar material being found.[3]
Both components of this system are massive main sequence stars[3] with a combined stellar classification of B1/2(III)n.[4] One member of the pair displays β Cep type pulsational behavior.[8] Mass estimates give a primary with 16.3 times the mass of the Sun and a secondary with about half that.[11]