Delta Pictoris

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]

A light curve for Delta Pictoris, plotted from TESS data[14]

Delta Pictoris

Location of δ Pictoris (circled)
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]