Delta Scorpii
 Location of δ Sco (circled) |
|
| Observation data Epoch J2000 Equinox J2000 |
|
|---|---|
| Constellation | Scorpius |
| Right ascension | 16h 00m 20.00528s[1] |
| Declination | –22° 37′ 18.1431″[1] |
| Apparent magnitude (V) | 2.307[2] (1.6[3] - 2.32[4]) |
| Characteristics | |
| Spectral type | B0.3 IV[5] + B1-3V[6] |
| U−B color index | –0.920[2] |
| B−V color index | –0.124[2] |
| Variable type | γ Cas[4] |
| Astrometry | |
| Radial velocity (Rv) | –7[7] km/s |
| Proper motion (μ) | RA: -10.21[1] mas/yr Dec.: -35.41[1] mas/yr |
| Parallax (π) | 6.64 ± 0.89[1] mas |
| Distance | 136.0[6] pc |
| Absolute magnitude (MV) | –3.8[8] |
| Orbit[6][9] | |
| Period (P) | 10.8092 ± 0.0005 yr |
| Semi-major axis (a) | 0.09874 ± 0.00007" (13.5 ± 0.1 AU) |
| Eccentricity (e) | 0.936 ± 0.003 |
| Inclination (i) | 36 ± 1° |
| Longitude of the node (Ω) | 174.0 ± 2.5° |
| Periastron epoch (T) | 2011 July 3rd |
| Argument of periastron (ω) (secondary) |
−2.3 ± 3.8° |
| Semi-amplitude (K1) (primary) |
23.9 ± 0.8 km/s |
| Details | |
| Mass | 13 + 8.2[6] M☉ |
| Radius | 6.7[10](A) R☉ |
| Luminosity | 38,000[11](A) L☉ |
| Surface gravity (log g) | 3.92[8](A) cgs |
| Temperature | 27,400[11] + 20-24,000[6] K |
| Rotational velocity (v sin i) | 180[5](A) km/s |
| Age | 9-10[11][6] Myr |
| Other designations | |
| Database references | |
| SIMBAD | data |
Delta Scorpii (δ Sco, δ Scorpii) is a star in the constellation Scorpius. It has the traditional name Dschubba.
Because it is near the ecliptic δ Scorpii is occasionally occulted by the Moon, or (extremely rarely) by planets. It was once used as a spectroscopic standard for the B0 IV classification, but is now considered too unusual and variable.[6]
Delta Scorpii is a proper motion member of the Upper Scorpius subgroup of the Scorpius–Centaurus OB association, the nearest such co-moving association of massive stars to the Sun.[8][11] The Upper Scorpius subgroup contains thousands of young stars with mean age 11 million years at average distance of 470 light years (145 parsecs).[11]
System
Dschubba is a binary star. The primary is a B class subgiant surrounded by a disc of material spun off by the rapidly rotating star. The secondary orbits every 10.5 years in a highly elongated elliptical orbit. The secondary appears to be normal B class main sequence star. There have been reports that Delta Scorpii A is itself a very close spectroscopic binary, but this does not appear to be the case. The presence of a third star in the system is still being debated.[3]
Variability
Delta Scorpii is a Gamma Cassiopeiae variable star. This type of star shows irregular slow brightness variations of a few hundredths of a magnitude due to material surrounding the star.
In June 2000, Delta Scorpii was observed by Sebastian Otero to be 0.1 magnitudes brighter than normal. Its brightness has varied since then and has reached at least as high as magnitude 1.6, altering the familiar appearance of Scorpius. Spectra taken after the outburst began have shown that the star is throwing off luminous gases from its equatorial region. The companion passed close by in 2011, again resulting in the star peaking at 1.65 between 5 and 15 July 2011.[13][3]
References
- ↑ 1.0 1.1 1.2 1.3 1.4 Lua error in package.lua at line 80: module 'strict' not found.
- ↑ 2.0 2.1 2.2 Lua error in package.lua at line 80: module 'strict' not found.
- ↑ 3.0 3.1 3.2 Lua error in package.lua at line 80: module 'strict' not found.
- ↑ 4.0 4.1 Lua error in package.lua at line 80: module 'strict' not found.
- ↑ 5.0 5.1 Lua error in package.lua at line 80: module 'strict' not found.
- ↑ 6.0 6.1 6.2 6.3 6.4 6.5 6.6 Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ 8.0 8.1 8.2 Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ 11.0 11.1 11.2 11.3 11.4 Lua error in package.lua at line 80: module 'strict' not found.
- ↑ 12.0 12.1 12.2 Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
External links
- *Jim Kaler's Stars, University of Illinois: Dschubba
- Delta Scorpii brighter than ever (Sky and Telescope, February 4, 2002)
- Delta Scorpii still showing off (Sky and Telescope, June 25, 2003)
- Delta Scorpii: the birth of a Be star (AAVSO article)
