Delta Scorpii
 Dschubba is δ star in one of the Scorpion's claws. |
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| Observation data Epoch J2000 Equinox J2000 |
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|---|---|
| Constellation | Scorpius |
| Right ascension | 16h 00m 20.00528s[1] |
| Declination | –22° 37′ 18.1431″[1] |
| Apparent magnitude (V) | 2.307[2] |
| Characteristics | |
| Spectral type | B0.3 IV[3] |
| U−B color index | –0.920[2] |
| B−V color index | –0.124[2] |
| Variable type | γ Cas |
| Astrometry | |
| Radial velocity (Rv) | –7[4] 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 | approx. 490 ly (approx. 150 pc) |
| Absolute magnitude (MV) | –3.8[5] |
| Orbit[6] | |
| Period (P) | 10.811 ± 0.01 yr |
| Semimajor axis (a) | 98.74 ± 0.07 mas |
| Eccentricity (e) | 0.9403 ± 0.0008 |
| Inclination (i) | 30.2 ± 0.7° |
| Longitude of the node (Ω) | 174.0 ± 2.5° |
| Periastron epoch (T) | 2000.6941 ± 0.003 |
| Argument of periastron (ω) (secondary) |
0.7 ± 2.9° |
| Semi-amplitude (K1) (primary) |
23.9 ± 0.1 km/s |
| Details | |
| Mass | 19.7 ± 0.1,[7] 14.6-14.9[8] M☉ |
| Radius | 6.7[9] R☉ |
| Luminosity | 45,700,[3] 38,000[8] L☉ |
| Surface gravity (log g) | 3.92[5] |
| Temperature | 29,500,[3] 27,400[8] K |
| Rotational velocity (v sin i) | 180[3] km/s |
| Age | 4.8 ± 0.2,[7] 9-10[8] Myr |
| Other designations | |
Delta Scorpii (δ Sco, δ Scorpii) is a star in the constellation Scorpius. It has the traditional name Dschubba (or Dzuba, from Arabic jabhat, "forehead" (of the scorpion) or also Iclarcrau or Iclarkrav.
Because Delta Scorpii is near the ecliptic it is occasionally occulted by the Moon, or (extremely rarely) by planets.
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.[5][8] The Upper Scorpius subgroup contains thousands of young stars with mean age 11 million years at average distance of 470 light years (145 parsecs).[8] A recent analysis[8] of the HR diagram position for Delta Scorpii estimates its effective temperature to be 27,400 Kelvin with a luminosity of 38,000 Suns, consistent with an isochronal age of 9-10 million years and an estimated mass of 14.6-14.9 solar masses.
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Variability [edit]
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 as high as magnitude 1.65, 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. As of 2005 the flareup continues. Although the brightness varies, it remains well above its previous constant magnitude.
The companion passed close by in 2011, again resulting in the star peaking at 1.65 between 5 and 15 July 2011.[10]
Companion stars [edit]
Dschubba is accompanied by a class B star that orbits the primary every 20 days at a distance comparable to the distance from the Sun to Mercury. Furthermore, there is a star that takes about 10 years to orbit Dschubba in a highly eccentric orbit that takes it close in to the primary once a decade. The last close encounter of these two stars happened in mid-2000 and it may have triggered the outburst of the primary star. A possible fourth companion star lies at about twice the distance again from the main star.[citation needed]
References [edit]
- ^ a b c d e van Leeuwen, F. (November 2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357.
- ^ a b c Gutierrez-Moreno, Adelina; Moreno, Hugo (June 1968), "A photometric investigation of the Scorpio-Centaurus association", Astrophysical Journal Supplement 15: 459, Bibcode:1968ApJS...15..459G, doi:10.1086/190168
- ^ a b c d Balona, L. A.; Dziembowski, W. A. (October 1999), "Excitation and visibility of high-degree modes in stars", Monthly Notices of the Royal Astronomical Society 309 (1): 221–232, Bibcode:1999MNRAS.309..221B, doi:10.1046/j.1365-8711.1999.02821.x
- ^ Evans, D. S. (June 20–24, 1966), "The Revision of the General Catalogue of Radial Velocities", in Batten, Alan Henry; Heard, John Frederick, Determination of Radial Velocities and their Applications, Proceedings from IAU Symposium no. 30, University of Toronto: International Astronomical Union, Bibcode:1967IAUS...30...57E
- ^ a b c de Geus, P. T.; de Zeeuw; Lub, J. (June 1989), "Physical parameters of stars in the Scorpio-Centaurus OB association", Astronomy and Astrophysics 216 (1-2): 44–61, Bibcode:1989A&A...216...44D
- ^ Meilland, A. et al. (August 2011), "The binary Be star δ Scorpii at high spectral and spatial resolution. I. Disk geometry and kinematics before the 2011 periastron", Astronomy & Astrophysics 532: A80, arXiv:1106.1746, Bibcode:2011A&A...532A..80M, doi:10.1051/0004-6361/201116798
- ^ a b Tetzlaff, N.; Neuhäuser, R.; Hohle, M. M. (january 2011), "A catalogue of young runaway Hipparcos stars within 3 kpc from the Sun", Monthly Notices of the Royal Astronomical Society 410 (1): 190–200, arXiv:1007.4883, Bibcode:2011MNRAS.410..190T, doi:10.1111/j.1365-2966.2010.17434.x
- ^ a b c d e f g Mark J. Pecaut, Eric E. Mamajek, & Eric J. Bubar (February 2012). "A Revised Age for Upper Scorpius and the Star Formation History among the F-type Members of the Scorpius-Centaurus OB Association". Astrophysical Journal 746 (2): 154.
- ^ Underhill, A. B. et al. (November 1979), "Effective temperatures, angular diameters, distances and linear radii for 160 O and B stars", Monthly Notices of the Royal Astronomical Society 189: 601–605, Bibcode:1979MNRAS.189..601U
- ^ Sigismondi, Costantino (2011), Differential photometry of delta Scorpii during 2011 periastron
External links [edit]
- *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)
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