Delta Tucanae

Delta Tucanae (δ Tuc, δ Tucanae) is a common proper motion[3] pair located in the southwestern corner of the southern constellation of Tucana.[8] Based upon an annual parallax shift of 13.00 mas as seen from Earth, is approximately 250 light years from the Sun. It is visible to the naked eye with a combined apparent visual magnitude of +4.48.[2] As of 2013, the two components had an angular separation of 7.0 arc seconds along a position angle of 282°.[9]

Delta Tucanae A/B
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Tucana
Right ascension  22h 27m 19.96745s[1]
Declination −64° 57′ 58.8775″[1]
Apparent magnitude (V) +4.48[2] (A: 4.52, B: 8.85)[3]
Characteristics
Spectral type B9 Vn + G0 V Fe−2[3]
U−B color index A: −0.07, B: −0.02[3]
B−V color index A: −0.02, B: +0.51[3]
Astrometry
Proper motion (μ) RA: +68.45[1] mas/yr
Dec.: +10.06[1] mas/yr
Parallax (π)13.00 ± 0.48[1] mas
Distance251 ± 9 ly
(77 ± 3 pc)
Absolute magnitude (MV)A: 0.20, B: 4.50[3]
Details
δ Tuc A
Mass2.99[4] M☉
Radius2.7[5] R☉
Surface gravity (log g)4.11±0.14[4] cgs
Temperature11,271±383[4] K
Rotational velocity (v sin i)224[6] km/s
Age232[4] Myr
Other designations
δ Tuc, CP−65° 4044, HD 212581, HIP 110838, HR 8540, SAO 255222, WDS J22273-6458AB[7]
Database references
SIMBADdata

The brighter primary, component A, is blue-white hued star a visual magnitude of 4.52.[3] It is a B-type main-sequence star with a stellar classification of B9 Vn,[3] where the 'n' suffix indicates "nebulous" absorption lines due to the star's rotation. It is spinning rapidly with a projected rotational velocity of 224 km/s,[6] which is giving the star an oblate shape with an equatorial bulge that is an estimated 12% larger than the polar radius.[10] The star has about three times the mass of the Sun and is around 232 million years old.[4]

The magnitude 8.85[3] companion, component B, is a G-type main-sequence star. It has a classification of G0 V Fe−2,[3] with the suffix indicating an underabundance of iron in the star's photosphere.

References
  1. van Leeuwen, F. (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.
  2. Nicolet, B. (1978), "Photoelectric photometric Catalogue of homogeneous measurements in the UBV System", Astronomy and Astrophysics Supplement Series, 34: 1–49, Bibcode:1978A&AS...34....1N.
  3. Corbally, C. J. (1984), "Close visual binaries. I - MK classifications", Astrophysical Journal Supplement Series, 55: 657, Bibcode:1984ApJS...55..657C, doi:10.1086/190973.
  4. David, Trevor J.; Hillenbrand, Lynne A. (2015), "The Ages of Early-Type Stars: Strömgren Photometric Methods Calibrated, Validated, Tested, and Applied to Hosts and Prospective Hosts of Directly Imaged Exoplanets", The Astrophysical Journal, 804 (2): 146, arXiv:1501.03154, Bibcode:2015ApJ...804..146D, doi:10.1088/0004-637X/804/2/146.
  5. Pasinetti Fracassini, L. E.; Pastori, L.; Covino, S.; Pozzi, A. (February 2001), "Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS)", Astronomy and Astrophysics (3rd ed.), 367: 521–524, arXiv:astro-ph/0012289, Bibcode:2001A&A...367..521P, doi:10.1051/0004-6361:20000451.
  6. Royer, F.; et al. (October 2002), "Rotational velocities of A-type stars in the northern hemisphere. II. Measurement of v sin i", Astronomy and Astrophysics, 393: 897–911, arXiv:astro-ph/0205255, Bibcode:2002A&A...393..897R, doi:10.1051/0004-6361:20020943.
  7. "del Tuc". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-04-22.
  8. Streicher, Magda (2005), "Deepsky Delights", Monthly Notes of the Astronomical Society of Southern Africa, 64 (9–10): 172–74, Bibcode:1907GOAMM..67G...2C.
  9. Mason, B. D.; et al. (2014), "The Washington Visual Double Star Catalog", The Astronomical Journal, 122: 3466–3471, Bibcode:2001AJ....122.3466M, doi:10.1086/323920.
  10. Belle, G. T. (2012), "Interferometric observations of rapidly rotating stars", The Astronomy and Astrophysics Review, 20: 51, arXiv:1204.2572, Bibcode:2012A&ARv..20...51V, doi:10.1007/s00159-012-0051-2.
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