Delta2 Tauri

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Delta2 Tauri
Taurus IAU.svg
Red circle.svg
Location of δ2 Tauri (circled)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Taurus
Right ascension  04h 24m 05.75985s[1]
Declination +17° 26′ 38.8583″[1]
Apparent magnitude (V) +4.80[2]
Spectral type A2 Vs[3]
U−B color index +0.12[2]
B−V color index +0.15[2]
Radial velocity (Rv)+37.1[4] km/s
Proper motion (μ) RA: +108.16[1] mas/yr
Dec.: −34.66[1] mas/yr
Parallax (π)20.21 ± 0.40[1] mas
Distance161 ± 3 ly
(49.5 ± 1.0 pc)
Absolute magnitude (MV)+1.62[5]
Mass1.79[6] M
Radius1.8[7] R
Luminosity27[8] L
Surface gravity (log g)4.15[4] cgs
Temperature7,997[4] K
Metallicity [Fe/H]+0.14[4] dex
Rotational velocity (v sin i)42[4] km/s
Age449[6] Myr
Other designations
δ2 Tau, 64 Tauri, BD+17°714, HD 27819, HIP 20542, HR 1380, SAO 93907[9]
Database references

Delta2 Tauri (δ2 Tauri) is a solitary,[10] white-hued star in the zodiac constellation of Taurus. Based upon an annual parallax shift of 20.21 mas as seen from Earth,[1] it is located roughly 161 light years distant from the Sun. It is separated from δ1 Tauri by 0.3° on the sky[11] and is faintly visible to the naked eye with an apparent visual magnitude of +4.80.[2] The star is considered a member of the Hyades cluster.[12]

At the estimated age of 449 million years,[6] this is an A-type main-sequence star with a stellar classification of A2 Vs,[3] where the 's' suffix indicates narrow (sharp) absorption lines. It has 1.8[6] times the mass of the Sun and about 1.8[7] times the Sun's radius. The star is radiating 27[8] times the Sun's luminosity from its photosphere at an effective temperature of 7,997 K.[4]

δ2 Tauri is a source of X-ray emission with a luminosity of 101.1×1020 W. Since A-type stars are not normally a source of X-rays, this emission may be coming from an unknown companion or from a line of sight source.[13]


  1. ^ a b c d e f 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. ^ a b c d Johnson, H. L.; et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory, 4 (99), Bibcode:1966CoLPL...4...99J.
  3. ^ a b Paunzen, E.; et al. (July 2001), "A spectroscopic survey for λ Bootis stars. II. The observational data", Astronomy and Astrophysics, 373: 625–632, Bibcode:2001A&A...373..625P, doi:10.1051/0004-6361:20010630.
  4. ^ a b c d e f Gebran, M.; et al. (May 2016), "A new method for the inversion of atmospheric parameters of A/Am stars", Astronomy & Astrophysics, 589: 10, arXiv:1603.01146, Bibcode:2016A&A...589A..83G, doi:10.1051/0004-6361/201528052, A83.
  5. ^ Eggen, Olin J. (July 1998), "The Age Range of Hyades Stars", The Astronomical Journal, 116 (1): 284–292, Bibcode:1998AJ....116..284E, doi:10.1086/300413.
  6. ^ a b c d 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.
  7. ^ a b Pasinetti Fracassini, L. E.; et al. (February 2001), "Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS)", Astronomy and Astrophysics (Third ed.), 367: 521–524, arXiv:astro-ph/0012289, Bibcode:2001A&A...367..521P, doi:10.1051/0004-6361:20000451.
  8. ^ a b Zorec, J.; Royer, F. (2012), "Rotational velocities of A-type stars. IV. Evolution of rotational velocities", Astronomy & Astrophysics, 537: A120, arXiv:1201.2052, Bibcode:2012A&A...537A.120Z, doi:10.1051/0004-6361/201117691.
  9. ^ "del02 Tau". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-08-07.
  10. ^ Eggleton, P. P.; Tokovinin, A. A. (September 2008), "A catalogue of multiplicity among bright stellar systems", Monthly Notices of the Royal Astronomical Society, 389 (2): 869–879, arXiv:0806.2878, Bibcode:2008MNRAS.389..869E, doi:10.1111/j.1365-2966.2008.13596.x.
  11. ^ O'Meara, Stephen James (2016), Deep-Sky Companions: The Caldwell Objects, Cambridge University Press, p. 195, ISBN 1107083974.
  12. ^ Gebran, M.; Vick, M.; Monier, R.; Fossati, L. (November 2010), "Chemical composition of A and F dwarfs members of the Hyades open cluster", Astronomy and Astrophysics, 523: 13, arXiv:1006.5284, Bibcode:2010A&A...523A..71G, doi:10.1051/0004-6361/200913273, A71.
  13. ^ Schröder, C.; Schmitt, J. H. M. M. (November 2007), "X-ray emission from A-type stars", Astronomy and Astrophysics, 475 (2): 677–684, Bibcode:2007A&A...475..677S, doi:10.1051/0004-6361:20077429.