Pi Tucanae

Pi Tucanae (π Tuc, π Tucanae) is a double star[5] in the southern constellation of Tucana. It is visible to the naked eye with a combined apparent visual magnitude of +5.49.[2] Based upon an annual parallax shift of 10.25 mas as seen from Earth, it is located around 317 light years from the Sun.

Pi Tucanae
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Tucana
Right ascension 0h 20m 39.03682s[1]
Declination −69° 37′ 29.6821″[1]
Apparent magnitude (V) +5.49[2]
Characteristics
Spectral type B9 V[3]
U−B color index −0.11[2]
B−V color index −0.05[2]
Astrometry
Radial velocity (Rv)+10.50±2.60[4] km/s
Proper motion (μ) RA: −3.53[1] mas/yr
Dec.: −0.10[1] mas/yr
Parallax (π)10.25 ± 0.21 mas[1]
Distance318 ± 7 ly
(98 ± 2 pc)
Absolute magnitude (MV)+0.57[5]
Details
π Tuc A
Mass2.8+0.21
−0.18[6] M☉
Luminosity59[7] L☉
Surface gravity (log g)4.0±0.14[6] cgs
Temperature11,393±387[6] K
Rotational velocity (v sin i)236[8] km/s
Age206+48
−79[6] Myr
π Tuc B
Mass0.60[5] M☉
Luminosity0.063[5] L☉
Temperature3,890[5] K
Other designations
π Tuc, CPD−70° 12, FK5 2018, HD 1685, HIP 1647, HR 83, SAO 248167[9]
Database references
SIMBADdata

The brighter star, component A, is a B-type main sequence star with a stellar classification of B9 V.[3] At an age of about 206 million years,[6] it is spinning rapidly with a projected rotational velocity of 236.[8] The star has an estimated 2.8[6] times the mass of the Sun and radiates 59[7] times the solar luminosity from its photosphere at an effective temperature of 11,393 K.[6]

There is a nearby visual companion, component B, but the two stars may not form a physical pair. This star has a K-band magnitude of 10.1 and is a source of X-ray emission. It has 60% of the Sun's mass and just 6.3% of the Sun's luminosity, with an effective temperature of 3,890 K.[5] The pair have an angular separation of 2.28 arc seconds along a position angle of 211.4°, which corresponds to a projected separation of 214.1 AU.[5]

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, S2CID 18759600.
  2. Cousins, A. W. J.; Lagerweij, H. C. (1971), "UBV Observations of Variable Stars", Monthly Notes of the Astronomical Society of Southern Africa, 30: 12, Bibcode:1971MNSSA..30...12C.
  3. Houk, Nancy (1979), Michigan catalogue of two-dimensional spectral types for the HD stars, vol. 1, Ann Arbor, Michigan: Dept. of Astronomy, University of Michigan, Bibcode:1978mcts.book.....H.
  4. de Bruijne, J. H. J.; Eilers, A.-C. (October 2012), "Radial velocities for the HIPPARCOS-Gaia Hundred-Thousand-Proper-Motion project", Astronomy & Astrophysics, 546: 14, arXiv:1208.3048, Bibcode:2012A&A...546A..61D, doi:10.1051/0004-6361/201219219, S2CID 59451347, A61.
  5. Hubrig, S.; et al. (June 2001), "Search for low-mass PMS companions around X-ray selected late B stars", Astronomy and Astrophysics, 372: 152–164, arXiv:astro-ph/0103201, Bibcode:2001A&A...372..152H, doi:10.1051/0004-6361:20010452, S2CID 17507782.
  6. Gullikson, Kevin; et al. (August 2016), "The Close Companion Mass-ratio Distribution of Intermediate-mass Stars", The Astronomical Journal, 152 (2): 13, arXiv:1604.06456, Bibcode:2016AJ....152...40G, doi:10.3847/0004-6256/152/2/40, S2CID 119179065, 40.
  7. McDonald, I.; et al. (2012), "Fundamental Parameters and Infrared Excesses of Hipparcos Stars", Monthly Notices of the Royal Astronomical Society, 427 (1): 343–57, arXiv:1208.2037, Bibcode:2012MNRAS.427..343M, doi:10.1111/j.1365-2966.2012.21873.x, S2CID 118665352.
  8. Royer, F.; et al. (February 2007), "Rotational velocities of A-type stars. III. Velocity distributions", Astronomy and Astrophysics, 463 (2): 671–682, arXiv:astro-ph/0610785, Bibcode:2007A&A...463..671R, doi:10.1051/0004-6361:20065224, S2CID 18475298.
  9. "pi. Tuc -- Double or multiple star", SIMBAD Astronomical Database, Centre de Données astronomiques de Strasbourg, retrieved 2017-04-20.
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