Pi1 Orionis

Pi1 Orionis (π1 Ori, π1 Orionis) is a star in the equatorial constellation of Orion. It is faintly visible to the naked eye with an apparent visual magnitude of 4.74.[2] Based upon an annual parallax shift of 28.04 mas,[1] it is located about 116 light years from the Sun.

For other stars with this Bayer designation, see Pi Orionis.
π1 Orionis
Location of π1 Orionis (circled)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Orion
Right ascension 04h 54m 53.72877s[1]
Declination +10° 09′ 02.9952″[1]
Apparent magnitude (V) 4.74[2]
Characteristics
Spectral type A3 Va[3]
U−B color index +0.09[2]
B−V color index +0.08[2]
Astrometry
Proper motion (μ) RA: +41.49[1] mas/yr
Dec.: −128.73[1] mas/yr
Parallax (π)28.04 ± 0.25[1] mas
Distance116 ± 1 ly
(35.7 ± 0.3 pc)
Absolute magnitude (MV)1.76±0.08[4]
Details
Mass1.97±0.07[4] M☉
Radius1.67[5] R☉
Luminosity16.6[5] L☉
Surface gravity (log g)4.15[3] cgs
Temperature8,611[3] K
Metallicity [Fe/H]−1.24[3] dex
Rotational velocity (v sin i)120[6] km/s
Age100[5] Myr
Other designations
π1 Ori, 7 Orionis, BD+09°683, HD 31295, HIP 22845, HR 1570, SAO 94201[7]
Database references
SIMBADdata

This is an A-type main sequence star with a stellar classification of A3 Va.[3] It is a Lambda Boötis star,[8] which means the spectrum shows lower than expected abundances for heavier elements.[9] Pi1 Orionis is a relatively young star, just 100 million years old,[5] and is spinning fairly rapidly with a projected rotational velocity of 120 km/s.[6] It has nearly double[4] the mass of the sun and 167% of the Sun's radius. The star radiates 16.6[5] times the solar luminosity from its outer atmosphere at an effective temperature of 8,611 K.[3]

An infrared excess indicates there is a debris disk with a temperature of 80 K orbiting 49 AU from the star. The dust has a combined mass 2.2% that of the Earth.[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. Mermilliod, J.-C. (1986), "Compilation of Eggen's UBV data, transformed to UBV (unpublished)", Catalogue of Eggen's UBV Data, SIMBAD, Bibcode:1986EgUBV........0M.
  3. Gray, R. O.; et al. (July 2006), "Contributions to the Nearby Stars (NStars) Project: spectroscopy of stars earlier than M0 within 40 pc-The Southern Sample", The Astronomical Journal, 132 (1): 161–170, arXiv:astro-ph/0603770, Bibcode:2006AJ....132..161G, doi:10.1086/504637, S2CID 119476992.
  4. Gerbaldi, M.; et al. (June 1999), "Search for reference A0 dwarf stars: Masses and luminosities revisited with HIPPARCOS parallaxes", Astronomy and Astrophysics Supplement, 137 (2): 273–292, Bibcode:1999A&AS..137..273G, doi:10.1051/aas:1999248.
  5. Rhee, Joseph H.; et al. (May 2007), "Characterization of Dusty Debris Disks: The IRAS and Hipparcos Catalogs", The Astrophysical Journal, 660 (2): 1556–1571, arXiv:astro-ph/0609555, Bibcode:2007ApJ...660.1556R, doi:10.1086/509912, S2CID 11879505.
  6. 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.
  7. "* pi.01 Ori". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2016-11-15.
  8. Gray, R. O.; Corbally, C. J. (August 1993), "A search for Lambda Bootis stars in OB associations", Astronomical Journal, 106 (2): 632–636, Bibcode:1993AJ....106..632G, doi:10.1086/116668.
  9. Kamp, I.; et al. (April 2008), "λ Bootis stars: Current status and new insights from Spitzer", Contributions of the Astronomical Observatory Skalnaté Pleso, 38 (2): 147–156, Bibcode:2008CoSka..38..147K.
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