HD 16955

HD 16955, also known as HR 803, is a double or multiple star. With an apparent visual magnitude of 6.376,[2] is lies at or below the nominal limit for visibility with a typical naked eye. The measured annual parallax shift is 9.59 milliarcseconds, which yields an estimated distance of around 340 light years. The star is moving closer to the Sun with a heliocentric radial velocity of around -10 km/s.[5]

HD 15524
Observation data
Epoch J2000      Equinox J2000
Constellation Aries
Right ascension  02h 43m 51.24421s[1]
Declination +25° 38′ 18.0493″[1]
Apparent magnitude (V) 6.376[2]
Characteristics
Spectral type A3 V[3]
B−V color index 0.089±0.002[4]
Astrometry
Radial velocity (Rv)−10.3±3.1[5] km/s
Proper motion (μ) RA: −4.98±0.70[1] mas/yr
Dec.: +6.04±0.52[1] mas/yr
Parallax (π)9.59 ± 0.76[1] mas
Distance340 ± 30 ly
(104 ± 8 pc)
Absolute magnitude (MV)+1.18±0.13[2]
Details
HD 16955 A
Mass2.25±0.08[6] M☉
Luminosity26.9+3.3
−2.9[2] L☉
Temperature8,450±164[2] K
Rotational velocity (v sin i)175[7] km/s
Other designations
BD+25° 441, HD 16955, HIP 12744, HR 803, SAO 75539[8]
Database references
SIMBADdata

This is an A-type main-sequence star with a stellar classification of A3 V.[3] Hauck et al. (1995) identified this as a Lambda Boötis star with a circumstellar shell,[9] but this now appears to be unlikely.[2] It has 2.25[6] times the mass of the Sun and is spinning rapidly with a projected rotational velocity of 175 km/s.[7] The star is radiating about 27[2] times the Sun's luminosity from its photosphere at an effective temperature of roughly 8,450 K.[2]

HD 16955 has a magnitude 10.36 companion, component B, which is located, as of 2015, at an angular separation of 3.0 arcseconds along a position angle of 19°.[10] This is the likely source for the detected X-ray emission with a luminosity of 262.5×1020 W coming from these coordinates, since A-type stars are not expected to emit X-rays.[11] Component C is a more distant magnitude 12.94 companion located at a separation of 51.10 arcseconds along a position angle of 92°, as of 2015.[10]

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. Murphy, Simon J.; Paunzen, Ernst (April 2017), "Gaia's view of the λ Boo star puzzle", Monthly Notices of the Royal Astronomical Society, 466 (1): 546−555, arXiv:1612.01528, Bibcode:2017MNRAS.466..546M, doi:10.1093/mnras/stw3141
  3. Cowley, A.; et al. (April 1969). "A study of the bright A stars. I. A catalogue of spectral classifications". Astronomical Journal. 74: 375–406. Bibcode:1969AJ.....74..375C. doi:10.1086/110819.
  4. Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015.
  5. Gontcharov, G. A. (November 2006). "Pulkovo Compilation of Radial Velocities for 35495 Hipparcos stars in a common system". Astronomy Letters. 32 (11): 759–771. arXiv:1606.08053. Bibcode:2006AstL...32..759G. doi:10.1134/S1063773706110065.
  6. 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.
  7. 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.
  8. "HD 16955". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2018-02-26.
  9. Hauck, B.; et al. (March 1995), "Three other λ Bootis stars with a shell", Astronomy and Astrophysics Supplement, 109: 505−510, Bibcode:1995A&AS..109..505H
  10. Mason, B. D.; et al. (2014), "The Washington Visual Double Star Catalog", The Astronomical Journal, 122 (6): 3466–3471, Bibcode:2001AJ....122.3466M, doi:10.1086/323920.
  11. 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.
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