Chi Scorpii

Chi Scorpii, Latinized from χ Scorpii, is a single[10] star in the zodiac constellation of Scorpius. It has an orange hue and can be faintly seen with the naked eye with an apparent visual magnitude of 5.22.[2] Based upon parallax measurements, this star is around 409 light years from the Sun. The star is drifting closer with a radial velocity of −23.6 km/s.[4]

χ Scorpii
Observation data
Epoch J2000      Equinox J2000
Constellation Scorpius
Right ascension 16h 13m 50.90692s[1]
Declination −11° 50′ 15.9055″[1]
Apparent magnitude (V) 5.22[2]
Characteristics
Spectral type K3 III[3]
U−B color index +1.54[2]
B−V color index +1.42[2]
Astrometry
Radial velocity (Rv)−23.61±0.1[4] km/s
Proper motion (μ) RA: −5.630 mas/yr
Dec.: −9.062 mas/yr
Parallax (π)7.9805 ± 0.1645[5] mas
Distance409 ± 8 ly
(125 ± 3 pc)
Absolute magnitude (MV)−0.08[6]
Details[7]
Mass1.09±0.15 M☉
Radius26.76±0.75 R☉
Luminosity190.9±10.5 L☉
Surface gravity (log g)1.66±0.05 cgs
Temperature4,151±13 K
Metallicity [Fe/H]−0.01±0.10 dex
Rotational velocity (v sin i)8[8] km/s
Age8.39±2.64 Gyr
Other designations
χ Sco, 17 Scorpii, BD−11°4096, GC 21828, HD 145897, HIP 79540, HR 6048, SAO 159793, 2MASS J16135090-1150160[9]
Database references
SIMBADdata

This is an aging K-type giant star with a stellar classification of K3 III,[3] which means it has exhausted the supply of hydrogen at its core. There is a 57% chance that this evolved star is on the horizontal branch and a 43% chance it is still on the red-giant branch. If it is on the former, the star is estimated to have 1.09 times the mass of the Sun, nearly 27 times the solar radius and shines with 191 times the Sun's luminosity. It is around 8 billion years old.[7]

Planetary system

One superjovian planet orbiting Chi Scorpii was detected in 2020 on a mildly eccentric orbit utilizing a radial velocity method.[11]

The Chi Scorpii planetary system[12]
Companion
(in order from star)		 Mass Semimajor axis
(AU)		 Orbital period
(days)		 Eccentricity Inclination Radius
b ≥4.32+0.15
−0.12 MJ		 1.45±0.02 573.4±2.0 0.06+0.03
−0.02		 — —

References
  1. Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
  2. Mermilliod, J.-C. (1986), Compilation of Eggen's UBV data, transformed to UBV (unpublished), SIMBAD, Bibcode:1986EgUBV........0M.
  3. Houk, N.; Swift, C. (1999), "Michigan catalogue of two-dimensional spectral types for the HD Stars", Michigan Spectral Survey, 5, Bibcode:1999MSS...C05....0H.
  4. Nidever, David L.; et al. (August 2002), "Radial Velocities for 889 Late-Type Stars", The Astrophysical Journal Supplement Series, 141 (2): 503–522, arXiv:astro-ph/0112477, Bibcode:2002ApJS..141..503N, doi:10.1086/340570.
  5. 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.
  6. 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.
  7. Reffert, Sabine; et al. (2015), "Precise radial velocities of giant stars. VII. Occurrence rate of giant extrasolar planets as a function of mass and metallicity", Astronomy & Astrophysics, 574: A116, arXiv:1412.4634, Bibcode:2015A&A...574A.116R, doi:10.1051/0004-6361/201322360, hdl:10722/215277. Values are for the slightly higher probability horizontal branch model fit.
  8. Bernacca, P. L.; Perinotto, M. (1970), "A catalogue of stellar rotational velocities", Contributi Osservatorio Astronomico di Padova in Asiago, 239 (1), Bibcode:1970CoAsi.239....1B.
  9. "chi Sco -- Star", SIMBAD Astronomical Database, Centre de Données astronomiques de Strasbourg, retrieved 2016-09-24.
  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. Pinto, Marcelo Tala; Reffert, Sabine; Quirrenbach, Andreas; Stock, Stephan; Trifonov, Trifon; Mitchell, David S. (2020). "Precise radial velocities of giant stars". Astronomy & Astrophysics. 644: A1. doi:10.1051/0004-6361/202038285.
  12. 17 Sco b on exoplanet.eu
  • Kaler, James B. (August 12, 2016), "Chi and Psi Scorpii", Stars, University of Illinois, retrieved 2016-09-25.
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