9 Boötis

9 Boötis is a single,[8] variable star in the northern constellation of Boötes,[7] located around 630 light years away from the Sun.[1] It is visible to the naked eye as a faint, orange-hued star with a baseline apparent visual magnitude of 5.02.[2] This object is moving closer to the Earth with a heliocentric radial velocity of −41 km/s.[2]

9 Boötis
Observation data
Epoch J2000      Equinox J2000
Constellation Boötes
Right ascension  13h 56m 34.18044s[1]
Declination +27° 29′ 31.4851″[1]
Apparent magnitude (V) 5.02[2]
Characteristics
Evolutionary stage giant
Spectral type K3 III[3]
B−V color index 1.441±0.005[2]
Variable type suspected irregular[4]
Astrometry
Radial velocity (Rv)−41.07±0.14[2] km/s
Proper motion (μ) RA: +28.665[1] mas/yr
Dec.: –47.779[1] mas/yr
Parallax (π)5.1990 ± 0.1461 mas
Distance630 ± 20 ly
(192 ± 5 pc)
Absolute magnitude (MV)−1.23[2]
Details
Radius54.74+0.52
−2.22[1] R☉
Luminosity716±24[1] L☉
Surface gravity (log g)1.85[5] cgs
Temperature4,197[6] K
Metallicity [Fe/H]−0.27[5] dex
Rotational velocity (v sin i)1.5[6] km/s
Other designations
9 Boo, NSV 6502, BD+28°2278, GC 18850, HD 121710, HIP 68103, HR 5247, SAO 83084[7]
Database references
SIMBADdata

This is an aging giant star with a stellar classification of K3 III,[3] which indicates it has exhausted the hydrogen at its core and evolved of the main sequence. As a consequence, its outer atmosphere has swollen to 55 times the radius of the Sun.[1] It is a suspected irregular variable that ranges in photographic magnitude from 6.1 down to 6.6.[4][9] 9 Boötis is considered mildly lithium-rich with a moderate level of chromospheric activity.[10] It is radiating 716[1] times the luminosity of the Sun from its enlarged photosphere at an effective temperature of 4,197 K.[6]

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. 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.
  3. Keenan, Philip C.; McNeil, Raymond C. (1989), "The Perkins catalog of revised MK types for the cooler stars", Astrophysical Journal Supplement Series, 71: 245, Bibcode:1989ApJS...71..245K, doi:10.1086/191373, ISSN 0067-0049.
  4. Samus, N. N.; et al. (2017), "General Catalogue of Variable Stars", Astronomy Reports, 5.1, 61 (1): 80–88, Bibcode:2017ARep...61...80S.
  5. McWilliam, Andrew (December 1990), "High-resolution spectroscopic survey of 671 GK giants. I - Stellar atmosphere parameters and abundances", Astrophysical Journal Supplement Series, 74: 1075–1128, Bibcode:1990ApJS...74.1075M, doi:10.1086/191527.
  6. Rebull, Luisa M.; et al. (October 2015), "On Infrared Excesses Associated with Li-rich K Giants", The Astronomical Journal, 150 (4): 45, arXiv:1507.00708, Bibcode:2015AJ....150..123R, doi:10.1088/0004-6256/150/4/123, 123.
  7. "9 Boo". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved April 25, 2019.
  8. 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.
  9. "NSV 6502", The International Variable Star Index, American Association of Variable Star Observers, retrieved 2019-04-26.
  10. Fekel, Francis C.; Balachandran, Suchitra (February 1993), "Lithium and rapid rotation in chromospherically active single giants", Astrophysical Journal, Part 1, 403 (2): 708–721, Bibcode:1993ApJ...403..708F, doi:10.1086/172242.
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