13 Boötis

13 Boötis is a solitary[8] variable star in the northern constellation of Boötes, and is positioned near the western constellation border with Ursa Major. It has the variable star designation CF Boötis, often abbreviated CF Boo, while 13 Boötis is the star's Flamsteed designation. This star has a reddish hue and is faintly visible to the naked eye with an apparent visual magnitude that fluctuates around 5.26.[2] It is located at a distance of approximately 700 light years from the Sun based on parallax, but is drifting closer with a radial velocity of −14 km/s.[2]

13 Boötis
Observation data
Epoch J2000      Equinox J2000
Constellation Boötes
Right ascension 14h 08m 17.30243s[1]
Declination +49° 27′ 29.3993″[1]
Apparent magnitude (V) 5.26[2] (5.29 to 5.38)[3]
Characteristics
Spectral type M1.5III[4]
U−B color index +1.92[5]
B−V color index +1.637±0.010[2]
Variable type Lb[3]
Astrometry
Radial velocity (Rv)−13.92±0.06[2] km/s
Proper motion (μ) RA: −58.584[1] mas/yr
Dec.: 59.801[1] mas/yr
Parallax (π)4.6635 ± 0.1756 mas[1]
Distance700 ± 30 ly
(214 ± 8 pc)
Absolute magnitude (MV)−0.87[2]
Details
Mass0.8-2.6[6] M☉
Radius74+10
−12[1] R☉
Luminosity1,114±48[1] L☉
Temperature3,889+379
−248[1] K
Other designations
13 Boo, CF Boo, BD+50°2047, FK5 3124, GC 19095, HD 123782, HIP 69068, HR 5300, SAO 44905, CCDM 14082+4927, WDS 14083+4927[7]
Database references
SIMBADdata

This is an aging red giant star on the asymptotic giant branch[9] with a stellar classification of M1.5III,[4] which is interpreted by stellar evolutionary models to mean it has exhausted the supply of hydrogen at its core then cooled and expanded off the main sequence. It is classified as a slow irregular variable of the Lb type, and its brightness has been observed to vary from +5.29 down to +5.38.[3] The star has ~74 times the girth of the Sun and is radiating 1,114 times the Sun's luminosity from its swollen photosphere at an effective temperature of 3,889 K.[1]

There is a magnitude 11.05 visual companion located at an angular separation of 76.40 arcseconds from the brighter star, along a position angle of 270°. This was first reported by William Herschel in 1783.[10]

Possible planetary system

In 1991, Duquennoy & Mayor[11] reported the possible presence of a low-mass object (of likely substellar nature) orbiting the red giant 13 Bootis. They set a minimum mass of 30 times that of Jupiter (likely a brown dwarf) and estimated an orbital period of 1.35 years. So far there has been no confirmation about the presence a substellar object.

The 13 Boötis planetary system
Companion
(in order from star)		 Mass Semimajor axis
(AU)		 Orbital period
(days)		 Eccentricity Inclination Radius
b (unconfirmed) ≥30 MJ ≥1.25 494 0.21 — —

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. S2CID 119257644.
  3. Samus, N. N.; et al. (2017). "General Catalogue of Variable Stars". Astronomy Reports. 5.1. 61 (1): 80–88. Bibcode:2017ARep...61...80S. doi:10.1134/S1063772917010085. S2CID 125853869.
  4. 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.
  5. Mermilliod, J.-C. (1986). "Compilation of Eggen's UBV data, transformed to UBV (unpublished)". Catalogue of Eggen's UBV Data. Bibcode:1986EgUBV........0M.
  6. Alvarez, R.; Mennessier, M. -O. (1997). "Determination of Miras temperatures from TiO and VO bands. Estimates of distances". Astronomy and Astrophysics. 317: 761–768. Bibcode:1997A&A...317..761A.
  7. "* 13 Boo". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 25 May 2017.
  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. S2CID 14878976.
  9. Eggen, Olin J. (July 1992). "Asymptotic giant branch stars near the sun". Astronomical Journal. 104 (1): 275–313. Bibcode:1992AJ....104..275E. doi:10.1086/116239.
  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. Duquennoy, A.; Mayor, M. (1991). "Multiplicity among solar-type stars in the solar neighbourhood. II - Distribution of the orbital elements in an unbiased sample". Astronomy and Astrophysics. 248 (2): 485–524. Bibcode:1991A&A...248..485D.
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