36 Ursae Majoris

36 Ursae Majoris is a double star[3] in the northern constellation of Ursa Major. With an apparent visual magnitude of 4.82,[2] it can be seen with the naked eye in suitable dark skies. Based upon parallax measurements, this star lies at a distance of 41.7 light-years (12.8 parsecs) from Earth.[1]

36 Ursae Majoris
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Ursa Major
Right ascension 10h 30m 37.5798s[1]
Declination +55° 58′ 49.931″[1]
Apparent magnitude (V) 4.82[2]
Characteristics
Spectral type F8 V[3]
U−B color index –0.01[2]
B−V color index +0.52[2]
Astrometry
Radial velocity (Rv)+8.5[4] km/s
Proper motion (μ) RA: –176.71[1] mas/yr
Dec.: –33.21[1] mas/yr
Parallax (π)78.25 ± 0.28[1] mas
Distance41.7 ± 0.1 ly
(12.78 ± 0.05 pc)
Absolute magnitude (MV)4.29[4]
Details
Mass1.121[5] M☉
Radius1.091 ± 0.020[6] R☉
Luminosity1.605 ± 0.042[6] L☉
Surface gravity (log g)4.36[7] cgs
Temperature6,233 ± 68[6] K
Metallicity [Fe/H]–0.18[7] dex
Rotational velocity (v sin i)5.5[8] km/s
Age2.7[4] Gyr
Other designations
36 Ursae Majoris, BD+56 1459, FK5 394, HD 90839, HIP 51459, HR 4112, SAO 27670.[3]
Database references
SIMBADThe system
A
B

This star is a solar analog—meaning it has physical properties that make it similar to the Sun. It has 12% more mass and a radius 15% larger than the Sun,[5] with an estimated age of 2.7 billion years.[4] The spectrum of this star matches a stellar classification of F8 V, which indicates this is a main sequence star that is generating energy at its core through the nuclear fusion of hydrogen. The energy is being radiated into space from its outer envelope at an effective temperature of 6,126 K.[9] This gives the star the characteristic yellow-white hue of an F-type star.[10]

36 Ursae Majoris has a magnitude 8.86 common proper motion companion with about half this star's mass[11] at an angular separation of 122.5″ along a position angle of 303°, as of 2012. A second companion with a magnitude of 11.44 is located at an angular separation of 240.6″ along a position angle of 292°, as of 2004.[12]

Hunt for substellar objects

According to Nelson & Angel (1998),[13] 36 Ursae Majoris could host one or two (or at least three) jovian planets (or even brown dwarfs) at wide separations from the host star, with orbital periods of 10–15, 25 and 50 years respectively. The authors have set upper limits of 1.1–2, 5.3 and 24 Jupiter masses for the putative planetary objects. Also Lippincott (1983)[14] had previously noticed the possible presence of a massive unseen companion (with nearly 70 times the mass of Jupiter, just below the stellar regime, thus a brown dwarf). Putative parameters for the substellar object show an orbital period of 18 years and quite a high eccentricity (e=0.8). Even Campbell et al. 1988[15] inferred the existence of planetary objects or even brown dwarfs less massive than 14 Jupiter masses around 36 Ursae Majoris.

Nevertheless, no certain planetary companion has yet been detected or confirmed. The McDonald Observatory team has set limits to the presence of one or more planets[16] with masses between 0.13 and 2.5 Jupiter masses and average separations spanning between 0.05 and 5.2 AU.

An infrared excess has been detected around this star, most likely indicating the presence of a circumstellar disk at a radius of 38.6 AU. The temperature of this dust is 50 K.[17]

References
  1. van Leeuwen, F. (November 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. Johnson, H. L.; et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory, 4 (99), Bibcode:1966CoLPL...4...99J
  3. "HR 4112 -- Star in double system", SIMBAD, Centre de Données astronomiques de Strasbourg, retrieved 2012-01-30
  4. Nordström, B.; et al. (May 2004), "The Geneva-Copenhagen survey of the Solar neighbourhood. Ages, metallicities, and kinematic properties of ˜14 000 F and G dwarfs", Astronomy and Astrophysics, 418 (3): 989–1019, arXiv:astro-ph/0405198, Bibcode:2004A&A...418..989N, doi:10.1051/0004-6361:20035959
  5. Takeda, Genya; et al. (February 2007), "Structure and Evolution of Nearby Stars with Planets. II. Physical Properties of ~1000 Cool Stars from the SPOCS Catalog", The Astrophysical Journal Supplement Series, 168 (2): 297–318, arXiv:astro-ph/0607235, Bibcode:2007ApJS..168..297T, doi:10.1086/509763
  6. Boyajian, Tabetha S.; et al. (February 2012), "Stellar Diameters and Temperatures. I. Main-sequence A, F, and G Stars", The Astrophysical Journal, 746 (1): 101, arXiv:1112.3316, Bibcode:2012ApJ...746..101B, doi:10.1088/0004-637X/746/1/101. See Table 10.
  7. Chen, Y. Q.; et al. (February 2000), "Chemical composition of 90 F and G disk dwarfs", Astronomy and Astrophysics Supplement, 141: 491–506, arXiv:astro-ph/9912342, Bibcode:2000A&AS..141..491C, doi:10.1051/aas:2000124
  8. Schröder, C.; Reiners, A.; Schmitt, J. H. M. M. (January 2009), "Ca II HK emission in rapidly rotating stars. Evidence for an onset of the solar-type dynamo" (PDF), Astronomy and Astrophysics, 493 (3): 1099–1107, Bibcode:2009A&A...493.1099S, doi:10.1051/0004-6361:200810377
  9. Valenti, Jeff A.; Fischer, Debra A. (July 2005), "Spectroscopic Properties of Cool Stars (SPOCS). I. 1040 F, G, and K Dwarfs from Keck, Lick, and AAT Planet Search Programs", The Astrophysical Journal Supplement Series, 159 (1): 141–166, Bibcode:2005ApJS..159..141V, doi:10.1086/430500
  10. "The Colour of Stars", Australia Telescope, Outreach and Education, Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, archived from the original on March 10, 2012, retrieved 2012-01-16
  11. Tokovinin, Andrei (April 2014), "From Binaries to Multiples. II. Hierarchical Multiplicity of F and G Dwarfs", The Astronomical Journal, 147 (4): 14, arXiv:1401.6827, Bibcode:2014AJ....147...87T, doi:10.1088/0004-6256/147/4/87, 87.
  12. Mason, B. D.; et al. (2014), The Washington Visual Double Star Catalog, Bibcode:2001AJ....122.3466M, doi:10.1086/323920, retrieved 2015-11-02.
  13. The Range of Masses and Periods Explored by Radial Velocity Searches for Planetary Companions
  14. An unseen companion to 36 Ursae Majoris A from analysis of plates taken with the Sproul 61-CM refractor
  15. A search for substellar companions to southern solar-type stars
  16. Detection Limits from the McDonald Observatory Planet Search Program
  17. Eiroa, C.; et al. (July 2013). "DUst around NEarby Stars. The survey observational results". Astronomy & Astrophysics. 555: A11. arXiv:1305.0155. Bibcode:2013A&A...555A..11E. doi:10.1051/0004-6361/201321050.
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