33 Boötis
33 Boötis is a star with a brown dwarf companion in the northern constellation Boötes, located 190 light years away from the Sun. It is visible to the naked eye as a faint, white-hued star with an apparent visual magnitude of 5.39.[2] The object is moving closer to the Earth with a heliocentric radial velocity of −13 km/s,[2] and is catalogued as a member of the Pleiades supercluster.[9]
This is an ordinary A-type main-sequence star with a stellar classification of A1 V.[4] It is a source of X-ray emission, but early A-type stars are not expected to be X-ray sources, so this may indicate it has an undetected companion.[10] 33 Boötis is 142 million years old[7] with a projected rotational velocity of 86 km/s.[7] The star has 2.07 times the mass of the Sun,[5] 1.84 times the Sun's radius and is radiating 21.2 times the luminosity of the Sun from its photosphere[5] at an effective temperature of 9,224 K.[1]
33 Boötis is orbited by a brown dwarf with roughly 60 times the mass of Jupiter and 1.7 times the radius. It takes roughly 26 years to complete one highly-eccentric orbit, coming as close as 1.4 AU at periastron and as distant as 21 AU at apoastron.[a] The companion was detected in 2025 from observations with the Subaru and Keck telescopes, as well as Hipparcos and Gaia astrometry.[5]
Notes
- ^ Calculated using the equations a(1 + e) and a(1 − e) for apoastron and periastron, respectively, where a is the semi-major axis and e is the eccentricity.
References
- ^ a b c d e f g h i Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
- ^ a b c d e 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.
- ^ Zorec, J.; Royer, F. (2012). "Rotational velocities of A-type stars. IV. Evolution of rotational velocities". Astronomy and Astrophysics. 537: A120. arXiv:1201.2052. Bibcode:2012A&A...537A.120Z. doi:10.1051/0004-6361/201117691.
- ^ a b 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.
- ^ a b c d e f g h i j k l El Morsy, Mona; Currie, Thayne; et al. (December 2025). "OASIS Survey Direct Imaging and Astrometric Discovery of HIP 71618 B: A Substellar Companion Suitable for the Roman Coronagraph Technology Demonstration". The Astrophysical Journal Letters. arXiv:2512.02126.
- ^ Gebran, M.; et al. (May 2016), "A new method for the inversion of atmospheric parameters of A/Am stars", Astronomy & Astrophysics, 589: 10, arXiv:1603.01146, Bibcode:2016A&A...589A..83G, doi:10.1051/0004-6361/201528052, S2CID 118549566, A83.
- ^ a b c d David, Trevor J.; Hillenbrand, Lynne A. (2015), "The Ages of Early-Type Stars: Strömgren Photometric Methods Calibrated, Validated, Tested, and Applied to Hosts and Prospective Hosts of Directly Imaged Exoplanets", The Astrophysical Journal, 804 (2): 146, arXiv:1501.03154, Bibcode:2015ApJ...804..146D, doi:10.1088/0004-637X/804/2/146, S2CID 33401607.
- ^ "33 Boo". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved May 11, 2019.
- ^ Eggen, O. J. (December 1992), "The Kinematics of Young Disk Population Supercluster Members", Astronomical Journal, 104: 2141, Bibcode:1992AJ....104.2141E, doi:10.1086/116389.
- ^ De Rosa, R. J.; et al. (July 2011), "The Volume-limited A-Star (VAST) survey - I. Companions and the unexpected X-ray detection of B6-A7 stars", Monthly Notices of the Royal Astronomical Society, 415 (1): 854–866, arXiv:1103.4363, Bibcode:2011MNRAS.415..854D, doi:10.1111/j.1365-2966.2011.18765.x, S2CID 84181878.