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  • 21 Aug, 2019

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HD 114762
HD 114762 is a triple star system approximately 125 light-years (38.2 pc) away in the constellation Coma Berenices. It consists of a yellow-white F-type main-sequence star (HD 114762 A) and two red dwarf companions (HD 114762 Ab & HD 114762 B) approximately 0.36 & 130 AU distant. Both are low-metal subdwarfs. Planets around such metal-poor stars are rare (three known cases are HD 22781, HD 111232, and HD 181720). A telescope or strong binoculars are needed to view the primary. HD 114762 had been used by scientists as a "standard star", one whose radial velocity is well established, but with the discovery of the spectroscopic companion HD 114762 Ab its usefulness as a standard has been called into question.

The red dwarf companion is classified as an ultra-cool dwarf, with a spectral type around M9. With a visual magnitude of 15 and separated from the primary by only three arcseconds, it can only be seen with a powerful telescope. It is estimated to be around 10 billion years old, although the properties of such low-mass stars are very similar across a wide range of ages. It is calculated have only 8% of the mass of the Sun, a tenth of its radius, and with a temperature of about 2,645 K it produces less than a thousandth of its luminosity.

Spectroscopic companion

Main article: HD 114762 b

In 1989, a companion object, HD 114762 Ab, was found orbiting HD 114762 A by Latham, et al., using Doppler spectroscopy, but its existence was not confirmed until 1991 by Cochran, et al. Its orbital distance and revolution is similar to that of Mercury, though it has twice the eccentricity. It has a minimum mass of 10.69 MJ, and thus was originally thought to be a massive exoplanet; however, in 2019, its inclination was determined by Gaia astrometry, giving it a true mass of 107 MJ. This makes it a red dwarf star, or a massive brown dwarf. A 2020 study provided further confirmation of this, and revised the mass upwards to 147 MJ, and in 2022 this mass was revised upwards still further, to 0.293 M☉, based on Gaia DR3 data and a similar upwards revision to the mass of the primary star.

References

  1. ^ 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.
  2. ^ Kane, Stephen R.; et al. (2011). "Revised Orbit and Transit Exclusion for HD 114762b". The Astrophysical Journal Letters. 735 (2). L41. arXiv:1106.1434. Bibcode:2011ApJ...735L..41K. doi:10.1088/2041-8205/735/2/L41. S2CID 118409104.
  3. ^ Patience, J.; White, R. J.; Ghez, A. M.; McCabe, C.; McLean, I. S.; et al. (December 2002). "Stellar Companions to Stars with Planets". The Astrophysical Journal. 581 (1): 654–665. arXiv:astro-ph/0207538. Bibcode:2002ApJ...581..654P. doi:10.1086/342982. S2CID 119519887.
  4. ^ Kiefer, Flavien (17 October 2019). "Determining the mass of the planetary candidate HD 114762 b using Gaia". Astronomy & Astrophysics. 632: L9. arXiv:1910.07835. Bibcode:2019A&A...632L...9K. doi:10.1051/0004-6361/201936942. S2CID 204743831.
  5. ^ Bowler, Brendan P.; Liu, Michael C.; Cushing, Michael C. (2009). "The Benchmark Ultracool Subdwarf HD 114762B: A Test of Low-metallicity Atmospheric and Evolutionary Models". The Astrophysical Journal. 706 (2): 1114. arXiv:0910.1604. Bibcode:2009ApJ...706.1114B. doi:10.1088/0004-637X/706/2/1114. S2CID 119112746.
  6. ^ Winn, Joshua N. (September 2022). "Joint Constraints on Exoplanetary Orbits from Gaia DR3 and Doppler Data". The Astronomical Journal. 164 (5): 196. arXiv:2209.05516. Bibcode:2022AJ....164..196W. doi:10.3847/1538-3881/ac9126. S2CID 252211643.
  7. ^ Kiefer, F.; et al. (January 2021). "Determining the true mass of radial-velocity exoplanets with Gaia. Nine planet candidates in the brown dwarf or stellar regime and 27 confirmed planets". Astronomy & Astrophysics. 645 A7. arXiv:2009.14164. Bibcode:2021A&A...645A...7K. doi:10.1051/0004-6361/202039168. S2CID 221995447.
  8. ^ "HD 114762". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-01-16.
  9. ^ Adibekyan, Vardan (2019), "Heavy Metal Rules. I. Exoplanet Incidence and Metallicity", Geosciences, 9 (3): 105, arXiv:1902.04493, Bibcode:2019Geosc...9..105A, doi:10.3390/geosciences9030105, S2CID 119089419
  10. ^ Maugh II, Thomas H. (4 August 1988). "Other Planets, Other Suns: Astronomers Say Star's Wobble Tells a Story". Los Angeles Times. Retrieved 7 September 2014.
  11. ^ Latham, David W.; Mazeh, Tsevi; Stefanik, Robert P.; Mayor, Michel; Burki, Gilbert (May 1989). "The unseen companion of HD114762 - A probable brown dwarf". Nature. 339 (6219): 38–40. Bibcode:1989Natur.339...38L. doi:10.1038/339038a0. S2CID 4324036.
  12. ^ Cochran, William D.; Hatzes, Artie P.; Hancock, Terry J. (10 October 1991). "Constraints on the Companion Object to HD 114762". The Astrophysical Journal. 380: L35–L38. Bibcode:1991ApJ...380L..35C. doi:10.1086/186167.


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