HD 76920

HD 76920
Location of HD 76920 (circled)
Observation data
Epoch J2000.0[1]      Equinox J2000.0[1]
Constellation Volans
Right ascension 08h 55m 16.81719s
Declination −67° 15′ 55.7009″
Apparent magnitude (V) 7.82[2]
Characteristics
Evolutionary stage Red-giant branch star[3]
Spectral type K1 III[3]
B−V color index 1.11[2]
J−H color index 0.537[4]
J−K color index 0.693[4]
Astrometry
Radial velocity (Rv)20.09 ± 0.14[5] km/s
Proper motion (μ) RA: 25.253[6] mas/yr
Dec.: 25.659[6] mas/yr
Parallax (π)5.4618 ± 0.0187 mas[6]
Distance597 ± 2 ly
(183.1 ± 0.6 pc)
Details[3]
Mass1.22±0.11 M☉
Radius8.68±0.34 R☉
Luminosity29.5+1.3
−1.0[7] L☉
Surface gravity (log g)2.648±0.037 cgs
Temperature4664±53 K
Metallicity [Fe/H]−0.19±0.06 dex
Rotational velocity (v sin i)2.5±0.3[7] km/s
Age5.2±1.4 Gyr
Other designations
CD−66° 659, CPD−66° 943, Gaia DR2 5224124307320401024, HD 76920, HIP 43803, SAO 250379, PPM 357010, TIC 302372658, TYC 8939-1192-1, GSC 08939-01192, 2MASS J08551682-6715555[1]
Database references
SIMBADdata

HD 76920 is a solitary[8] orange-hued star with an orbiting exoplanetary companion in the southern constellation of Volans, close to the border with Carina. With an apparent magnitude of 7.82, it is too faint to be seen by the naked eye from Earth but is readily observable through binoculars.[9] It is located at a distance of 597 light-years (183 parsecs) according to Gaia EDR3 parallax measurements, and is moving away at a heliocentric radial velocity of 20.09 km/s.

Stellar properties

This is an aging giant star with a stellar classification of K1 III. At the age of 5.2±1.4 billion years, it has evolved past the main sequence after depleting its hydrogen supply at the core. It is currently in the midst of ascending the red-giant branch (RGB), fast approaching the RGB bump, where deep stellar convection temporarily stalls the ascent. As expected of RGB stars, it exhibits solar-like oscillations. It has 1.22 times the mass of the Sun but has expanded to 8.68 times the Sun's radius.[3] The star is radiating 29.5 times the luminosity of the Sun from its inflated photosphere at an effective temperature of 4,664 K (4,391 °C; 7,936 °F).[7]

Planetary system

In 2017, radial-velocity observations made using spectrographs at the Anglo-Australian Telescope, the Cerro Tololo Inter-American Observatory, and the MPG/ESO telescope revealed the existence of an exoplanet around HD 76920.[8] The planet, HD 76920 b, is an eccentric Jupiter with a minimum mass of 3.57 MJ[3] and a very high orbital eccentricity of 0.8782,[7] which at the time of discovery made it the most eccentric known planet orbiting an evolved star. Since the host star appears to be single, this was likely caused by a scattering event rather than Kozai oscillations.[8]

Because of its high eccentricity, despite an Earth-like semi-major axis of 1.165 AU and a period of 415.891 days (1.13865 years), the planet approaches the star to within 2.4 stellar radii at its perihelion.[7] This is currently not causing any substantial orbital decay; thus the planet is expected to survive for the next 50–80 million years without falling into the star.[7] However, after about 100 million years, stellar evolution and tidal interactions will doom it to be engulfed.[3]

The planet has a relatively high probability (16%) to transit its host star, but such a transit has yet to be detected by TESS.[7]

The HD 76920 planetary system[3]
Companion
(in order from star) 		Mass Semimajor axis
(AU) 		Orbital period
(days) 		Eccentricity Inclination Radius
b ≥ 3.57 ± 0.22 MJ 1.165 ± 0.035 415.891 +0.043
−0.039[7] 		0.8782 ± 0.0025[7] — 1.17[10] RJ

See also

References

  1. ^ a b "HD 76920". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 23 December 2024.
  2. ^ a b Høg, E.; Fabricius, C.; Makarov, V. V.; et al. (February 2000). "The Tycho-2 Catalogue of the 2.5 Million Brightest Stars". Astronomy and Astrophysics. 355 (1): L27 – L30. Bibcode:2000A&A...355L..27H.
  3. ^ a b c d e f g Jiang, Chen; Wu, Tao; Feinstein, Adina D.; et al. (1 March 2023). "TESS Asteroseismic Analysis of HD 76920: The Giant Star Hosting an Extremely Eccentric Exoplanet". The Astrophysical Journal. 945 (1): 20. arXiv:2302.01102. Bibcode:2023ApJ...945...20J. doi:10.3847/1538-4357/acb8ac. ISSN 0004-637X.
  4. ^ a b Cutri, Roc M.; Skrutskie, Michael F.; Van Dyk, Schuyler D.; et al. (2003). "VizieR Online Data Catalog: 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)". CDS/ADC Collection of Electronic Catalogues. 2246: II/246. Bibcode:2003yCat.2246....0C.
  5. ^ 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.
  6. ^ a b c Brown, A. G. A.; et al. (Gaia collaboration) (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics. 649: A1. arXiv:2012.01533. Bibcode:2021A&A...649A...1G. doi:10.1051/0004-6361/202039657. S2CID 227254300. (Erratum: doi:10.1051/0004-6361/202039657e). Gaia EDR3 record for this source at VizieR.
  7. ^ a b c d e f g h i Bergmann, C.; Jones, M. I.; Zhao, J.; et al. (2021). "HD 76920 b pinned down: A detailed analysis of the most eccentric planetary system around an evolved star". Publications of the Astronomical Society of Australia. 38. arXiv:2102.08902. Bibcode:2021PASA...38...19B. doi:10.1017/pasa.2021.8. ISSN 1323-3580.
  8. ^ a b c Wittenmyer, Robert A.; Jones, M. I.; Horner, Jonathan; et al. (1 December 2017). "The Pan-Pacific Planet Search. VII. The Most Eccentric Planet Orbiting a Giant Star". The Astronomical Journal. 154 (6): 274. arXiv:1711.05378. Bibcode:2017AJ....154..274W. doi:10.3847/1538-3881/aa9894. ISSN 0004-6256.
  9. ^ Zarenski, Ed (2004). "Limiting Magnitude in Binoculars" (PDF). Cloudy Nights. Archived (PDF) from the original on 21 July 2011. Retrieved 6 May 2011.
  10. ^ "HD 76920 b - NASA Science". Retrieved 23 December 2024.