HD 19467 is a star with an orbiting brown dwarf companion in the equatorial constellation of Eridanus. It has an apparent visual magnitude of 6.97, which is a challenge to view with the naked eye. The system is located at a distance of 104.5 light years based on parallax measurements, and is drifting further away with a radial velocity of 7 km/s. It has a high proper motion, traversing the celestial sphere at an angular rate of 0.258 arcsec yr−1. Based on the motion and chemical abundances of this star it has been considered a likely member of the Wolf 630 group of co-moving stars, although its age estimate is inconsistent with that assignment.

The spectrum of HD 19467 presents as a G-type main-sequence star with a stellar classification of G3 V. It has been identified as a solar twin based on the similarity of its physical properties to the Sun. This is an older star, with age estimates range from 5.4 up to 10.1 billion years, depending on the study. It is considered a thin disk star, which should theoretically limit the age to no more than 8 billion years. The spin rate is correspondingly low with a rotation period of 29.5 days. Based on the abundance of iron, the metallicity is lower than solar. The level of magnetic activity in the star's chromosphere as well as X-ray emission are at most below the equivalent level in the Sun.

Brown dwarf

In 2014, a survey team announced the discovery of a brown dwarf in orbit around HD 19467. The presence of an low-mass companion was indicated via an acceleration trend in radial velocity time series data collected between 1996 and 2021. The object was then directly imaged using the NIRC-2 instrument at the Keck Observatory. Designated HD 19467 B, it was located at an angular separation of 1.6″ from the host star. Astrometric observations taken over a 1.1 year period demonstrated that the object is clearly associated with HD 19467 A, having a similar parallax and proper motion. The radial velocity data indicated a minimum mass of 51.9+3.6 −4.3 MJ, with a brightness and colors matching a T-dwarf.

The spectrum of this object was taken at the Palomar Observatory, finding a spectral type of T5.5±1. It was measured as having an effective temperature of 978 K and, like the host star, a sub-solar metallicity. Orbital analysis was used to infer a mass of 65.4 MJ, which is near the substellar mass boundary. It has a highly eccentric orbit with period estimates ranging from 320 to 420 years, depending on the study.

See also

  • Scholz's Star – a star with a brown dwarf companion of similar mass to HD 19467 B

Further reading

  • Mesa, D.; et al. (July 2020), "Characterizing brown dwarf companions with IRDIS long-slit spectroscopy: HD 1160 B and HD 19467 B", Monthly Notices of the Royal Astronomical Society, 495 (4): 4279–4290, arXiv:, Bibcode:, doi:.
  • Wood, Charlotte; et al. (January 2018), "Precise Ages for the Benchmark Brown Dwarfs HD 19467 B and HD 4747 B", American Astronomical Society, AAS Meeting #231, 231, id. 450.05, Bibcode:.
  • Jensen-Clem, Rebecca; et al. (April 2016), "Point Source Polarimetry with the Gemini Planet Imager: Sensitivity Characterization with T5.5 Dwarf Companion HD 19467 B", The Astrophysical Journal, 820 (2), id. 111, arXiv:, Bibcode:, doi:.