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Star in the constellation Eridanus From Wikipedia, the free encyclopedia
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,[1] 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,[2] and is drifting further away with a radial velocity of 7 km/s.[5] It has a high proper motion, traversing the celestial sphere at an angular rate of 0.258 arcsec yr−1.[11] 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.[12]
Observation data Epoch J2000.0 Equinox J2000.0 | |
---|---|
Constellation | Eridanus[1] |
Right ascension | 03h 07m 18.575s[2] |
Declination | −13° 45′ 42.42″[2] |
Apparent magnitude (V) | 6.97[1] |
Characteristics | |
Evolutionary stage | main sequence[3] |
Spectral type | G3 V[4] + T5.5±1.0[3] |
B−V color index | 0.645±0.010[1] |
Astrometry | |
Radial velocity (Rv) | 6.953±0.0003[5] km/s |
Proper motion (μ) | RA: −8.694 mas/yr[2] Dec.: −260.642 mas/yr[2] |
Parallax (π) | 31.2191 ± 0.024 mas[2] |
Distance | 104.47 ± 0.08 ly (32.03 ± 0.02 pc) |
Absolute magnitude (MV) | 4.52[1] |
Orbit[6] | |
Primary | HD 19467 A |
Companion | HD 19467 B |
Period (P) | 398+95 −93 yr |
Semi-major axis (a) | 54±9 AU |
Eccentricity (e) | 0.56±0.09 |
Inclination (i) | 129.8+8.1 −5.1° |
Longitude of the node (Ω) | 134.8±4.5° |
Periastron epoch (T) | 2,512,264+12,428 −12,637 BJD |
Argument of periastron (ω) (secondary) | 64.2+5.5 −6.3° |
Details | |
HD 19467 A | |
Mass | 0.96±0.02[7] M☉ |
Radius | 1.20±0.03[7] R☉ |
Luminosity | 1.42±0.06[7] L☉ |
Surface gravity (log g) | 4.28±0.04[7] cgs |
Temperature | 5,747±40[7] K |
Metallicity [Fe/H] | −0.11±0.01[6] dex |
Rotation | 29.53±0.16 d[6] |
Rotational velocity (v sin i) | 1.6±0.5[6] km/s |
Age | 5.4+1.9 −1.3 Gyr[3] 10.06+1.16 −0.82[8] Gyr |
HD 19467 B | |
Mass | 65.4+5.9 −4.6[3] MJup |
Luminosity | (6.49±0.98)×10−6[8] L☉ |
Temperature | 978+20 −43[9] K |
Metallicity [Fe/H] | −0.15±0.02[8] dex |
Other designations | |
Database references | |
SIMBAD | data |
The spectrum of HD 19467 presents as a G-type main-sequence star with a stellar classification of G3 V.[4] It has been identified as a solar twin based on the similarity of its physical properties to the Sun.[13] This is an older star,[6] with age estimates range from 5.4[3] up to 10.1 billion years,[8] depending on the study. It is considered a thin disk star, which should theoretically limit the age to no more than 8 billion years.[6] The spin rate is correspondingly low with a rotation period of 29.5 days.[6] Based on the abundance of iron, the metallicity is lower than solar.[14][6] 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.[3]
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.[15]
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.[9] 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.[3]
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