HD 38529
Binary star system in the constellation Orion
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HD 38529 (138 G. Orionis)[13] is a binary star system approximately 138 light-years away in the constellation of Orion.
 | |
| Observation data Epoch J2000.0 Equinox ICRS | |
|---|---|
| Constellation | Orion[1] |
| HD 38529 A | |
| Right ascension | 05h 46m 34.91314s[2] |
| Declination | +01° 10′ 05.5029″[2] |
| Apparent magnitude (V) | +5.95[3] |
| HD 38529 B | |
| Right ascension | 05h 46m 19.37663s[4] |
| Declination | +01° 12′ 47.2640″[4] |
| Apparent magnitude (V) | +13.35[5] |
| Characteristics | |
| HD 38529 A | |
| Evolutionary stage | subgiant[2] |
| Spectral type | G4IV[3] |
| B−V color index | 0.773[3] |
| HD 38529 B | |
| Evolutionary stage | main sequence[6] |
| Spectral type | M3.0V[5] |
| Astrometry | |
| HD 38529 A | |
| Radial velocity (Rv) | 30.19±0.12[2] km/s |
| Proper motion (μ) | RA: −77.806 mas/yr[2] Dec.: −141.363 mas/yr[2] |
| Parallax (π) | 23.5714±0.0422 mas[2] |
| Distance | 138.4 ± 0.2 ly (42.42 ± 0.08 pc) |
| Absolute magnitude (MV) | +2.81[3] |
| HD 38529 B | |
| Radial velocity (Rv) | 30.94±0.43[4] km/s |
| Proper motion (μ) | RA: −78.612 mas/yr[4] Dec.: −142.084 mas/yr[4] |
| Parallax (π) | 23.7139±0.0168 mas[4] |
| Distance | 137.54 ± 0.10 ly (42.17 ± 0.03 pc) |
| Absolute magnitude (MV) | +10.23[citation needed] |
| Details | |
| HD 38529 A | |
| Mass | 1.479±0.037[7] M☉ |
| Radius | 2.678±0.026[7] R☉ |
| Luminosity | 6.16±0.15[7] L☉ |
| Surface gravity (log g) | 3.83±0.06[8] cgs |
| Temperature | 5619±44[8] K |
| Metallicity [Fe/H] | 0.38±0.03[8] dex |
| Rotation | 37.0±0.4 d[8] |
| Rotational velocity (v sin i) | 3.20±0.50[8] km/s |
| Age | 3.07±0.39[7] Gyr |
| HD 38529 B | |
| Mass | 0.494[9] M☉ |
| Radius | 0.496[9] R☉ |
| Luminosity | 0.033[9] L☉ |
| Surface gravity (log g) | 4.74[9] cgs |
| Temperature | 3,487[9] K |
| Metallicity [Fe/H] | 0.39[6] dex |
| Rotational velocity (v sin i) | 17[6] km/s |
| Other designations | |
| RAG 1, WDS J05466+0110AB[10] | |
| HD 38529 A: BD+01°1126, HIP 27253, HR 1988, WDS J05466+0110A[11] | |
| HD 38529 B: WDS J05466+0110B, LP 598-99, 2MASS J05461937+0112471[12] | |
| Database references | |
| SIMBAD | A |
| B | |
| Exoplanet Archive | data |
HD 38529 A
HD 38529 A is a yellow subgiant star of spectral type G4IV,[14] though it has also been classified as a main sequence dwarf of type G4V[5] and a borderline giant star of type G8III/IV.[15] It is about 48% more massive than the Sun.[7]
Two substellar companions are known in orbit around this star, including one with a mass near the deuterium fusion limit that is often used as the dividing line between giant planets and brown dwarfs. There is a debris disk located at least 86 astronomical units from the star.[16] Its orbit is probably mildly misaligned with the planetary orbits, by 21−45°.[17]
Planetary system
In 2001, the planet HD 38529 b was discovered orbiting the star HD 38529 A by Debra Fischer and collaborators who detected it using the Doppler spectroscopy technique.[14] It has a mass at least 78% that of Jupiter and orbits very close to the star, just beyond the distance limit for hot Jupiters. It does not transit the star.[8]
In 2003, a massive superjovian HD 38529 c was found orbiting at 3.68 AU with a minimum mass of 12.7 Jupiter masses.[3] Astrometric measurements from the Hipparcos satellite gave a best fit inclination of 160° and a true mass 37 times that of Jupiter, turning this planet into a brown dwarf.[18]
Further study of the system using Hubble Space Telescope astrometry revised the mass of HD 38529 c downwards to 17.7 Jupiter masses and suggested the presence of an additional planet, orbiting in the gap between HD 38529 b and c.[19] The possible third planet was refuted after additional radial velocity measurements were collected.[8] Subsequent astrometric studies have found masses for HD 38529 c ranging from just 10.4 MJ[20] to 18 MJ,[17] with the most recent value as of 2025 being 12.9 MJ.[21]
| Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (days) |
Eccentricity | Inclination (°) |
Radius |
|---|---|---|---|---|---|---|
| b | ≥0.8047±0.0139 MJ | 0.1278±0.0006 | 14.30978±0.00033 | 0.259±0.016 | — | — |
| c | 12.93+0.70 −0.49 MJ |
3.604+0.043 −0.042 |
2127.8+3.3 −3.2 |
0.3507+0.0057 −0.0051 |
104.2+8.9 −11 |
— |
| Debris disk | 46+38 −27–208±54 AU |
71+10 −7° |
— | |||
HD 38529 B
HD 38529 B is a common proper motion stellar companion to HD 38529 A at a projected distance of about ~12000 astronomical units. The star is a red dwarf of spectral type M3.0V.[5] Wide binary stars such as HD 38529 AB have been shown to be vulnerable to disruption by galactic tides and perturbations by passing stars.[22]