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HD 109271 is a wide binary star system in the constellation of Virgo. The brighter member of the binary has a pair of orbiting exoplanets. With an apparent visual magnitude of 8.05,[2] it cannot be seen with the naked eye. Parallax measurements made by Gaia put the star at a distance of 181 light-years (55 parsecs) away from the Sun, but it is drifting closer with a radial velocity of −5 km/s.[4] The system shows a high proper motion, traversing the celestial sphere at an angular rate of 0.232 arcsec yr−1.[7]
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Virgo |
| Right ascension | 12h 33m 35.555s[1] |
| Declination | −11° 37′ 18.73″[1] |
| Apparent magnitude (V) | 8.05 ± 0.01[2] |
| Characteristics | |
| Spectral type | G5 V[2] + DA[3] |
| B−V color index | +0.658±0.002[2] |
| Astrometry | |
| Radial velocity (Rv) | −4.971±0.0011[4] km/s |
| Proper motion (μ) | RA: −169.971 mas/yr[1] Dec.: 81.000 mas/yr[1] |
| Parallax (π) | 17.9082 ± 0.0379 mas[1] |
| Distance | 182.1 ± 0.4 ly (55.8 ± 0.1 pc) |
| Absolute magnitude (MV) | 4.1±0.1[2] |
| Position (relative to HD 109271 A)[3] | |
| Component | HD 109271 B |
| Epoch of observation | 2018 |
| Angular distance | 5.425″ |
| Position angle | 267.354° |
| Projected separation | 304 AU |
| Details[2] | |
| HD 109271 A | |
| Mass | 1.047±0.024 M☉ |
| Radius | 1.295+0.023 −0.020[5] R☉ |
| Luminosity | 1.649±0.008[5] L☉ |
| Surface gravity (log g) | 4.28±0.10 cgs |
| Temperature | 5,783±62 K |
| Metallicity [Fe/H] | 0.10±0.05 dex |
| Rotational velocity (v sin i) | 2.7 km/s |
| Age | 7.3±1.2 Gyr |
| HD 109271 B | |
| Mass | ~0.6[3] M☉ |
| Other designations | |
| Database references | |
| SIMBAD | data |
| Exoplanet Archive | data |
The primary component is an ordinary G-type main-sequence star with a stellar classification of G5 V. It is a much older star than the Sun with an age of about 7.3 billion years, and is spinning with a projected rotational velocity of 2.7 km/s.[2] This star has 7% more mass than the Sun and a 30% greater girth.[5] The abundance of iron, a measure of the star's metallicity, is similar but slightly higher than in the Sun.[2] It is radiating 1.65[5] times the luminosity of the Sun from its photosphere at an effective temperature of around 5,783 K.[2]
In 2020, a white dwarf companion of 0.6 M☉ was found orbiting the primary at an angular separation of 5.4″ along a position angle of 267°. At the distance of this system, this corresponds to a projected separation of 304 AU. That is, they are physically separated by at least this distance. Additional stellar companions are ruled out down to a separation of 0.15″ from the primary.[3]
From 2003 to 2012, the star was under observance from the High Accuracy Radial Velocity Planet Searcher (HARPS).[2] In 2012, two eccentric hot Neptune-mass planets were deduced by radial velocity. They were published in January 2013. These are close to a 1:4 resonance, so the system is similar to HD 69830. A third Neptune in the Venus zone was hypothesised from the data. These planets managed to survive the post main-sequence epoch of the companion star, when it shed much of its original mass.[3]
| Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (days) |
Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| b | >0.054 ± 0.004 MJ | 0.079 ± 0.001 | 7.8543 ± 0.0009 | 0.25 ± 0.08 | — | — |
| c | >0.076 ± 0.007 MJ | 0.196 ± 0.003 | 30.93 ± 0.02 | 0.15 ± 0.09 | — | — |
| d (unconfirmed) | >1.3 neptune MJ | 1 | 430 | 0.36 | — | — |
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