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HD 195019 is a binary star system in the northern constellation of Delphinus. The brighter star has a close orbiting exoplanet companion. This system is located at a distance of 122 light years from the Sun based on parallax measurements,[1] but it is drifting closer with a radial velocity of −91.3 km/s.[6] Although it has an absolute magnitude of 4.01,[5] at that distance the system is considered too faint to be viewed with the naked eye, having a combined apparent visual magnitude of 6.87.[5] However, it should be readily visible with a pair of binoculars or a small telescope.[13]
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Delphinus |
| Right ascension | 20h 28m 18.6367s[1] |
| Declination | +18° 46′ 10.180″[1] |
| Apparent magnitude (V) | 6.97 + 10.60[2] |
| Characteristics | |
| Spectral type | G1V[3] + K3:[4] |
| B−V color index | 0.662±0.007[5] |
| Astrometry | |
| Radial velocity (Rv) | −91.290±0.0039[6] km/s |
| Proper motion (μ) | RA: 349.620(16) mas/yr[1] Dec.: −56.618(19) mas/yr[1] |
| Parallax (π) | 26.6465 ± 0.0225 mas[1] |
| Distance | 122.4 ± 0.1 ly (37.53 ± 0.03 pc) |
| Absolute magnitude (MV) | 4.01[5] |
| Details[7] | |
| HD 195019 A | |
| Mass | 1.08±0.01[8] M☉ |
| Radius | 1.47±0.04[8] R☉ |
| Luminosity | 2.23±0.02[8] L☉ |
| Surface gravity (log g) | 4.13±0.02[8] cgs |
| Temperature | 5,825±56[8] K |
| Metallicity [Fe/H] | 0.068±0.030[9] dex |
| Rotational velocity (v sin i) | 2.47±0.50[9] km/s |
| Age | 7.7±0.7[8] Gyr |
| HD 195019 B | |
| Mass | 0.7[10] M☉ |
| Surface gravity (log g) | 4.46[11] cgs |
| Temperature | 4,652[11] K |
| Rotational velocity (v sin i) | 1.71[11] km/s |
| Other designations | |
| Database references | |
| SIMBAD | data |
The spectrum of the primary member, designated component A, presents as a G-type main-sequence star with a stellar classification of G1V.[3] An older stellar classification of G3 V/IV[14] suggested it may be near the end of its main sequence lifespan and is evolving into a subgiant star.[13] This is an older star with an estimated age of nearly 8[8] billion years and a low level of magnetic activity in its chromosphere.[8] The abundance of iron is near solar.[9] The star has a mass similar to the Sun but a larger radius. It is radiating 2.23 times the luminosity of the Sun from its photosphere at an effective temperature of 5,825 K.[8]
The co-moving companion, component B, was first reported by G. W. Hough in 1881. As of 2016, it is located at an angular separation of 3.40″ along a position angle of 334° relative to the primary.[2] This corresponds to a projected separation of 131 AU. This is a K-type star with 70% of the mass of the Sun[10] and is magnitude 10.60.[2]
In 1998, a planet was discovered at Lick Observatory utilizing a radial velocity method, orbiting around Star HD 195019 A.[14] A search of astrometric observations from Hipparcos suggested this may be a stellar object in a near polar orbit.[15][16][13] However, interferometric observations ruled out a stellar companion in this orbit with high likelihood.[17]
| Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (days) |
Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| b | >3.69 ± 0.30 MJ | 0.1388 ± 0.0080 | 18.20132 ± 0.00039 | 0.0138 ± 0.0044 | — | — |
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