HP Draconis
Binary star in the constellation Draco
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HP Draconis is a binary star system in the constellation of Draco. At an apparent magnitude of +7.974, it is not visible to the naked eye. Parallax measurements give a distance of 259 light-years (79 parsecs).
(8.234 (primary eclipse), 8.204 (secondary eclipse))[4]
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Draco[2] |
| Right ascension | 18h 54m 53.4810s[3] |
| Declination | +51° 18′ 29.792″[3] |
| Apparent magnitude (V) | 7.974[4] (8.234 (primary eclipse), 8.204 (secondary eclipse))[4] |
| Characteristics | |
| Evolutionary stage | Main sequence + main sequence[4] |
| Spectral type | F9V + F9V[2] |
| Variable type | Eclipsing binary[5] |
| Astrometry | |
| Radial velocity (Rv) | −16.07±0.63[6] km/s |
| Proper motion (μ) | RA: +23.234 mas/yr[3] Dec.: +83.306 mas/yr[3] |
| Parallax (π) | 12.6153±0.0516 mas[3] |
| Distance | 259 ± 1 ly (79.3 ± 0.3 pc) |
| Absolute magnitude (MV) | 3.46±0.08[4] |
| Orbit[5] | |
| Period (P) | 10.76154±0.00009[6] days |
| Semi-major axis (a) | 26.814±0.017 R☉ |
| Eccentricity (e) | 0.03647±0.00011 |
| Inclination (i) | 87.5554±0.0060° |
| Argument of periastron (ω) (primary) | 41.38±0.19° |
| Semi-amplitude (K1) (primary) | 61.971±0.056 km/s |
| Semi-amplitude (K2) (secondary) | 64.067±0.060 km/s |
| Details[5] | |
| HP Draconis A | |
| Mass | 1.1354±0.0023 M☉ |
| Radius | 1.2474±0.0046 R☉ |
| Luminosity | 1.82+0.19 −0.17 L☉ |
| Surface gravity (log g) | 4.3012±0.0032 cgs |
| Temperature | 6,000±150 K |
| Rotational velocity (v sin i) | 5.864±0.021 km/s |
| Age | 3.5 Gyr |
| HP Draconis B | |
| Mass | 1.0984±0.0022 M☉ |
| Radius | 1.1498±0.0049 R☉ |
| Luminosity | 1.48+0.12 −0.11 L☉ |
| Surface gravity (log g) | 4.3376±0.0037 cgs |
| Temperature | 5,935±150 K |
| Rotational velocity (v sin i) | 5.406±0.023 km/s |
| Age | 3.5 Gyr |
| Other designations | |
| BD+51°2459, HD 175900, HIP 92835, TYC 3552-394-1[7] | |
| Database references | |
| SIMBAD | data |
Characteristics
This is an eclipsing binary system whose components are detached.[5] Each 10.76 days (the orbital period of the system),[8] the apparent magnitude of the system drops to 0.26 in the primary (deeper) eclipse and to 0.23 in the secondary eclipse.[4] The variability of this system was discovered in 1997 by the Hipparcos satellite, and it was given its variable-star designation HP Draconis in 1999.[5]
The components of this binary system are separated by 26.814 solar radii (18,654,000 km; 0.12470 au) with an eccentricity of 0.036.[5] Both are F-type main-sequence stars with identical stellar classifications of F9V.[2] Star A has 1.135 times the mass, 1.247 times the radius, and 1.8 times the luminosity of the Sun, while star B has 1.098 times the mass, 1.15 times the radius, and 1.48 times the Sun's luminosity. The effective temperatures are 6,000 and 5,935 K,[5] giving them the yellow-white hue typical of late-type F-type stars.[9] The estimated age of the system is 3.5 billion years. There is evidence of a third component in the system from eclipse timing variations.[5]
HP Draconis makes a wide triple system with a white dwarf that has a projected separation of 1,140 astronomical units, giving an estimated orbital period of 23,000 years. This companion has 0.45 times the Sun's mass, a temperature of 7,087±205 K and has been a white dwarf for an estimated 1.15 billion years.[10]