HD 174881
Binary star in the constellation Lyra
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HD 174881 is a binary star located in the northern constellation of Lyra, the lyre. This system has an apparent visual magnitude of +6.209,[3] making it faintly visible to the naked eye only in very dark skies, with no light pollution. Based on dynamical parallax measurements inferred from the binary's orbit, it is about 1,300 light-years distant. At that distance, the apparent magnitude is diminished by 0.22 magnitudes due to extinction by gas and dust between Earth and HD 174881.[4]
 | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Lyra[1] |
| Right ascension | 18h 51m 35.8920s[2] |
| Declination | +28° 47′ 01.219″[2] |
| Apparent magnitude (V) | +6.209[3] |
| Characteristics | |
| Evolutionary stage | red giant branch (A) red clump (B)[4] |
| Spectral type | K1II-III[4] |
| Astrometry | |
| Radial velocity (Rv) | −19.101+0.034 −0.043[4] km/s |
| Proper motion (μ) | RA: +1.649 mas/yr[2] Dec.: +4.811 mas/yr[2] |
| Parallax (π) | 2.525+0.014 −0.015 mas[4] |
| Distance | 1,290+7.8 −7.2 ly (396.0+2.4 −2.2 pc)[4] |
| Absolute magnitude (MV) | −1.462±0.065 (A)[4] −1.042±0.066 (B)[4] |
| Orbit[4] | |
| Primary | A |
| Name | B |
| Period (P) | 215.1166+0.0092 −0.0072 days |
| Semi-major axis (a) | 1.3336+0.0060 −0.0051 AU |
| Eccentricity (e) | 0.12162+0.00063 −0.00064 |
| Inclination (i) | 38.73±0.17° |
| Longitude of the node (Ω) | 263.65±0.15° |
| Argument of periastron (ω) (primary) | 101.98+0.36 −0.34° |
| Semi-amplitude (K1) (primary) | 21.594±0.053 km/s |
| Semi-amplitude (K2) (secondary) | 20.924+0.062 −0.057 km/s |
| Details[4] | |
| A | |
| Mass | 3.367+0.045 −0.041 M☉ |
| Radius | 34.0±1.3 R☉ |
| Luminosity | 456 L☉ |
| Surface gravity (log g) | 1.903±0.033 cgs |
| Temperature | 4,620±150 K |
| Age | 255–273 Myr |
| B | |
| Mass | 3.476±0.043 M☉ |
| Radius | 22.7±1.8 R☉ |
| Luminosity | 250 L☉ |
| Surface gravity (log g) | 2.262+0.075 −0.059 cgs |
| Temperature | 4,880±150 K |
| Age | 255–273 Myr |
| Other designations | |
| BD+28 3104, HD 174881, HIP 92550, HR 7112, SAO 86512 | |
| Database references | |
| SIMBAD | data |
This binary system is composed of two evolved giant stars that exhausted their hydrogen supply at their core and expanded in size. They complete an orbit around each other every 215 days (7.1 months), and are separated by 1.3 astronomical units. The orbit is close to circular, with a low eccentricity of 0.12. The primary and secondary star are over three times more massive than the Sun, with radii 34 and 23 times higher, respectively, and luminosities 460 and 250 times solar. Their effective temperatures are 4,620 and 4,880 K,[4] giving them an orange hue typical of K-type stars.[5] The age of the system is estimated at 250 million years.[4]
HD 174881 was first detected as a binary in 1995 by spectroscopic observations. Subsequently, observations have been made that significantly improved the orbit and spatially resolved the binary for the first time, as well as providing valuable tests of stellar evolution in evolved stars.[4]
There is evidence of an infrared excess around this system, suggesting it is surrounded by cold dust with temperatures between 15 and 20 K. This could also explain the observed extinction.[4]