16 Lyrae
Astrometric binary star system in the constellation Lyra
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16 Lyrae is a suspected astrometric binary[9] star system in the constellation Lyra,[8] located 126 light years away from the Sun based on parallax.[1] It is visible to the naked eye as a dim, white-hued star with a combined apparent visual magnitude of 5.00.[2] The system is moving further away from the Earth with a heliocentric radial velocity of +4.36 km/s.[1] It is a suspected member of the Ursa Major Moving Group stream.[10]
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Lyra |
| Right ascension | 19h 01m 26.38262s[1] |
| Declination | +46° 56′ 05.1475″[1] |
| Apparent magnitude (V) | 5.00[2] |
| Characteristics | |
| Evolutionary stage | main sequence[3] |
| Spectral type | A6 IV[4] or A7 V[5] |
| B−V color index | +0.186±0.005[2] |
| Astrometry | |
| Radial velocity (Rv) | +4.36±0.21[1] km/s |
| Proper motion (μ) | RA: +22.004 mas/yr[1] Dec.: −80.894 mas/yr[1] |
| Parallax (π) | 25.7832±0.0688 mas[1] |
| Distance | 126.5 ± 0.3 ly (38.8 ± 0.1 pc) |
| Absolute magnitude (MV) | +2.13[2] |
| Details[6] | |
| Mass | 1.722±0.013 M☉ |
| Radius | 1.644+0.025 −0.023 (equatorial) 1.622+0.023 −0.022 (polar) R☉ |
| Luminosity | 10.45+0.30 −0.28 L☉ |
| Surface gravity (log g) | 4.28[7] cgs |
| Temperature | 8,028 (equator) 8,242 (polar) K |
| Rotational velocity (v sin i) | 85.1+16.3 −31.6 km/s |
| Age | 401+31 −32 Myr |
| Other designations | |
| 16 Lyr, NSV 11677, BD+46°2602, HD 177196, HIP 93408, HR 7215, SAO 48011, WDS J19014+4656A, GSC 03545-03041[8] | |
| Database references | |
| SIMBAD | data |
Cowley et al. (1969) found a stellar classification of A7 V[5] for the visible component, matching an A-type main-sequence star that is generating energy through hydrogen fusion at its core. Abt and Morrell (1995) instead listed a class of A6 IV,[4] suggesting it has left the main sequence and become a subgiant star.
16 Lyrae is 72% more massive than the Sun and irradiates 10.5 times the Sun's luminosity. It is 401 million years old with a high rate of spin, showing a projected rotational velocity of 85 km/s. The fast rotation make this star slightly oblate, with an equatorial radius of 1.644 R☉ and a polar radius of 1.622 R☉. Its effective temperature also vary across its surface due to rotation, from 8,200 K in the poles to 8,000 K in the equator.[6]
This system is a source for X-ray emission with a luminosity of 105.3×1020 W, which is most likely coming from the unseen companion.[11]