HR 4098, also known as HD 90508, is a binary star system in the northern constellation of Ursa Major at a distance of 75 light years. This object is barely visible to the naked eye as a dim, yellow star with an apparent visual magnitude of 6.45. It is approaching the Earth with a heliocentric radial velocity of 7.2±0.2 km/s.[3]
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Ursa Major |
| Right ascension | 10h 28m 03.8821s[1] |
| Declination | +48° 47′ 05.6554″[1] |
| Apparent magnitude (V) | 6.45[2] |
| Characteristics | |
| HD 90508A | |
| Spectral type | G0V[1] |
| Apparent magnitude (g) | 6.28[3] |
| HD 90508B | |
| Apparent magnitude (g) | 11.72[4] |
| Astrometry | |
| HD 90508A | |
| Radial velocity (Rv) | -7.2±0.2[3] km/s |
| Proper motion (μ) | RA: 83.79±0.03 mas/yr[3] Dec.: -896.055±0.04 mas/yr[3] |
| Parallax (π) | 43.4944 ± 0.0386 mas[3] |
| Distance | 74.99 ± 0.07 ly (22.99 ± 0.02 pc) |
| HD 90508B | |
| Proper motion (μ) | RA: 81.80±0.03 mas/yr[4] Dec.: -880.66±0.03 mas/yr[4] |
| Parallax (π) | 43.4822 ± 0.0452 mas[4] |
| Distance | 75.01 ± 0.08 ly (23.00 ± 0.02 pc) |
| Orbit[5] | |
| Primary | HD 90508A |
| Companion | HD 90508B |
| Period (P) | 590±208 yr |
| Semi-major axis (a) | 4.67±0.12" (107 AU) |
| Eccentricity (e) | 0 |
| Inclination (i) | 81.4±3.5° |
| Longitude of the node (Ω) | 16.5±1.9° |
| Periastron epoch (T) | 1958.6±16.8 |
| Details[6] | |
| HD 95508A | |
| Mass | 0.86±0.03 M☉ |
| Radius | 1.12±0.03 R☉ |
| Surface gravity (log g) | 4.3±0.1 cgs |
| Temperature | 5720±100 K |
| Metallicity [Fe/H] | -0.23[7] dex |
| Rotation | 18.0±2.7 d[8] |
| Rotational velocity (v sin i) | 1.0[8] km/s |
| Age | 10.5±2[9] Gyr |
| HD 95508B | |
| Mass | 0.25±0.01 M☉ |
| Other designations | |
| HD 90508A: Gliese 392A, TYC 8176-283-1, LHS 2267, LTT 12795, NLTT 24398, Gaia DR2 834571523535702528 | |
| HD 90508B: Gliese 392B, LHS 2266, NLTT 24397, Gaia DR2 834571523535693184 | |
| Database references | |
| SIMBAD | data |
The star system is a visual binary with a 3.466″ projected separation,[10] identified as such in 1994–1997.[5][10] The orbit of the binary is wide and highly uncertain[10] due to the long period and high inclination.[5]
The larger star, HD 90508A, is a very old main-sequence star approaching a turn-off from the main sequence.[11] Very little dust remains in the stellar system, therefore the starlight of HR 4098 is one of the standards for non-polarized emission, polarization being below 0.2% in all bands.[12] Unlike the majority of G-class stars, HD 90508A has a direct correlation between brightness and stellar activity. This behavior is shared with HD 88986 and the Sun.[13]
Very little is known about the companion, which could be a K-class or M-class dwarf star.[6]