  | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Cassiopeia |
| Right ascension | 00h 58m 31.06245s[1] |
| Declination | +66° 21′ 06.4522″[1] |
| Apparent magnitude (V) | 5.97[2] |
| Characteristics | |
| Spectral type | A0 III[3] |
| U−Bcolor index | −0.13[2] |
| B−Vcolor index | −0.02[2] |
| Astrometry | |
| Radial velocity (Rv) | −10.3[4] km/s |
| Proper motion (μ) | RA: +43.81[1]mas/yr Dec.: −13.62[1]mas/yr |
| Parallax (π) | 9.31±0.33 mas[1] |
| Distance | 350 ± 10 ly (107 ± 4 pc) |
| Absolute magnitude (MV) | 0.3[5] |
| Orbit[6] | |
| Period (P) | 6.82054 days |
| Eccentricity (e) | 0 |
| Inclination (i) | 20.5° |
| Semi-amplitude (K1) (primary) | 24.60 km/s |
| Semi-amplitude (K2) (secondary) | 38.43 km/s |
| Details | |
| A | |
| Mass | 2.5[6] M☉ |
| Surface gravity (log g) | 4.0[7] cgs |
| Temperature | 11,400[7] K |
| B | |
| Surface gravity (log g) | 4.5[7] cgs |
| Temperature | 7,800[7] K |
| Rotational velocity (v sin i) | 3.2+0.3 −1.9[7] km/s |
| Other designations | |
| HR 273,HD 5550,HIP 4572,BD+65°115 | |
| Database references | |
| SIMBAD | data |
HR 273 is achemically peculiarspectroscopic binary system in the northerncircumpolar constellation ofCassiopeia. It has anapparent visual magnitude of 5.9 making itfaintly visible to the naked eye from dark suburban skies.Parallax measurements with theHipparcos spacecraft put this system at a distance of roughly 350 light years.[1]
The primary, HR 273 A, is anAp star[8] and the secondary is anAm star, making this a very unusual binary system. The primary has a magnetic field of 65gauss, amongst the weakest seen in any Ap star. The magnetic field in the secondary is too weak to detect.[7]
Component A has a spectral type of A0 III, and has unusually strong lines ofstrontium,chromium, andeuropium so it is known as a SrCrEu star.[6] Although some spectral lines of the secondary star can be clearly distinguished, its spectral type cannot be clearly assigned. It is thought to be a late class A star, cooler than the primary. The primary star has been rotationally braked so that its rotational period closely matches its orbital period.[7]
