HD 27563
  | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Eridanus |
| Right ascension | 04h 20m 42.8341s |
| Declination | −07° 35′ 32.986″ |
| Apparent magnitude (V) | 5.84 |
| Characteristics | |
| Spectral type | B5III or B7II |
| Apparent magnitude (U) | 5.23 |
| Apparent magnitude (B) | 5.710 |
| Apparent magnitude (G) | 5.829944 |
| Apparent magnitude (J) | 6.026 |
| Apparent magnitude (H) | 6.109 |
| Apparent magnitude (K) | 6.113 |
| Variable type | SPB |
| Astrometry | |
| Radial velocity (Rv) | 11.20±4.3 km/s |
| Proper motion (μ) | RA: 3.540 mas/yr Dec.: −2.298 mas/yr |
| Parallax (π) | 3.7763 ± 0.0612 mas |
| Distance | 860 ± 10 ly (265 ± 4 pc) |
| Absolute magnitude (MV) | −1.05 |
| Details | |
| Mass | 4.3 M☉ |
| Radius | 2.8 R☉ |
| Luminosity | 687 L☉ |
| Surface gravity (log g) | 3.69 cgs |
| Temperature | 13,315 K |
| Rotational velocity (v sin i) | 34 km/s |
| Age | 180 Myr |
| Other designations | |
| Database references | |
| SIMBAD | data |
HD 27563, also known by the Bayer designation d Eridani, is a single star in Eridanus, in the direction of the Orion–Eridanus Superbubble, that is faintly visible to the naked eye at a magnitude of about 5.84. Cowley (1972) classifies this star as spectral type B5III, but Houk and Swift (1999) catalog it as B7II.
It was used as a comparison star for 46 Eridani in four separate runs at La Silla Observatory in the 1970s and 1980s, but in 1989, both stars were found to be variable with similar periods of about four days, and HD 27563 assigned the designation EM Eridani. Despite the lack of reliable comparisons for EM Eridani, it was found that the power spectrum of its light curve is remarkably noisy, with two or four prominent oscillation periods centered around 3.9215 d, and is classified as a slowly pulsating B-type star.