OU Andromedae
OU Andromedae (also HR 9024) is a rotationally variable star in the constellation Andromeda. Varying between magnitudes 5.87 and 5.94, it has been classified as an FK Comae Berenices variable, but the classification is still uncertain. It has a spectral classification of G1IIIe, meaning that it is a giant star that shows emission lines in its spectrum. It is also likely in its horizontal branch phase of evolution.
The light curve of an X-ray flare observed in 2001 by the Chandra X-ray Observatory is shown. This flare is believed to have been produced by a coronal mass ejection. (Adapted from Argiroffi et al., 2019) | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Andromeda |
| Right ascension | 23h 49m 40.9598s |
| Declination | +36° 25′ 31.0082″ |
| Apparent magnitude (V) | 5.87 - 5.94 |
| Characteristics | |
| Spectral type | G1 IIIe |
| Apparent magnitude (G) | 5.6187 |
| Apparent magnitude (J) | 4.723 |
| Apparent magnitude (H) | 4.208 |
| Apparent magnitude (K) | 4.097 |
| B−V color index | 0.79 |
| Variable type | FK Com |
| Astrometry | |
| Radial velocity (Rv) | −1.89±0.25 km/s |
| Proper motion (μ) | RA: −0.858±0.094 mas/yr Dec.: −47.402±0.078 mas/yr |
| Parallax (π) | 7.1692 ± 0.0677 mas |
| Distance | 455 ± 4 ly (139 ± 1 pc) |
| Details | |
| Mass | 2.85 M☉ |
| Radius | 9.46 R☉ |
| Luminosity | 71.2 L☉ |
| Surface gravity (log g) | 2.8 cgs |
| Temperature | 5,360 K |
| Metallicity [Fe/H] | −0.07 dex |
| Rotation | 24.3 days |
| Rotational velocity (v sin i) | 21.5 km/s |
| Age | 645 – 891 Myr |
| Other designations | |
| Database references | |
| SIMBAD | data |
In 1985, Jeffrey Hopkins et al. discovered that HR 9024 is a variable star, with a period of ~23.3 days. It was given the variable star designation OU Andromedae in 1986. Paola Testa et al. reported that the star showed X-ray flare activity, in 2007.
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