AC Andromedae
Variable star in the constellation Andromeda
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AC Andromedae (AC And) is a variable star in the constellation Andromeda. Its maximum apparent visual magnitude is 10.77, but can be seen fainter down to a magnitude of 11.9.
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Andromeda |
| Right ascension | 23h 18m 02.34605s[2] |
| Declination | +48° 46′ 58.3403″[2] |
| Apparent magnitude (V) | 10.7 – 11.9[3] |
| Characteristics | |
| Spectral type | F5[4] |
| Apparent magnitude (B) | 11.48[5] |
| Apparent magnitude (V) | 10.90[5] |
| Apparent magnitude (G) | 10.9002[2] |
| Apparent magnitude (J) | 9.646[6] |
| Apparent magnitude (H) | 9.483[6] |
| Apparent magnitude (K) | 9.345[6] |
| B−V color index | 0.5389[5] |
| Variable type | Peculiar[3] |
| Astrometry | |
| Radial velocity (Rv) | −50.0±2.8[7] km/s |
| Proper motion (μ) | RA: −2.160±0.012 [2] mas/yr Dec.: −2.345±0.013[2] mas/yr |
| Parallax (π) | 0.4948±0.0138 mas[2] |
| Distance | 6,600 ± 200 ly (2,020 ± 60 pc) |
| Absolute magnitude (MV) | −0.82[4] |
| Details | |
| Mass | 3.4[2] M☉ |
| Radius | 11[2] R☉ |
| Luminosity | 170[2] L☉ |
| Surface gravity (log g) | 2.76[8] cgs |
| Temperature | 6,315[9] K |
| Metallicity [Fe/H] | −1.46[8] dex |
| Age | 271[2] Myr |
| Other designations | |
| 2MASS J23180234+4846582, BD+47 4104, HIP 115046, TYC 3644-2114-1 | |
| Database references | |
| SIMBAD | data |
AC Andromedae was first reported to be a variable star by Paul Guthnick and Richard Prager in 1927. They noted that it varied in brightness rapidly, with no discernible period.[10][11]
The nature of AC Andromedae is still not determined. Its light curve shows clearly three radial pulsation modes, the fundamental one with a period of 0.71 days, and the first two overtones of 0.525 and 0.421 days, respectively. It is then unclear if it belongs to the class of RR Lyrae variables or to the one of Delta Scuti variables.[12][13] Another study points at AC And as an intermediate object between classical Cepheids and Delta Scuti variables.[4] The physical parameters of the star itself would be different depending on which class it belongs to.
By late 2018, the AC Andromedae was classified as rare "triple-mode" subtype of the dwarf cepheid (high-amplitude Delta Scuti variable).[14][15]