AE Andromedae
| Observation data Epoch J2000 Equinox J2000 |
|
|---|---|
| Constellation | Andromeda |
| Right ascension | 00h 43m 02.52s |
| Declination | +41° 49′ 12.2″ |
| Apparent magnitude (V) | 17.0-17.9 |
| Characteristics | |
| Spectral type | LBV |
| U−B color index | ~ −0.9 |
| B−V color index | ~ +0.1 |
| Variable type | LBV |
| Astrometry | |
| Radial velocity (Rv) | -193 km/s |
| Distance | ~2.5Mly ly (~780kpc pc) |
| Absolute magnitude (MV) | −7.0 to −10.2 |
| Details | |
| Mass | 50-120 M☉ |
| Radius | 55 R☉ |
| Luminosity | 450,000-700,000 L☉ |
| Temperature | 20,000 K |
| Other designations | |
| Database references | |
| SIMBAD | data |
AE Andromedae (AE And) is a luminous blue variable (LBV), a type of variable star. The star is one of the most luminous variables in M31, the Andromeda Galaxy.
The star was discovered to be variable in 1928, with a photographic magnitude range of 14.7-15.6, at the Harvard College Observatory and designated HV 4476. A year later it was given the variable star designation AE Andromedae. At that time it was the brightest stellar object in M31 and maintained a similar brightness for about 20 years.
Early in the investigations leading to the definition of LBVs, AE And was identified as similar to the five Hubble-Sandage variables: Var A, Var B, Var C, and Var 2 in M33, and Var 19 in M31 (=AF Andromedae). On the basis of color-color comparisons, it was assigned as spectral type B and described as related to the P Cygni variables. Observations from 1960 to 1970 showed irregular variations in the B (blue) magnitude between 16.2 and 17.6, with very similar V magnitudes, and U magnitudes around 0.4 brighter. The first detailed spectrum was published in 1975.
AE And is seen to have a peculiar emission line spectrum described as very much like Eta Carinae, likely due to a dense stellar wind. The spectrum in 2010 showed weaker emission lines and some weak and variable absorption lines.
AE And has prominent allowed and forbidden FeII and hydrogen lines in its emission spectrum, as well as weaker HeI and NII lines. Some features suggest a B2-B3 spectral type but the emission and variability defy a normal classification.
The 250.7 nm FeII line is unusually strong in emission. The same feature in Eta Carinae's spectrum has been attributed to a UV laser.
AE And was the brightest star in M31 when it was first noticed during an outburst, at an apparent magnitude around 15, equivalent to an absolute magnitude of -10.2, or around a million times brighter than the Sun. This implies that the outburst may have increased the luminosity of the star, which would be unusual for an LBV. The temperature at that time is not known because of a lack of spectra or multiband photometry, but a typical LBV is around 8,000K during an outburst.
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