 SU Andromedae in optical light | |
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Andromeda |
| Right ascension | 00h 04m 36.4076s[1] |
| Declination | +43° 33′ 04.7264″[1] |
| Apparent magnitude (V) | 8.0 to 8.5[2] |
| Characteristics | |
| Spectral type | C6,4(C5II)[2] |
| U−Bcolor index | +4.13[3] |
| B−Vcolor index | +2.58[3] |
| Variable type | LC[2] |
| Astrometry | |
| Proper motion (μ) | RA: −3.362±0.058[1]mas/yr Dec.: −2.097±0.040[1]mas/yr |
| Parallax (π) | 0.6979±0.0439 mas[1] |
| Distance | 4,700 ± 300 ly (1,430 ± 90 pc) |
| Absolute magnitude (MV) | −2.2[4] |
| Details | |
| SU And | |
| Luminosity | 2,535[5] L☉ |
| Temperature | 2,905[5] K |
| co-moving companion | |
| Radius | 1.95[6] R☉ |
| Luminosity | 9.833[6] L☉ |
| Temperature | 7,311[6] K |
| Other designations | |
| SU Andromedae, SU And,HD 225217,HIP 363,BD+42 4827 | |
| Database references | |
| SIMBAD | data |
SU Andromedae is acarbon star in the constellation ofAndromeda. It is avariable star classified as aslow irregular pulsating supergiant, and varies from anapparent visual magnitude of 8.5 at minimum brightness to a magnitude of 8.0 at maximum brightness with no clear period.[2]
Thomas Espin noted the possible variability of this star in 1895.[8]Williamina Fleming, in 1906, was examining photographic plates taken for the purpose of creating theHenry Draper Catalogue when she independently discovered and confirmed it as a variable star.[9]
The spectrum of SU Andromedae is dominated bySwan bands from the moleculeC2. These stars were classified as type N under the Harvard scheme, stars with the blue continuum completely obscured by molecular absorption bands. Carbon star spectral types were later refined in the Morgan-Keenan system and SU Andromedae was typically classified as C64,[10] indicating a fairly cool carbon star and the subscript 4 showing modest Swan band intensity.[11]
Under the modern revised Morgan-Keenan system, SU Andromedae is classified as C-N5 C26-.[12] The C-N spectral type is to distinguish those stars from the C-R type where the blue continuum is not entirely hidden by absorption bands. A classification based on the infrared spectrum is C5 II, again a moderately cool carbon star with aluminosity class of II for abright giant.[3]
SU Andromedae is 22" from a magnitude 12.77 star, probably an F0main sequence star. This star has aGaia Data Release 2 parallax of0.7479±0.0905[6] and anabsolute magnitude of about +2.4. It has an almost identical space motion as SU Andromedae and is assumed to be a distant co-moving companion. Based on that assumption, the absolute magnitude of SU Andromedae is calculated to be about −2.2.[4]
