| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Apus |
| Right ascension | 15h 09m 24.53660s [2] |
| Declination | −72° 03′ 45.1828″ [2] |
| Apparent magnitude (V) | 9.6 - 17.0 [3] |
| Characteristics | |
| Evolutionary stage | post-AGB [4] |
| Spectral type | R3 [5] |
| U−B color index | +0.66 [6] |
| B−V color index | +1.26 [6] |
| Variable type | R Coronae Borealis [3] |
| Astrometry | |
| Radial velocity (Rv) | −75.0 [7] km/s |
| Proper motion (μ) | RA: −6.632 mas/yr [2] Dec.: −2.155 mas/yr [2] |
| Parallax (π) | 0.2243±0.0171 mas [2] |
| Distance | 15,000 ± 1,000 ly (4,500 ± 300 pc) |
| Absolute bolometric magnitude (Mbol) | −2.68 (at max) [8] |
| Details | |
| Mass | 0.6 or 1 [9] M☉ |
| Radius | 132±9 [10] R☉ |
| Luminosity | 960 [11] L☉ |
| Temperature | 4,500 - 5,115 [12] K |
| Other designations | |
| S Aps, CD−71°1120, CPD−71°1743, HD 133444, HIP 74179, 2MASS J15092452-7203451 [13] | |
| Database references | |
| SIMBAD | data |
S Apodis, also known as HD 133444 is a variable star located in the southern circumpolar constellation Apus. It has an apparent magnitude ranging from 9.6 to 17, [3] which is below the limit for naked eye visibility. The object is located relatively far at a distance of approximately 15,000 light years based on Gaia DR3 parallax measurements, [2] but it is drifting closer with a heliocentric radial velocity of −75 km/s . [7]
HD 133444 was discovered to be a variable star by Williamina Fleming, who examined images of the star on 58 photographic plates taken from 1889 through 1895. The discovery was announced in 1896. [14] Annie Jump Cannon included the star, with its variable star designation S Apodis, in her 1907 Second Catalogue of Variable Stars. [15] However, its nature as a carbon star was not observed until 1967 by astronomer Brian Warner. [16] In 1973, HD 133444 was listed as a R Coronae Borealis variable. [17] These are extremely hydrogen-deficient supergiants thought to have arisen as the result of the merger of two white dwarfs [18] and fewer than 100 have been discovered as of 2013. [19] A decade later, S Apodis was observed to have a change it its pulsation mode. [9]
S Apodis has a stellar classification of R3, indicating that it is a R-type carbon star. It has a mass of either 0.6 M☉ or 1 M☉, [9] depending on the model. However, it has expanded to an average radius 132 times that of the Sun. [10] It radiates 960 times the luminosity of the Sun [11] from its photosphere at an effective temperature of 4,500–5,115 K , [12] giving it an orange hue. An infrared excess has been detected around the star, indicating the presence of circumstellar dust. The dust has a temperature of 730 K. [20]
