| |
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Apus |
| Right ascension | 15h09m 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 velocityof−75 km/s.[7]
HD 133444 has been known to be a variable star since 1896.[14] However, its nature as a carbon star was not observed until 1967 by astronomer Brian Warner.[15] In 1973, HD 133444 was listed as a R Coronae Borealis variable. [16] These are extremely hydrogen-deficient supergiants thought to have arisen as the result of the merger of two white dwarfs[17] and fewer than 100 have been discovered as of 2013.[18] 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 temperatureof4,500–5,115 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.[19]
