R Apodis (HD 131109; HR 5540; 18 G. Apodis) is a solitary star[13] in the constellation Apus. It is faintly visible to the naked eye as an orange-hued point of light with an apparent magnitude of 5.36.[2] Gaia DR3 parallax measurements imply a distance of 413 light-years[1] and it is drifting closer with a heliocentric radial velocity of −31.2 km/s.[6] At its current distance, R Apodis' brightness is diminished by an interstellar extinction of 0.26 magnitudes[14] and it has an absolute magnitude of −0.22.[7]
Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
---|---|
Constellation | Apus |
Right ascension | 14h 57m 52.98352s[1] |
Declination | −76° 39′ 45.5569″[1] |
Apparent magnitude (V) | 5.36±0.01[2] |
Characteristics | |
Spectral type | K4 III:[3] |
B−V color index | +1.44[4] |
Variable type | constant[5] |
Astrometry | |
Radial velocity (Rv) | −31.20±0.08[6] km/s |
Proper motion (μ) | RA: −69.161 mas/yr[1] Dec.: −16.583 mas/yr[1] |
Parallax (π) | 7.8879 ± 0.0867 mas[1] |
Distance | 413 ± 5 ly (127 ± 1 pc) |
Absolute magnitude (MV) | −0.22±0.16[7] |
Details | |
Mass | 1.10±0.18[6] M☉ |
Radius | 30.1±1.5[8] R☉ |
Luminosity | 293+9 −10[1] L☉ |
Surface gravity (log g) | 1.62[9] cgs |
Temperature | 4282±33[10] K |
Metallicity [Fe/H] | −0.29±0.05[6] dex |
Rotational velocity (v sin i) | <1.3[11] km/s |
Age | 5.68±2.42[6] Gyr |
Other designations | |
Database references | |
SIMBAD | data |
HD 131109 was the first star observed to be variable in the constellation; It was first discovered in 1873 by Benjamin Apthorp Gould. Later, it was hastily given the variable star designation R Apodis in a 1907 variable star catalogue despite it being a suspected variable star at the time.[15] However, observations conducted in a 1952 field star survey revealed that R Apodis was not variable at all.[16] Keenan & Pitts (1980) found that it varied between magnitudes 5.5 and 6.1, but this was never confirmed.[17] Hipparcos photometric data revealed that R Apodis indeed had a constant brightness.[18] It has since been listed as a class CST: in the General Catalog of Variable Stars.[5]
R Apodis has a stellar classification of K4 III:,[3] indicating that it is an evolved K-type giant that has ceased hydrogen fusion at its core and left the main sequence. However, there is uncertainty about the luminosity class. It has a comparable mass to the Sun but at the age of 5.68 billion years,[6] it has expanded to 30.1 times the radius of the Sun.[8] It radiates 293 times the luminosity of the Sun[1] from its enlarged photosphere at an effective temperature of 4,282 K.[10] R Apodis is metal deficient with an iron abundance roughly half of the Sun's[6] and it spins slowly with a projected rotational velocity lower than 1.3 km/s.[11]