Kappa2 Apodis
Double star in the constellation Apus
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Kappa2 Apodis is a double star in the southern circumpolar constellation of Apus. Its identifier is a Bayer designation that is Latinized from κ2 Apodis, and abbreviated Kap2 Aps or κ2 Aps, respectively. This star is located at a distance of approximately 720 light-years (220 parsecs) from Earth, based upon parallax measurements with a 1.4% margin of error.[2] They are approaching the Sun with a radial velocity of −19 km/s.[5] The pair have a combined apparent visual magnitude of +5.65,[3] which makes the system faintly visible to the naked eye.
 | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Apus[1] |
| Right ascension | 15h 40m 21.355s[2] |
| Declination | −73° 26′ 48.00″[2] |
| Apparent magnitude (V) | 5.65[3] |
| Characteristics | |
| Spectral type | B7 III-IV + K0 V[4] |
| U−B color index | −0.38[3] |
| B−V color index | −0.04[3] |
| Astrometry | |
| Radial velocity (Rv) | −19.0[5] km/s |
| Proper motion (μ) | RA: −15.517 mas/yr[2] Dec.: −26.408 mas/yr[2] |
| Parallax (π) | 4.5583±0.0823 mas[2] |
| Distance | 720 ± 10 ly (219 ± 4 pc) |
| Absolute magnitude (MV) | −1.24[1] + 6.50[6] |
| Details | |
| κ2 Aps A | |
| Mass | 4.995±0.250[7] M☉ |
| Radius | 5.555±0.278[7] R☉ |
| Luminosity | 316[8] L☉ |
| Surface gravity (log g) | 3.86[8] cgs |
| Temperature | 12,646[8] K |
| Age | 130[8] Myr |
| κ2 Aps C[8] | |
| Luminosity | 0.25[6] L☉ |
| Temperature | 5,127[6] K |
| Other designations | |
| κ2 Apodis, Kap2 Aps, κ2 Aps, CPD−73°1625, HD 138800, HIP 76750, HR 5782, SAO 257307[9] | |
| Database references | |
| SIMBAD | data |
The brighter star, designated κ2 Aps A, has a stellar classification of B7 III-IV, with the luminosity class of III-IV suggesting that it may lie in an intermediate stage between a subgiant and a giant star.[10] Based on observations with TESS, it is a pulsating B star of the Maia type.[11] This star is about 130[8] million years old with an estimated 5 times the mass and 5.6 times the radius of the Sun.[7] It is radiating 316[8] times the luminosity of the Sun from its photosphere at an effective temperature of 12,646 K.[8]
A faint companion, κ2 Aps C,[8] is a K-type main sequence star with a classification of K0 V. It has a visual magnitude of 12.5 and an angular separation of 15 arcseconds from the brighter member.[4] The pair have a projected separation of around 2,520 au.[6]