Kappa1 Apodis

Kappa¹ Apodis is a binary star^[4] system in the southern circumpolar constellation of Apus.^[1] Its idetifier is a Bayer designation that is Latinized from κ¹ Apodis, and abbreviated Kap¹ Aps or κ¹ Aps, respectively. Based upon parallax measurements, it is located roughly 1,060 light-years (325 parsecs) from Earth. The combined apparent visual magnitude of the system is 5.52,^[3] indicating that this is a faint, naked eye star that can be viewed in dark suburban skies. It is moving away from the Sun with a radial velocity of +62 km/s.^[7]

A light curve for Kappa¹ Apodis, plotted from TESS data^[12]

For other stars with this name, see Kappa Apodis.

Kappa¹ Apodis

Location of Kappa1 Apodis (circled)
Observation data Epoch J2000      Equinox J2000
Constellation	Apus[1]
Right ascension	15h 31m 30.82213s[2]
Declination	−73° 23′ 22.5295″[2]
Apparent magnitude (V)	5.52[3]
Characteristics
Spectral type	B1npe[4] + sdO[5]
U−B color index	−0.791[3]
B−V color index	−0.128[3]
Variable type	γ Cas[6]
Astrometry
Radial velocity (Rv)	+62[7] km/s
Proper motion (μ)	RA: +0.996 mas/yr[2] Dec.: −18.345 mas/yr[2]
Parallax (π)	3.0798±0.0717 mas[2]
Distance	1,060 ± 20 ly (325 ± 8 pc)
Absolute magnitude (MV)	−2.47[1]
Orbit[8]
Period (P)	192.1±0.1 d
Semi-major axis (a)	≥ 288.3±8.4 R☉
Eccentricity (e)	0 (assumed)
Inclination (i)	60±4°
Periastron epoch (T)	2458401.9±2.2 HJD
Semi-amplitude (K1) (primary)	9.09±0.08 km/s
Semi-amplitude (K2) (secondary)	66.87±1.84 km/s
Details
A
Mass	11.8±1.0[8] M☉
Radius	5.45±0.29[5] R☉
Luminosity	2,120[1] L☉
Surface gravity (log g)	3.90[9] cgs
Temperature	21,500[9] K
Rotational velocity (v sin i)	250[5] km/s
Age	5.6±1.0[10] Myr
B
Mass	1.60±0.14[8] M☉
Radius	0.44±0.06[5] R☉
Luminosity	446[5] L☉
Temperature	40,000[5] K
Other designations
κ1 Apodis, κ1 Aps, Kap1 Aps, CD−72°1139, CPD−72°1802, FK5 567, HD 137387, HIP 76013, HR 5730, SAO 257289, WDS J15315-7323A[11]
Database references
SIMBAD	data

This is a spectroscopic binary system, made up of a Be star and a subdwarf O star, which complete an orbit around each other every 192 days.^[8] The combined spectrum matches a stellar classification of B1npe.^[4] The 'e' suffix indicates that this is a Be star with emission lines in the spectrum. An 'n' means that the absorption lines in the spectrum are broadened from the Doppler effect as a result of rapid rotation. Finally, the 'p' shows some peculiarity in the spectrum. It is classified as a Gamma Cassiopeiae type variable star and its brightness varies from magnitude +5.43 to +5.61.

This is a runaway star with a peculiar velocity of 69.8±4.7 km/s.^[10] Because it is a binary star system, it was most likely not turned into a runaway system as the result of a supernova explosion.^[4]

A 12th-magnitude orange K-type subgiant^[13] located at an angular separation of 27 arcseconds has a much smaller parallax than Kappa¹ Apodis and is a distant background object.^[14]