Gamma Circini

Gamma Circini, Latinized from γ Circini, is a star system in the constellation Circinus. It was noted as a double star by Herschel in 1835, who estimated the separation as 1 arc second.^[11] It is visible to the naked eye with an apparent visual magnitude of 4.51.^[2] Based upon an annual parallax shift of 7.27 mas,^[1] it is about 450 light-years away.

A light curve for Gamma Circini, plotted from TESS data^[12]

γ Circini

Location of y Circini (circled)
Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Circinus
Right ascension	15h 23m 22.64294s[1]
Declination	−59° 19′ 14.8131″[1]
Apparent magnitude (V)	4.51[2] (4.94 + 5.73)[3]
Characteristics
Spectral type	B5 IV[4] + F8 V[2]
Variable type	Be[5]
Astrometry
Radial velocity (Rv)	16.90±1.78[6] km/s
Proper motion (μ)	RA: −12.97[1] mas/yr Dec.: −34.24[1] mas/yr
Parallax (π)	7.27±0.81 mas[1]
Distance	approx. 450 ly (approx. 140 pc)
Absolute magnitude (MV)	−1.18[7]
Orbit[4]
Period (P)	258 yr
Semi-major axis (a)	2.576″
Eccentricity (e)	0.931
Details
γ Cir A
Mass	6.0±0.3[8] M☉
Temperature	15,135[9] K
Age	63.1±19.6[8] Myr
γ Cir B
Temperature	4,786[9] K
Other designations
γ Cir, CPD−58°5908, HIP 75323, HR 5704, SAO 242463[10]
γ Cir A: HD 136415
γ Cir B: HD 136416
Database references
SIMBAD	γ Cir AB
	γ Cir A
	γ Cir B

This is a wide binary star system and may even be a triple star.^[9] The two visible components orbit each other with a preliminary estimated period of 258 years and a large eccentricity of 0.931.^[4] As of 2014, the visible components have an angular separation of 0.80 arc seconds on a position angle of 359°.^[3]

The primary star, component A, is a B-type subgiant star with a stellar classification of B5 IV.^[4] Based upon isochrone curve fitting it is hypothesized to be a pair of matching B5 stars,^[9] and is a Be variable with an uncertain maximum.^[5] It has an effective temperature of 15,135^[9] K and an estimated mass six^[8] times that of the Sun. The companion, component B, is an F-type main-sequence star with a stellar classification of F8 V.^[2] It has an effective temperature of 4,786^[9] K.