Lambda Pavonis

λ Pavonis, Latinized as Lambda Pavonis, is a single,^[13] variable star in the southern constellation of Pavo. It is a blue-white hued star that is faintly visible to the naked eye with an apparent visual magnitude that fluctuates around 4.22.^[2] This object is located approximately 1,400 light years from the Sun, based upon parallax. It is a member of the Scorpius–Centaurus association.^[14]

A light curve for Lambda Pavonis, plotted from TESS data^[15]

Lambda Pavonis

Location of λ Pavonis (circled)
Observation data Epoch J2000      Equinox J2000
Constellation	Pavo
Right ascension	18h 52m 13.03427s[1]
Declination	−62° 11′ 15.3324″[1]
Apparent magnitude (V)	4.22[2] (4.00 - 4.26)[3]
Characteristics
Spectral type	B2Ve[4] or B2II–IIIe[5]
U−B color index	−0.88[6]
B−V color index	−0.15[2]
Variable type	γ Cas[3]
Astrometry
Radial velocity (Rv)	+9.0±4.1[7] km/s
Proper motion (μ)	RA: −1.86[1] mas/yr Dec.: −13.02[1] mas/yr
Parallax (π)	2.28±0.18 mas[1]
Distance	1,400 ± 100 ly (440 ± 30 pc)
Absolute magnitude (MV)	−3.97[2]
Details
Mass	12.5[8] M☉
Radius	9±1[9] (polar) R☉
Luminosity	8,450[2] L☉
Temperature	20,300[10] K
Rotational velocity (v sin i)	190[11] km/s
Other designations
λ Pav, CD−62°1254, FK5 704, GC 25823, HD 173948, HIP 92609, HR 7074, SAO 254393, CCDM J18522-6212A, WDS J18522-6211[12]
Database references
SIMBAD	data

This is a massive Be star, a rapidly rotating hot blue star which has developed a gas disk around it. It is a γ Cassiopeiae variable or shell star which has occasionally brightened to magnitude 4.0.^[3] The stellar classification of B2Ve^[4] suggests it is a B-type main-sequence star that is generating energy through core hydrogen fusion. This star is spinning rapidly with a projected rotational velocity of 190 km/s.^[11] This is giving the star an oblate shape with an equatorial bulge that is an estimated 10% larger than the polar radius.^[16] Lambda Pavonis has 12.5^[8] times the mass of the Sun and nine times the Sun's polar radius.^[9] It is radiating 8,450^[2] times the luminosity of the Sun from its photosphere at an effective temperature of 20,300 K.^[10]

Variations in signals coming from Lambda Pavonis have led to a debate on whether it is a binary, single or pulsating variable star.^[14]