λ Eri is classified in theGeneral Catalogue of Variable Stars as aBeta Cephei variable.[13] TheAAVSO International Variable Star Index defines aLERI type of variation. λ Eri is classified as LERI + GCAS since it shows both short term periodic variations and longer timescale eruptive variation.[6] It was one of the first stars where short-period variations were found.[4] The line profile variability periods are 0.702d and 0.269d, with intermittently present periods of 0.6d and 0.75d. Thephotometricamplitude of the variation is 0.010 magnitude.[5]
This is agiant orsubgiantBe star with astellar classification of B2 IVne[4] or B2 III(e)p,[5] depending on the source. It is spinning rapidly with aprojected rotational velocity of 327 km/s.[7] Compare this to the estimatedbreak-up velocity of 440 km/s.[14] This rotation is giving the star anoblate shape with anequatorial bulge that is 25% larger than the polar radius.[15] The most likely rotation period is deemed to be twice the period of variation, or 1.4 days.[4] The star also possesses a rotating circumstellar disc, seen edge on, which makes Lambda Eri a "shell star", where the disk appears more opaque than usual.[16]
Like most Be stars, Lambda Eridani emits softX-rays. In 1993, a giant X-ray flare was observed in which the X-ray luminosity increased by a factor of six over a 39-hour period.[4] Lambda Eridani has about nine times themass of the Sun, and seven times theSun's radius. It radiates 14,700 times thesolar luminosity from itsouter atmosphere at aneffective temperature of22,362 K.
^abcHoffleit, D.; Warren, W. H. (1995). "Bright Star Catalogue".VizieR On-line Data Catalog: V/50. Originally Published in: 1964BS....C......0H.5050 (5th Revised ed.).Bibcode:1995yCat.5050....0H.
^abZorec, J.; Frémat, Y.; Domiciano De Souza, A.; Royer, F.; Cidale, L.; Hubert, A.-M.; Semaan, T.; Martayan, C.; Cochetti, Y. R.; Arias, M. L.; Aidelman, Y.; Stee, P. (2017). "Critical study of the distribution of rotational velocities of Be stars".Astronomy & Astrophysics.595: A132.arXiv:1702.07684.Bibcode:2016A&A...595A.132Z.doi:10.1051/0004-6361/201628760.
^Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)".VizieR.1.Bibcode:2009yCat....102025S.
