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OGLE-LMC-CEP0227 is an eclipsing binary and Cepheid variable star,[6] pulsating every 3.8 days.[4] The star, in the Large Magellanic Cloud, was the first Cepheid star system found to be orbiting exactly edge on.[4]

A near-infrared (I band) light curve for OGLE-LMC-CEP0227, adapted from Pietrzyński et al. (2010).[4] The main plot shows the eclipse light curve, with the Cepheid variation removed, and the inset plot shows the Cepheid variation.
A near-infrared (I band) light curve for OGLE-LMC-CEP0227, adapted from Pietrzyński et al. (2010).[4] The main plot shows the eclipse light curve, with the Cepheid variation removed, and the inset plot shows the Cepheid variation.
OGLE-LMC-CEP0227

Artist’s impression of OGLE-LMC-CEP0227
Credit: ESO
Observation data
Epoch J2000      Equinox J2000
Constellation Mensa
Right ascension 04h 52m 15.678s[1]
Declination −70° 14′ 31.33″[1]
Apparent magnitude (V) 15.317[2]
Characteristics
Spectral type F7Ib + G4II[3][lower-alpha 1]
Apparent magnitude (J) 13.727[1]
Apparent magnitude (H) 13.217[1]
Apparent magnitude (K) 13.262[1]
Variable type Eclipsing binary, δ Cep[4]
Astrometry
Distance163,000[5] ly
(50,000 pc)
Orbit[3]
Period (P)309.404±0.002 days
Semi-major axis (a)389.86±0.77
Eccentricity (e)0.1659±0.0006
Inclination (i)86.833±0.016°
Argument of periastron (ω)
(secondary)		342.0±0.6°
Details[3][lower-alpha 1]
A (Cepheid)
Mass4.165±0.032 M☉
Radius34.92±0.34 R☉
Luminosity1,439 L☉
Surface gravity (log g)1.971±0.011 cgs
Temperature6,050±160 K
B
Mass4.134±0.037 M☉
Radius44.85±0.29 R☉
Surface gravity (log g)1.751±0.010 cgs
Temperature5,120±130 K
Rotational velocity (v sin i)11.1±1.2 km/s
Other designations
2MASS J04521567-7014313
Database references
SIMBADdata

The OGLE-LMC-CEP0227 system contains two stars which orbit each other almost exactly 'edge on' to the line of sight from the Earth. This unique configuration has allowed astronomers to refine their understanding of classical Cepheid variable stars. Studies of this system have allowed astronomers to measure the Cepheid mass with unprecedented accuracy. There is still disagreement over whether the pulsational properties accurately match the mass derived from the observed orbit.[4][6]

The two stars orbit each other every 309 days, and each has a mass close to 4.1 M☉. The primary component has an effective temperature of 6,050 K and the secondary a temperature of 5,120 K.[3]


Notes


  1. The spectral type, radius, gravity, temperature, luminosity, and observed magnitudes for the Cepheid are mean values, since the star pulsates regularly.

References


  1. Cutri, Roc M.; Skrutskie, Michael F.; Van Dyk, Schuyler D.; Beichman, Charles A.; Carpenter, John M.; Chester, Thomas; Cambresy, Laurent; Evans, Tracey E.; Fowler, John W.; Gizis, John E.; Howard, Elizabeth V.; Huchra, John P.; Jarrett, Thomas H.; Kopan, Eugene L.; Kirkpatrick, J. Davy; Light, Robert M.; Marsh, Kenneth A.; McCallon, Howard L.; Schneider, Stephen E.; Stiening, Rae; Sykes, Matthew J.; Weinberg, Martin D.; Wheaton, William A.; Wheelock, Sherry L.; Zacarias, N. (2003). "VizieR Online Data Catalog: 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)". CDS/ADC Collection of Electronic Catalogues. 2246: II/246. Bibcode:2003yCat.2246....0C.
  2. Soszynski, I.; Poleski, R.; Udalski, A.; Szymanski, M. K.; Kubiak, M.; Pietrzynski, G.; Wyrzykowski, L.; Szewczyk, O.; Ulaczyk, K. (2008). "The Optical Gravitational Lensing Experiment. The OGLE-III Catalog of Variable Stars. I. Classical Cepheids in the Large Magellanic Cloud". Acta Astronomica. 58: 163. arXiv:0808.2210. Bibcode:2008AcA....58..163S.
  3. Pilecki, B. (2013). "Physical parameters and the projection factor of the classical Cepheid in the binary system OGLE-LMC-CEP-0227". Monthly Notices of the Royal Astronomical Society. 436 (2): 953–967. arXiv:1308.5023. Bibcode:2013MNRAS.436..953P. doi:10.1093/mnras/stt1529. S2CID 119127008.
  4. Pietrzyński, G.; Thompson, I. B.; Gieren, W.; Graczyk, D.; Bono, G.; Udalski, A.; Soszyński, I.; Minniti, D.; Pilecki, B. (2010). "The dynamical mass of a classical Cepheid variable star in an eclipsing binary system". Nature. 468 (7323): 542–4. arXiv:1012.0231. Bibcode:2010Natur.468..542P. doi:10.1038/nature09598. PMID 21107425. S2CID 4413016.
  5. Pietrzyński, G; D. Graczyk; W. Gieren; I. B. Thompson; B. Pilecki; A. Udalski; I. Soszyński; et al. (7 March 2013). "An eclipsing-binary distance to the Large Magellanic Cloud accurate to two per cent". Nature. 495 (7439): 76–79. arXiv:1303.2063. Bibcode:2013Natur.495...76P. doi:10.1038/nature11878. PMID 23467166. S2CID 4417699.
  6. Neilson, H. R.; Langer, N. (2012). "Is there a mass discrepancy in the Cepheid binary OGLE-LMC-CEP0227?". Astronomy & Astrophysics. 537: A26. arXiv:1110.6657. Bibcode:2012A&A...537A..26N. doi:10.1051/0004-6361/201117829. S2CID 118394822.

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