LO Pegasi

A visual band light curve for LO Pegasi. The main plot (adapted from Karmakar et al.[1]) shows the long-term variability. Inset plot "A" (adapted from Kiraga[2]) shows the periodic variability, and inset "B" (also adapted from Karmakar et al.[1]) shows a flare.
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Pegasus
Right ascension 21h 31m 01.714s[3]
Declination 23° 20′ 07.37″[3]
Apparent magnitude (V) 9.23[4] (9.04 to 9.27)[5]
Characteristics
Spectral type K3Vke[6]
B−V color index 1.050±0.015[4]
Variable type BY Dra[5]
Astrometry
Radial velocity (Rv)−23.36±1.75[7] km/s
Proper motion (μ) RA: 134.654 mas/yr[3]
Dec.: −144.889 mas/yr[3]
Parallax (π)41.2912 ± 0.0169 mas[3]
Distance78.99 ± 0.03 ly
(24.218 ± 0.010 pc)
Absolute magnitude (MV)7.26[4]
Details[8]
Mass0.66±0.02 M☉
Radius0.72±0.10 R☉
Luminosity0.25±0.02 L☉
Surface gravity (log g)4.5±0.5 cgs
Temperature4,750±250 K
Rotation0.4236 d[9]
Rotational velocity (v sin i)48.2±2.5[10] km/s
Age10–300[11] Myr
Other designations
LO Peg, AG+23 2203, BD+22 4409, GJ 4199, HIP 106231, WDS J21310+2320A[12]
Database references
SIMBADdata

LO Pegasi is a single star[13] in the northern constellation of Pegasus that has been the subject of numerous scientific studies.[14] LO Pegasi, abbreviated LO Peg, is the variable star designation. It is too faint to be viewed with the naked eye, having an apparent visual magnitude that ranges from 9.04 down to 9.27.[5] Based on parallax measurements, LO Peg is located at a distance of 79 light years from the Sun. It is a member of the young AB Doradus moving group,[13][11] and is drifting closer with a radial velocity of −23 km/s.[7]

This is a K-type main-sequence star with a stellar classification of K3Vke,[6] where the 'k' suffix indicates interstellar absorption lines and 'e' means there are emission lines in the spectrum. It became of interest to astronomers when significant X-ray emission was detected from this star in 1994. R. D. Jeffries and associates reported flare activity based on a rotationally-broadened hydrogen α emission line and found the star varied in brightness.[15]

LO Peg is an ultrafast rotator, completing a full rotation every 10.15 hours.[16] It is classified as a BY Draconis variable that is magnetically active and has star spots. The combination of non-uniform surface brightness and rotation makes it appear to vary in luminosity.[5] Up to 25.7% of the surface is covered in spots. Long term changes in periodicity suggest activity cycles, similar to the solar cycle,[1] with periods of approximately 3 and 7.4 years.[11] The element lithium has been detected in its atmosphere, whose abundance, in combination with the star's rapid rotation, indicates this is a young star with an age of no more than a few hundred million years.[15]

See also

References

  1. 1 2 3 Karmakar, Subhajeet; et al. (July 2016), "LO Peg: surface differential rotation, flares, and spot-topographic evolution", Monthly Notices of the Royal Astronomical Society, 459 (3): 3112–3129, arXiv:1608.06522, Bibcode:2016MNRAS.459.3112K, doi:10.1093/mnras/stw855.
  2. ↑ Kiraga, M. (March 2012). "ASAS Photometry of ROSAT Sources. I. Periodic Variable Stars Coincident with Bright Sources from the ROSAT All Sky Survey" (PDF). Acta Astronomica. 62 (1): 67–95. arXiv:1204.3825. Bibcode:2012AcA....62...67K. Retrieved 23 June 2022.
  3. 1 2 3 4 5 Brown, A. G. A.; et al. (Gaia collaboration) (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics. 649: A1. arXiv:2012.01533. Bibcode:2021A&A...649A...1G. doi:10.1051/0004-6361/202039657. S2CID 227254300. (Erratum: doi:10.1051/0004-6361/202039657e). Gaia EDR3 record for this source at VizieR.
  4. 1 2 3 Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015, S2CID 119257644.
  5. 1 2 3 4 Samus', N. N; et al. (2017), "General catalogue of variable stars", Astronomy Reports, GCVS 5.1, 61 (1): 80, Bibcode:2017ARep...61...80S, doi:10.1134/S1063772917010085, S2CID 125853869.
  6. 1 2 Gray, R. O.; et al. (2003), "Contributions to the Nearby Stars (NStars) Project: Spectroscopy of Stars Earlier than M0 within 40 Parsecs: The Northern Sample. I", The Astronomical Journal, 126 (4): 2048, arXiv:astro-ph/0308182, Bibcode:2003AJ....126.2048G, doi:10.1086/378365, S2CID 119417105.
  7. 1 2 Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
  8. ↑ Pandey, J. C.; et al. (September 2005), "Optical and X-Ray Studies of Chromospherically Active Stars: FR Cancri, HD 95559, and LO Pegasi", The Astronomical Journal, 130 (3): 1231–1246, arXiv:astro-ph/0506010, Bibcode:2005AJ....130.1231P, doi:10.1086/432539, S2CID 119357548.
  9. ↑ Strassmeier, Klaus G. (September 2009), "Starspots", The Astronomy and Astrophysics Review, 17 (3): 251–308, Bibcode:2009A&ARv..17..251S, doi:10.1007/s00159-009-0020-6.
  10. ↑ Frasca, A.; et al. (May 1, 2018), "A spectroscopic survey of the youngest field stars in the solar neighborhood . II. The optically faint sample", Astronomy and Astrophysics, 612: A96, arXiv:1801.00671, Bibcode:2018A&A...612A..96F, doi:10.1051/0004-6361/201732028, ISSN 0004-6361, S2CID 119537437.
  11. 1 2 3 Savanov, I. S.; et al. (September 2016), "Photometric Observations of LO Peg in 2014-2015", Acta Astronomica, 66 (3): 381–390, Bibcode:2016AcA....66..381S.
  12. ↑ "LO Peg", SIMBAD, Centre de données astronomiques de Strasbourg, retrieved 2022-03-28.
  13. 1 2 Azulay, R.; et al. (June 2017), "Young, active radio stars in the AB Doradus moving group", Astronomy & Astrophysics, 602: 15, arXiv:1703.08877, Bibcode:2017A&A...602A..57A, doi:10.1051/0004-6361/201629899, S2CID 73553147, A57.
  14. ↑ Savanov, I.; et al. (May 2019), "Activity of rapidly rotating dwarf LO Peg an [sic] giant FK Com", Contributions of the Astronomical Observatory Skalnaté Pleso, 49 (2): 415–419, Bibcode:2019CoSka..49..415S.
  15. 1 2 Jeffries, R. D.; et al. (September 1994), "BD +22 4409 : a rapidly rotating, low-mass member of the Local Association", Monthly Notices of the Royal Astronomical Society, 270: 153–172, Bibcode:1994MNRAS.270..153J, doi:10.1093/mnras/270.1.153.
  16. ↑ Lalitha, S.; et al. (February 10, 2017), "Structure and variability in the corona of the ultrafast rotator LO Pegasi", Astronomy & Astrophysics, 602: 11, arXiv:1702.03158, Bibcode:2017A&A...602A..26L, doi:10.1051/0004-6361/201629482, S2CID 55929044, A26.

Further reading

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