LO Pegasi

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]

  1. ^ a b c Cite error: The named reference Karmakar_et_al_2016 was invoked but never defined (see the help page).
  2. ^ Cite error: The named reference Kiraga was invoked but never defined (see the help page).
  3. ^ a b c d Cite error: The named reference GaiaEDR3 was invoked but never defined (see the help page).
  4. ^ a b c Cite error: The named reference Anderson_Francis_2012 was invoked but never defined (see the help page).
  5. ^ a b c d Cite error: The named reference Samus_et_al_2017 was invoked but never defined (see the help page).
  6. ^ a b Cite error: The named reference Gray_et_al_2003 was invoked but never defined (see the help page).
  7. ^ a b Cite error: The named reference GaiaDR2 was invoked but never defined (see the help page).
  8. ^ Cite error: The named reference Pandey_et_al_2005 was invoked but never defined (see the help page).
  9. ^ Cite error: The named reference Strassmeier2009 was invoked but never defined (see the help page).
  10. ^ Cite error: The named reference Frasca_et_al_2018 was invoked but never defined (see the help page).
  11. ^ a b c Cite error: The named reference Savanov_et_al_2016 was invoked but never defined (see the help page).
  12. ^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  13. ^ a b Cite error: The named reference Azulay_et_al_2017 was invoked but never defined (see the help page).
  14. ^ Cite error: The named reference Savanov_et_al_2019 was invoked but never defined (see the help page).
  15. ^ a b Cite error: The named reference Jeffries_et_al_1994 was invoked but never defined (see the help page).
  16. ^ Cite error: The named reference Lalitha_et_al_2017 was invoked but never defined (see the help page).