LO Pegasi

Star in the constellation Pegasus

LO Pegasi
Observation data Epoch J2000.0 Equinox J2000.0
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.
Constellation	Pegasus
Right ascension	21^h 31^m 01.714^s^[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 (R_v)	−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]
Distance	78.99 ± 0.03 ly (24.218 ± 0.010 pc)
Absolute magnitude (M_V)	7.26^[4]

Details^[8]

Mass	0.66±0.02 `M`_☉
Radius	0.72±0.10 `R`_☉
Luminosity	0.25±0.02 `L`_☉
Surface gravity (log g)	4.5±0.5 cgs
Temperature	4,750±250 K
Rotation	0.4236 d^[9]
Rotational velocity (v sin i)	48.2±2.5^[10] km/s
Age	10–300^[11] Myr

Other designations
LO Peg, AG+23 2203, BD+22 4409, GJ 4199, HIP 106231, WDS J21310+2320A^[12]
Database references
SIMBAD	data

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]

References

^ ^a ^b ^c 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.
^ Kiraga, M. (2012), "ASAS photometry of ROSAT sources I. Periodic variable stars coincident with bright sources from ROSAT all sky survey", Acta Astronomica, 62 (1): 67, arXiv:1204.3825, Bibcode:2012AcA....62...67K
^ ^a ^b ^c ^d 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.
^ ^a ^b ^c 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.
^ ^a ^b ^c ^d 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.
^ ^a ^b 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.
^ ^a ^b 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.
^ 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.
^ 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.
^ 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, S2CID 119537437.
^ ^a ^b ^c 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.
^ "LO Peg", SIMBAD, Centre de données astronomiques de Strasbourg, retrieved 2022-03-28.
^ ^a ^b 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.
^ 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.
^ ^a ^b 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.
^ 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.

Boehm, V. A.; Rishi, A.; Harmon, R. (January 2020). "Imaging Starspots on LO Pegasi, 2014-2019". Bulletin of the American Astronomical Society. 52 (1). Bibcode:2020AAS...23527304B.
Savanov, I. S.; et al. (July 2018), "Photometric Observations of LO Peg in 2017", Astrophysical Bulletin, 73 (3): 344–350, Bibcode:2018AstBu..73..344S, doi:10.1134/S1990341318030082, S2CID 255380166.
Pandey, S. B.; et al. (December 2014), "Long-term spot topography and multi-band flare analysis of active ultra-fast rotator LO Peg", Proceedings of Swift: 10 Years of Discovery (SWIFT 10), held 2-5 December 2014 at La Sapienza University, Rome, Italy, p. 155, Bibcode:2014styd.confE.155P, doi:10.22323/1.233.0155.
Pandey, J. C.; et al. (August 2011), "Optical polarimetry and photometry of young sun-like star LO Peg", The Physics of Sun and Star Spots, Proceedings of the International Astronomical Union, IAU Symposium, vol. 273, pp. 455–459, Bibcode:2011IAUS..273..455P, doi:10.1017/S1743921311015766.
Taš, G. (January 2011), "Long-term photometry of the ultra-fast rotator LO Peg", Astronomische Nachrichten, 332 (1): 57–64, Bibcode:2011AN....332...57T, doi:10.1002/asna.201011487.
Pandey, J. C.; et al. (June 2009), "LO Pegasi: an investigation of multiband optical polarization", Monthly Notices of the Royal Astronomical Society, 396 (2): 1004–1011, arXiv:0903.2558, Bibcode:2009MNRAS.396.1004P, doi:10.1111/j.1365-2966.2009.14762.x, S2CID 15894406.
Barnes, J. R.; et al. (February 2005), "LO Peg in 1998: star-spot patterns and differential rotation", Monthly Notices of the Royal Astronomical Society, 356 (4): 1501–1508, arXiv:astro-ph/0410596, Bibcode:2005MNRAS.356.1501B, doi:10.1111/j.1365-2966.2004.08588.x, S2CID 11650283.
Harmon, R. O.; Saranathan, V. (December 2004), "Spot topography of BD+22o 4409 (LO Peg) using Matrix Light-curve Inversion", Bulletin of the American Astronomical Society, 36: 1361, Bibcode:2004AAS...205.1410H.
Piluso, N.; et al. (June 2008), "Doppler imaging of the young late-type star LO Pegasi (BD+22°4409) in 2003 September", Monthly Notices of the Royal Astronomical Society, 387 (1): 237–246, arXiv:0802.3957, Bibcode:2008MNRAS.387..237P, doi:10.1111/j.1365-2966.2008.13153.x, S2CID 119236039.
Csorvási, R. (September 2006), Forgács-Dajka, E. (ed.), "Photometry of LO Pegasi in B, V, R colors", Proceedings of the 4th Workshop of Young Researchers in Astronomy & Astrophysics; Budapest, Hungary, 11-13 January, 2006, vol. 17, Astronomy Department of the Eötvös University (PADEU), p. 95, Bibcode:2006PADEU..17...95C.
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.
Barnes, J. R.; et al. (February 2005), "LO Peg in 1998: star-spot patterns and differential rotation", Monthly Notices of the Royal Astronomical Society, 356 (4): 1501–1508, arXiv:astro-ph/0410596, Bibcode:2005MNRAS.356.1501B, doi:10.1111/j.1365-2966.2004.08588.x, S2CID 11650283.
Dal, H. A.; Tas, G. (March 2003), "New Photoelectric Photometry of the Young Star LO Pegasi", Information Bulletin on Variable Stars, 5390 (1): 1, Bibcode:2003IBVS.5390....1D.
Lister, T. A.; et al. (August 1999), "Doppler imaging of BD+22° 4409 (LO Peg) using least-squares deconvolution", Monthly Notices of the Royal Astronomical Society, 307 (3): 685–694, Bibcode:1999MNRAS.307..685L, doi:10.1046/j.1365-8711.1999.02662.x.
Eibe, M. T.; et al. (January 1999), "Evidence for large-scale, global mass inflow and flaring on the late-type fast rotator BD+22 deg 4409", Astronomy and Astrophysics, 341: 527–538, Bibcode:1999A&A...341..527E.
Robb, R. M.; Cardinal, R. D. (August 1995), "Optical Observations of the Active Star RE J2131+233", Information Bulletin on Variable Stars, 4221 (1): 1, Bibcode:1995IBVS.4221....1R.

Constellation of Pegasus

Stars

Bayer	α (Markab) β (Scheat) γ (Algenib) δ (Alpheratz) ε (Enif) ζ (Homam) η (Matar) θ (Biham) ι κ λ μ (Sadalbari) ν ξ ο π¹ π² ρ σ τ (Salm) υ (Alkarab) φ χ ψ
Flamsteed	1 2 3 4 5 7 9 11 12 13 14 15 16 17 18 19 20 21 23 25 28 30 31 32 33 34 35 36 37 38 39 40 41 45 51 (Helvetios) 52 55 56 57 58 59 60 61 63 64 65 66 67 69 70 71 72 73 74 75 76 77 78 79 80 82 83 85 86 87 23 Psc 34 Vul
Variable	R S U W Z RU RV RZ SV TW TY AG AQ AT AU AV AW BB BH BK BO BP BX BY DH DI DY EE EF EQ EZ GT GX HN HO HP HR HX II IK IM IP KT KU LL LO LS MS MT NV NZ OY PT V342 V343 V354 V363 V372 V376 V391
HR	19 49 8116 8219 8221 8231 8250 8257 8258 8274 8292 8325 8341 8348 8358 8359 8364 8372 8391 8397 8412 8415 8435 8441 8455 8456 8458 8460 8461 8466 8475 8482 8491 8503 8514 8543 8555 8564 8587 8604 8605 8608 8631 8638 8642 8737 8784 8788 8792 8824 8831 8833 8838 8839 8873 8922 8942 8953 8970 9039 9055 9078 9109
HD	434 204603 205011 205422 205603 206689 206793 208897 209709 210890 211076 213025 215549 215733 219196 219828 220288 220773 221170 221493 225292
Other	BD+14 4559 (Solaris) BD +17 4708 BD +28 4211 GD 246 Gl 829 Gl 880 HAT-P-8 NGC 8 NGC 18 NGC 30 PG 2131+066 PG 2303+243 PSR B2127+11C PSR B2303+30 Q2343-BX418 WASP-10 WASP-21 (Tangra) WASP-52 (Anadolu) WASP-59 WASP-60 (Morava) X2127+119 3C 454.3

Exoplanets	51 Pegasi b WASP-10b BD+14 4559 b (Pirx) TOI-5678 b HD 209458 b HR 8799 b c d e

Star
clusters

Other	Balbinot 1 Messier 15

Nebulae

Other	Pease 1

Galaxies

NGC	1 2 9 14 15 16 22 23 26 41 42 52 7033 7034 7042 7043 7053 7056 7066 7068 7074 7085 7190 7217 7236 7237 7303 7315 7317 7318 7319 7320 7320c 7331 7332 7448 7454 7457 7469 7479 7610 7619 7625 7673 7674 7678 7720 7741 7742 NGC 7752 NGC 7753 7767 7773 7800 7814
Other	BX442 CTA-102 Einstein Cross Huchra's lens IC 5337 Markarian 335 Pegasus Dwarf Irregular Galaxy Pegasus Dwarf Spheroidal Galaxy Q2343-BX418