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U Pegasi - Wikipedia

From Wikipedia, the free encyclopedia

U Pegasi
Observation data Epoch J2000.0 Equinox J2000.0
A visual band light curve for U Pegasi, plotted from data published by Zhai et al. (1984)^[1]
Constellation	Pegasus^[2]
Right ascension	23^h 57^m 58.477^s^[3]
Declination	+15° 57′ 10.09″^[3]
Apparent magnitude (V)	9.23 Min I: 10.07 Min II: 9.73^[4]
Characteristics
Evolutionary stage	main sequence^[5]
Spectral type	G2 V + G2: V:^[5]
B−V color index	0.648±0.033^[2]
Variable type	W UMa^[6]
Astrometry

Radial velocity (R_v)	−28.5±4.7^[4] km/s
Proper motion (μ)	RA: 34.598 mas/yr^[3] Dec.: 17.389 mas/yr^[3]
Parallax (π)	5.4708 ± 0.0193 mas^[3]
Distance	596 ± 2 ly (182.8 ± 0.6 pc)
Absolute magnitude (M_V)	3.88^[2]

Orbit^[5]
Period (P)	8.995 h
Eccentricity (e)	0 (assumed)
Inclination (i)	76.1^[7]°
Semi-amplitude (K₁) (primary)	77.6±1.1 km/s
Semi-amplitude (K₂) (secondary)	246.5±1.4 km/s
Details
Primary
Mass	1.224±0.003^[8] `M`_☉
Radius	1.149±0.009^[8] `R`_☉
Luminosity	1.29^[7] `L`_☉
Surface gravity (log g)	4.32^[8] cgs
Temperature	5,860^[8] (polar) K
Secondary
Mass	0.379±0.002^[8] `M`_☉
Radius	0.744±0.002^[8] `R`_☉
Luminosity	0.55^[7] `L`_☉
Surface gravity (log g)	4.27^[8] cgs
Temperature	5,785±7^[8] (polar) K
Other designations
U Peg, BD+15° 4915, HIP 118149, SAO 108933, PPM 143009, WDS J23579+1557A^[9]
Database references
SIMBAD	data

U Pegasi is a binary star system in the constellation of Pegasus, abbreviated U Peg. The pair form an eclipsing binary with a combined peak apparent visual magnitude of 9.23,^[4] which is far too faint to be visible to the naked eye. During the primary eclipse the magnitude decreases to 10.07, while the secondary eclipse only drops to magnitude 9.73.^[4] This system is located at a distance of approximately 596 light years from the Sun based on parallax measurements, but is drifting closer with a radial velocity of around −28.5 km/s.^[4]

The variable luminosity of this system was discovered by S. C. Chandler in 1895. He found it to have a continuously varying light curve with a period of 5.192 h.^[10] Observing the star photometrically, in 1898 E. C. Pickering and O. Wendell determined a longer period of 8.995 h.^[11] H. Shapley published orbital measures for this eclipsing binary in 1913, estimating their relative luminosities and radii.^[12] It was determined to be a variable of the W Ursae Majoris type,^[13] and in 1945 the orbital period was shown to vary over time.^[14]

Properties

This is a double-lined spectroscopic binary star system with an orbital period of 8.995 hours.^[5] Their orbital separation is just 2.533 R_☉.^[7] The inclination of the orbital plane is at an angle of 76.1°^[7] to the plane of the sky from the Earth, so the components are seen to eclipse each other during an orbit. The deeper eclipse occurs when the cooler secondary overlaps the primary star. They belong to the W sub-class of W UMa eclipsing variables.^[15]

The larger member of this system is a G-type main-sequence star with a stellar classification of G2 V.^[5] The primary has a larger mass and radius than the Sun, while the secondary component is significantly smaller and less massive.^[8] The pair are in over-contact by about 14.9%, which allows a considerable amount of energy transfer between the two stars.^[15] As a consequence, the two components show similar effective temperatures and spectral classes. The cooler component displays a significant level of star spot activity that causes the light curve to vary anomalously over time.^[15] The system has an X-ray luminosity of 1.449×10³⁰ erg·s⁻¹.^[16]

The long term change in the orbital period may be explained by mass transfer between the components,^[17] with the matter streaming from the more massive to the less massive star.^[8] The overall period change indicates this mass transfer is occurring at an average rate of (3.7±0.3)×10⁻⁸ M_☉·yr⁻¹. Periodicity in the change rate suggests there may be a third orbiting component in the system with a period of 62 ± 3 years. If so, it would need to have a mass of at least 0.32±0.13 M_☉, which is high enough to be a star.^[18]

References

^ Zhai, D. S.; Leung, K. C.; Zhang, R. X. (September 1984). "A new photoelectric investigation of the W UMa system U Pegasi". Astronomy and Astrophysics, Supplement Series. 57: 487–494. Bibcode:1984A&AS...57..487Z. Retrieved 6 October 2024.
^ ^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 Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
^ ^a ^b ^c ^d ^e Gontcharov, G. A. (2006), "Pulkovo compilation of radial velocities for 35495 stars in a common system", Astronomy Letters, 32 (11): 759–771, arXiv:1606.08053, Bibcode:2006AstL...32..759G, doi:10.1134/S1063773706110065, S2CID 119231169.
^ ^a ^b ^c ^d ^e Lu, W. (November 1985), "A new spectroscopic orbit of the W Ursae Majoris system U Pegasi", Publications of the Astronomical Society of the Pacific, 97: 1086–1091, Bibcode:1985PASP...97.1086L, doi:10.1086/131667, S2CID 122867676.
^ Samus, N. N.; et al. (2017), "General Catalogue of Variable Stars", Astronomy Reports, GCVS 5.1, 61 (1): 80–88, Bibcode:2017ARep...61...80S, doi:10.1134/S1063772917010085, S2CID 255195566.
^ ^a ^b ^c ^d ^e Latković, Olivera; et al. (May 2021), "Statistics of 700 Individually Studied W UMa Stars", The Astrophysical Journal Supplement Series, 254 (1), id. 10, arXiv:2103.06693, Bibcode:2021ApJS..254...10L, doi:10.3847/1538-4365/abeb23.
^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j Pribulla, T.; Vanko, M. (April 2002), "Photoelectric photometry of eclipsing contact binaries: U Peg, YY CrB, OU Ser and EQ Tau", Contributions of the Astronomical Observatory Skalnate Pleso, 32 (1): 79–98, Bibcode:2002CoSka..32...79P.
^ "U Peg", SIMBAD, Centre de données astronomiques de Strasbourg, retrieved 2024-01-28.
^ Chandler, S. C. (November 1895), "On a new variable of peculiar character, 8598 U Pegasi", Astronomical Journal, 15 (358): 181, Bibcode:1895AJ.....15..181C, doi:10.1086/102319.
^ Pickering, E. C.; Wendell, O. C. (February 1898), "The variable star U Pegasi", Astrophysical Journal, 7: 141–145, Bibcode:1898ApJ.....7..141P, doi:10.1086/140447.
^ Shapley, H. (September 1913), "The orbits of eighty-seven eclipsing binaries---a summary", Astrophysical Journal, 38: 158–174, Bibcode:1913ApJ....38..158S, doi:10.1086/142018.
^ Schilt, J. (June 1927), "On the Width of Spectral Lines as a Consequence of Rapid Rotation, in Stars of the W Ursae Majoris Type", Publications of the Astronomical Society of the Pacific, 39 (229): 160, Bibcode:1927PASP...39..160S, doi:10.1086/123698.
^ Recillas, Felix; Jones Woodward, Edith (March 1945), "A study of the eclipsing binary U Pegasi, BD +15°4915", Astronomical Journal, 51: 101, Bibcode:1945AJ.....51..101R, doi:10.1086/105834.
^ ^a ^b ^c Djurašević, G.; et al. (March 2001), "A photometric study of the W UMa-type system U Pegasi", Astronomy and Astrophysics, 367 (3): 840–847, Bibcode:2001A&A...367..840D, doi:10.1051/0004-6361:20000493.
^ Liu, Junhui; et al. (July 2022), "X-ray emission of contact binary variables within 1 kpc", Astronomy & Astrophysics, 663, id. A115, arXiv:2205.13210, Bibcode:2022A&A...663A.115L, doi:10.1051/0004-6361/202142963.
^ Zhai, Di-sheng; et al. (June 1985), "A new photometric study of the binary U Pegasi", Acta Astronomica Sinica, 25 (2): 336–347, Bibcode:1985ChA&A...9...98Z, doi:10.1016/0275-1062(85)90002-5.
^ Tvardovskyi, D. E.; et al. (2017), "Effects of the Mass Transfer and Presence of the Third Components in Close Binary Stellar Systems", Odessa Astronomical Publications, 30: 135–139, arXiv:1711.04831, Bibcode:2017OAP....30..135T, doi:10.18524/1810-4215.2017.30.115463.

Vaccaro, T. R.; et al. (December 2010), Prša, Andrej; Zejda, Miloslav (eds.), "Distance to U Pegasi by the DDE Algorithm", Binaries - Key to Comprehension of the Universe. Proceedings of a conference held June 8–12, 2009 in Brno, Czech Republic, vol. 435, San Francisco: Astronomical Society of the Pacific, p. 89, arXiv:0908.2137, Bibcode:2010ASPC..435...89V.{{citation}}: CS1 maint: date and year (link)
Edalat, M. T.; Taheri, M. (December 2001), "The Photometric Observations and the Light Curve Analysis of U Pegasi", Astrophysics and Space Science, 278 (4): 375–384, doi:10.1023/A:1013195114799, S2CID 118363795.
Maupome, L.; et al. (October 1991), "Photoelectric observations of W UMa stars: U Pegasi and AB Andromedae.", Revista Mexicana de Astronomía y Astrofísica, 22: 235, Bibcode:1991RMxAA..22..235M.
Zhai, Di-Sheng; Zhang, Xiao-Yu (March 1989), "Analysis of the variations in the light curve of U Pegasi and starspot activity", Chinese Astronomy and Astrophysics, 13 (1): 97–104, Bibcode:1989ChA&A..13...97Z, doi:10.1016/0275-1062(89)90064-7.
Zhai, Di-sheng; Lu, Wen-xian (September 1988), "A combined solution of the light curve and velocity curve of U pegasi", Acta Astronomica Sinica, 29 (3): 9–15, Bibcode:1988ChA&A..12..223Z, doi:10.1016/0275-1062(88)90051-3.
Zhai, Disheng; et al. (1988), "Simultaneous light and velocity curve solution and probable starspot activities for the W Uma system U Pegasi", Vistas in Astronomy, 31 (1): 349, Bibcode:1988VA.....31..349Z, doi:10.1016/0083-6656(88)90225-5, S2CID 122565520.
Lafta, S. J.; Grainger, J. F. (April 1986), "A Photoelectric Study of the W-Ursae System U-Pegasi", Astrophysics and Space Science, 121 (1): 61–81, Bibcode:1986Ap&SS.121...61L, doi:10.1007/BF00648263, S2CID 120267326.
Rovithis, P.; Rovithis-Livaniou, H. (October 1982), "Photoelectric observations of the eclipsing binary U Pegasi", Astrophysics and Space Science, 87 (1–2): 287–295, Bibcode:1982Ap&SS..87..287R, doi:10.1007/BF00648924, S2CID 122296476.
Russo, G.; et al. (February 1982), "Determination of parameters of W UMa system. II : TW Cet, S Ant, U Peg, ER Ori.", Astronomy and Astrophysics, Supplement Series, 47: 211–216, Bibcode:1982A&AS...47..211R.
Rigterink, P. V. (May 1972), "A new analysis of the eclipsing binary, U Pegasi", Astronomical Journal, 77: 319–329, Bibcode:1972AJ.....77..319R, doi:10.1086/111286.
Binnendijk, L. (March 1960), "The light variation and orbital elements of U Pegasi", Astronomical Journal, 65: 88–96, Bibcode:1960AJ.....65...88B, doi:10.1086/108194.
Huruhata, Masaaki (August 1952), "Flaring Phenomena in U Pegasi", Publications of the Astronomical Society of the Pacific, 64 (379): 200, Bibcode:1952PASP...64..200H, doi:10.1086/126463, S2CID 122860173.
Lafara, Robert (January 1952), "A Photoelectric Study of U Pegasi in Two Colors", Astrophysical Journal, 115: 14, Bibcode:1952ApJ...115...14L, doi:10.1086/145504.

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 (Dimidium) 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 7312 7315 7317 7318 7319 7320 7320c 7331 7332 7427 7448 7454 7457 7466 7469 7479 7610 7619 7625 7673 7674 7678 7720 7726 7735 7741 7742 NGC 7752 NGC 7753 7767 7769 7773 7800 7814
Other	BX442 CTA-102 Einstein Cross Huchra's lens IC 5145 IC 5337 Markarian 335 Pegasus Dwarf Irregular Galaxy Pegasus Dwarf Spheroidal Galaxy Q2343-BX418

Galaxy clusters	Abell 2390 NGC 7331 Group Stephan's Quintet

Astronomical events	SN 1990U SN 2008ha SN 2013fs

Properties

References

Further reading