Astronomy:U Pegasi

From HandWiki
Short description: Binary star in the constellation Pegasus
U Pegasi
Observation data
Equinox J2000.0]] (ICRS)
Constellation Pegasus[1]
Right ascension  23h 57m 58.477s[2]
Declination +15° 57′ 10.09″[2]
Apparent magnitude (V) 9.23
Min I: 10.07
Min II: 9.73[3]
Characteristics
Evolutionary stage main sequence[4]
Spectral type G2 V + G2: V:[4]
B−V color index 0.648±0.033[1]
Variable type W UMa[5]
Astrometry
Radial velocity (Rv)−28.5±4.7[3] km/s
Proper motion (μ) RA: 34.598[2] mas/yr
Dec.: 17.389[2] mas/yr
Parallax (π)5.4708 ± 0.0193[2] mas
Distance596 ± 2 ly
(182.8 ± 0.6 pc)
Absolute magnitude (MV)3.88[1]
Orbit[4]
Period (P)8.995 h
Eccentricity (e)0 (assumed)
Inclination (i)76.1[6]°
Semi-amplitude (K1)
(primary)		77.6±1.1 km/s
Semi-amplitude (K2)
(secondary)		246.5±1.4 km/s
Details
Primary
Mass1.224±0.003[7] M☉
Radius1.149±0.009[7] R☉
Luminosity1.29[6] L☉
Surface gravity (log g)4.32[7] cgs
Temperature5,860[7] (polar) K
Secondary
Mass0.379±0.002[7] M☉
Radius0.744±0.002[7] R☉
Luminosity0.55[6] L☉
Surface gravity (log g)4.27[7] cgs
Temperature5,785±7[7] (polar) K
Other designations
U Peg, BD+15° 4915, HIP 118149, SAO 108933, PPM 143009, WDS J23579+1557A[8]
Database references
SIMBADdata

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,[3] 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.[3] 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.[3]

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.[9] Observing the star photometrically, in 1898 E. C. Pickering and O. Wendell determined a longer period of 8.995 h.[10] H. Shapley published orbital measures for this eclipsing binary in 1913, estimating their relative luminosities and radii.[11] It was determined to be a variable of the W Ursae Majoris type,[12] and in 1945 the orbital period was shown to vary over time.[13]

Properties

This is a double-lined spectroscopic binary star system with an orbital period of 8.995 hours.[4] Their orbital separation is just 2.533 R☉.[6] The inclination of the orbital plane is at an angle of 76.1°[6] 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.[14]

The larger member of this system is a G-type main-sequence star with a stellar classification of G2 V.[4] The primary has a larger mass and radius than the Sun, while the secondary component is significantly smaller and less massive.[7] The pair are in over-contact by about 14.9%, which allows a considerable amount of energy transfer between the two stars.[14] 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.[14] The system has an X-ray luminosity of 1.449×1030 erg·s−1.[15]

The long term change in the orbital period may be explained by mass transfer between the components,[16] with the matter streaming from the more massive to the less massive star.[7] 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.[17]

References

  1. ↑ 1.0 1.1 1.2 Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters 38 (5): 331, doi:10.1134/S1063773712050015, Bibcode: 2012AstL...38..331A. 
  2. ↑ 2.0 2.1 2.2 2.3 Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940  Gaia DR3 record for this source at VizieR.
  3. ↑ 3.0 3.1 3.2 3.3 3.4 Gontcharov, G. A. (2006), "Pulkovo compilation of radial velocities for 35495 stars in a common system", Astronomy Letters 32 (11): 759–771, doi:10.1134/S1063773706110065, Bibcode: 2006AstL...32..759G. 
  4. ↑ 4.0 4.1 4.2 4.3 4.4 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, doi:10.1086/131667, Bibcode: 1985PASP...97.1086L. 
  5. ↑ Samus, N. N. et al. (2017), "General Catalogue of Variable Stars", Astronomy Reports, GCVS 5.1 61 (1): 80–88, doi:10.1134/S1063772917010085, Bibcode: 2017ARep...61...80S. 
  6. ↑ 6.0 6.1 6.2 6.3 6.4 Latković, Olivera et al. (May 2021), "Statistics of 700 Individually Studied W UMa Stars", The Astrophysical Journal Supplement Series 254 (1): id. 10, doi:10.3847/1538-4365/abeb23, Bibcode: 2021ApJS..254...10L. 
  7. ↑ 7.0 7.1 7.2 7.3 7.4 7.5 7.6 7.7 7.8 7.9 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. 
  8. ↑ "U Peg". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=U+Peg. 
  9. ↑ Chandler, S. C. (November 1895), "On a new variable of peculiar character, 8598 U Pegasi", Astronomical Journal 15 (358): 181, doi:10.1086/102319, Bibcode: 1895AJ.....15..181C. 
  10. ↑ "The variable star U Pegasi", Astrophysical Journal 7: 141–145, February 1898, doi:10.1086/140447, Bibcode: 1898ApJ.....7..141P. 
  11. ↑ Shapley, H. (September 1913), "The orbits of eighty-seven eclipsing binaries---a summary", Astrophysical Journal 38: 158–174, doi:10.1086/142018, Bibcode: 1913ApJ....38..158S. 
  12. ↑ 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, doi:10.1086/123698, Bibcode: 1927PASP...39..160S. 
  13. ↑ Recillas, Felix (March 1945), "A study of the eclipsing binary U Pegasi, BD +15°4915", Astronomical Journal 51: 101, doi:10.1086/105834, Bibcode: 1945AJ.....51..101R. 
  14. ↑ 14.0 14.1 14.2 Djurašević, G. et al. (March 2001), "A photometric study of the W UMa-type system U Pegasi", Astronomy and Astrophysics 367 (3): 840–847, doi:10.1051/0004-6361:20000493, Bibcode: 2001A&A...367..840D. 
  15. ↑ Liu, Junhui et al. (July 2022), "X-ray emission of contact binary variables within 1 kpc", Astronomy & Astrophysics 663: id. A115, doi:10.1051/0004-6361/202142963, Bibcode: 2022A&A...663A.115L. 
  16. ↑ Zhai, Di-sheng et al. (June 1985), "A new photometric study of the binary U Pegasi", Acta Astronomica Sinica 25 (2): 336–347, doi:10.1016/0275-1062(85)90002-5, Bibcode: 1985ChA&A...9...98Z. 
  17. ↑ 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, doi:10.18524/1810-4215.2017.30.115463, Bibcode: 2017OAP....30..135T. 

Further reading

  • 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 (San Francisco: Astronomical Society of the Pacific) 435: p. 89, Bibcode: 2010ASPC..435...89V. 
  • 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. 
  • Maupome, L. et al. (October 1991), "Photoelectric observations of W UMa stars: U Pegasi and AB Andromedae.", Revista Mexicana de Astronomia y Astrofisica 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, doi:10.1016/0275-1062(89)90064-7, Bibcode: 1989ChA&A..13...97Z. 
  • 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, doi:10.1016/0275-1062(88)90051-3, Bibcode: 1988ChA&A..12..223Z. 
  • 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, doi:10.1016/0083-6656(88)90225-5, Bibcode: 1988VA.....31..349Z. 
  • 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, doi:10.1007/BF00648263, Bibcode: 1986Ap&SS.121...61L. 
  • Zhai, D. S. et al. (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. 
  • Rovithis, P.; Rovithis-Livaniou, H. (October 1982), "Photoelectric observations of the eclipsing binary U Pegasi", Astrophysics and Space Science 87 (1–2): 287–295, doi:10.1007/BF00648924, Bibcode: 1982Ap&SS..87..287R. 
  • 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, doi:10.1086/111286, Bibcode: 1972AJ.....77..319R. 
  • Binnendijk, L. (March 1960), "The light variation and orbital elements of U Pegasi", Astronomical Journal 65: 88–96, doi:10.1086/108194, Bibcode: 1960AJ.....65...88B. 
  • Huruhata, Masaaki (August 1952), "Flaring Phenomena in U Pegasi", Publications of the Astronomical Society of the Pacific 64 (379): 200, doi:10.1086/126463, Bibcode: 1952PASP...64..200H. 
  • Lafara, Robert (January 1952), "A Photoelectric Study of U Pegasi in Two Colors", Astrophysical Journal 115: 14, doi:10.1086/145504, Bibcode: 1952ApJ...115...14L. 



Retrieved from "https://handwiki.org/wiki/index.php?title=Astronomy:U_Pegasi&oldid=3348295"