ER Vulpeculae

ER Vulpeculae is a binary star system in the northern constellation of Vulpecula, abbreviated ER Vul. It is a variable star system with a brightness that ranges from an apparent visual magnitude of 7.27 down to 7.49,[3] which is too faint to be visible to the naked eye. This system is located at a distance of 165 light years from the Sun based on parallax measurements. It is drifting closer with a radial velocity of −25 km/s.[6]

ER Vulpeculae

A light curve for ER Vulpeculae, plotted from TESS data[1]
Observation data
Epoch J2000      Equinox J2000
Constellation Vulpecula
Right ascension 21h 02m 25.907s[2]
Declination 27° 48′ 26.44″[2]
Apparent magnitude (V) 7.27 to 7.49[3]
Characteristics
Spectral type G0V + G5V[4]
B−V color index 0.614±0.010[5]
Variable type W UMa/RS CVn[3]
Astrometry
Radial velocity (Rv)−24.6±0.5[6] km/s
Proper motion (μ) RA: 87.102 mas/yr[2]
Dec.: 6.364 mas/yr[2]
Parallax (π)19.8012 ± 0.0187 mas[2]
Distance164.7 ± 0.2 ly
(50.50 ± 0.05 pc)
Absolute magnitude (MV)3.75[5] (4.28 + 4.31)[7]
Orbit
Period (P)0.698095 d[8]
Semi-major axis (a)4.28±0.04 AU[8]
Eccentricity (e)0.017±0.007[9]
Inclination (i)66.63[8]°
Periastron epoch (T)2,445,220.40964 JD[8]
Argument of periastron (ω)
(secondary)		62.6±29.0[9]°
Semi-amplitude (K1)
(primary)		138.67±2.06[8] km/s
Semi-amplitude (K2)
(secondary)		146.13±1.90[8] km/s
Details
ER Vul A
Mass1.108±0.033[8] M☉
Radius1.16±0.06[7] R☉
Luminosity1.56±0.15[7] L☉
Temperature5,900[4] K
Rotational velocity (v sin i)84[8] km/s
ER Vul B
Mass1.052±0.034[8] M☉
Radius1.18±0.14[7] R☉
Luminosity1.52±0.37[7] L☉
Temperature5,750[4] K
Rotational velocity (v sin i)78[8] km/s
Other designations
ER Vul, CD+27°3952, HD 200391, HIP 103833, SAO 89396, PPM 112323[10]
Database references
SIMBADdata

This star was observed to be a double-lined spectroscopic binary by R. J. Northcott[11] in 1946,[9] indicating this is a binary star system where the individual spectra of each component is visible. G. A. Bakos found it to be a candidate eclipsing binary in 1955, and orbital elements were produced in 1956. The light curve of the system showed a very short orbital period of 16.75 hours and was found to vary continually between the minima. Both components were classified as G-type main-sequence stars.[9]

The wavy shape of the light curve of ER Vul resembles those of a W UMa star for a detached binary, indicating that the stars are not in direct contact but are close enough to gravitationally distort their shapes. By 1967, studies showed unexplained fluctuations in the light curve.[12] H. E. Bond in 1970 found calcium H and K lines in emission.[13] D. S. Hall classified the ER Vul system as a short period RS Canum Venaticorum variable in 1970, based on the spectral type and emission lines.[14] These emission lines suggest some form of chromospheric activity on the star. Dark star spots were proposed as an explanation of the intrinsic variability of these types of stars by H. M. Al-Naimiy,[15] and ER Vul was determined to be heavily spotted.[16]

The corona of ER Vul was found to be a strong source of soft X-rays by F. M. Walter and S. Bowyer in 1981.[17][15] The eclipsing nature of the system was confirmed by T. H. Kadouri in 1981, with the primary eclipse being an occultation.[15] Radio emission was detected with the VLA in 1992, and it was found to be the one of the most luminous main-sequence stars known in that band.[18] Due to gravitational interaction that has forced a tidal lock with their close orbit, both stars are rotating rapidly – more than 40 times the rotation rate of the Sun, which is driving their magnetic dynamo. They show the "strongest coronal and chromospheric emissions of any main-sequence G-type star".[19]

C. İbanoğlu and associates in 1993 were able to explain the light curve of this system through a combination of "proximity effects, wavelike distortions, mutual eclipses, and short-term light fluctuations".[20] By measuring variations in Hydrogen alpha emission, Ö. Çakırlı and associates in 2003 found that cooler secondary component is the more active of the pair.[7] However, other observers have observed that the primary is the more active. This changeover may be the result of magnetic interaction between the stars.[8] In 2005, E. Shkolnik and associates discovered a high-velocity stream passing between the stars toward the secondary component. This stream is creating a large active area on the companion.[21]

References
  1. MAST: Barbara A. Mikulski Archive for Space Telescopes, Space Telescope Science Institute, retrieved 21 August 2022.
  2. 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.
  3. Samus, N. N.; et al. (2017), "General Catalogue of Variable Stars", Astronomy Reports, 5.1, 61 (1): 80–88, Bibcode:2017ARep...61...80S, doi:10.1134/S1063772917010085, S2CID 125853869.
  4. 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.
  5. 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.
  6. Karataș, Yüksel; et al. (2004), "Kinematics of chromospherically active binaries and evidence of an orbital period decrease in binary evolution", Monthly Notices of the Royal Astronomical Society, 349 (3): 1069–1092, arXiv:astro-ph/0404219, Bibcode:2004MNRAS.349.1069K, doi:10.1111/j.1365-2966.2004.07588.x, S2CID 15290475.
  7. Çakırlı, Ö.; et al. (March 2003), "Hα variations of the RS CVn type binary ER Vulpeculae", Astronomy and Astrophysics, 400: 257–264, Bibcode:2003A&A...400..257C, doi:10.1051/0004-6361:20021885, S2CID 122676294.
  8. Özavcı, İ.; et al. (May 2019), "Surface inhomogeneities of the eclipsing binary ER Vul", Contributions of the Astronomical Observatory Skalnaté Pleso, 49 (2): 278–286, Bibcode:2019CoSka..49..278O.
  9. Northcott, Ruth J.; Bakos, Gustav A. (May 1956), "A new eclipsing spectroscopic binary, HD 200391", Astronomical Journal, 61: 188, Bibcode:1956AJ.....61..188N, doi:10.1086/107417.
  10. "ER Vul". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2022-08-18.
  11. Heard, J. F. (October 1956), "Reports of observatories, 1955-56", Astronomical Journal, 61: 318, Bibcode:1956AJ.....61..318H, doi:10.1086/107352.
  12. Northcott, Ruth J.; Bakos, Gustav A. (February 1967), "Spectroscopic and photometric observations of ER Vulpeculas", Astronomical Journal, 72: 89, Bibcode:1967AJ.....72...89N, doi:10.1086/110205.
  13. Bond, Howard E. (April 1970), "New Peculiar Stars Noted on Objective-Prism Plates", Publications of the Astronomical Society of the Pacific, 82 (485): 321, Bibcode:1970PASP...82..321B, doi:10.1086/128911, S2CID 119525277.
  14. Hall, D. S. (1976), Fitch, W. S. (ed.), "The RS CVn Binaries and Binaries with Similar Properties", Multiple Periodic Variable Stars, Proceedings of IAU Colloq. 29, held in Budapest, Hungary, 1–5 September 1975, Astrophysics and Space Science Library, D. Reidel Publishers, vol. 60, p. 287, Bibcode:1976ASSL...60..287H, doi:10.1007/978-94-010-1175-4_15, ISBN 978-94-010-1177-8, S2CID 120775716.
  15. Ibanoglu, C.; et al. (August 1987), "Light curve variations in ER vulpeculae", Astrophysics and Space Science, 136 (2): 225–229, Bibcode:1987Ap&SS.136..225I, doi:10.1007/BF00642114, S2CID 119647294.
  16. Rucinski, S. M. (1979), "Sizes of spots in spotted stars", Acta Astronomica, 29: 203–209, Bibcode:1979AcA....29..203R.
  17. Walter, F. M.; Bowyer, S. (April 1981), "On the coronae of rapidly rotating stars. I. The relation between rotation and coronal activity in RS CVn systems.", Astrophysical Journal, 245: 671–676, Bibcode:1981ApJ...245..671W, doi:10.1086/158842.
  18. Rucinski, S. M. (December 1992), "VLA Radio Light Curves of ER Vulpeculae at 3.6 and 6 CM", Publications of the Astronomical Society of the Pacific, 104: 1177, Bibcode:1992PASP..104.1177R, doi:10.1086/133106, S2CID 121394464.
  19. Bradstreet, D. H.; et al. (December 1993), "The Hyperactive Double Suns of the Binary ER Vulpeculae", Bulletin of the American Astronomical Society, 25: 1425, Bibcode:1993AAS...183.8504B.
  20. Ibanoglu, C.; et al. (March 1993), "Photometry of ER Vulpeculae : photometric analysis with the WINK-10 code", Astronomy and Astrophysics, 269: 310–318, Bibcode:1993A&A...269..310I.
  21. Shkolnik, Evgenya; et al. (August 2005), "Investigating Ca II Emission in the RS Canum Venaticorum Binary ER Vulpeculae Using the Broadening Function Formalism", The Astronomical Journal, 130 (2): 799–808, arXiv:astro-ph/0504428, Bibcode:2005AJ....130..799S, doi:10.1086/431364, S2CID 119096436.

Further reading
  • Crăciun, Maria; et al. (April 2015), "Detection of low-level periodic signals through enhanced self-correlation method. The case of ER Vulpeculae", Monthly Notices of the Royal Astronomical Society, 448 (3): 2066–2076, Bibcode:2015MNRAS.448.2066C, doi:10.1093/mnras/stv108.
  • Xiang, Yue; et al. (February 2015), "Doppler images of the eclipsing binary ER Vulpeculae", Monthly Notices of the Royal Astronomical Society, 447 (1): 567–576, arXiv:1411.5531, Bibcode:2015MNRAS.447..567X, doi:10.1093/mnras/stu2458.
  • Pop, Alexandru; Vamoş, Călin (October 2013), "Orbital period modulation of the eclipsing binary system ER Vulpeculae: Real or not?", New Astronomy, 23: 27–35, Bibcode:2013NewA...23...27P, doi:10.1016/j.newast.2013.02.003.
  • Harmanec, P.; et al. (February 2004), "An improved ephemeris and physical elements of ER Vul", Astronomy and Astrophysics, 415: 289–297, Bibcode:2004A&A...415..289H, doi:10.1051/0004-6361:20034614.
  • Kjurkchieva, D. P.; et al. (June 2003), "Spectroscopic and photometric observations of the short-period RS CVn-type star ER Vulpeculae", Astronomy and Astrophysics, 404 (2): 611–620, Bibcode:2003A&A...404..611K, doi:10.1051/0004-6361:20030489.
  • Duemmler, R.; et al. (May 2003), "The radial velocities and physical parameters of ER Vul", Astronomy and Astrophysics, 402 (2): 745–754, Bibcode:2003A&A...402..745D, doi:10.1051/0004-6361:20030299, S2CID 250602183.
  • Ekmekči, F.; et al. (March 2002), "Chromospherically active binary systems, RT And and ER Vul: 1995-1998 observations and spot distributions", Astronomische Nachrichten, 323 (1): 31–35, Bibcode:2002AN....323...31E, doi:10.1002/1521-3994(200203)323:1<31::AID-ASNA31>3.0.CO;2-2.
  • Osten, Rachel A.; et al. (January 2002), "Multiwavelength Observations of Three Short-Period Active Binary Systems: ER Vulpeculae, CC Eridani, and EI Eridani", The Astrophysical Journal Supplement Series, 138 (1): 99–120, Bibcode:2002ApJS..138...99O, doi:10.1086/323666, S2CID 122667001.
  • Qian, S. B. (2001), Brekke, Pål; et al. (eds.), "Possible Magnetic Activity Cycles of Four Chromospherically Active Binaries: ER Vul, UV Psc, AR Lac and BH Vir", Recent Insights into the Physics of the Sun and Heliosphere: Highlights from SOHO and Other Space Missions, Proceedings of IAU Symposium 203, Astronomical Society of the Pacific, vol. 203, p. 437, Bibcode:2001IAUS..203..437Q, ISBN 1-58381-069-2.
  • Rucinski, Slavek M. (March 1998), "VLA Observations of Radio Variability of ER Vulpeculae in 1995", The Publications of the Astronomical Society of the Pacific, 110 (745): 272–275, arXiv:astro-ph/9710112, Bibcode:1998PASP..110..272R, doi:10.1086/316140, S2CID 18809148.
  • Lazaro, C.; Arevalo, M. J. (June 1997), "Time-Resolved Spectroscopy of RS CVn Short-Period Systems. I. CG Cyg, BH Vir, and ER Vul", The Astronomical Journal, 113: 2283, Bibcode:1997AJ....113.2283L, doi:10.1086/118439.
  • Gunn, A. G.; Doyle, J. G. (February 1997), "Environments of active close binaries. I. ER Vulpeculae", Astronomy and Astrophysics, 318: 60–72, Bibcode:1997A&A...318...60G.
  • Oláh, K.; Kövári, Zs. (1997), "Spot temperatures in binaries with two active components: By Dra and Er Vul", Astronomical and Astrophysical Transactions, 13 (4): 295–299, Bibcode:1997A&AT...13..295O, doi:10.1080/10556799708202971.
  • Edalati, M. T.; Zeinali, F. (December 1995), "The Photometric Observations of ER Vulpeculae: Photometric Analysis with the W-D Code", Astrophysics and Space Science, 234 (2): 271–280, Bibcode:1995Ap&SS.234..271E, doi:10.1007/BF00627672, S2CID 119974452.
  • Zeinali, F.; et al. (May 1995), "Photoelectric Observations of the Eclipsing Variable ER Vulpeculae", Information Bulletin on Variable Stars, 4190: 1, Bibcode:1995IBVS.4190....1Z.
  • Olah, K.; et al. (November 1994), "The active close binary system ER Vulpeculae", Astronomy and Astrophysics, 291: 110–120, Bibcode:1994A&A...291..110O.
  • Eryurt, D.; et al. (December 1991), "The Light Curve of ER Vulpeculae", Information Bulletin on Variable Stars, 3692: 1, Bibcode:1991IBVS.3692....1E.
  • Guinan, E. F.; et al. (September 1991), "Simultaneous IUE and Ground-Based Observations of ER Vul Over Two Orbits", Bulletin of the American Astronomical Society, 23: 1412, Bibcode:1991BAAS...23.1412G.
  • Rucinski, S. M. (August 1991), "The radio light curve of ER Vulpeculae", Journal of the Royal Astronomical Society of Canada, 85: 184, Bibcode:1991JRASC..85..184R.
  • Srivastava, R. K.; et al. (August 1991), "UBV Photometry of ER-Vulpeculae", Astrophysics and Space Science, 182 (2): 281–287, Bibcode:1991Ap&SS.182..281S, doi:10.1007/BF00645007, S2CID 121685056.
  • Bradstreet, D. H.; Guinan, E. F. (August 1991), Marsden, B. G. (ed.), "ER Vulpeculae", IAU Circular, vol. 5329, p. 1, Bibcode:1991IAUC.5329....1B.
  • Heckert, P. A.; Zeilik, M. (July 1991), "1988 and 1989 BV Photometry of ER Vul", Information Bulletin on Variable Stars, 3636: 1, Bibcode:1991IBVS.3636....1H.
  • Fernández-Figueroa, M. J.; et al. (1991), Tuominen, I.; et al. (eds.), "CAII H and K Spectroscopy of ER-Vulpeculae", The Sun and Cool Stars. Activity, Magnetism, Dynamos. Proceedings of Colloquium No. 130 of the International Astronomical Union, held in Helsinki, Finland, July 17–20, 1990, Berlin, Germany; New York, NY: Springer-Verlag, vol. 380, no. 130, p. 483, Bibcode:1991LNP...380..483F, doi:10.1007/3-540-53955-7_185, ISBN 3-540-53955-7.
  • Hill, G.; et al. (November 1990), "Studies of late-type binaries. IV. The physical parameters of ER Vulpeculae", Astronomy and Astrophysics, 238: 145, Bibcode:1990A&A...238..145H.
  • Mennella, V. (August 1990), "Time-scale variability of the light curves of ER Vulpeculae.", Astronomy and Astrophysics, 234: 203, Bibcode:1990A&A...234..203M.
  • Keskin, Varol (July 1990), "Lightcurve Variations of the RS-Canum Type Eclipsing Binary ER-Vulpeculae", Astrophysics and Space Science, 169 (1–2): 165–170, Bibcode:1990Ap&SS.169..165K, doi:10.1007/BF00640705, S2CID 189850100.
  • Arevalo, M. J.; et al. (September 1988), "Photometric Study of ER Vul", The Astronomical Journal, 96: 1061, Bibcode:1988AJ.....96.1061A, doi:10.1086/114866.
  • Evren, S. (January 1988), "Light curve variations of ER Vulpeculae in 1984 and 1985 observing seasons", Astrophysics and Space Science, 140 (1): 125–130, Bibcode:1988Ap&SS.140..125E, doi:10.1007/BF00643536, S2CID 121317907.
  • Akan, M. C.; et al. (August 1987), "B, V Photometry of ER Vulpeculae", Information Bulletin on Variable Stars, 3059: 1, Bibcode:1987IBVS.3059....1A.
  • White, N. E.; et al. (August 1987), "An EXOSAT observation of 1.5 orbital cycles of the 0.7 day short-period RS CVn system ER Vul", Monthly Notices of the Royal Astronomical Society, 227 (3): 545–551, Bibcode:1987MNRAS.227..545W, doi:10.1093/mnras/227.3.545.
  • Arevalo, M. J.; Fuensalida, J. J. (December 1985), "1984 UBVR Light Curves of ER Vul", Information Bulletin on Variable Stars, 2831: 1, Bibcode:1985IBVS.2831....1A.
  • Ibanoglu, C.; Akan, M. C.; Evren, S.; Tunca, Z. (August 1985), "Photoelectric Observations of ER Vulpeculae", Information Bulletin on Variable Stars, 2782: 1, Bibcode:1985IBVS.2782....1I.
  • Barden, S. C. (March 1984), "The Hα Nature of the Short Period RS CVn Systems HD86590, σαCr B, ER Vul and UV Psc.", Bulletin of the American Astronomical Society, 16: 473, Bibcode:1984BAAS...16..473B.
  • Zeilik, M.; et al. (November 1982), "1982 Photometry of ER Vul", Information Bulletin on Variable Stars, 2221: 1, Bibcode:1982IBVS.2221....1Z.
  • McLean, B. J. (November 1982), "A spectroscopic investigation of the eclipsing variable ER Vul", Monthly Notices of the Royal Astronomical Society, 201: 421–427, Bibcode:1982MNRAS.201..421M, doi:10.1093/mnras/201.2.421.
  • Kadouri, T. H. (December 1981), "BVR Photoelectric Observations of ER Vul June, July, 1981", Information Bulletin on Variable Stars, 2057: 1, Bibcode:1981IBVS.2057....1K.
  • Al-Naimiy, H. M. K. (January 1981), "Photometric observations and light curve analysis of the peculiar system ER Vul", Astronomy and Astrophysics Supplement Series, 43: 85–90, Bibcode:1981A&AS...43...85A.
  • Al-Naimiy, H. M. (October 1978), "Observation of the Peculiar Eclipsing Variable ER Vulpeculae", Information Bulletin on Variable Stars, 1481: 1, Bibcode:1978IBVS.1481....1A.


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