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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.

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