EQ Pegasi

EQ Pegasi is a nearby binary system of two red dwarfs. Both components are flare stars, with spectral types of M4Ve and M6Ve respectively, and a current separation between the components of 5.8 arcseconds. The system is at a distance of 20.4 light-years, and is 950 million years old.[14]

EQ Pegasi
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Pegasus
EQ Pegasi A
Right ascension 23h 31m 52.1743s[1]
Declination +19° 56′ 14.1284″[1]
Apparent magnitude (V) 10.38 (min)[2]
EQ Pegasi B
Right ascension 23h 31m 52.5741s[3]
Declination +19° 56′ 14.0041″[3]
Apparent magnitude (V) 12.58 (min)[2]
Characteristics
EQ Pegasi A
Evolutionary stage red dwarf
Spectral type M4Ve[2]
Variable type Flare star[2]

A visual band light curve for EQ Pegasi A, adapted from Norton et al. (2007)[4]
EQ Pegasi B
Evolutionary stage red dwarf
Spectral type M6Ve[2]
Variable type Flare star[2]

An ultraviolet band light curve for a flare on EQ Pegasi B, adapted from Mathioudakis et al. (2006)[5]
Astrometry
EQ Pegasi A
Proper motion (μ) RA: 577.605±0.133[1] mas/yr
Dec.: −59.640±0.096[1] mas/yr
Parallax (π)159.6634 ± 0.0341 mas[6]
Distance20.428 ± 0.004 ly
(6.263 ± 0.001 pc)
EQ Pegasi B
Proper motion (μ) RA: 553.472±0.193[3] mas/yr
Dec.: 20.338±0.142[3] mas/yr
Parallax (π)159.9085 ± 0.0513 mas[7]
Distance20.396 ± 0.007 ly
(6.254 ± 0.002 pc)
Orbit[8]
Period (P)359 yr
Semi-major axis (a)6.87″
Eccentricity (e)0.20
Inclination (i)123.5°
Details
A
Mass0.36[9] M☉
Luminosity0.019[10] L☉
Temperature3,585[1] K
B
Mass0.19[9] M☉
Luminosity0.008[10] L☉
Temperature3,309[3] K
Other designations
EQ Peg, BD+19° 5116, GJ 896, HIP 116132, WDS J23317+1956AB, G 68-24, G 129-19, G 128-71, LFT 1799, LHS 3965, LTT 16919, NLTT 57135[11]
EQ Peg A: TYC 1723-23-1, 2MASS J23315208+1956142[12]
EQ Peg B: LFT 1800, LHS 3966, LTT 16920, NLTT 57136, TYC 1723-23-2, 2MASS J23315244+1956138[13]
Database references
SIMBADThe system
A
B
EQ
Location of EQ Pegasi in the constellation Pegasus

Discovery

EQ Pegasi was first noticed to be a binary star by Carl A. Wirtanen who in the course of a systematic survey of the McCormick Observatory photographic plates for M-type dwarfs, detected a companion about two magnitudes fainter at a separation of 3.5 arcseconds.[15]

Both components are also though to be single-lined spectroscopic binaries, with faint companions that have not been resolved in orbits of a few years.[9]

In culture

In 1998, it was the basis of a hoax, as a telecommunications company claimed it had discovered "alien" signals originating from the star.[16]

References
  1. 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.
  2. Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S. 1: B/gcvs. Bibcode:2009yCat....102025S.
  3. 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.
  4. Norton, A. J.; Wheatley, P. J.; West, R. G.; Haswell, C. A.; Street, R. A.; Collier Cameron, A.; Christian, D. J.; Clarkson, W. I.; Enoch, B.; Gallaway, M.; Hellier, C.; Horne, K.; Irwin, J.; Kane, S. R.; Lister, T. A.; Nicholas, J. P.; Parley, N.; Pollacco, D.; Ryans, R.; Skillen, I.; WilsonD. M. (May 2007). "New periodic variable stars coincident with ROSAT sources discovered using SuperWASP". Astronomy and Astrophysics. 467 (2): 785–905. doi:10.1051/0004-6361:20077084. Retrieved 11 February 2022.
  5. Mathioudakis, M.; Bloomfield, D. S.; Jess, D. B.; Dhillon, V. S.; Marsh, T. R. (September 2006). "The periodic variations of a white-light flare observed with ULTRACAM". Astronomy and Astrophysics. 456 (1): 323–327. doi:10.1051/0004-6361:20054752. Retrieved 12 February 2022.
  6. 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. Gaia EDR3 record for this source at VizieR.
  7. 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. Gaia EDR3 record for this source at VizieR.
  8. Heintz, W. D. (1984). "Orbits of 16 visual binaries". The Astronomical Journal. 89: 1063. Bibcode:1984AJ.....89.1063H. doi:10.1086/113602.
  9. Tokovinin, A. "Multiple Star Catalog". Retrieved 2019-08-12.
  10. Morales, J. C.; Ribas, I.; Jordi, C. (2008). "The effect of activity on stellar temperatures and radii". Astronomy and Astrophysics. 478 (2): 507. arXiv:0711.3523. Bibcode:2008A&A...478..507M. doi:10.1051/0004-6361:20078324. S2CID 16238033.
  11. "BD+19 5116". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 18 August 2017.
  12. "BD+19 5116A". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 18 August 2017.
  13. "BD+19 5116A". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 18 August 2017.
  14. Crosley, M. K.; Osten, R. A. (2018). "Constraining Stellar Coronal Mass Ejections through Multi-wavelength Analysis of the Active M Dwarf EQ Peg". The Astrophysical Journal. 856 (1). 39. arXiv:1802.03440. Bibcode:2018ApJ...856...39C. doi:10.3847/1538-4357/aaaec2. S2CID 55448675.
  15. Wirtanen, C. A. (1941). "A New dMe Double Star". Publications of the Astronomical Society of the Pacific. 53 (316): 340. Bibcode:1941PASP...53..340W. doi:10.1086/125371.
  16. "BBC News | Sci/Tech | Alien hoax dismays scientists". news.bbc.co.uk. Retrieved 2018-09-25.
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