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.[10]

EQ Pegasi

Observation data Epoch J2000.0      Equinox J2000.0
Constellation	Pegasus
EQ Pegasi A
Right ascension	23^h 31^m 52.1743^s[1]
Declination	+19° 56′ 14.1284″[1]
Apparent magnitude (V)	10.38 (min)[2]
EQ Pegasi B
Right ascension	23^h 31^m 52.5741^s[3]
Declination	+19° 56′ 14.0041″[3]
Apparent magnitude (V)	12.58 (min)[2]
Characteristics
A
Evolutionary stage	red dwarf
Spectral type	M4Ve[2]
Variable type	Flare star[2]
B
Evolutionary stage	red dwarf
Spectral type	M6Ve[2]
Variable type	Flare star[2]
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)	159.7098 ± 0.0827[1] mas
Distance	20.42 ± 0.01 ly (6.261 ± 0.003 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)	160.0598 ± 0.1079[3] mas
Distance	20.38 ± 0.01 ly (6.248 ± 0.004 pc)
Orbit[4]
Period (P)	359 yr
Semi-major axis (a)	6.87″
Eccentricity (e)	0.20
Inclination (i)	123.5°
Details
A
Mass	0.36[5] M☉
Luminosity	0.019[6] L☉
Temperature	3,585[1] K
B
Mass	0.19[5] M☉
Luminosity	0.008[6] L☉
Temperature	3,309[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[7]
EQ Peg A: TYC 1723-23-1, 2MASS J23315208+1956142[8]
EQ Peg B: LFT 1800, LHS 3966, LTT 16920, NLTT 57136, TYC 1723-23-2, 2MASS J23315244+1956138[9]
Database references
SIMBAD	The system
	A
	B

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.[11]

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.[5]

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.[12]

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. Heintz, W. D. (1984). "Orbits of 16 visual binaries". The Astronomical Journal. 89: 1063. Bibcode:1984AJ.....89.1063H. doi:10.1086/113602.
5. Tokovinin, A. "Multiple Star Catalog". Retrieved 2019-08-12.
6. 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.
7. "BD+19 5116". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 18 August 2017.
8. "BD+19 5116A". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 18 August 2017.
9. "BD+19 5116A". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 18 August 2017.
10. 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.
11. 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.
12. "BBC News | Sci/Tech | Alien hoax dismays scientists". news.bbc.co.uk. Retrieved 2018-09-25.