EQ Pegasi

EQ Pegasi

EQ Location of EQ Pegasi in the constellation Pegasus
Observation data Epoch J2000.0       Equinox J2000.0
Constellation	Pegasus
EQ Pegasi A
Right ascension	23h 31m 52.17385s [1]
Declination	+19° 56′ 14.1304″ [1]
Apparent magnitude  (V)	10.38 (min) [2]
EQ Pegasi B
Right ascension	23h 31m 52.57534s [3]
Declination	+19° 56′ 14.0050″ [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]
EQ Pegasi B
Evolutionary stage	red dwarf
Spectral type	M6Ve [2]
Variable type	Flare star [2]
Astrometry
EQ Pegasi A
Radial velocity (Rv)	−0.21±0.82 [1] km/s
Proper motion (μ)	RA: 578.009(35) mas/yr [1] Dec.: −59.769(23) mas/yr [1]
Parallax (π)	159.6634±0.0341  mas [1]
Distance	20.428 ± 0.004  ly (6.263 ± 0.001  pc)
EQ Pegasi B
Proper motion (μ)	RA: 552.349(55) mas/yr [3] Dec.: 20.275(36) mas/yr [3]
Parallax (π)	159.9085±0.0513  mas [3]
Distance	20.396 ± 0.007  ly (6.254 ± 0.002  pc)
Orbit [4]
Period (P)	83,664.63 ± 1.98 days (229.0613 ± 0.0054  a)
Semi-major axis (a)	5.05797±0.00043" (31.635±0.033  AU )
Eccentricity (e)	0.108047±0.000053
Inclination (i)	130.065±0.010°
Longitude of the node (Ω)	255.0919±0.0034°
Periastron epoch (T)	2,401,891.34±1.19
Argument of periastron (ω) (secondary)	307.1416±0.0045°
Details
A
Mass	0.43599±0.00092 [4]   M☉
Radius	0.409±0.016 [5]   R☉
Luminosity	0.019 [6]   L☉
Temperature	3,353±60 [5]   K
Rotation	1.061 days [7]
B
Mass	0.16527±0.00025 [4]   M☉
Radius	0.303±0.013 [5]   R☉
Luminosity	0.008 [6]   L☉
Temperature	3,072±60 [5]   K
Rotation	0.404 days [7]
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 [8]
EQ Peg A: TYC 1723-23-1, 2MASS J23315208+1956142 [9]
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
Exoplanet Archive	data

EQ Pegasi (also known as Gliese 896) 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] The primary star is orbited by one known exoplanet. ^[4]

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 were also thought to be single-lined spectroscopic binaries, with faint companions that have not been resolved in orbits of a few years, ^{[12] [13]} but this is no longer thought to be the case. A 2021 study of nearby stars states that "the spectroscopic binarity classification [...] is almost certainly due to activity". ^[14]

Planetary system

In 2022, a Jovian planet was discovered in orbit around the system's primary star via radio astrometry. Along with the planet around TVLM 513-46546, this is the first confirmed exoplanet discovered entirely using astrometry. ^[4]

The Gliese 896 A planetary system ^[4]

Companion (in order from star)	Mass	Semimajor axis (AU)	Orbital period (days)	Eccentricity	Inclination	Radius
b	2.26±0.57  MJ	0.64282±0.00068	284.39±1.47	0.35±0.19	69.20±25.61 °	—

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. ^[15]

Gallery

• 
  A visual band light curve for EQ Pegasi A, adapted from Norton et al. (2007) ^[16]
• 
  An ultraviolet band light curve for a flare on EQ Pegasi B, adapted from Mathioudakis et al. (2006) ^[17]

References

1. Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv: 2208.00211 . Bibcode:2023A&A...674A...1G. doi: 10.1051/0004-6361/202243940 . S2CID   244398875. Gaia DR3 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. Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv: 2208.00211 . Bibcode:2023A&A...674A...1G. doi: 10.1051/0004-6361/202243940 . S2CID   244398875. Gaia DR3 record for this source at VizieR.
4. Curiel, Salvador; Ortiz-León, Gisela N.; Mioduszewski, Amy J.; Sanchez-Bermudez, Joel (September 2022). "3D Orbital Architecture of a Dwarf Binary System and Its Planetary Companion". The Astronomical Journal . 164 (3): 93. arXiv: 2208.14553 . Bibcode:2022AJ....164...93C. doi: 10.3847/1538-3881/ac7c66 . S2CID   251953478.
5. Mann, Andrew W.; et al. (May 2015). "How to Constrain Your M Dwarf: Measuring Effective Temperature, Bolometric Luminosity, Mass, and Radius". The Astrophysical Journal. 804 (1): 38. arXiv: 1501.01635 . Bibcode:2015ApJ...804...64M. doi:10.1088/0004-637X/804/1/64. S2CID   19269312. 64.
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. Morin, J.; Donati, J.-F.; et al. (October 2008). "Large-scale magnetic topologies of mid M dwarfs". Monthly Notices of the Royal Astronomical Society . 390 (2): 567–581. arXiv: 0808.1423 . Bibcode:2008MNRAS.390..567M. doi: 10.1111/j.1365-2966.2008.13809.x . S2CID   11240756.
8. "BD+19 5116". 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. Tokovinin, A. "Multiple Star Catalog" . Retrieved 2019-08-12.
13. Delfosse, X.; Forveille, T.; et al. (April 1999). "New neighbours. I. 13 new companions to nearby M dwarfs". Astronomy and Astrophysics . 344: 897–910. arXiv: astro-ph/9812008 . Bibcode:1999A&A...344..897D.
14. Reylé, Céline; Jardine, Kevin; Fouqué, Pascal; Caballero, Jose A.; Smart, Richard L.; Sozzetti, Alessandro (30 April 2021). "The 10 parsec sample in the Gaia era". Astronomy & Astrophysics . 650: A201. arXiv: 2104.14972 . Bibcode:2021A&A...650A.201R. doi:10.1051/0004-6361/202140985. S2CID   233476431. Data available at https://gruze.org/10pc/
15. "BBC News | Sci/Tech | Alien hoax dismays scientists". news.bbc.co.uk. Retrieved 2018-09-25.
16. 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. arXiv: astro-ph/0702631 . Bibcode:2007A&A...467..785N. doi:10.1051/0004-6361:20077084. S2CID   16358048 . Retrieved 11 February 2022.
17. 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. arXiv: astro-ph/0605196 . Bibcode:2006A&A...456..323M. doi:10.1051/0004-6361:20054752. S2CID   8572363 . Retrieved 12 February 2022.