EQ Pegasi
Star system in the constellation Pegasus
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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 (6.25 parsecs) and is 950 million years old.[10] The primary star is orbited by one known exoplanet.[4]
  EQ Location of EQ Pegasi in the constellation Pegasus | |
| Observation data Epoch J2000.0 Equinox ICRS | |
|---|---|
| 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 |
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]
| 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
Gallery
An ultraviolet band light curve for a flare on EQ Pegasi B, adapted from Mathioudakis et al. (2006)[17]
