II Pegasi
| Observation data Epoch J2000 Equinox J2000 |
|
|---|---|
| Constellation | Pegasus |
| Right ascension | 23h 55m 04.05313s[1] |
| Declination | +28° 38' 01.2422"'[1] |
| Apparent magnitude (V) | 7.4[2] |
| Characteristics | |
| II Pegasi A | |
| Evolutionary stage | subgiant[3] |
| Spectral type | K2 IV[3] |
| Variable type | RS CVn[1] |
| II Pegasi B | |
| Evolutionary stage | main sequence[3] |
| Spectral type | M0-M3 V[3] |
| Astrometry | |
| II Pegasi A | |
| Radial velocity (Rv) | -20.50[1] km/s |
| Proper motion (μ) | RA: 576.22[1] mas/yr Dec.: 34.69[1] mas/yr |
| Parallax (π) | 25.06 ± 0.51[1] mas |
| Distance | 130 ± 3 ly (39.9 ± 0.8 pc) |
| Absolute magnitude (MV) | 3.8[3] |
| Details | |
| II Pegasi A | |
| Mass | 0.8[3] M☉ |
| Radius | 3.4[3] R☉ |
| Luminosity | 1.06 L☉ |
| Surface gravity (log g) | 3.2[3] cgs |
| Temperature | 4600[3] K |
| II Pegasi B | |
| Mass | 0.4[3] M☉ |
| Luminosity | 0.53 L☉ |
| Other designations | |
| Database references | |
| SIMBAD | data |
II Pegasi is a binary star system in the constellation of Pegasus with an apparent magnitude of 7.4 and a distance of 130 light years. It is a very active RS Canum Venaticorum variable (RS CVn), a close binary system with active starspots.[1]
The primary (II Pegasi A) is a cool subgiant, an orange K-type star. It has begun to evolve off the main sequence and expand.[3] Starspots cover about 40% of its surface. The star produces intense flares observable at all wavelengths.[4]
Its smaller companion (II Pegasi B) is too close to have been observed directly. It is a red dwarf, an M-type main sequence star. The stars are tidally locked in a very close orbit with a period of 6.7 days and a separation of a few stellar radii.[3]
X-ray flares from II Pegasi A were observed with the Ariel 5 satellite in the 1970s and with later x-ray observatories. In December 2005 a superflare was detected by the Swift Gamma-Ray Burst Mission.[2] It was the largest stellar flare ever seen and was a hundred million times more energetic than The Sun's typical solar flare.[5]
References
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- ↑ 2.0 2.1 Lua error in package.lua at line 80: module 'strict' not found.
- ↑ 3.00 3.01 3.02 3.03 3.04 3.05 3.06 3.07 3.08 3.09 3.10 3.11 Lua error in package.lua at line 80: module 'strict' not found.
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