Observation data Epoch J2000 Equinox J2000 | |
---|---|
Constellation | Equuleus |
Right ascension | 21h 18m 52.02476s[1] |
Declination | +11° 12′ 12.1752″[1] |
Apparent magnitude (V) | 5.97[2] |
Characteristics | |
Spectral type | K5 III[2] |
B−V color index | 1.648[3] |
Astrometry | |
Radial velocity (Rv) | −37.3±2.5[4] km/s |
Proper motion (μ) | RA: +23.728 mas/yr Dec.: +15.448 mas/yr |
Parallax (π) | 2.7415 ± 0.1321 mas[1] |
Distance | 1,190 ± 60 ly (360 ± 20 pc) |
Absolute magnitude (MV) | −1.97[3] |
Orbit[5] | |
Period (P) | 999.8±2.4 d |
Eccentricity (e) | 0.229±0.018 |
Periastron epoch (T) | 53771 ± 12 MJD |
Argument of periastron (ω) (secondary) | 3±5° |
Semi-amplitude (K1) (primary) | 4.09±0.08 km/s |
Details | |
Luminosity | 5.15[2] L☉ |
Rotational velocity (v sin i) | 4.4[6] km/s |
Other designations | |
Database references | |
SIMBAD | data |
HD 202951 is a probable binary star system located in the northern constellation of Equuleus. It is near the lower limit of visibility to the naked eye, having an apparent visual magnitude of 5.97.[2] The distance to this system can be estimated from the annual parallax shift of 2.74 mas,[1] yielding a value of roughly 1,190 light years. It is moving closer with a heliocentric radial velocity of −37 km/s.[4]
Griffin (2012) found this to be a single-lined spectroscopic binary system with an orbital period of 2.7373 ± 0.0066 yr and an eccentricity of 0.23. The a sin i value for the primary component is 54.8 ± 1.1 Gm (0.366 ± 0.007 AU), where a is the semimajor axis and i is the (unknown) orbital inclination. This value provides a lower bound for the actual semimajor axis.[5]
The visible component is an evolved K-type giant star with a stellar classification of K5 III.[2] It is a candidate variable star of unknown type, showing an amplitude variation of 0.0115 magnitude with a frequency of 0.47645 times per day, or one cycle per 2.1 days.[8] X-ray emission has been detected from this system.[9]