HD 202951
# HD 202951

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. The distance to this system can be estimated from the annual parallax shift of 2.74 mas, yielding a value of roughly 1,190 light years. It is moving closer with a heliocentric radial velocity of −37 km/s.

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.

The visible component is an evolved K-type giant star with a stellar classification of K5 III. 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. X-ray emission has been detected from this system.

