HD 202951

HD 202951
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]
Distance1,190 ± 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
Luminosity5.15[2] L☉
Rotational velocity (v sin i)4.4[6] km/s
Other designations
NSV 25543, BD+10° 4516, FK5 3700, HD 202951, HIP 105224, HR 8149, SAO 107020[7]
Database references
SIMBADdata

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]

  1. ^ a b c d Cite error: The named reference GaiaDR2 was invoked but never defined (see the help page).
  2. ^ a b c d e Cite error: The named reference Anderson2012 was invoked but never defined (see the help page).
  3. ^ a b Cite error: The named reference Ryon2009 was invoked but never defined (see the help page).
  4. ^ a b Cite error: The named reference Gontcharov2006 was invoked but never defined (see the help page).
  5. ^ a b Cite error: The named reference Griffin2012 was invoked but never defined (see the help page).
  6. ^ Cite error: The named reference DeMedeiros2002 was invoked but never defined (see the help page).
  7. ^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  8. ^ Cite error: The named reference koen2002 was invoked but never defined (see the help page).
  9. ^ Cite error: The named reference smith2000 was invoked but never defined (see the help page).