Astronomy:HD 202951
  | |
| Observation data Equinox J2000.0]] (ICRS) | |
|---|---|
| Constellation | Equuleus[1] |
| Right ascension | 21h 18m 52.02694s[2] |
| Declination | +11° 12′ 12.1708″[2] |
| Apparent magnitude (V) | 5.97[1] |
| Characteristics | |
| Evolutionary stage | red giant branch[2] |
| Spectral type | K5 III[1] |
| B−V color index | 1.648[3] |
| Astrometry | |
| Radial velocity (Rv) | −37.3±2.5[4] km/s |
| Proper motion (μ) | RA: +21.643[2] mas/yr Dec.: +15.723[2] mas/yr |
| Parallax (π) | 3.3390 ± 0.1317[2] mas |
| Distance | 980 ± 40 ly (300 ± 10 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 | |
| Mass | 1.15[6] M☉ |
| Radius | 85[7] R☉ |
| Luminosity | 2,202[2] L☉ |
| Surface gravity (log g) | 1.29[6] cgs |
| Temperature | 3,805[8] K |
| Metallicity [Fe/H] | −0.26[6] dex |
| Rotational velocity (v sin i) | 4.4[9] km/s |
| Age | 10.7[8] Gyr |
| 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.[1] The distance to this system can be estimated from the annual parallax shift of 3.34 mas,[2] yielding a value of roughly 980 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 astronomical unit|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.[1] 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.[11] X-ray emission has been detected from this system.[12]
References
- ↑ 1.0 1.1 1.2 1.3 1.4 Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters 38 (5): 331. doi:10.1134/S1063773712050015. Bibcode: 2012AstL...38..331A XHIP record for this object at VizieR.
- ↑ 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940 Gaia DR3 record for this source at VizieR.
- ↑ 3.0 3.1 Ryon, Jenna et al. (August 2009), "Comparing the Ca ii H and K Emission Lines in Red Giant Stars", Publications of the Astronomical Society of the Pacific 121 (882): 842, doi:10.1086/605456, Bibcode: 2009PASP..121..842R.
- ↑ 4.0 4.1 Gontcharov, G. A. (2006), "Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system", Astronomy Letters 32 (11): 759–771, doi:10.1134/S1063773706110065, Bibcode: 2006AstL...32..759G.
- ↑ 5.0 5.1 Griffin, R. F. (February 2012), "Spectroscopic binary orbits from photoelectric radial velocities - Paper 222: HR 4241, HR 7208, HR 8026, and HR 8149", The Observatory 132 (1): 16–33, Bibcode: 2012Obs...132...16G.
- ↑ 6.0 6.1 6.2 Khalatyan, A.; Anders, F.; Chiappini, C.; Queiroz, A. B. A.; Nepal, S.; Dal Ponte, M.; Jordi, C.; Guiglion, G. et al. (2024). "Transferring spectroscopic stellar labels to 217 million Gaia DR3 XP stars with SHBoost". Astronomy and Astrophysics 691: A98. doi:10.1051/0004-6361/202451427. Bibcode: 2024A&A...691A..98K.
- ↑ Stassun, Keivan G. et al. (2019). "The Revised TESS Input Catalog and Candidate Target List". The Astronomical Journal 158 (4): 138. doi:10.3847/1538-3881/ab3467. Bibcode: 2019AJ....158..138S.
- ↑ 8.0 8.1 Kordopatis, G.; Schultheis, M.; McMillan, P. J.; Palicio, P. A.; De Laverny, P.; Recio-Blanco, A.; Creevey, O.; Álvarez, M. A. et al. (2023). "Stellar ages, masses, extinctions, and orbital parameters based on spectroscopic parameters of Gaia DR3". Astronomy and Astrophysics 669: A104. doi:10.1051/0004-6361/202244283. Bibcode: 2023A&A...669A.104K.
- ↑ De Medeiros, J. R. et al. (October 2002), "The Rotation of Binary Systems with Evolved Components", The Astrophysical Journal 578 (2): 943–950, doi:10.1086/342613, Bibcode: 2002ApJ...578..943D.
- ↑ "HD 202951". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=HD+202951.
- ↑ Koen, Chris; Eyer, Laurent (2002), "New periodic variables from the Hipparcos epoch photometry", Monthly Notices of the Royal Astronomical Society 331 (1): 45–59, doi:10.1046/j.1365-8711.2002.05150.x, Bibcode: 2002MNRAS.331...45K.
- ↑ Smith, Graeme H.; Shetrone, Matthew D. (2000), "CaII K Emission-Line Asymmetry among Red Giants Detected by the ROSAT Satellite", The Publications of the Astronomical Society of the Pacific 112 (776): 1320, doi:10.1086/316634, Bibcode: 2000PASP..112.1320S.
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