HD 203857 is a double star in the constellation Cygnus. It is near the lower limit of visibility to the naked eye, having a combined apparent visual magnitude of 6.46.[2] The distance to the primary component is approsimatly 1,230 light years based on parallax, and it has an absolute magnitude of −0.75.[2] The star is drifting closer to the Sun with a radial velocity of −6.3 km/s.[1] It has a stellar classification of K5[3] and is known to be evolved. The star likely hosts an extrasolar planet, though yet unconfirmed.
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Cygnus |
| Right ascension | 21h 23m 48.38864s[1] |
| Declination | +37° 21′ 05.3177″[1] |
| Apparent magnitude (V) | 6.46[2] |
| Characteristics | |
| Spectral type | K5[3] |
| B−V color index | 1.472±0.006[2] |
| Astrometry | |
| Radial velocity (Rv) | −6.26±0.16[1] km/s |
| Proper motion (μ) | RA: −5.999[1] mas/yr Dec.: −8.364[1] mas/yr |
| Parallax (π) | 2.6601 ± 0.0417 mas[1] |
| Distance | 1,230 ± 20 ly (376 ± 6 pc) |
| Absolute magnitude (MV) | −0.75[2] |
| Details[4] | |
| Mass | 1.7 M☉ |
| Radius | 46-50 R☉ |
| Luminosity | 513 L☉ |
| Temperature | 4,080 K |
| Other designations | |
| Database references | |
| SIMBAD | data |
HD 203857 is listed in the Washington Double Star Catalogue as having five visual companions. It is separated by six arc-minutes from HD 203784, an F-type subgiant, though it is likely they are actually not gravitationally–bound.[4] HD 203784 is thought to be closer to us and less luminous than HD 203857.[6] There are also fainter stars at 23″ and 178″. HD 203784 has a 13th-magnitude star and a 14th-magnitude star within 20″.[7]
Substellar companion
editOkayama Planet Search team has published a paper in late 2008 reporting investigations on radial velocity variations observed for a set of evolved stars, announcing possible detection of a substellar companion orbiting the giant star HD 203857.[4] Orbital period is estimated 2.3 years, but planet has still to be confirmed.
| Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (days) |
Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| b (unconfirmed) | ≥8.1 MJ | 2.1 | 836.8 | 0.3 | — | — |
References
edit- ^ a b c d e f g Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
- ^ a b c d e Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015, S2CID 119257644.
- ^ a b Hoffleit, Dorrit; Jaschek, Carlos (1991), The Bright star catalogue (5th Revised ed.), New Haven, Conn.: Yale University Observatory, Bibcode:1991bsc..book.....H.
- ^ a b c Toyota, Eri; et al. (February 2009), "Radial Velocity Search for Extrasolar Planets in Visual Binary Systems", Publications of the Astronomical Society of Japan, 61 (1): 19–28, Bibcode:2009PASJ...61...19T, doi:10.1093/pasj/61.1.19, hdl:20.500.14094/90001422.
- ^ "HD 203857". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2020-03-09.
- ^ Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
- ^ Finzi, A.; Wolf, R. A. (1967), "Type I Supernovae", The Astrophysical Journal, 150: 115, Bibcode:1967ApJ...150..115F, doi:10.1086/149317.