Kappa Delphini

κ Delphini (Latinised as Kappa Delphini, abbreviated to κ Del or kappa Del) is a binary star system in the constellation Delphinus. It is faintly visible to the naked eye, with an apparent magnitude of 5.05.[2] It is located about 98.8 light-years away, based on its parallax.[1]

κ Delphini
Location of κ Delphini (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Delphinus
Right ascension 20h 39m 07.78430s[1]
Declination +10° 05′ 10.3383″[1]
Apparent magnitude (V) 5.05[2]
Characteristics
Spectral type G1IV + ? + K2IV[3]
U−B color index 0.235[4]
B−V color index 0.69[4]
Astrometry
Radial velocity (Rv)-53.51[2] km/s
Proper motion (μ) RA: 323.83[1] mas/yr
Dec.: 21.80[1] mas/yr
Parallax (π)33.0268 ± 0.1631 mas[5]
Distance98.8 ± 0.5 ly
(30.3 ± 0.1 pc)
Absolute magnitude (MV)2.7[6]
Orbit[6]
Period (P)45 ± 5 yr
Semi-major axis (a)0.520 ± 0.030″
Eccentricity (e)0.8 ± 0.4
Inclination (i)107 ± 18°
Longitude of the node (Ω)326 ± 17°
Periastron epoch (T)B 1971.2 ± 1.8
Argument of periastron (ω)
(secondary)		8 ± 34°
Details[7]
κ Del Aa
Mass1.43 M☉
Luminosity8.3 L☉
Surface gravity (log g)3.69 cgs
Temperature5,643 K
Metallicity [Fe/H]+0.01 dex
Rotational velocity (v sin i)1.77 km/s
Age3.1 Gyr
κ Del Ab
Mass0.4±0.2[6] M☉
Other designations
κ Del, 7 Delphini, BD+09° 4600, HD 196755, HIP 101916, HR 7896, SAO 126059, CCDM J20392+1005A, WDS J20391+1005A[2]
Database references
SIMBADdata

Kappa Delphini is an astrometric binary. The primary star is an early G-type subgiant star. It has a mass 1.61 times that of the Sun, and is 6.8 times more luminous. The companion star regularly perturbs the G-type primary star primary, causing it to wobble around the barycenter. From this, an orbital period of 45 years has been calculated.[6] The secondary star is a low-mass star, at only 0.4 M☉.[6]

A third star is 12th magnitude ADS 14101 B, 10″ away in 2001, but it is a background object. HD 196794 is an 8th magnitude K2 subgiant 214″ away is at the same distance as κ Delphini and shares a common proper motion.[6]

References
  1. van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. S2CID 18759600. Vizier catalog entry
  2. "* kap Del". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 26 December 2016.
  3. Eggl, S.; Pilat-Lohinger, E.; Funk, B.; Georgakarakos, N.; Haghighipour, N. (2012). "Circumstellar habitable zones of binary-star systems in the solar neighbourhood". Monthly Notices of the Royal Astronomical Society. 428 (4): 3104. arXiv:1210.5411. Bibcode:2013MNRAS.428.3104E. doi:10.1093/mnras/sts257.
  4. Mermilliod, J.-C. (1986). "Compilation of Eggen's UBV data, transformed to UBV (unpublished)". Catalogue of Eggen's UBV Data: 0. Bibcode:1986EgUBV........0M.
  5. 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.
  6. Gontcharov, G.A.; Kiyaeva, O.V. (2010). "Photocentric orbits from a direct combination of ground-based astrometry with Hipparcos II. Preliminary orbits for six astrometric binaries". New Astronomy. 15 (3): 324–331. arXiv:1606.08182. Bibcode:2010NewA...15..324G. doi:10.1016/j.newast.2009.09.006. S2CID 119252073.
  7. Niedzielski, A.; Deka-Szymankiewicz, B.; Adamczyk, M.; Adamów, M.; Nowak, G.; Wolszczan, A. (2016). "The Penn State - Toruń Centre for Astronomy Planet Search stars". Astronomy and Astrophysics. 585: A73. Bibcode:2016A&A...585A..73N. doi:10.1051/0004-6361/201527362.
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