Kappa Tucanae

Kappa Tucanae
Location of κ Tucanae (circled in red)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Tucana
κ Tuc AB
Right ascension 01h 15m 46.0891s (A)[1]
01h 15m 46.5740s (B)[2]
Declination −68° 52′ 33.401″ (A)[1]
−68° 52′ 33.516″ (B)[2]
Apparent magnitude (V) 4.88 + 7.54[3]
κ Tuc C
Right ascension 01h 15m 01.0248s[4]
Declination −68° 49′ 08.374″[4]
Apparent magnitude (V) 7.76[3]
κ Tuc D
Right ascension 01h 15m 00.7519s[5]
Declination −68° 49′ 07.791″[5]
Apparent magnitude (V) 8.26[3]
Characteristics
Evolutionary stage Subgiant (Aa)
Main sequence (others)[3][6]
Spectral type F6IV (Aa)[3]
M3.5V/M4.5V (Ab)[6]
G5V (B)[3]
K2V (C)[3]
K3V (D)[3]
B−V color index 0.48[7]
Astrometry
AB
Radial velocity (Rv)+7.7±1.7[8] km/s
Proper motion (μ) RA: +386.257 mas/yr[2]
Dec.: +82.069 mas/yr[2]
Parallax (π)47.6500±0.0203 mas[2]
Distance68.45 ± 0.03 ly
(20.986 ± 0.009 pc)
Absolute magnitude (MV)3.50[7]
Orbit[6]
Primaryκ Tuc Aa
Companionκ Tuc Ab
Period (P)8.14+0.11
−0.10 years
Semi-major axis (a)4.822+0.077
−0.071 AU
Eccentricity (e)0.9356±0.0024
Inclination (i)126.13±0.80°
Longitude of the node (Ω)189.0+1.1
−1.0°
Periastron epoch (T)60,219.8±1.8 MJD
Argument of periastron (ω)
(secondary)		180.0+1.5
−1.4°
Semi-amplitude (K1)
(primary)		8 km/s
Orbit[3]
Primaryκ Tuc A
Companionκ Tuc B
Period (P)1,122±28[6] years
Semi-major axis (a)7.03±0.07″
Eccentricity (e)0.40
Inclination (i)128.5±1.1°
Longitude of the node (Ω)323.1±0.5°
Periastron epoch (T)2086.7±4.1
Argument of periastron (ω)
(secondary)		61.3±1.6°
Orbit[3]
Primaryκ Tuc C
Companionκ Tuc D
Period (P)85.12±0.11 years
Semi-major axis (a)1.094±0.007″
Eccentricity (e)0.039±0.002
Inclination (i)31.3±0.5°
Longitude of the node (Ω)141.0±0.9°
Periastron epoch (T)1916.92±1.20
Argument of periastron (ω)
(secondary)		135.7±4.6°
Details
κ Tuc Aa
Mass1.37+0.06
−0.04[9] M☉
Radius1.71±0.05[9] R☉
Luminosity4.59±0.31[9] L☉
Temperature6,457+57
−66[9] K
Rotational velocity (v sin i)61.1±3.1[7] km/s
Age2.28+0.43
−0.42[9] Gyr
κ Tuc Ab
Mass0.33±0.10[6] M☉
Age~2[3] Gyr
κ Tuc B
Mass0.88[3] M☉
Radius0.831±0.050[10] R☉
Luminosity0.421±0.010[10] L☉
Surface gravity (log g)4.53±0.08[10] cgs
Temperature5,145[3] K
Age~2[3] Gyr
κ Tuc C
Mass0.86[3] M☉
Radius0.93±0.07[11] R☉
Luminosity0.387±0.009[11] L☉
Temperature5,062[3] K
Age~2[3] Gyr
κ Tuc D
Mass0.80[3] M☉
Radius0.71±0.05[11] R☉
Luminosity0.239±0.007[11] L☉
Temperature4,850[3] K
Age~2[3] Gyr
Other designations
κ Tuc, WDS J01158-6853[12]
AB: CD−69°52, GJ 55.3, GJ 9049, HD 7788, HIP 5896, HR 377, SAO 248346[12]
CD: CD−69°51, GJ 55.1, HD 7693, HIP 5842, SAO 248342
Database references
SIMBADA
B
CD
C
D

Kappa Tucanae, Latinised from κ Tucanae, is a quintuple[3] star system in the southern constellation Tucana. It is visible to the naked eye as a faint point of light with a combined apparent visual magnitude of +4.86.[13] The system is located approximately 68 light years from the Sun based on parallax, and is drifting further away with a radial velocity of +8 km/s.[8]

Temporally variable excess emission, likely originating from hot exozodiacal dust, has been detected around Kappa Tucanae A.[14][15]

Characteristics

Aa
Period = 8.14 yr
Ab
Period = 1122 yr
B
318″ separation
C
Period = 85.12 yr
D

Hierarchy of orbits in the κ Tucanae system

The Kappa Tucanae system consists of five stars in a complex, hierarchical architecture, with nested orbits. The system consists of two sets of stars separated by 318 arcseconds, which corresponds to a projected separation of 6,700 astronomical units. The estimated orbital period is 300,000 years.[3]

The first set contains three stars. The primary star, Kappa Tucanae Aa, is an F-type subgiant with an apparent magnitude of 4.88. It forms an astrometric binary with Kappa Tucanae Ab, which is a red dwarf with an orbital period of 8.14 years and a mass of 0.33 solar masses,[6] being too faint to be detected using photometry.[3] This inner system is orbited by the magnitude 7.54 Kappa Tucanae B, a G-type main-sequence star[3] that completes an orbit around the inner pair every 1,122 years.[6]

The second set of stars consists of the magnitude +7.76 C, and the magnitude +8.26 D; both are K-type main-sequence stars that orbit around each other once every 85.12 years.[3]

Exozodiacal dust

Excess emission in near-infrared was detected around the primary star of the system, Kappa Tucanae A, and was interpreted as hot exozodiacal dust.[14] This excess emission is variable in time, dimming below detection limit and re-appearing on timescales of a year.[15] Spectral energy distribution modelling suggests that Kappa Tucanae's exozodical dust may consist of amorphous carbon, though other forms of carbon or silicates cannot be ruled out. The best fit model of the exozodi is a narrow ring of hot dust located between 0.1 and 0.29 au, with temperatures between 940 and 1,430 K (667 and 1,160 °C; 1,230 and 2,110 °F). The paper rejects a stellar companion as the source of the excess emission.[16]

The periastron of the companion star Kappa Tucanae Ab coincides with the location of the hot exozodi dust. The star could interact with the dust through gravity, irradiation, or stellar wind.[6]

References

  1. ^ a b Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
  2. ^ a b c d Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
  3. ^ a b c d e f g h i j k l m n o p q r s t u v w x y Tokovinin, Andrei (2020-06-01). "Nearby Quintuple Systems κ Tucanae and ξ Scorpii". The Astronomical Journal. 159 (6): 265. arXiv:2005.04057. Bibcode:2020AJ....159..265T. doi:10.3847/1538-3881/ab8af1. ISSN 0004-6256.
  4. ^ a b Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
  5. ^ a b Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
  6. ^ a b c d e f g h Stuber, T. A.; Mérand, A.; Kirchschlager, F.; et al. (2026-01-02). "Interferometric Detection and Orbit Modeling of the Subcomponent in the Hot-dust System κ Tuc A: A Low-mass Star on an Eccentric Orbit in a Hierarchical-quintuple System". The Astronomical Journal. 171 (1): 1. arXiv:2512.03209. Bibcode:2026AJ....171....1S. doi:10.3847/1538-3881/adfe66. ISSN 0004-6256.
  7. ^ a b c Ammler-von Eiff, Matthias; Reiners, Ansgar (June 2012). "New measurements of rotation and differential rotation in A-F stars: are there two populations of differentially rotating stars?". Astronomy & Astrophysics. 542: A116. arXiv:1204.2459. Bibcode:2012A&A...542A.116A. doi:10.1051/0004-6361/201118724. S2CID 53666672.
  8. ^ a b 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.
  9. ^ a b c d e Harada, Caleb K.; et al. (June 2024). "Setting the Stage for the Search for Life with the Habitable Worlds Observatory: Properties of 164 Promising Planet-survey Targets". The Astrophysical Journal Supplement Series. 272 (2). id. 30. arXiv:2401.03047. Bibcode:2024ApJS..272...30H. doi:10.3847/1538-4365/ad3e81.
  10. ^ a b c Stassun, Keivan G.; Oelkers, Ryan J.; Paegert, Martin; Torres, Guillermo; Pepper, Joshua; De Lee, Nathan; Collins, Kevin; Latham, David W.; Muirhead, Philip S.; Chittidi, Jay; Rojas-Ayala, Bárbara; Fleming, Scott W.; Rose, Mark E.; Tenenbaum, Peter; Ting, Eric B. (2019-10-01). "The Revised TESS Input Catalog and Candidate Target List". The Astronomical Journal. 158 (4): 138. arXiv:1905.10694. Bibcode:2019AJ....158..138S. doi:10.3847/1538-3881/ab3467. ISSN 0004-6256.
  11. ^ a b c d Hardegree-Ullman, Kevin K.; Apai, Dániel; Bergsten, Galen J.; Pascucci, Ilaria; López-Morales, Mercedes (2023). "Bioverse: A Comprehensive Assessment of the Capabilities of Extremely Large Telescopes to Probe Earth-like O2 Levels in Nearby Transiting Habitable-zone Exoplanets". The Astronomical Journal. 165 (6): 267. arXiv:2304.12490. Bibcode:2023AJ....165..267H. doi:10.3847/1538-3881/acd1ec.
  12. ^ a b "Kappa Tucanae". SIMBAD. Centre de données astronomiques de Strasbourg.
  13. ^ Hoffleit, D.; Warren, W. H., Jr. (1995-11-01). "VizieR Online Data Catalog: Bright Star Catalogue, 5th Revised Ed. (Hoffleit+, 1991)". VizieR Online Data Catalog. 5050: V/50. Bibcode:1995yCat.5050....0H. Kappa Tucanae's database entry at VizieR.
  14. ^ a b Ertel, S.; Absil, O.; Defrère, D.; et al. (2014). "A near-infrared interferometric survey of debris-disk stars". Astronomy & Astrophysics. 570. EDP Sciences: A128. arXiv:1409.6143. Bibcode:2014A&A...570A.128E. doi:10.1051/0004-6361/201424438. ISSN 0004-6361.
  15. ^ a b Ertel, S.; Defrère, D.; Absil, O.; et al. (2016-10-26). "A near-infrared interferometric survey of debris-disc stars. V. PIONIER search for variability". Astronomy & Astrophysics. 595. EDP Sciences: A44. arXiv:1608.05731. Bibcode:2016A&A...595A..44E. doi:10.1051/0004-6361/201527721. ISSN 0004-6361.
  16. ^ Kirchschlager, Florian; Ertel, Steve; Wolf, Sebastian; Matter, Alexis; Krivov, Alexander V. (2020-09-09). "First L band detection of hot exozodiacal dust with VLTI/MATISSE". Monthly Notices of the Royal Astronomical Society. 499 (1): L47-L52. arXiv:2009.02334. Bibcode:2020MNRAS.499L..47K. doi:10.3847/1538-3881/adfe66.
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