Tucana-Horologium association


The Tucana-Horologium association or Tucana Horologium moving group is a stellar association with an age of 45 ± 4 Myr and it is one of the largest stellar associations within 100 parsec. The association has a similar size as the Beta Pictoris moving group and contains, like BPMG, more than 12 stars with spectral type B, A and F. The association is named after two southern constellations, the constellation Tucana and the constellation Horologium.
The group was at first not recognized as an individual group, but stars within the group were first assigned to the Great Austral Young Association. Only later did it become clear that this complex is divided into three groups: the Tucana-Horologium association, the Carina association and the Columba association.

Members

The members of this young group are potential targets for directly imaged circumstellar disks and exoplanets. The stars in this group are located closely to earth and the planets are young, so that they give off more infrared light, which is suited for directly imaging techniques. AB Pictoris was considered a good member of Tuc-Hor, but it is more likely a member of the Carina association.
The brightest identified member of the association is the massive star Alpha Pavonis, which is leaving the main sequence. The association also contains stars of Beta Tucanae, which contains multiple stars. Another notable member is DS Tucanae, which is a binary star, with the primary having one exoplanet transiting in front of the star.
Several members have a detected debris disk around them. Examples are HD 1466, HD 10472, DK Ceti, CPD-74 192, HD 21997, HD 32195, HD 37484, HD 38206, V1358 Orionis and HD 85672. The star HD 202917 has a debris disk that was directly imaged with the Hubble Space Telescope. The brown dwarf 2MASS J02265658-5327032 is likely a member of the Tuc-Hor association and has a circumstellar disk, which is unusual for its age. Some researchers call these relatively old disks Peter Pan disks.
Examples for directly imaged planets in the association are 2MASS 0219-3925 b and 2MASS 0103 b.
The list below shows some members of the group. The list is focused on B-type, A-type and F-type stars and other stars/brown dwarfs are included if they are notable. The list is sorted after the brightness.
Namedistance spectral typebrightness
α Pavonis179B2IV1.91
φ Eridani154B8V3.56
ε Hydri152B9IV4.12
HD 2884135B9V4.36
HD 24072172B9.5Van4.71
HD 2885166A2V4.77
η Tucanae154A1Va+n4.99
HD 3003150A0V5.07
HD 24071172A1Va5.25
HD 20121139F4V+F9V6.01
HD 154431181A5V6.07
HD 19545177A3V6.18
HD 12894151F4V6.45
HD 207964152F0IV6.56
HD 200798227A5/6IV/V6.70
HD 30051220F2IV7.12
HD 24636186F3IV/V7.13
HD 207575153F6V7.22
HD 1466140F8V7.45
HD 53842189F5V7.46
HD 20385159F6V7.49
HD 13246149F7V7.50
HD 17250186F7V7.88
HD 32195205F7V8.12
DS Tucanae149G6V8.49
DK Ceti135G4V8.66
HD 202917153G7V8.67
BS Indi172G9V8.87
CC Phoenicis130K1V9.38
BO Microscopii218K3Ve9.45
V857 Arae194G8V9.50
AT Columbae254K1Ve9.58
CT Tucanae144M0Ve11.47
GJ 3054134M1.5V11.97
AF Horologii142M2Ve12.13
2MASS 0103154M5.0+L15.40
2MASS 0219-3925131M6γ+L4γ11.32
2MASS J02265658-5327032152L0δ15.40