Triple star system in the constellation Pyxis
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! style="text-align: center; background-color: #FFFFC0;" colspan="2" | Observation dataEpoch J2000
      Equinox J2000
! style="text-align:left" | Constellation
! style="text-align:left" | Right ascension
! style="text-align:left" | Declination
! style="text-align:left" | Apparent magnitude (V)
! style="background-color: #FFFFC0; text-align: center;" colspan="2"| Characteristics
! style="text-align:left" | Spectral type
! style="text-align:left" | B−V 
! style="text-align:left" | J−H 
! style="text-align:left" | J−K 
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HD 73752 is a multiple star system located in the southern constellation of Pyxis. With an apparent magnitude of 5.17, it can be faintly seen by the naked eye from Earth as a yellow-hued dot of light. As such, it is listed in the Bright Star Catalogue as HR 3430. It is located at a distance of approximately according to Gaia EDR3 parallax measurements, and is receding at a heliocentric radial velocity of 52.13 km/s.
Physical properties.
The system is roughly seven billion years old, much older than the Solar System (), and belongs to the thin disk population of the Milky Way.
The primary star, HD 73752 Aa, is an aging subgiant, a star that has fused all the hydrogen in its core into helium and evolved past the main sequence, with the spectral type G5IV. It is 21% more massive than the Sun, equivalent to a typical F-type main-sequence star with the spectral type F7V, but has expanded to a radius of 1.68 R☉. It radiates 2.31 times the luminosity of the Sun from its photosphere at an effective temperature of . The entire system is very metal-rich with a metallicity of +0.32, which equates to an iron abundance 100.32 ≈ 2.1 times that of the Sun. A low-mass close companion, Ab, orbits Aa in a orbit, but its precise parameters remain uncertain.
The secondary star, which is in a 127-year binary orbit with the Aa/Ab pair, is a G-type or K-type main-sequence star similar to the Sun in mass and radius, but substantially cooler at . As such, it emits only three-fifths the Sun's luminosity.
Multiplicity.
HD 73752 has been known to be a close visual binary since 1874. As early as 1943, a third unseen component was suspected, though this suggestion of a ~0.1 M☉ object in a 35-year orbit remained inconclusive, and a 1967 study turned up little evidence. Radial velocity variations were observed in 1980 and 2006 that strongly implied a low-mass object, though the orbital parameters could not be obtained. In 2016, HD 73752 A was finally confirmed to be a spectroscopic binary.
Additionally, another possible companion, 13.7 magnitudes fainter than the primary in the H band, was noticed at a separation of 4".50 in right ascension and 6".02 in declination, but this has not been followed up on.
Circumstellar disc.
HD 73752 has been referred to as a "Vega-like star," a star that exhibits excess infrared emission due to an optically thin dusty circumstellar disc containing almost no gas. Because this star is past the main sequence, the process in which the emissions are produced may diverge from that of younger such stars e.g., Epsilon Eridani, HD 53143, HD 69830, and HD 98800. In 2012, a debris disc was detected at a distance of 21 AU from the primary, an unstable position close to the secondary star's orbit at 34 AU. Despite this, a 2019 study did not find any significant infrared excess at a wavelength of .
References.
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