Tau9 Eridani
A binary star with a magnetic chemically peculiar primary.
Tau9 Eridani (τ9 Eri) is a binary star system in the constellation Eridanus, visible to the naked eye with an apparent visual magnitude of 4.63. It is notable as a double-lined spectroscopic binary and for its primary component being a magnetic chemically peculiar star of the Alpha² Canum Venaticorum variable type.
- Apparent visual magnitude
- 4.63
- Distance
- ~327 light years
- Orbital period
- 5.95382 days
- Orbital eccentricity
- 0.12
- Primary mass
- 3.26 solar masses
- Primary radius
- 3.1 solar radii
- Primary effective temperature
- 10,866 K
Lore & Background
Tau9 Eridani is a double-lined spectroscopic binary system with an orbital period of 5.95382 days and an eccentricity of 0.12. The primary component, τ9 Eri A, is a B-type main-sequence star that shows abundance anomalies in its silicon absorption lines, classifying it as a magnetic chemically peculiar star. It is an Alpha² Canum Venaticorum variable with a rotational periodicity of 5.954 days. The averaged strength of its stellar effective magnetic field is recorded, though its value is not specified in the available data.
The primary star has an estimated mass of 3.26 times that of the Sun and a radius of 3.1 solar radii. It shines with 166 times the solar luminosity from an outer atmosphere at an effective temperature of 10,866 K, and it spins with a projected rotational velocity of 30 km/s. The secondary star, designated Tau9 Eridani B, is a late A-type or early F-type star with a mass of 1.6 solar masses and an effective temperature of 7,530 K.
Reader's Guide
Tau9 Eridani holds significance as a binary system that provides insights into the properties of magnetic chemically peculiar stars and their interactions in close orbits. The primary's classification as an Alpha² Canum Venaticorum variable, with a rotational period nearly identical to the orbital period, suggests a possible synchronization between rotation and revolution, a feature of interest in stellar astrophysics. The system's double-lined spectroscopic nature allows direct measurement of both components' masses and temperatures, contributing to models of stellar evolution for intermediate-mass stars. The presence of a magnetic field in the primary, combined with its chemical peculiarities, makes it a valuable target for studying the effects of magnetic fields on stellar atmospheres and element diffusion. The secondary, being a late A-type or early F-type star, complements the primary in understanding binary star formation and mass ratios. The system's distance of roughly 327 light years places it within a range accessible for detailed photometric and spectroscopic studies, such as those from TESS, which have provided light curves revealing its variability.
Did You Know?
- The primary component is an Alpha² Canum Venaticorum variable with a rotational period of 5.954 days.
- The primary star has 3.26 times the mass of the Sun and 3.1 times its radius.
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