HR 6384
A suspected ellipsoidal variable in Ara with an 80-day period.
HR 6384, also known as V829 Arae, is a binary star system located in the southern constellation Ara (the Altar). It is just barely visible without a telescope, with a combined apparent visual magnitude that varies around 6.153. The system lies roughly 1,300 light-years from the Sun and is moving closer at a radial velocity of about −34 km/s.
The system is a close, interacting binary. Its secondary component is hot, with a spectral class of A or hotter. The primary is an aging red giant or bright giant, classified as M1/M2II/III, currently on the asymptotic giant branch. Having exhausted its core hydrogen, this star has expanded to 160 times the Sun's diameter and radiates 3,562 times the Sun's luminosity from its photosphere, which has an effective temperature of 3,562 K.
The system is suspected to be an ellipsoidal variable, with a period of 80 days and a magnitude variation of 0.08. Its variability was announced in 1985 by W. S. G. Walker and colleagues, based on three-color photometry at Auckland Observatory in New Zealand, and it received the variable star designation V829 Arae in 1987.
- Apparent magnitude
- 6.153 (variable)
- Distance
- ~1,300 ly
- Radial velocity
- −34 km/s
- Variable star designation
- V829 Arae
- Period
- 80 days
- Amplitude
- 0.08 magnitude
- Spectral type
- M1/M2II/III (primary)
Lore & Background
In 1985, W. S. G. Walker et al. announced that HR 6384 is a variable star, based on three color photometry undertaken at Auckland Observatory in New Zealand. It was given its variable star designation, V829 Arae, in 1987. The system appears to be a close, interacting binary with a hot secondary component of class A or hotter. It forms a suspected ellipsoidal variable with a period of 80 days and an amplitude variation of 0.08 in magnitude.
The primary component is an aging red giant or bright giant with a stellar classification of M1/M2II/III, currently on the asymptotic giant branch. With the supply of hydrogen at its core exhausted, it has expanded to 160 times the girth of the Sun. It is radiating 3,562 times the luminosity of the Sun from its enlarged photosphere at an effective temperature of 3,562 K. The system is drifting closer with a radial velocity of around −34 km/s.
Reader's Guide
HR 6384 (V829 Arae) is significant as a suspected ellipsoidal variable in a close binary system, offering insight into the behavior of interacting binaries where one component is an evolved red giant on the asymptotic giant branch. The 80-day period and small amplitude of 0.08 magnitude suggest tidal distortion of the primary by its hot companion, a class A or hotter star. The system's distance of about 1,300 light-years and its faint naked-eye visibility make it a target for both amateur and professional studies of evolved stars in binary configurations. The primary's expansion to 160 solar radii and its high luminosity (3,562 times the Sun) at a relatively cool temperature of 3,562 K exemplify the late stages of stellar evolution. The discovery by Walker et al. using three-color photometry at Auckland Observatory in New Zealand and its subsequent variable star designation in 1987 mark it as a well-documented variable in the southern sky. Its negative radial velocity indicates it is approaching the Solar System, adding a kinematic dimension to its study.
Did You Know?
- HR 6384 is also designated V829 Arae.
- The system has a suspected ellipsoidal variability with an 80-day period.
- It is located about 1,300 light-years from Earth in the constellation Ara.
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