HD 9289

Did You Know?

• In 2012, a previously undetected visual companion was discovered at a separation of 0.441 arcseconds to the east-northeast of HD 9289.
• The probability that the two stars are unrelated and aligned by chance is very low (2.16 %).
• The secondary star is about 1.70 magnitudes fainter than the primary when observed in the K band.

Stellar properties

HD 9289 is an A-type main-sequence star with the spectral type A3 SrEuCr, indicating strong spectral lines of strontium, europium, and chromium characteristic of an Ap star. It radiates roughly 8.7 times the luminosity of the Sun from its photosphere and possesses a magnetic field with a strength of 2.0 kG, which is 3,000–9,000 times stronger than Earth's magnetic field. The star was first classified as a rapidly oscillating Ap star (roAp) in 1993 when it was found to pulsate at multiple periods clustered around 10.5 minutes. Additional observations confirmed rotational amplitude modulation similar to that of HR 1217. In 2011, new pulsation frequencies were discovered, the strongest at 1585.936 μHz with an amplitude of 0.63 mmag; few were consistent with initial reports, possibly due to aliasing or an innate shift in pulsation behavior. The rotational period was constrained in 2012 and revised slightly upward in 2021.