HR 3600

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HR 3600, also known as IZ Velorum, is a bluish-white star in the southern constellation Vela. With an apparent magnitude of about 5.54, it is barely visible to the naked eye under dark skies. It sits about 494 light-years away and is moving away from us at about 22.8 km/s.

This star is a hot B-type main-sequence star (B5V) with around 4 solar masses and 3.2 solar radii. Its surface temperature is about 14,966 K, and it shines with a bolometric luminosity of roughly 535 times that of the Sun (the visual-band luminosity is about 151 LSun). Its absolute visual magnitude is around −0.71. The surface gravity is log g ≈ 4.30, and it rotates relatively slowly (v sin i ≈ 50 km/s).

HR 3600 has many catalog names (HD 77475, HIP 44299, etc.) and is located in IZ Velorum.

Variability: It is a candidate Slowly Pulsating B-type (SPB) star, but its variability is not well understood. Early studies suggested multiple long periods (about 9.6, 14.4, and 10.7 days) and even a possible close binary period around 2.2 days. Later work favored a shorter single period (around 1 day, or possibly 0.9 days). Because the star rotates slowly, the exact cause of its brightness changes—whether pulsations or something else—remains unclear.