HH Carinae is a semidetached spectroscopic and eclipsing binary in the constellation of Carina. It consists of an O-type main-sequence star and a blue giant or subgiant.
Observational history
HH Carinae was first observed in the late 1890s at Cape Observatory by astronomers Sir David Gill and Jacobus Cornelius Kapteyn in the Cape Photographic Durchmusterung. It was later added to the General Catalogue of Variable Stars between 1948 and 1968 and was first characterised in 1968.
It was characterised in detail in 1985 and in 2021.
Star system
HH Carinae consists of two stars with respective spectral types of O9 V and B0 III–IV. The less massive B-type component is tidally locked to the more massive O-type component.
Its distance based on the parallax provided in Gaia DR3 is pc. This is consistent with the photometric distance derived from a visual extinction of 1.722, of pc.
Primary
The primary has a rotational velocity of 220 km s-1, nearly three times faster than its synchronous rotational velocity of km s-1. This is attributed to roche lobe overflow from the secondary, which speeds up the primary's rotation. It is smaller, less luminous but more massive than the secondary.
Secondary
The secondary has filled its roche lobe and is tidally locked to the primary. It having left the main-sequence indicates that it has lost a significant amount of mass. It is estimated to lose mass at a rate of approximately yr-1, however, to be measured with high accuracy, orbital period analysis would be required.
It has been identified as having spectral type B0 III–IV due to its strong SiIV and OII lines that are observed as it passes in front of the primary.
Circumstellar envelope
The system is surrounded by a circumstellar envelope, identifiable due to a double peak in Hα emission, with an effective temperature of K. It is heterogeneous as its temperature and density vary slightly, likely due to interaction between stellar winds and matter transferred from the secondary to the L1 point. The inner shell has a radius of and the outer shell has one of .
OB association membership
Due to the system's presumed young age, it is likely to have originated from an OB association. The two nearest known associations to HH Carinae are Car OB1 and Car OB2, which have respective space velocities of (U, V, W) = (, , ) km s-1 and (U, V, W) = (, , ) km s-1, inconsistent with the (U, V, W) = (, , ) km s-1, suggesting that it is unrelated to both and may have otherwise formed in an undiscovered association.
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