HD 146389 (also known as WASP-38), is a star with a yellow-white hue in the northern constellation of Hercules. The star was given the formal name Irena by the International Astronomical Union in January 2020.^[8][9] It is invisible to the naked eye with an apparent visual magnitude of 9.4^[2] The star is located at a distance of approximately 446 light years from the Sun based on parallax, but is drifting closer with a radial velocity of −9 km/s.^[1] The star is known to host one exoplanet, designated WASP-38b or formally named 'Iztok'.

The stellar classification of HD 146389 is F8,^[3] which is an F-type star of uncertain luminosity class. The age of the star is uncertain. It shows a low lithium abundance, which suggests an age of more than 5 billion years. However, the rotation rate indicates an age closer to one billion.^[2] The study in 2015 utilizing Chandra X-ray Observatory, have failed to detect any X-ray emissions from the star during planetary eclipse, which may indicate an unusually low coronal activity or the presence of absorbing gas ring formed by atmosphere escaping planet WASP-38 b.^[10] The star is 33% larger and 20% more massive than the Sun.^[4] It is radiating nearly three^[1] times the luminosity of the Sun at an effective temperature of 6,150 K.^[4]

The "hot Jupiter" class planet WASP-38 b, later named 'Iztok', was discovered around HD 146389 in 2010.^[2] The planet is losing significant amount of gas, estimated to 0.023 Earth masses per billion years.^[3] In 2013, it was found the planetary orbit is surprisingly well aligned with the rotational axis of the parent star, despite the noticeable orbital eccentricity.^[11][4]

A 2012 study, utilizing a Rossiter–McLaughlin effect, have determined the orbital plane of WASP-38b is poorly constrained but probably aligned with the equatorial plane of the star, misalignment equal to 15⁺³³
₋₄₃°.^[12]