HD 146389
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. It is invisible to the naked eye with an apparent visual magnitude of 9.4 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. The star is known to host one exoplanet, designated WASP-38b or formally named 'Iztok'.
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Hercules |
| Right ascension | 16h 15m 50.36526s |
| Declination | 10° 01′ 57.2844″ |
| Apparent magnitude (V) | 9.447±0.024 |
| Characteristics | |
| Spectral type | F8 |
| B−V color index | 0.476 |
| J−H color index | 0.181 |
| J−K color index | 0.289 |
| Astrometry | |
| Radial velocity (Rv) | −9.06±0.53 km/s |
| Proper motion (μ) | RA: −31.073 mas/yr Dec.: −39.171 mas/yr |
| Parallax (π) | 7.3115 ± 0.0429 mas |
| Distance | 446 ± 3 ly (136.8 ± 0.8 pc) |
| Details | |
| Mass | 1.203±0.036 M☉ |
| Radius | 1.331+0.030 −0.025 R☉ |
| Luminosity | 2.838±0.024 L☉ |
| Surface gravity (log g) | 4.25+0.012 −0.013 cgs |
| Temperature | 6,150±80 K |
| Metallicity [Fe/H] | 0.06 dex |
| Rotational velocity (v sin i) | 8.6±0.4 km/s |
| Age | 350 Myr 400±500 Myr |
| Other designations | |
| Database references | |
| SIMBAD | data |
The stellar classification of HD 146389 is F8, 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. 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. The star is 33% larger and 20% more massive than the Sun. It is radiating nearly three times the luminosity of the Sun at an effective temperature of 6,150 K.