HD 146389

HD 146389 (also known as WASP-38), is the yellow-white main sequence star in the constellation of Hercules. The star was given the formal name Irena by the International Astronomical Union in January 2020.[3] The star is known to host one exoplanet, designated WASP-38b or formally named 'Iztok'.

HD 146389
Observation data
Epoch J2000      Equinox
Constellation Hercules
Right ascension  16h 15m 50.3653s
Declination 10° 01′ 57.2844″
Apparent magnitude (V) 9.39
Characteristics
Evolutionary stage main sequence star
Spectral type F8V
B−V color index 0.476
J−H color index 0.181
J−K color index 0.289
Astrometry
Radial velocity (Rv)-9.797±0.0035 km/s
Proper motion (μ) RA: -31.073±0.053 mas/yr
Dec.: -39.171±0.037 mas/yr
Parallax (π)7.3115 ± 0.0429[1] mas
Distance446 ± 3 ly
(136.8 ± 0.8 pc)
Details
Mass1.203±0.036 M☉
Radius1.331+0.03
−0.025 R☉
Luminosity2.4 L☉
Surface gravity (log g)4.25+0.012
−0.013[2] cgs
Temperature6150±80 K
Metallicity [Fe/H]-0.12±0.07 dex
Rotational velocity (v sin i)8.6±0.4[2] km/s
Age3+2
−2[2] Gyr
Other designations
WASP-38, BD +10 2980, 2MASS J16155036+1001572, Gaia DR2 4453211899986180352
Database references
SIMBADdata

Star characteristics

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.[4]

Planetary system

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.[5] In 2013, it was found the planetary orbit is surprisingly well aligned with the rotational axis of the parent star, despite of the noticeable orbital eccentricity.[6][7]

The study in 2012, 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°.[8]

The WASP-38 planetary system[2]
Companion
(in order from star)		 Mass Semimajor axis
(AU)		 Orbital period
(days)		 Eccentricity Inclination Radius
b (Iztok) 2.691±0.036 MJ 0.07522+0.00074
−0.00075		 6.871815+0.000045
−0.000042		 0.0314+0.0046
−0.0041		 89.69+0.3
−0.25°		 1.094+0.029
−0.028 RJ
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gollark: Some are worse than others.
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gollark: "yes, my server is perfectly secure as long as nobody does things I don't want them to to it"

References
  1. HD 146389 - Star
  2. Barros, S. C. C.; Faedi, F.; Collier Cameron, A.; Lister, T. A.; McCormac, J.; Pollacco, D.; Simpson, E. K.; Smalley, B.; Street, R. A.; Todd, I.; Triaud, A. H. M. J.; Boisse, I.; Bouchy, F.; Hébrard, G.; Moutou, C.; Pepe, F.; Queloz, D.; Santerne, A.; Segransan, D.; Udry, S.; Bento, J.; Butters, O. W.; Enoch, B.; Haswell, C. A.; Hellier, C.; Keenan, F. P.; Miller, G. R. M.; Moulds, V.; Norton, A. J.; et al. (2011). "WASP-38b: A transiting exoplanet in an eccentric, 6.87d period orbit". Astronomy & Astrophysics. 525: A54. arXiv:1010.0849. Bibcode:2011A&A...525A..54B. doi:10.1051/0004-6361/201015800.
  3. The IAU announces names for WASP exoplanets
  4. Salz, M.; Schneider, P. C.; Czesla, S.; Schmitt, J. H. M. M. (2015). "High-energy irradiation and mass loss rates of hot Jupiters in the solar neighborhood". Astronomy & Astrophysics. 576: A42. arXiv:1502.00576. Bibcode:2015A&A...576A..42S. doi:10.1051/0004-6361/201425243.
  5. Ehrenreich, D.; Désert, J.-M. (2011). "Mass-loss rates for transiting exoplanets". Astronomy & Astrophysics. 529: A136. arXiv:1103.0011. Bibcode:2011A&A...529A.136E. doi:10.1051/0004-6361/201016356.
  6. Simpson, E. K.; Pollacco, D.; Cameron, A. Collier; Hébrard, G.; Anderson, D. R.; Barros, S. C. C.; Boisse, I.; Bouchy, F.; Faedi, F.; Gillon, M.; Hebb, L.; Keenan, F. P.; Miller, G. R. M.; Moutou, C.; Queloz, D.; Skillen, I.; Sorensen, P.; Stempels, H. C.; Triaud, A.; Watson, C. A.; Wilson, P. A. (2011). "The spin-orbit angles of the transiting exoplanets WASP-1b, WASP-24b, WASP-38b and HAT-P-8b from Rossiter-Mc Laughlin observations". Monthly Notices of the Royal Astronomical Society. 414 (4): 3023–3035. arXiv:1011.5664. Bibcode:2011MNRAS.414.3023S. doi:10.1111/j.1365-2966.2011.18603.x.
  7. Brown, D. J. A.; Collier Cameron, A.; Díaz, R. F.; Doyle, A. P.; Gillon, M.; Lendl, M.; Smalley, B.; Triaud, A. H. M. J.; Anderson, D. R.; Enoch, B.; Hellier, C.; Maxted, P. F. L.; Miller, G. R. M.; Pollacco, D.; Queloz, D.; Boisse, I.; Hébrard, G. (2012). "Analysis of Spin-Orbit Alignment in the Wasp-32, Wasp-38, and Hat-P-27/Wasp-40 Systems". The Astrophysical Journal. 760 (2): 139. arXiv:1303.5649. Bibcode:2012ApJ...760..139B. doi:10.1088/0004-637X/760/2/139.
  8. Obliquities of Hot Jupiter host stars: Evidence for tidal interactions and primordial misalignments, 2012, arXiv:1206.6105
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