Astronomy:HD 146389

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Short description: Star in the constellation Hercules
WASP-38 / Irena
Observation data
Equinox J2000.0]] (ICRS)
Constellation Hercules
Right ascension  16h 15m 50.36526s[1]
Declination 10° 01′ 57.2844″[1]
Apparent magnitude (V) 9.447±0.024[2]
Characteristics
Spectral type F8[3]
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[1] km/s
Proper motion (μ) RA: −31.073[1] mas/yr
Dec.: −39.171[1] mas/yr
Parallax (π)7.3115 ± 0.0429[1] mas
Distance446 ± 3 ly
(136.8 ± 0.8 pc)
Details
Mass1.203±0.036[4] M☉
Radius1.331+0.030
−0.025[4] R☉
Luminosity2.838±0.024[1] L☉
Surface gravity (log g)4.25+0.012
−0.013[2] cgs
Temperature6,150±80[4] K
Metallicity [Fe/H]0.06[5] dex
Rotational velocity (v sin i)8.6±0.4[2] km/s
Age350 Myr[5]
400±500[6] Myr
Other designations
BD+10°2980, Gaia DR2 4453211899986180352, HD 146389, SAO 102042, 2MASS J16155036+1001572, WASP 38[7]
Database references
SIMBADdata

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]

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.[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]

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

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 Brown, A. G. A. (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics 616: A1. doi:10.1051/0004-6361/201833051. Bibcode: 2018A&A...616A...1G.  Gaia DR2 record for this source at VizieR.
  2. ↑ 2.0 2.1 2.2 2.3 2.4 2.5 2.6 Barros, S. C. C. et al. (2011). "WASP-38b: A transiting exoplanet in an eccentric, 6.87d period orbit". Astronomy & Astrophysics 525: A54. doi:10.1051/0004-6361/201015800. Bibcode: 2011A&A...525A..54B. 
  3. ↑ 3.0 3.1 3.2 Ehrenreich, D.; Désert, J.-M. (2011). "Mass-loss rates for transiting exoplanets". Astronomy & Astrophysics 529: A136. doi:10.1051/0004-6361/201016356. Bibcode: 2011A&A...529A.136E. 
  4. ↑ 4.0 4.1 4.2 4.3 4.4 4.5 Brown, D. J. A. et al. (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. doi:10.1088/0004-637X/760/2/139. Bibcode: 2012ApJ...760..139B. 
  5. ↑ 5.0 5.1 Delgado Mena, E. et al. (April 2015). "Li abundances in F stars: planets, rotation, and Galactic evolution". Astronomy & Astrophysics 576: A69. doi:10.1051/0004-6361/201425433. A69. Bibcode: 2015A&A...576A..69D. 
  6. ↑ Bonfanti, A. et al. (2015). "Revising the ages of planet-hosting stars". Astronomy and Astrophysics 575: A18. doi:10.1051/0004-6361/201424951. Bibcode: 2015A&A...575A..18B. 
  7. ↑ "HD 146389". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=HD+146389. 
  8. ↑ "IAU Catalog of Star Names (IAU-CSN)". IAU Division C Working Group on Star Names (WGSN). January 1, 2021. https://www.pas.rochester.edu/~emamajek/WGSN/IAU-CSN.txt. 
  9. ↑ "The IAU announces names for WASP exoplanets". WASP Planets. 5 January 2020. https://wasp-planets.net/2020/01/05/the-iau-announces-names-for-wasp-exoplanets/. 
  10. ↑ Salz, M. et al. (2015). "High-energy irradiation and mass loss rates of hot Jupiters in the solar neighborhood". Astronomy & Astrophysics 576: A42. doi:10.1051/0004-6361/201425243. Bibcode: 2015A&A...576A..42S. 
  11. ↑ Simpson, E. K. et al. (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. doi:10.1111/j.1365-2966.2011.18603.x. Bibcode: 2011MNRAS.414.3023S. 
  12. ↑ Albrecht, Simon et al. (2012), "Obliquities of Hot Jupiter host stars: Evidence for tidal interactions and primordial misalignments", The Astrophysical Journal 757 (1): 18, doi:10.1088/0004-637X/757/1/18, Bibcode: 2012ApJ...757...18A 

Coordinates: Sky map 16h 15m 50.3653s, +10° 01′ 57.2844″



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