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[1]
Right ascension  16h 15m 50.36533s[2]
Declination +10° 01′ 57.2843″[2]
Apparent magnitude (V) 9.447±0.024[3]
Characteristics
Spectral type F8[4]
B−V color index 0.476[citation needed]
J−H color index 0.181[citation needed]
J−K color index 0.289[citation needed]
Astrometry
Radial velocity (Rv)−9.24±0.23[2] km/s
Proper motion (μ) RA: −31.135[2] mas/yr
Dec.: −39.167[2] mas/yr
Parallax (π)7.3373 ± 0.0181[2] mas
Distance445 ± 1 ly
(136.3 ± 0.3 pc)
Details
Mass1.203±0.036[5] M☉
Radius1.331+0.030
−0.025[5] R☉
Luminosity2.838±0.024[6] L☉
Surface gravity (log g)4.25+0.012
−0.013[3] cgs
Temperature6,150±80[5] K
Metallicity [Fe/H]0.06[7] dex
Rotational velocity (v sin i)8.6±0.4[3] km/s
Age350 Myr[7]
400±500[8] Myr
Other designations
Irena, BD+10°2980, HD 146389, SAO 102042, 2MASS J16155036+1001572[9]
Database references
SIMBADdata
Exoplanet Archivedata

HD 146389, also known as WASP-38 and named Irena,[10] is a star with a yellow-white hue in the northern constellation of Hercules. It is invisible to the naked eye with an apparent visual magnitude of 9.4[3] The star is located at a distance of approximately 445 light-years from the Sun based on parallax, but is drifting closer with a radial velocity of −9 km/s.[2] The star is known to host one exoplanet, designated WASP-38b or formally named Iztok.

Nomenclature

The designation HD 146389 comes from the Henry Draper Catalogue, while WASP-38 comes from the Wide Angle Search for Planets.

This was one of the systems selected to be named in the 2019 NameExoWorlds campaign during the 100th anniversary of the IAU, which assigned each country a star and planet to be named. This system was assigned to Slovenia. The approved names were Irena for the star and Iztok for the planet, named after characters from the Slovenian novel Pod svobodnim soncem.[11][12]

Characteristics

The stellar classification of HD 146389 is F8,[4] 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.[3] 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.[13] The star is 33% larger and 20% more massive than the Sun.[5] It is radiating nearly three[6] times the luminosity of the Sun at an effective temperature of 6,150 K.[5]

Planetary system

The hot Jupiter class planet WASP-38 b, later named Iztok, was discovered around HD 146389 in 2010.[3] The planet is losing significant amounts of gas, estimated to be 0.023 Earth masses per billion years.[4] 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.[14][5]

A 2012 study, utilizing the 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°.[15]

The WASP-38 planetary system[3]
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. ↑ Roman, Nancy G. (1987). "Identification of a constellation from a position". Publications of the Astronomical Society of the Pacific 99 (617): 695. doi:10.1086/132034. Bibcode: 1987PASP...99..695R  Constellation record for this object at VizieR.
  2. ↑ 2.0 2.1 2.2 2.3 2.4 2.5 Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940  Gaia DR3 record for this source at VizieR.
  3. ↑ 3.0 3.1 3.2 3.3 3.4 3.5 3.6 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. 
  4. ↑ 4.0 4.1 4.2 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. 
  5. ↑ 5.0 5.1 5.2 5.3 5.4 5.5 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. 
  6. ↑ 6.0 6.1 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.
  7. ↑ 7.0 7.1 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. 
  8. ↑ 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. 
  9. ↑ "HD 146389". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=HD+146389. 
  10. ↑ "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. 
  11. ↑ "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/. 
  12. ↑ "Approved names" (in en). http://www.nameexoworlds.iau.org/final-results. 
  13. ↑ 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. 
  14. ↑ 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. 
  15. ↑ 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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