HD 138289

HD 138289
location of HD 138289 on the map (circled)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Apus
Right ascension 15h 39m 18.39712s[1]
Declination −77° 55′ 04.8196″[1]
Apparent magnitude (V) 6.18±0.01[2]
Characteristics
Evolutionary stage horizontal branch[3]
Spectral type K2.5 IIIb CN1.5 Ba+0.5[4]
U−B color index +1.36[5]
B−V color index +1.21[5]
Astrometry
Radial velocity (Rv)+13.1[6] km/s
Proper motion (μ) RA: −79.376 mas/yr[1]
Dec.: −130.969 mas/yr[1]
Parallax (π)9.0832 ± 0.0204 mas[1]
Distance359.1 ± 0.8 ly
(110.1 ± 0.2 pc)
Absolute magnitude (MV)+1.21[7]
Details
Mass1.59[8] M☉
Radius13±0.7[9] R☉
Luminosity52.5+2.5
−2.4[10] L☉
Surface gravity (log g)2.71[8] cgs
Temperature4,672±100[11] K
Metallicity [Fe/H]−0.04[8] dex
Rotational velocity (v sin i)5.2±4.3[12] km/s
Age2.78+0.37
−0.52[1] Gyr
Other designations
32 G. Apodis[13], CPD−77°1134, FK5 3228, GC 20948, HD 138289, HIP 76664, HR 5757, SAO 257303[14]
Database references
SIMBADdata

HD 138289, also known as HR 5757, is a probable spectroscopic binary[12] located in the constellation Apus, the bird-of-paradise. It has an apparent magnitude of 6.18,[2] placing it near the limit for naked eye. Gaia DR3 parallax measurements place the object 359 light years away[1] and it is currently receding with a heliocentric radial velocity of 13.1 km/s.[6] At its current distance, HD 138289's brightness is diminished by 0.25 magnitudes due to extinction from interstellar dust.[15] It has an absolute magnitude of +1.21.[7]

The visible component has a stellar classification of K2.5 IIIb CN1.5 Ba+0.5,[4] indicating that it is a red giant with an anomalous overabundance of cyano radicals in its spectrum. The IIIb luminosity class indicates that it is a lower luminosity giant star. The Ba+0.5 suffix states that it is a mild barium star, whose barium abundance might have come from a hidden white dwarf companion. HD 138289 is estimated to be 2.8 billion years old,[1] enough time for it to cool and expand to 13 times the radius of the Sun.[9] It is now on the horizontal branch,[3] fusing helium at its core. At present it has 1.59 times the mass of the Sun and radiates 52.5 times the luminosity of the Sun[10] from its enlarged photosphere at an effective temperature of 4,672 K.[11] HD 138289 has a near solar metallicity and spins modestly with a poorly constrained projected rotational velocity of 5.2 km/s.[12]

  1. ^ a b c d e f g Cite error: The named reference GaiaDR3 was invoked but never defined (see the help page).
  2. ^ a b Cite error: The named reference Tycho2000 was invoked but never defined (see the help page).
  3. ^ a b Cite error: The named reference Laney2011 was invoked but never defined (see the help page).
  4. ^ a b Cite error: The named reference Keenan1989 was invoked but never defined (see the help page).
  5. ^ a b Cite error: The named reference Johnson1966 was invoked but never defined (see the help page).
  6. ^ a b Cite error: The named reference Evans1966 was invoked but never defined (see the help page).
  7. ^ a b Cite error: The named reference Anderson2012 was invoked but never defined (see the help page).
  8. ^ a b c Cite error: The named reference Liu2007 was invoked but never defined (see the help page).
  9. ^ a b Cite error: The named reference Kervella2004 was invoked but never defined (see the help page).
  10. ^ a b Cite error: The named reference Charbonnel2020 was invoked but never defined (see the help page).
  11. ^ a b Cite error: The named reference Stassun2019 was invoked but never defined (see the help page).
  12. ^ a b c Cite error: The named reference De Medeiros2014 was invoked but never defined (see the help page).
  13. ^ Cite error: The named reference Gould1879 was invoked but never defined (see the help page).
  14. ^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  15. ^ Cite error: The named reference Gontcharov2017 was invoked but never defined (see the help page).