HD 138289

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]

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]
Distance	359.1 ± 0.8 ly (110.1 ± 0.2 pc)
Absolute magnitude (MV)	+1.21[7]
Details
Mass	1.59[8] M☉
Radius	13±0.7[9] R☉
Luminosity	52.5+2.5 −2.4[10] L☉
Surface gravity (log g)	2.71[8] cgs
Temperature	4,672±100[11] K
Metallicity [Fe/H]	−0.04[8] dex
Rotational velocity (v sin i)	5.2±4.3[12] km/s
Age	2.78+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
SIMBAD	data

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]

References

1. Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
2. Høg, E.; Fabricius, C.; Makarov, V. V.; Urban, S.; Corbin, T.; Wycoff, G.; Bastian, U.; Schwekendiek, P.; Wicenec, A. (March 2000). "The Tycho-2 catalogue of the 2.5 million brightest stars". Astronomy and Astrophysics. 355: L27–L30. Bibcode:2000A&A...355L..27H. ISSN 0004-6361.
3. Laney, C. D.; Joner, M. D.; Pietrzyński, G. (11 November 2011). "A new Large Magellanic Cloud K-band distance from precision measurements of nearby red clump stars". Monthly Notices of the Royal Astronomical Society. 419 (2): 1637–1641. arXiv:1109.4800. Bibcode:2012MNRAS.419.1637L. doi:10.1111/j.1365-2966.2011.19826.x. ISSN 0035-8711.
4. Keenan, Philip C.; McNeil, Raymond C. (October 1989). "The Perkins catalog of revised MK types for the cooler stars". The Astrophysical Journal Supplement Series. 71: 245. Bibcode:1989ApJS...71..245K. doi:10.1086/191373. eISSN 1538-4365. ISSN 0067-0049.
5. Johnson, H. L.; Mitchell, R. I.; Iriarte, B.; Wisniewski, W. Z. (1966). "UBVRIJKL Photometry of the Bright Stars". Communications of the Lunar and Planetary Laboratory. 4: 99–110. Bibcode:1966CoLPL...4...99J.
6. Evans, David S. (June 20–24, 1966), "The Revision of the General Catalogue of Radial Velocities", in Batten, Alan Henry; Heard, John Frederick (eds.), Determination of Radial Velocities and their Applications, Proceedings from IAU Symposium no. 30, vol. 30, University of Toronto: International Astronomical Union, p. 57, Bibcode:1967IAUS...30...57E
7. Anderson, E.; Francis, Ch. (May 2012). "XHIP: An extended hipparcos compilation". Astronomy Letters. 38 (5): 331–346. arXiv:1108.4971. Bibcode:2012AstL...38..331A. doi:10.1134/S1063773712050015. eISSN 1562-6873. ISSN 1063-7737. S2CID 119257644.
8. Liu, Y. J.; Zhao, G.; Shi, J. R.; Pietrzyński, G.; Gieren, W. (7 November 2007). "The abundances of nearby red clump giants". Monthly Notices of the Royal Astronomical Society. 382 (2): 553–566. Bibcode:2007MNRAS.382..553L. doi:10.1111/j.1365-2966.2007.11852.x. eISSN 1365-2966. ISSN 0035-8711.
9. Kervella, P.; Thévenin, F.; Di Folco, E.; Ségransan, D. (October 2004). "The angular sizes of dwarf stars and subgiants". Astronomy & Astrophysics. 426 (1): 297–307. arXiv:astro-ph/0404180. Bibcode:2004A&A...426..297K. doi:10.1051/0004-6361:20035930. eISSN 1432-0746. ISSN 0004-6361.
10. Charbonnel, C.; Lagarde, N.; Jasniewicz, G.; North, P. L.; Shetrone, M.; Krugler Hollek, J.; Smith, V. V.; Smiljanic, R.; Palacios, A.; Ottoni, G. (January 2020). "Lithium in red giant stars: Constraining non-standard mixing with large surveys in the Gaia era". Astronomy & Astrophysics. 633: A34. arXiv:1910.12732. Bibcode:2020A&A...633A..34C. doi:10.1051/0004-6361/201936360. eISSN 1432-0746. ISSN 0004-6361.
11. Stassun, Keivan G.; et al. (9 September 2019). "The Revised TESS Input Catalog and Candidate Target List". The Astronomical Journal. 158 (4): 138. arXiv:1905.10694. Bibcode:2019AJ....158..138S. doi:10.3847/1538-3881/ab3467. eISSN 1538-3881. hdl:1721.1/124721. S2CID 166227927.
12. De Medeiros, J. R.; Alves, S.; Udry, S.; Andersen, J.; Nordström, B.; Mayor, M. (January 2014). "A catalog of rotational and radial velocities for evolved stars V: Southern stars". Astronomy & Astrophysics. 561: A126. arXiv:1312.3474. Bibcode:2014A&A...561A.126D. doi:10.1051/0004-6361/201220762. eISSN 1432-0746. ISSN 0004-6361. S2CID 54046583.
13. Gould, Benjamin Apthorp (1878). "Uranometria Argentina : brillantez y posicion de las estrellas fijas, hasta la septima magnitud, comprendidas dentro de cien grados del polo austral : con atlas". Resultados del Observatorio Nacional Argentino. 1. Bibcode:1879RNAO....1.....G.
14. "HD 138289". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 20 September 2015.
15. Gontcharov, George A.; Mosenkov, Aleksandr V. (28 September 2017). "Verifying reddening and extinction for Gaia DR1 TGAS main sequence stars". Monthly Notices of the Royal Astronomical Society. 472 (4): 3805–3820. arXiv:1709.01160. Bibcode:2017MNRAS.472.3805G. doi:10.1093/mnras/stx2219. eISSN 1365-2966. ISSN 0035-8711.