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HD 135485

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HD 135485
Observation data
Epoch J2000.0      Equinox ICRS
Constellation Libra[1]
Right ascension 15h 15m 45.257s[2]
Declination −14° 41′ 34.52″[2]
Apparent magnitude (V) 8.16[1]
Characteristics
Evolutionary stage horizontal branch[3]
Spectral type B3V[4] or B5IIp[5]
B−V color index −0.072±0.012[1]
Variable type constant[1]
Astrometry
Radial velocity (Rv)−3.2±0.6[6] km/s
Proper motion (μ) RA: 0.253 mas/yr[2]
Dec.: −34.906 mas/yr[2]
Parallax (π)4.4756±0.0377 mas[2]
Distance729 ± 6 ly
(223 ± 2 pc)
Absolute magnitude (MV)−2.03±0.11[7]
Details
Mass6.03±0.66[7] M☉
Radius2.65[8] R☉
Luminosity417[8] L☉
Surface gravity (log g)4.00±0.25[7] cgs
Temperature19,000[7] K
Rotational velocity (v sin i)2.00±0.50[7] km/s
Age12.0±1.5[7] Myr
Trundle et al (2001)[3]
Mass0.5 M☉
Radius1.2 R☉
Luminosity68+26
−21 L☉
Surface gravity (log g)4.0 cgs
Temperature15,500 K
Other designations
BD−14°4160, HD 135485, HIP 118149, SAO 159132, PPM 229981[9]
Database references
SIMBADdata

HD 135485 is a solitary, peculiar[3] star in the southern constellation of Libra.[1] It has an apparent visual magnitude of 8.16,[1] which is too faint to be visible to the typical naked eye. Based on a parallax measurement of 4.48 mas,[2] it is located at a distance of approximately 729 light-years (223 pc). The star is drifting closer to the Sun with a line of sight velocity component of −3 km/s.[6]

Observations

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In 1956, spectra of this star was found to show abnormally strong absorption lines of helium, suggesting a helium overabundance about ten times the normal level.[10] A 1973 study of a model atmosphere showed a much lower helium abundance; probably less than double the solar proportion. At this point, abundances of other elements suggested this may be a young, super-metal rich star,[11] a hypothesis later refuted. Further study showed the helium abundance is actually near normal, but the star shows unusually high metal abundances (where 'metal' refers to elements more massive than helium).[12] It displays general enrichment in all metals except nickel.[3][7]

HD 135485 has been assigned a stellar classification of B5 IIp,[5] presenting as a peculiar B-type bright giant. (N. Houk and M. Smith-Moore (1978) found a more ordinary class of B3V.[4]) Its position on the HR diagram matches an evolved star lying close to the blue horizontal branch (BHB). In that case, it is most likely a core helium fusing star with a hydrogen fusing envelope. A noticeably larger abundance of nitrogen suggests that material from carbon-nitrogen processing has made its way to the surface, and the star may have undergone helium flashes in the core region.[3] A 2007 study found evidence of vertical stratification of nitrogen and sulfur, with abundances increasing toward the upper atmosphere.[13] This was the first BHB star in which vertical stratification of metals has been observed.[14]

This is most likely an evolved star on the blue horizontal branch. It may have formed in a metal-rich region of the Milky Way, which could explain some of the abundance anomalies.[3] The high abundance of helium may indicate this is a young blue horizontal branch star which has not yet settled its helium component.[3] In the 2001 study by Trundle and associates, the BHB star has half the mass of the Sun and 120% of the Solar radius. It is radiating 68 times the luminosity of the Sun from its photosphere at an effective temperature of 15,500 K.[3]

Other studies assume it is a main sequence star matching the class found by Houk and Smith-Moore in 1978. Under this model, the star is an estimated 12 million years old with a slow projected rotational velocity of 2 km·s−1.[7] It has six[7] times the mass of the Sun and 2.7 times the Sun's radius.[8] This star is radiating 417[8] times the luminosity of the Sun at an effective temperature of 19,000 K.[7]

References

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  1. 1 2 3 4 5 6 Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015. XHIP record for this object at VizieR.
  2. 1 2 3 4 5 6 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.
  3. 1 2 3 4 5 6 7 8 Trundle, C.; et al. (November 2001), "A peculiar metal-rich star, HD 135485", Monthly Notices of the Royal Astronomical Society, 328 (1): 291–300, Bibcode:2001MNRAS.328..291T, doi:10.1046/j.1365-8711.2001.04872.x.
  4. 1 2 Houk, Nancy; Smith-Moore, M. (1978), Michigan Catalogue of Two-dimensional Spectral Types for the HD Stars, vol. 4, Ann Arbor: Dept. of Astronomy, University of Michigan, Bibcode:1988mcts.book.....H.
  5. 1 2 Danly, L.; et al. (March 1995), "Ultraviolet Observations toward HD 135485: Searching for Evidence of a Proposed High Velocity Cloud", Bulletin of the American Astronomical Society, 27: 860, Bibcode:1995AAS...186.3507D.
  6. 1 2 Gontcharov, G. A. (2006), "Pulkovo compilation of radial velocities for 35495 stars in a common system", Astronomy Letters, 32 (11): 759–771, arXiv:1606.08053, Bibcode:2006AstL...32..759G, doi:10.1134/S1063773706110065, S2CID 119231169.
  7. 1 2 3 4 5 6 7 8 9 10 Ünal, Kübra Özge; et al. (August 2025), "Chemical homogeneity in early B-type stars of the Orion Nebula ─ I. First determination of chlorine abundance in HD 37356 and revisions for ϵ CMa, γ Peg, and HD 135485", Monthly Notices of the Royal Astronomical Society, 541 (2): 1286–1304, Bibcode:2025MNRAS.541.1286U, doi:10.1093/mnras/staf913.
  8. 1 2 3 4 Glagolevskij, Yu. V. (2019), "On Properties of Main Sequence Magnetic Stars", Astrophysical Bulletin, 74 (1): 66, Bibcode:2019AstBu..74...66G, doi:10.1134/S1990341319010073.
  9. ↑ "HD 135485", SIMBAD, Centre de données astronomiques de Strasbourg, retrieved 2026-06-30.
  10. ↑ Stewart, John C. (February 1956), "The atmosphere of HD 135485", Astronomical Journal, 61: 13, Bibcode:1956AJ.....61...13S, doi:10.1086/107280.
  11. ↑ Dufton, P. L. (October 1973), "An early-type metal-rich star, HD 135485", Astronomy and Astrophysics, 28: 267, Bibcode:1973A&A....28..267D.
  12. ↑ Schönberner, D. (November 1973), "The atmosphere of the 'hydrogen-deficient' star HD 135485", Astronomy and Astrophysics, 28: 433, Bibcode:1973A&A....28..433S.
  13. ↑ Khalack, V. R.; et al. (May 2007), "Vertical abundance stratification in the blue horizontal branch star HD 135485", Astronomy and Astrophysics, 466 (2): 667–673, arXiv:astro-ph/0702134, Bibcode:2007A&A...466..667K, doi:10.1051/0004-6361:20066647.
  14. ↑ LeBlanc, F.; et al. (February 2025), "Comparison of observed vertical stratifications of iron in blue horizontal-branch stars to those predicted by atomic diffusion", Monthly Notices of the Royal Astronomical Society, 536 (4): 3739–3744, Bibcode:2025MNRAS.536.3739L, doi:10.1093/mnras/stae2800.
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