Astronomy:48 Librae

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Short description: Star in the constellation Libra
48 Librae
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A broad-band optical light curve for FX Librae, adapted from Ozuyar et al. (2018)[1]
Observation data
Equinox J2000.0]] (ICRS)
Constellation Libra[2]
Right ascension  15h 58m 11.36869s[3]
Declination −14° 16′ 45.6894″[3]
Apparent magnitude (V) 4.95[2]
Characteristics
Evolutionary stage main sequence[4]
Spectral type B3 Vsh[5][6]
B−V color index −0.08±0.11[2]
Variable type γ Cas[7]
Astrometry
Radial velocity (Rv)−7.5±1.8[8] km/s
Proper motion (μ) RA: −12.44[3] mas/yr
Dec.: −16.73[3] mas/yr
Parallax (π)6.97 ± 0.24[3] mas
Distance470 ± 20 ly
(143 ± 5 pc)
Absolute magnitude (MV)−0.83[2]
Details
Mass6.07[6] M☉
Radius4.12[6] R☉
Luminosity1,100[6] L☉
Surface gravity (log g)3.71±0.04[9] cgs
Temperature18,000±180[9] K
Rotation9.6 hours[1]
Rotational velocity (v sin i)400[6] km/s
Age10[10] Myr
Other designations
48 Lib, FX Lib, BD−13°4302, FK5 1417, HD 142983, HIP 78207, HR 5941, SAO 159607[11]
Database references
SIMBADdata

48 Librae is a single[6] shell star in the constellation Libra. It is a variable star with the designation FX Lib, ranging in magnitude from 4.74 to 4.96.[7] Based upon an annual parallax shift of 6.97±0.24 mas as seen from Earth's orbit, it is located approximately 470 light years from the Sun. It is a candidate member of the Upper Scorpius group of the Scorpius–Centaurus association, with the former having an age of about 11 million years.[12]

This is a main sequence Be star with a stellar classification of B3 Vsh,[5] although it has been variously classed as B3V, B5IIIp shell He-n, B6p shell, B4III, B3IV:e-shell, and B3 shell by different sources. As is the norm for a shell star, it is spinning very rapidly with a projected rotational velocity of 400 km/s − matching or exceeding 80% of the critical velocity.[6] This is giving the star a pronounced oblate shape with an equatorial bulge that is estimated to be 43% larger than the polar radius.[13] It has six times the mass of the Sun and four times the Sun's radius. The star is radiating 1,100[6] times the Sun's luminosity from its photosphere at an effective temperature of 18,000 K.[9]

The surrounding gaseous disk stretches out to at least 15[14] times the star's radius and is nearly aligned with the line of sight from the Earth, having an estimated inclination of 85°±3°.[6] Some time between 1931 and 1935, the disk became active and has remained so since that time, becoming the subject of multiple studies.[15] The unusual asymmetry in its emission lines have led to it being misclassified as a supergiant of type B8 Ia/Ib by SIMBAD and others. This asymmetry displays quasi-periodic behavior of the type found in about a third of all Be stars, with a period of about 10 to 17 years. This variation may arise from the precession of a one-armed density wave in the disk.[6]

When lettering Bayer designations to Scorpius, Johann Bayer accidentally gave the designation Phi Scorpii to what is now known to be 49 Librae and 48 Librae. That designation is no longer in use.[16]

References

  1. ↑ 1.0 1.1 Ozuyar, D.; Caliskan, S.; Stevens, I. R.; Elmasli, A. (November 2018). "Photometric and spectroscopic variability of the Be star 48 Lib: The relation between photometric variations and rotation". Publications of the Astronomical Society of Australia 35. doi:10.1017/pasa.2018.38. Bibcode: 2018PASA...35...34O. 
  2. ↑ 2.0 2.1 2.2 2.3 Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters 38 (5): 331. doi:10.1134/S1063773712050015. Bibcode: 2012AstL...38..331A  XHIP record for this object at VizieR.
  3. ↑ 3.0 3.1 3.2 3.3 3.4 van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics 474 (2): 653–664, doi:10.1051/0004-6361:20078357, Bibcode: 2007A&A...474..653V. 
  4. ↑ 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.
  5. ↑ 5.0 5.1 Rivinius, Thomas et al. (2013), "Classical Be stars. Rapidly rotating B stars with viscous Keplerian decretion disks", The Astronomy and Astrophysics Review 21: 69, doi:10.1007/s00159-013-0069-0, Bibcode: 2013A&ARv..21...69R. 
  6. ↑ 6.00 6.01 6.02 6.03 6.04 6.05 6.06 6.07 6.08 6.09 Silaj, J. et al. (July 2016), "Investigating the Circumstellar Disk of the Be Shell Star 48 Librae", The Astrophysical Journal 826 (1): 11, doi:10.3847/0004-637X/826/1/81, 81, Bibcode: 2016ApJ...826...81S. 
  7. ↑ 7.0 7.1 Samus, N. N. et al. (2017), "General Catalogue of Variable Stars", Astronomy Reports, GCVS 5.1 61 (1): 80–88, doi:10.1134/S1063772917010085, Bibcode: 2017ARep...61...80S. 
  8. ↑ de Bruijne, J. H. J.; Eilers, A.-C. (October 2012), "Radial velocities for the HIPPARCOS-Gaia Hundred-Thousand-Proper-Motion project", Astronomy & Astrophysics 546: 14, doi:10.1051/0004-6361/201219219, A61, Bibcode: 2012A&A...546A..61D. 
  9. ↑ 9.0 9.1 9.2 Arcos, C.; Kanaan, S.; Chávez, J.; Vanzi, L.; Araya, I.; Curé, M. (2018), "Stellar parameters and H α line profile variability of be stars in the BeSOS survey", Monthly Notices of the Royal Astronomical Society 474 (4): 5287, doi:10.1093/mnras/stx3075, Bibcode: 2018MNRAS.474.5287A. 
  10. ↑ Squicciarini, V.; Mazoyer, J.; Lagrange, A. -M.; Chomez, A.; Delorme, P.; Flasseur, O.; Kiefer, F.; Bergeon, S. et al. (2025). "The COBREX archival survey: Improved constraints on the occurrence rate of wide-orbit substellar companions: I. A uniform re-analysis of 400 stars from the GPIES survey". Astronomy and Astrophysics 693. doi:10.1051/0004-6361/202452310. Bibcode: 2025A&A...693A..54S. 
  11. ↑ "48 Lib". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=48+Lib. 
  12. ↑ Jang-Condell, Hannah et al. (August 2015), "Spitzer IRS Spectra of Debris Disks in the Scorpius–Centaurus OB Association", The Astrophysical Journal 808 (2): 19, doi:10.1088/0004-637X/808/2/167, 167, Bibcode: 2015ApJ...808..167J. 
  13. ↑ van Belle, Gerard T. (March 2012), "Interferometric observations of rapidly rotating stars", The Astronomy and Astrophysics Review 20 (1): 51, doi:10.1007/s00159-012-0051-2, Bibcode: 2012A&ARv..20...51V. 
  14. ↑ Štefl, S. et al. (April 2012), "New activity in the large circumstellar disk of the Be-shell star 48 Librae", Astronomy & Astrophysics 540: 12, doi:10.1051/0004-6361/201118054, A76, Bibcode: 2012A&A...540A..76S 
  15. ↑ Faraggiana, R. (June 1969), "A study of 48 Librae in the period 1950 - 1962", Astronomy and Astrophysics 2: 162, Bibcode: 1969A&A.....2..162F. 
  16. ↑ Chi and Psi Scorpii, http://stars.astro.illinois.edu/sow/chisco.html, retrieved 2025-07-13. 



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