Astronomy:48 Librae

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Short description: Star in the constellation Libra
48 Librae
Location of 48 Librae (circled in red)
Observation data
Equinox J2000.0]] (ICRS)
Constellation Libra[1]
Right ascension  15h 58m 11.36869s[2]
Declination −14° 16′ 45.6894″[2]
Apparent magnitude (V) 4.95[1]
Characteristics
Evolutionary stage main sequence[3]
Spectral type B3 Vsh[4][5]
B−V color index −0.08±0.11[1]
Variable type γ Cas[6]
Astrometry
Radial velocity (Rv)−7.5±1.8[7] km/s
Proper motion (μ) RA: −12.44[2] mas/yr
Dec.: −16.73[2] mas/yr
Parallax (π)6.97 ± 0.24[2] mas
Distance470 ± 20 ly
(143 ± 5 pc)
Absolute magnitude (MV)−0.83[1]
Details
Mass6.07[5] M☉
Radius4.12[5] R☉
Luminosity1,100[5] L☉
Surface gravity (log g)3.71±0.04[8] cgs
Temperature18,000±180[8] K
Rotation9.6 hours[9]
Rotational velocity (v sin i)400[5] 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[5] 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.[6] 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]

A broad-band optical light curve for FX Librae, adapted from Ozuyar et al. (2018)[9]

This is a main sequence Be star with a stellar classification of B3 Vsh,[4] 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.[5] 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[5] times the Sun's luminosity from its photosphere at an effective temperature of 18,000 K.[8]

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°.[5] 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.[5]

The Bayer designation Phi Scorpii has been associated with this star. No star is found at the position marked φ Scorpii in Johann Bayer's Uranometria.[16] The closest stars to that position are 48 and 49 Librae; 48 Librae is clearly shown but not given a designation while no star is shown at the position of 49 Librae. In his Uranographia Bode assigned the designation φ Scorpii to the star now known as 49 Librae.[17] The designation is no longer in use.[18]

References

  1. ↑ 1.0 1.1 1.2 1.3 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.
  2. ↑ 2.0 2.1 2.2 2.3 2.4 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. 
  3. ↑ 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.
  4. ↑ 4.0 4.1 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. 
  5. ↑ 5.00 5.01 5.02 5.03 5.04 5.05 5.06 5.07 5.08 5.09 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. 
  6. ↑ 6.0 6.1 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. 
  7. ↑ 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. 
  8. ↑ 8.0 8.1 8.2 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. 
  9. ↑ 9.0 9.1 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. 
  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), 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. ↑ Bayer, Johann; Mair, Alexander (1603) (in la). Uranometria. Excvdit Christophorvs Mangvs. https://books.google.com/books?id=5NrCIF5mnysC&dq=bayer+uranometria&pg=IA1. Retrieved 2025-11-10. 
  17. ↑ Ian Ridpath. "Scorpius". http://www.ianridpath.com/startales/scorpius.html. 
  18. ↑ Chi and Psi Scorpii, http://stars.astro.illinois.edu/sow/chisco.html, retrieved 2025-07-13. 



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