Astronomy:48 Librae
| Observation data Equinox J2000.0]] (ICRS) | |
|---|---|
| Constellation | Libra |
| Right ascension | 15h 58m 11.36869s[2] |
| Declination | −14° 16′ 45.6894″[2] |
| Apparent magnitude (V) | 4.95[3] |
| Characteristics | |
| Spectral type | B3 Vsh[4][5] |
| B−V color index | −0.08±0.11[3] |
| 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 |
| Distance | 470 ± 20 ly (143 ± 5 pc) |
| Absolute magnitude (MV) | −0.83[3] |
| Details[5] | |
| Mass | 6.07 M☉ |
| Radius | 4.12 R☉ |
| Luminosity | 1,100 L☉ |
| Temperature | 7,612[8] K |
| Rotational velocity (v sin i) | 400 km/s |
| Other designations | |
| Database references | |
| SIMBAD | data |
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 around 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.[10]
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.[11] 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 7,612 K.[8]
The surrounding gaseous disk stretches out to at least 15[12] 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.[13] 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]
References
- ↑ 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. https://ui.adsabs.harvard.edu/abs/2018PASA...35...34O. Retrieved 20 January 2022.
- ↑ 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.
- ↑ 3.0 3.1 3.2 Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters 38 (5): 331, doi:10.1134/S1063773712050015, Bibcode: 2012AstL...38..331A.
- ↑ 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.
- ↑ 5.0 5.1 5.2 5.3 5.4 5.5 5.6 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.
- ↑ 6.0 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.
- ↑ 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.
- ↑ 8.0 8.1 McDonald, I. et al. (2012), "Fundamental parameters and infrared excesses of Hipparcos stars", Monthly Notices of the Royal Astronomical Society 427 (1): 343–357, doi:10.1111/j.1365-2966.2012.21873.x, Bibcode: 2012MNRAS.427..343M.
- ↑ "48 Lib". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=48+Lib.
- ↑ 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.
- ↑ 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.
- ↑ 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
- ↑ Faraggiana, R. (June 1969), "A study of 48 Librae in the period 1950 - 1962", Astronomy and Astrophysics 2: 162, Bibcode: 1969A&A.....2..162F.
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