| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| 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 mas [2] |
| 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. Bibcode: 2018PASA...35...34O. doi: 10.1017/pasa.2018.38. S2CID 126232532. Retrieved 20 January 2022.
- ^ a b c d e van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv: 0708.1752, Bibcode: 2007A&A...474..653V, doi: 10.1051/0004-6361:20078357, S2CID 18759600.
- ^ a b c 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, S2CID 119257644.
- ^ a b Rivinius, Thomas; et al. (2013), "Classical Be stars. Rapidly rotating B stars with viscous Keplerian decretion disks", The Astronomy and Astrophysics Review, 21: 69, arXiv: 1310.3962, Bibcode: 2013A&ARv..21...69R, doi: 10.1007/s00159-013-0069-0, S2CID 118652497.
- ^ a b c d e f g Silaj, J.; et al. (July 2016), "Investigating the Circumstellar Disk of the Be Shell Star 48 Librae", The Astrophysical Journal, 826 (1): 11, arXiv: 1608.00943, Bibcode: 2016ApJ...826...81S, doi: 10.3847/0004-637X/826/1/81, S2CID 119112873, 81.
- ^ a b Samus, N. N.; et al. (2017), "General Catalogue of Variable Stars", Astronomy Reports, GCVS 5.1, 61 (1): 80–88, Bibcode: 2017ARep...61...80S, doi: 10.1134/S1063772917010085, S2CID 125853869.
- ^ 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, arXiv: 1208.3048, Bibcode: 2012A&A...546A..61D, doi: 10.1051/0004-6361/201219219, S2CID 59451347, A61.
- ^ a b McDonald, I.; et al. (2012), "Fundamental parameters and infrared excesses of Hipparcos stars", Monthly Notices of the Royal Astronomical Society, 427 (1): 343–357, arXiv: 1208.2037, Bibcode: 2012MNRAS.427..343M, doi: 10.1111/j.1365-2966.2012.21873.x, S2CID 118665352.
- ^ "48 Lib". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2018-03-04.
- ^ 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, arXiv: 1506.05428, Bibcode: 2015ApJ...808..167J, doi: 10.1088/0004-637X/808/2/167, S2CID 118549483, 167.
- ^ van Belle, Gerard T. (March 2012), "Interferometric observations of rapidly rotating stars", The Astronomy and Astrophysics Review, 20 (1): 51, arXiv: 1204.2572, Bibcode: 2012A&ARv..20...51V, doi: 10.1007/s00159-012-0051-2, S2CID 119273474.
- ^ Štefl, S.; et al. (April 2012), "New activity in the large circumstellar disk of the Be-shell star 48 Librae", Astronomy & Astrophysics, 540: 12, arXiv: 1202.4523, Bibcode: 2012A&A...540A..76S, doi: 10.1051/0004-6361/201118054, S2CID 54663995, A76
- ^ 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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| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| 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 mas [2] |
| 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. Bibcode: 2018PASA...35...34O. doi: 10.1017/pasa.2018.38. S2CID 126232532. Retrieved 20 January 2022.
- ^ a b c d e van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv: 0708.1752, Bibcode: 2007A&A...474..653V, doi: 10.1051/0004-6361:20078357, S2CID 18759600.
- ^ a b c 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, S2CID 119257644.
- ^ a b Rivinius, Thomas; et al. (2013), "Classical Be stars. Rapidly rotating B stars with viscous Keplerian decretion disks", The Astronomy and Astrophysics Review, 21: 69, arXiv: 1310.3962, Bibcode: 2013A&ARv..21...69R, doi: 10.1007/s00159-013-0069-0, S2CID 118652497.
- ^ a b c d e f g Silaj, J.; et al. (July 2016), "Investigating the Circumstellar Disk of the Be Shell Star 48 Librae", The Astrophysical Journal, 826 (1): 11, arXiv: 1608.00943, Bibcode: 2016ApJ...826...81S, doi: 10.3847/0004-637X/826/1/81, S2CID 119112873, 81.
- ^ a b Samus, N. N.; et al. (2017), "General Catalogue of Variable Stars", Astronomy Reports, GCVS 5.1, 61 (1): 80–88, Bibcode: 2017ARep...61...80S, doi: 10.1134/S1063772917010085, S2CID 125853869.
- ^ 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, arXiv: 1208.3048, Bibcode: 2012A&A...546A..61D, doi: 10.1051/0004-6361/201219219, S2CID 59451347, A61.
- ^ a b McDonald, I.; et al. (2012), "Fundamental parameters and infrared excesses of Hipparcos stars", Monthly Notices of the Royal Astronomical Society, 427 (1): 343–357, arXiv: 1208.2037, Bibcode: 2012MNRAS.427..343M, doi: 10.1111/j.1365-2966.2012.21873.x, S2CID 118665352.
- ^ "48 Lib". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2018-03-04.
- ^ 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, arXiv: 1506.05428, Bibcode: 2015ApJ...808..167J, doi: 10.1088/0004-637X/808/2/167, S2CID 118549483, 167.
- ^ van Belle, Gerard T. (March 2012), "Interferometric observations of rapidly rotating stars", The Astronomy and Astrophysics Review, 20 (1): 51, arXiv: 1204.2572, Bibcode: 2012A&ARv..20...51V, doi: 10.1007/s00159-012-0051-2, S2CID 119273474.
- ^ Štefl, S.; et al. (April 2012), "New activity in the large circumstellar disk of the Be-shell star 48 Librae", Astronomy & Astrophysics, 540: 12, arXiv: 1202.4523, Bibcode: 2012A&A...540A..76S, doi: 10.1051/0004-6361/201118054, S2CID 54663995, A76
- ^ 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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