48 Librae

48 Librae

A broad-band optical light curve for FX Librae, adapted from Ozuyar et al. (2018)[1]
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]
Distance470 ± 20 ly
(143 ± 5 pc)
Absolute magnitude (MV)−0.83[3]
Details[5]
Mass6.07 M☉
Radius4.12 R☉
Luminosity1,100 L☉
Temperature7,612[8] K
Rotational velocity (v sin i)400 km/s
Other designations
48 Lib, FX Lib, BD−13° 4302, FK5 1417, HD 142983, HIP 78207, HR 5941, SAO 159607[9]
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 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]

  1. ^ Cite error: The named reference Ozuyar2018 was invoked but never defined (see the help page).
  2. ^ a b c d e Cite error: The named reference vanLeeuwen2007 was invoked but never defined (see the help page).
  3. ^ a b c Cite error: The named reference Anderson2012 was invoked but never defined (see the help page).
  4. ^ a b Cite error: The named reference rivinius2013 was invoked but never defined (see the help page).
  5. ^ a b c d e f g Cite error: The named reference Silaj2016 was invoked but never defined (see the help page).
  6. ^ a b Cite error: The named reference Samus2017 was invoked but never defined (see the help page).
  7. ^ Cite error: The named reference deBruijne2012 was invoked but never defined (see the help page).
  8. ^ a b Cite error: The named reference McDonald2012 was invoked but never defined (see the help page).
  9. ^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  10. ^ Cite error: The named reference Condell2015 was invoked but never defined (see the help page).
  11. ^ Cite error: The named reference vanBelle2012 was invoked but never defined (see the help page).
  12. ^ Cite error: The named reference Stefl2012 was invoked but never defined (see the help page).
  13. ^ Cite error: The named reference Faraggiana1969 was invoked but never defined (see the help page).