{{short description|Star in the constellation Libra}} {{Starbox begin}} {{Starbox image | image = {{Location mark |image=Libra constellation map.svg|alt=|float=center|width=280 |label=|position=right |mark=Red circle.svg|mark_width=10|mark_link=48 Librae |x=150|y=360 }} | caption = Location of 48 Librae (circled in red) }} {{Starbox observe | epoch = J2000 | constell = [[Libra (constellation)|Libra]]<ref name=Anderson2012/> | ra = {{RA|15|58|11.36869}}<ref name=vanLeeuwen2007/> | dec = {{DEC|−14|16|45.6894}}<ref name=vanLeeuwen2007/> | appmag_v = 4.95<ref name=Anderson2012/> }} {{Starbox character | type = [[main sequence]]<ref name=dr3/> | class = B3 Vsh<ref name=rivinius2013/><ref name=Silaj2016/> | b-v = {{Val|−0.08|0.11}}<ref name=Anderson2012/> | u-b = | variable = [[Gamma Cassiopeiae variable|γ Cas]]<ref name=Samus2017/> }} {{Starbox astrometry | radial_v = {{Val|−7.5|1.8}}<ref name=deBruijne2012/> | prop_mo_ra = −12.44<ref name=vanLeeuwen2007/> | prop_mo_dec = −16.73<ref name=vanLeeuwen2007/> | parallax = 6.97 | p_error = 0.24 | parallax_footnote = <ref name=vanLeeuwen2007/> | absmag_v = −0.83<ref name=Anderson2012/> }} {{Starbox detail | mass = 6.07<ref name=Silaj2016/> | radius = 4.12<ref name=Silaj2016/> | luminosity = 1,100<ref name=Silaj2016/> | gravity = {{val|3.71|0.04}}<ref name=arcos2018/> | temperature = {{val|18000|180|fmt=commas}}<ref name=arcos2018/> | metal_fe = | rotation = 9.6 hours<ref name="Ozuyar2018"/> | rotational_velocity = 400<ref name=Silaj2016/> | age_myr = 10<ref name=squicciarini2025/> }} {{Starbox catalog | names = {{odlist | V=FX Lib | F=48 Lib | BD=−13°4302 | FK5=1417 | HD=142983 | HIP=78207 | HR=5941 | SAO=159607 | AAVSO=1552-14 }}<ref name=SIMBAD/> }} {{Starbox reference | Simbad = 48+Lib }} {{Starbox end}}
'''48 Librae''' is a single<ref name=Silaj2016/> [[shell star]] in the [[constellation]] [[Libra (constellation)|Libra]]. It is a [[variable star]] with the [[variable star designation|designation]] FX Lib, ranging in magnitude from 4.74 to 4.96.<ref name=Samus2017/> Based upon an annual [[stellar parallax|parallax shift]] of {{Val|6.97|0.24|ul=mas}} as seen from Earth's orbit, it is located approximately 470 [[light year]]s 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.<ref name=Condell2015/>
[[File:FXLibLightCurve.png|thumb|left|A broad-band optical [[light curve]] for FX Librae, adapted from Ozuyar ''et al.'' (2018)<ref name="Ozuyar2018"/>]] This is a [[B-type main-sequence star|main sequence]] [[Be star]] with a [[stellar classification]] of B3 Vsh,<ref name=rivinius2013/> 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 {{val|400|u=km/s}} − matching or exceeding 80% of the [[break-up velocity|critical velocity]].<ref name=Silaj2016/> This is giving the star a pronounced [[oblate spheroid|oblate shape]] with an [[equatorial bulge]] that is estimated to be 43% larger than the polar radius.<ref name=vanBelle2012/> It has six times the [[mass of the Sun]] and four times the [[Sun's radius]]. The star is radiating 1,100<ref name=Silaj2016/> times the [[Sun's luminosity]] from its [[photosphere]] at an [[effective temperature]] of 18,000 K.<ref name=arcos2018/>
The surrounding gaseous disk stretches out to at least 15<ref name=Stefl2012/> times the star's radius and is nearly aligned with the line of sight from the Earth, having an estimated [[inclination]] of {{Val|85|3|u=°}}.<ref name=Silaj2016/> Some time between 1931 and 1935, the disk became active and has remained so since that time, becoming the subject of multiple studies.<ref name=Faraggiana1969/> The unusual asymmetry in its [[emission line]]s have led to it being misclassified as a [[supergiant]] of type {{nowrap|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.<ref name=Silaj2016/>
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]].<ref name=bayer/> 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 [[Johann Elert Bode|Bode]] assigned the designation φ Scorpii to the star now known as 49 Librae.<ref name=startales/> The designation is no longer in use.<ref name=kaler-sco/>
==References== <references>
<ref name=SIMBAD>{{cite simbad | title=48 Lib | access-date=2018-03-04 }}</ref>
<ref name=dr3>{{cite Gaia DR3|6263223955904774656}}</ref>
<ref name="Ozuyar2018">{{cite journal |last1=Ozuyar |first1=D. |last2=Caliskan |first2=S. |last3=Stevens |first3=I. R. |last4=Elmasli |first4=A. |title=Photometric and spectroscopic variability of the Be star 48 Lib: The relation between photometric variations and rotation |journal=Publications of the Astronomical Society of Australia |date=November 2018 |volume=35 |article-number=e034 |doi=10.1017/pasa.2018.38 |bibcode=2018PASA...35...34O |s2cid=126232532 }}</ref>
<ref name=squicciarini2025>{{cite journal |bibcode=2025A&A...693A..54S |title=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 |last1=Squicciarini |first1=V. |last2=Mazoyer |first2=J. |last3=Lagrange |first3=A. -M. |last4=Chomez |first4=A. |last5=Delorme |first5=P. |last6=Flasseur |first6=O. |last7=Kiefer |first7=F. |last8=Bergeon |first8=S. |last9=Albert |first9=D. |last10=Meunier |first10=N. |journal=Astronomy and Astrophysics |date=2025 |volume=693 |doi=10.1051/0004-6361/202452310 |arxiv=2411.06157 }}</ref>
<ref name=vanLeeuwen2007>{{citation | title=Validation of the new Hipparcos reduction | last1=van Leeuwen | first1=F. | postscript=. | journal=Astronomy and Astrophysics | volume=474 | issue=2 | pages=653–664 | year=2007 | arxiv=0708.1752 | bibcode=2007A&A...474..653V | doi=10.1051/0004-6361:20078357 | s2cid=18759600 }}</ref>
<ref name=Anderson2012>{{cite XHIP|78207}}</ref>
<ref name=Samus2017>{{citation | display-authors=1 | last1=Samus | first1=N. N. | last2=Kazarovets | first2=E. V. | last3=Durlevich | first3=O. V. | last4=Kireeva | first4=N. N. | last5=Pastukhova | first5=E. N. | title=General Catalogue of Variable Stars | version=GCVS 5.1 | journal=Astronomy Reports | postscript=. | year=2017 | volume=61 | issue=1 | pages=80–88 | bibcode=2017ARep...61...80S | doi=10.1134/S1063772917010085 | s2cid=125853869 }}</ref>
<ref name=vanBelle2012>{{citation | last1=van Belle | first1=Gerard T. | title=Interferometric observations of rapidly rotating stars | journal=The Astronomy and Astrophysics Review | volume=20 | issue=1 | article-number=51 | date=March 2012 | doi=10.1007/s00159-012-0051-2 | bibcode=2012A&ARv..20...51V | arxiv=1204.2572 | s2cid=119273474 | postscript=. }}</ref>
<ref name=bayer>{{cite book | last1=Bayer | first1=Johann | last2=Mair | first2=Alexander | title=Uranometria | publisher=Excvdit Christophorvs Mangvs | date=1603 | url=https://books.google.com/books?id=5NrCIF5mnysC&dq=bayer+uranometria&pg=IA1 | language=la | access-date=2025-11-10 | page=}}</ref>
<ref name=startales>{{cite web |url=http://www.ianridpath.com/startales/scorpius.html |title=Scorpius |website=Star Tales |author=Ian Ridpath |author-link=Ian Ridpath |access-date=2025-09-10 }}</ref>
<ref name=kaler-sco>{{Citation |title=Chi and Psi Scorpii |url=http://stars.astro.illinois.edu/sow/chisco.html |access-date=2025-07-13 |website=stars.astro.illinois.edu |postscript=.}}</ref>
<ref name=arcos2018>{{citation |bibcode=2018MNRAS.474.5287A |title=Stellar parameters and H α line profile variability of be stars in the BeSOS survey |journal=Monthly Notices of the Royal Astronomical Society |volume=474 |issue=4 |pages=5287 |last1=Arcos |first1=C. |last2=Kanaan |first2=S. |last3=Chávez |first3=J. |last4=Vanzi |first4=L. |last5=Araya |first5=I. |last6=Curé |first6=M. |year=2018 |arxiv=1711.08675 |doi=10.1093/mnras/stx3075 |doi-access=free |postscript=.}}</ref>
<ref name=deBruijne2012>{{citation | last1=de Bruijne | first1=J. H. J. | last2=Eilers | first2=A.-C. | title=Radial velocities for the HIPPARCOS-Gaia Hundred-Thousand-Proper-Motion project | journal=Astronomy & Astrophysics | volume=546 | id=A61 | pages=14 | date=October 2012 | doi=10.1051/0004-6361/201219219 | bibcode=2012A&A...546A..61D | arxiv=1208.3048 | s2cid=59451347 | postscript=. }}</ref>
<ref name=Condell2015>{{citation | title=Spitzer IRS Spectra of Debris Disks in the Scorpius–Centaurus OB Association | last1=Jang-Condell | first1=Hannah | last2=Chen | first2=Christine H. | last3=Mittal | first3=Tushar | last4=Manoj | first4=P. | last5=Watson | first5=Dan | last6=Lisse | first6=Carey M. | last7=Nesvold | first7=Erika | last8=Kuchner | first8=Marc | journal=The Astrophysical Journal | display-authors=1 | volume=808 | issue=2 | id=167 | pages=19 | date=August 2015 | doi=10.1088/0004-637X/808/2/167 | bibcode=2015ApJ...808..167J | arxiv=1506.05428 | s2cid=118549483 | postscript=. }}</ref>
<ref name=Silaj2016>{{citation | title=Investigating the Circumstellar Disk of the Be Shell Star 48 Librae | display-authors=1 | last1=Silaj | first1=J. | last2=Jones | first2=C. E. | last3=Carciofi | first3=A. C. | last4=Escolano | first4=C. | last5=Okazaki | first5=A. T. | last6=Tycner | first6=C. | last7=Rivinius | first7=T. | last8=Klement | first8=R. | last9=Bednarski | first9=D. | journal=The Astrophysical Journal | volume=826 | issue=1 | id=81 | pages=11 | date=July 2016 | doi=10.3847/0004-637X/826/1/81 | bibcode=2016ApJ...826...81S | arxiv=1608.00943 | s2cid=119112873 | postscript=. | doi-access=free }}</ref>
<ref name=Stefl2012>{{citation | arxiv=1202.4523 | title=New activity in the large circumstellar disk of the Be-shell star 48 Librae | last1=Štefl | first1=S. | last2=Le Bouquin | first2=J. -B. | last3=Carciofi | first3=A. C. | last4=Rivinius | first4=T. | last5=Baade | first5=D. | last6=Rantakyrö | first6=F. | journal=Astronomy & Astrophysics | display-authors=1 | volume=540 | id=A76 | pages=12 | date=April 2012 | doi=10.1051/0004-6361/201118054 | bibcode=2012A&A...540A..76S | s2cid=54663995 }}</ref>
<ref name=Faraggiana1969>{{citation | title=A study of 48 Librae in the period 1950 - 1962 | last1=Faraggiana | first1=R. | journal=Astronomy and Astrophysics | volume=2 | page=162 | date=June 1969 | bibcode=1969A&A.....2..162F | postscript=. }}</ref>
<ref name=rivinius2013>{{citation | title=Classical Be stars. Rapidly rotating B stars with viscous Keplerian decretion disks | journal=The Astronomy and Astrophysics Review | display-authors=1 | last1=Rivinius | first1=Thomas | last2=Carciofi | first2=Alex C. | last3=Martayan | first3=Christophe | volume=21 | pages=69 | year=2013 | doi=10.1007/s00159-013-0069-0 | bibcode=2013A&ARv..21...69R | arxiv=1310.3962 | s2cid=118652497 | postscript=. }}</ref>
</references>
{{Stars of Libra}}
[[Category:B-type main-sequence stars]] [[Category:Shell stars]] [[Category:Libra (constellation)]] [[Category:Durchmusterung objects|BD-13 4302]] [[Category:Flamsteed objects|Librae, 48]] [[Category:Henry Draper Catalogue objects|142983]] [[Category:Hipparcos objects|078207]] [[Category:Bright Star Catalogue objects|5941]] [[Category:Objects with variable star designations|Librae, FX]]