GR Muscae

{{Short description|Star in the constellation Musca}} {{starbox short |constell= [[Musca (constellation)|Musca]] |name= GR Muscae |type= |ra= {{RA|12|57|37.153}}<ref name=SIMBAD>{{cite web |url =http://simbad.u-strasbg.fr/simbad/sim-id?Ident=GR+Mus&NbIdent=1&Radius=2&Radius.unit=arcmin&submit=submit+id |title = GR Muscae – Low Mass X-ray Binary |work = SIMBAD Astronomical Database|publisher=[[Centre de Données astronomiques de Strasbourg]] |accessdate = 9 March 2014}}</ref> |dec= {{DEC|-69|17|18.98}}<ref name=SIMBAD/> |appmag_v= 19.1<ref name=SIMBAD/> |Simbad=GR+Mus }}

[[File:GRMusLightCurve.png|thumb|left|[[Photometric_system#Photometric_letters|Visual band]] [[light curve]]s for GR Muscae, adapted from Cornelisse ''et al.'' (2013).<ref name="Cornelisse2013"/>]] '''GR Muscae''', also known as '''2S 1254-690''' is a binary star system in the [[constellation]] [[Musca (constellation)|Musca]] composed of a [[neutron star]] of between 1.2 and 1.8 times the mass of the [[Sun]] and a low-mass star likely to be around the mass of the Sun in close orbit.<ref name="Cornelisse2013">{{cite journal|author1=Cornelisse, R. |author2=Kotze, M.M. |author3=Casares, J. |author4=Charles, P.A. |author5=Hakala, P.J. |date=2013|title=The Origin of the Tilted Disc in the Low-mass X-ray Binary GR Mus (XB 1254-690)|journal=[[Monthly Notices of the Royal Astronomical Society]]|volume=436|issue=1|pages=910–20|arxiv=1309.4972|bibcode = 2013MNRAS.436..910C |doi = 10.1093/mnras/stt1654 |doi-access=free |s2cid=119242800 }}</ref> A magnitude 19 blue star was pinpointed as the optical counterpart of the X-ray source in 1978.<ref>{{cite journal|author1=Griffiths, R.E. |author2=Gursky, H. |author3=Schwartz, D.A. |author4=Schwarz, J. |author5=Bradt, H. |author6=Doxsey, R.E. |author7=Charles, P.A. |author8=Thorstensen, J. R. |date=1978|title=Positions and Identifications for Galactic X-ray Sources 2A1822-371 and 2S1254-690|journal=Nature|volume=276|issue=16|pages=247–49|bibcode = 1978Natur.276..247G |doi = 10.1038/276247a0 |s2cid=4372341 }}</ref> Its apparent magnitude varies from 18 to 19.1 over a period of 0.16 days.<ref name=AAVSOSY>{{Cite web | url=http://www.aavso.org/vsx/index.php?view=detail.top&oid=19876 | title=VSX : Detail for GR Mus |work=The International Variable Star Index |publisher=AAVSO}}</ref>

While the optical counterpart to the X-ray source was identified in 1978, optical variability was not detected until 1980, when a bright flare was seen that increased the white-light flux by a factor of two in a time interval of about 1.7 seconds.<ref name="Mason">{{cite journal |last1=Mason |first1=K. O. |last2=Middleditch |first2=J. |last3=Nelson |first3=J. E. |last4=White |first4=N. E. |title=An optical burst from the star identified with the X-ray source 2S1254-690 |journal=Nature |date=9 October 1980 |volume=287 |issue=5782 |pages=516–518 |bibcode=1980Natur.287..516M |doi=10.1038/287516a0 }}</ref> GR Muscae received its [[variable star designation]] in 1985.<ref name="Kholopov">{{cite journal |last1=Kholopov |first1=P. N. |last2=Samus |first2=N. N. |last3=Kazarovets |first3=E. V. |last4=Perova |first4=N. B. |title=The 67th Name-List of Variable Stars |journal=Information Bulletin on Variable Stars |date=March 1985 |volume=2681 |page=1 |bibcode=1985IBVS.2681....1K |url=https://ibvs.konkoly.hu/pub/ibvs/2601/2681.pdf |access-date=8 October 2024}}</ref>

The neutron star has an accretion disk that takes around 6.74 days to complete a revolution, and is inclined at an angle to the incoming stream of material from the donor star.<ref name="Cornelisse2013"/>

==References== {{reflist}}

[[Category:Musca]] [[Category:Objects with variable star designations|Muscae, GR]] [[Category:X-ray binaries]] [[Category:Neutron stars]]