# GR Muscae

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Star in the constellation Musca

GR Muscae Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) Constellation Musca Right ascension 12h 57m 37.153s[1] Declination −69° 17′ 18.98″[1] Apparent magnitude (V) 19.1[1] Database references SIMBAD data

[Visual band](/source/Photometric_system#Photometric_letters) [light curves](/source/Light_curve) for GR Muscae, adapted from Cornelisse *et al.* (2013).[2]

**GR Muscae**, also known as **2S 1254-690** is a binary star system in the [constellation](/source/Constellation) [Musca](/source/Musca_(constellation)) composed of a [neutron star](/source/Neutron_star) of between 1.2 and 1.8 times the mass of the [Sun](/source/Sun) and a low-mass star likely to be around the mass of the Sun in close orbit.[2] A magnitude 19 blue star was pinpointed as the optical counterpart of the X-ray source in 1978.[3] Its apparent magnitude varies from 18 to 19.1 over a period of 0.16 days.[4]

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.[5] GR Muscae received its [variable star designation](/source/Variable_star_designation) in 1985.[6]

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.[2]

## References

1. ^ [***a***](#cite_ref-SIMBAD_1-0) [***b***](#cite_ref-SIMBAD_1-1) [***c***](#cite_ref-SIMBAD_1-2) ["GR Muscae – Low Mass X-ray Binary"](http://simbad.u-strasbg.fr/simbad/sim-id?Ident=GR+Mus&NbIdent=1&Radius=2&Radius.unit=arcmin&submit=submit+id). *SIMBAD Astronomical Database*. [Centre de Données astronomiques de Strasbourg](/source/Centre_de_Donn%C3%A9es_astronomiques_de_Strasbourg). Retrieved 9 March 2014.

1. ^ [***a***](#cite_ref-Cornelisse2013_2-0) [***b***](#cite_ref-Cornelisse2013_2-1) [***c***](#cite_ref-Cornelisse2013_2-2) Cornelisse, R.; Kotze, M.M.; Casares, J.; Charles, P.A.; Hakala, P.J. (2013). ["The Origin of the Tilted Disc in the Low-mass X-ray Binary GR Mus (XB 1254-690)"](https://doi.org/10.1093%2Fmnras%2Fstt1654). *[Monthly Notices of the Royal Astronomical Society](/source/Monthly_Notices_of_the_Royal_Astronomical_Society)*. **436** (1): 910–20. [arXiv](/source/ArXiv_(identifier)):[1309.4972](https://arxiv.org/abs/1309.4972). [Bibcode](/source/Bibcode_(identifier)):[2013MNRAS.436..910C](https://ui.adsabs.harvard.edu/abs/2013MNRAS.436..910C). [doi](/source/Doi_(identifier)):[10.1093/mnras/stt1654](https://doi.org/10.1093%2Fmnras%2Fstt1654). [S2CID](/source/S2CID_(identifier)) [119242800](https://api.semanticscholar.org/CorpusID:119242800).

1. **[^](#cite_ref-3)** Griffiths, R.E.; Gursky, H.; Schwartz, D.A.; Schwarz, J.; Bradt, H.; Doxsey, R.E.; Charles, P.A.; Thorstensen, J. R. (1978). "Positions and Identifications for Galactic X-ray Sources 2A1822-371 and 2S1254-690". *Nature*. **276** (16): 247–49. [Bibcode](/source/Bibcode_(identifier)):[1978Natur.276..247G](https://ui.adsabs.harvard.edu/abs/1978Natur.276..247G). [doi](/source/Doi_(identifier)):[10.1038/276247a0](https://doi.org/10.1038%2F276247a0). [S2CID](/source/S2CID_(identifier)) [4372341](https://api.semanticscholar.org/CorpusID:4372341).

1. **[^](#cite_ref-AAVSOSY_4-0)** ["VSX : Detail for GR Mus"](http://www.aavso.org/vsx/index.php?view=detail.top&oid=19876). *The International Variable Star Index*. AAVSO.

1. **[^](#cite_ref-Mason_5-0)** Mason, K. O.; Middleditch, J.; Nelson, J. E.; White, N. E. (9 October 1980). "An optical burst from the star identified with the X-ray source 2S1254-690". *Nature*. **287** (5782): 516–518. [Bibcode](/source/Bibcode_(identifier)):[1980Natur.287..516M](https://ui.adsabs.harvard.edu/abs/1980Natur.287..516M). [doi](/source/Doi_(identifier)):[10.1038/287516a0](https://doi.org/10.1038%2F287516a0).

1. **[^](#cite_ref-Kholopov_6-0)** Kholopov, P. N.; Samus, N. N.; Kazarovets, E. V.; Perova, N. B. (March 1985). ["The 67th Name-List of Variable Stars"](https://ibvs.konkoly.hu/pub/ibvs/2601/2681.pdf) (PDF). *Information Bulletin on Variable Stars*. **2681**: 1. [Bibcode](/source/Bibcode_(identifier)):[1985IBVS.2681....1K](https://ui.adsabs.harvard.edu/abs/1985IBVS.2681....1K). Retrieved 8 October 2024.

v t e Constellation of Musca List of stars in Musca Musca in Chinese astronomy Stars Bayer α β γ δ ε ζ1 ζ2 η θ ι1 ι2 λ μ λ Cha Variable R S SY TU GQ GR GU GT KR MP V357 HR 4538 4549 5002 HD 111232 112410 Other Gliese 440 PSR J1141−6545 YSES 1 YSES 2 YSES 2b Exoplanets HD 111232 b Star clusters NGC 4372 NGC 4463 NGC 4815 NGC 4833 Nebulae NGC 5189 Other BHR 71 Dark Doodad Nebula Engraved Hourglass Nebula G299.2-2.9 Category

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Adapted from the Wikipedia article [GR Muscae](https://en.wikipedia.org/wiki/GR_Muscae) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/GR_Muscae?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.