Theta Muscae

{{short description|Star in the constellation Musca}}

{{starbox begin

|name= Theta Muscae

}}

{{Starbox image

| image=

{{Location mark

|image=Musca constellation map.svg

|float=center

|alt=

|label=

|position=right

|width=280

|mark=Red circle.svg

|mark_width=10

|mark_link=θ Muscae

|x=364|y=220

}}

|caption=Location of θ Mus (circled)

}}

{{Starbox observe

|epoch=J2000

|ra= {{RA|13|08|07.15286}}{{cite journal|bibcode=2007A&A...474..653V|title=Validation of the new Hipparcos reduction|journal=Astronomy and Astrophysics|volume=474|issue=2|pages=653–664|last1=Van Leeuwen|first1=F.|year=2007|doi=10.1051/0004-6361:20078357|arxiv = 0708.1752 |s2cid=18759600}}

|dec= {{DEC|-65|18|21.6819}}

|appmag_v=5.53{{cite journal|bibcode=2002yCat.2237....0D|title=VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system|journal=CDS/ADC Collection of Electronic Catalogues|volume=2237|pages=0|last1=Ducati|first1=J. R.|year=2002}} {{nowrap|(5.662 + 7.555{{cite journal|bibcode=2000A&A...355L..27H|title=The Tycho-2 catalogue of the 2.5 million brightest stars|journal=Astronomy and Astrophysics|volume=355|pages=L27|last1=Høg|first1=E.|last2=Fabricius|first2=C.|last3=Makarov|first3=V. V.|last4=Urban|first4=S.|last5=Corbin|first5=T.|last6=Wycoff|first6=G.|last7=Bastian|first7=U.|last8=Schwekendiek|first8=P.|last9=Wicenec|first9=A.|year=2000|doi=10.1888/0333750888/2862}})}}

|constell= Musca

}}

{{Starbox character

|component = θ Mus A

|class= WC5/6 + O6/7V + O9.5/B0Iab

|b-v=−0.43

|u-b=−0.91{{cite journal|bibcode=1977A&A....54..607M|title=The Wolf-Rayet binary theta Muscae|journal=Astronomy and Astrophysics|volume=54|pages=607|last1=Moffat|first1=A. F. J.|last2=Seggewiss|first2=W.|year=1977}}

|variable=Eclipsing + WR{{cite journal|bibcode=2009yCat....102025S|title=VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)|journal=VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S|volume=1|display-authors=etal|last1=Samus|first1=N. N.|last2=Durlevich|first2=O. V.|year=2009}}

}}

{{Starbox character|no_heading=y

|component = B

|class= O9III{{cite journal|bibcode=2014ApJS..211...10S|title=The Galactic O-Star Spectroscopic Survey (GOSSS). II. Bright Southern Stars|journal=The Astrophysical Journal Supplement|volume=211|pages=10|last1=Sota|first1=A.|last2=Maíz Apellániz|first2=J.|last3=Morrell|first3=N. I.|author-link3=Nidia Morrell|last4=Barbá|first4=R. H.|last5=Walborn|first5=N. R.|last6=Gamen|first6=R. C.|last7=Arias|first7=J. I.|last8=Alfaro|first8=E. J.|year=2014|issue=1|doi=10.1088/0067-0049/211/1/10|arxiv = 1312.6222 |s2cid=118847528}}

|b-v=−0.055

|u-b=−0.90

}}

{{Starbox astrometry

| radial_v=−28.4{{citation | last=Wilson | first=Ralph Elmer | year=1953 | title=General Catalogue of Stellar Radial Velocities | journal=Washington | publisher=Carnegie Institution of Washington | location=Washington | bibcode=1953GCRV..C......0W | postscript=. }}

| prop_mo_ra=−2.10

| prop_mo_dec=−11.52

| parallax=0.26

| p_error=0.48

| parallax_footnote=

| dist_pc=2,270

| dist_ly=7,400

| absmag_v=−6.2{{cite journal|last1=Hidayat|first1=Bambang|last2=Admiranto|first2=A. Gunawan|last3=Van Der Hucht|first3=Karel A.|author-link3=Karel van der Hucht|title=Wolf-Rayet binaries: Evolutionary causes for their distribution in the Galaxy|journal=Astrophysics and Space Science|volume=99|issue=1–2|year=1984|pages=175–190|issn=0004-640X|doi=10.1007/BF00650243|bibcode=1984Ap&SS..99..175H|s2cid=189850123}}

}}

{{Starbox orbit

| reference =

| period_unitless = {{val|19.1375|ul=days}}

| eccentricity = 0.00 (assumed)

| inclination = {{val|49|6}}

| k1 = {{val|221|6}}

}}

{{Starbox detail

|component1 = WR

|mass = <11.5{{cite journal|bibcode=2000A&A...360..227N|title=Mass-loss rates of Wolf-Rayet stars as a function of stellar parameters|journal=Astronomy and Astrophysics|volume=360|pages=227|last1=Nugis|first1=T.|last2=Lamers|first2=H. J. G. L. M.|year=2000}}

|radius =

|luminosity = 234,000

|temperature=

|component2 = O

|mass2 = 44{{Cite journal|last1=Hill|first1=G. M.|last2=Moffat|first2=A. F. J.|last3=St-Louis|first3=N.|date=1 October 2002|title=Modelling the colliding-winds spectra of the 19-d WR + OB binary in the massive triple system Muscae|journal=Monthly Notices of the Royal Astronomical Society|language=en|volume=335|issue=4|pages=1069–1078|bibcode=2002MNRAS.335.1069H|doi=10.1046/j.1365-8711.2002.05694.x|issn=0035-8711|s2cid=121923927|doi-access=free}}

|luminosity2 = 295,000{{Cite journal|last1=Sugawara|first1=Y.|last2=Tsuboi|first2=Y.|last3=Maeda|first3=Y.|date=October 2008|title=Redshifted emission lines and radiative recombination continuum from the Wolf-Rayet binary θ Muscae: evidence for a triplet system?|journal=Astronomy & Astrophysics|volume=490|issue=1|pages=259–264|arxiv=0810.1208|bibcode=2008A&A...490..259S|doi=10.1051/0004-6361:20079302|doi-access=free|issn=0004-6361|s2cid=118447784}}

|metal =

|rotation =

|age_myr =

}}

{{Starbox catalog

|names=Theta Muscae, CD−64°699, HR 4952, HD 113904, HIP 64094, GSC 08997-02337, SAO 252162, PPM 359890, GC 17788, UCAC3 50-186265, IRAS 15465+2818, WR 48

}}

{{Starbox reference

|Simbad=Theta+Muscae

}}

{{Starbox end}}

Theta Muscae (θ Muscae) is a multiple star system in the southern constellation Musca ("the Fly"), containing a Wolf-Rayet star and two massive companions. With an apparent magnitude of 5.5, it is the second-brightest Wolf–Rayet star in the sky,{{cite book | author1 = C. de Loore | author2 = A.J. Willis | date = 6 December 2012 | title = Wolf-Rayet Stars: Observations, Physics, Evolution | publisher = Springer Science & Business Media | pages = 310– | isbn = 9789400979109 | url = https://books.google.com/books?id=o8XoCAAAQBAJ&pg=PA310}} although much of the visual brightness comes from the massive companions and it is not one of the closest of its type.

Description

Theta Muscae is a remote triple star system, the primary component of which is a carbon-sequence Wolf–Rayet star. This is a variety of highly-luminous hot blue star that has blown off its hydrogen envelope and is emitting heavier elements, in this case carbon, amid a strong stellar wind. Theta Muscae is the second-brightest such star in the sky after Gamma Velorum in Vela. θ Mus is beyond the current reach of useful visual parallax measurements, but has been estimated as around 7,400 light-years (460 million astronomical units) from Earth. While cataloging the stars in the far-southern sky, French explorer and astronomer Nicolas-Louis de Lacaille gave the star its Bayer designation in 1756.{{cite book | last = Wagman | first = Morton | date = 2003 | title = Lost Stars: Lost, Missing and Troublesome Stars from the Catalogues of Johannes Bayer, Nicholas Louis de Lacaille, John Flamsteed, and Sundry Others | publisher = The McDonald & Woodward Publishing Company | location = Blacksburg, VA | isbn = 978-0-939923-78-6 |pages=213–14}}

Triple system

The triple star θ Muscae A is composed of two parts: a spectroscopic binary system composed of the Wolf–Rayet star (spectral type: WC5 or 6) and an O-type main-sequence star (spectral type: O6 or O7) that orbit each other every 19 days and a blue supergiant (spectral type: O9.5/B0Iab) set about 46 milliarcseconds apart from them. If the system's estimated distance from Earth is accurate, the binary stars are about 0.5 AU apart and the supergiant about 100 AU apart from them. Although the Wolf–Rayet star dominates the spectrum, it is visually only about a quarter of the brightness of the supergiant companion.{{cite journal|author=Sugawara, Y.|author2=Tsuboi, Y.|author3=Maeda, Y.|date=2008|title=Redshifted emission lines and radiative recombination continuum from the Wolf–Rayet binary θ Muscae: evidence for a triplet system?|journal=Astronomy & Astrophysics|volume=490|issue=1|pages=259–64|doi=10.1051/0004-6361:20079302|arxiv = 0810.1208 |bibcode = 2008A&A...490..259S |s2cid=118447784}} All three are highly luminous: combined, they are likely to be over a million times as luminous as the Sun. The stellar winds of the Wolf–Rayet star and its close companion are so powerful that they form a shock front where they meet.{{cite journal|author= Hill, G. M.|author2= Moffat, A. F. J.|author3= St-Louis, N.|date=2002|title=Modelling the colliding-winds spectra of the 19-d WR + OB binary in the massive triple system Theta Muscae|journal=Monthly Notices of the Royal Astronomical Society|volume=335|issue=4|pages=1069–78|bibcode= 2002MNRAS.335.1069H|doi = 10.1046/j.1365-8711.2002.05694.x |doi-access=free}} The front produces X-rays.

Nebula

A surrounding emission nebula is now thought to be a supernova remnant, not directly connected to θ Muscae.{{cite journal|author=Stupar, M.|author2=Parker, Q.A.|author3=Filipovic, M.D.|date=2010|title=The optical emission nebulae in the vicinity of WR 48 (Θ Mus); True Wolf–Rayet ejecta or unconnected supernova remnant?|journal=Monthly Notices of the Royal Astronomical Society|volume=401|issue=3|pages=1760–69|arxiv = 0910.1546 |bibcode = 2010MNRAS.401.1760S |doi = 10.1111/j.1365-2966.2009.15814.x |doi-access=free |s2cid=119192064}}

References