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- References
{{Starbox begin
| name= X Crucis
}}
| image =
| caption=
}-> {{Starbox observe
| epoch=J2000
| constell = Crux
| ra = {{RA|12|46|22.2678}}[1]
| dec = {{DEC|-59|07|29.120}}[1]
| appmag_v = 8.1 - 8.7[3]
}}{{Starbox character
| class = G1Ib
| b-v = +0.87[5]
| u-b =
| variable = δ Cep[3]
}}{{Starbox astrometry
| radial_v = -25.0[7]
| prop_mo_ra = -8.2[8]
| prop_mo_dec = -0.9[8]
| parallax =
| p_error =
| parallax_footnote =
| absmag_v = −3.9[10]
}}{{Starbox detail
| mass = 4.3[10]
| radius = 50[12]
| luminosity = 2,884[10]
| temperature = 5,180 - 6,029[14]
| gravity = 1.69[10]
| metal_fe =
| rotational_velocity =
| age_myr =
}}{{Starbox catalog
|names=X Crucis, X Cru, HD 110945, SAO 240231, CPD−58°4490, 2MASS J12462227-5907290, TYC 8659-1943-1, AN 186.1906, GCRV 63538, PPM 341282, AAVSO 1240-58, CD−58°4731, GSC 08659-01943, CPC 20 3918, HV 1298
}}{{Starbox reference
| Simbad=X+Crucis
}}{{Starbox end}}X Crucis is a classical Cepheid variable star in the southern constellation of Crux. X Crucis is a pulsating variable star with am extremely regular amplitude and period. Its apparent magnitude varies from 8.1 to 8.7 every 6.22 days. This type of variable is known as a Cepheid after δ Cephei, the first example to be discovered. X Crucis is a population I star and so is a classical or type I Cepheid variable, to be distinguished from older low-mass stars called type II Cepheid variables.[3] Classical Cepheids pulsate radially so that their size varies. X Crucis pulsates in its fundamental mode and its properties indicate that it is crossing the instability strip for the third time as its evolves back to cooler temperatures.[10] Its radius varies by about {{solar radius|5}} during each cycle, approximately 8% of its mean radius. At the same time its temperature varies between 5,180 and 6,029 K. The radius and temperature do not vary in sync, with the smallest size occurring as the temperature is approaching its maximum. The brightness increases rapidly to a maximum when the star is hottest, then decreases more slowly. This is one of the properties that indicate fundamental mode pulsation.[12][14] References1. ^1 {{Cite book|chapter=B, V, I, photometry of Southern Cepheids|title= University of Michigan Catalogue of Two-dimensional Spectral Types for the HD Stars. Volume I. Declinations -90_ to -53_ƒ0|last1= Dean|first1= J.F.|year=1977|bibcode= 1975mcts.book.....H | location=Ann Arbor |publisher=University of Michigan}}
2. ^1 2 {{cite journal|bibcode=1998A&A...335L..65H|title=The TYCHO Reference Catalogue|journal=Astronomy and Astrophysics|volume=335|pages=L65|author1=Hog|first1=E.|last2=Kuzmin|first2=A.|last3=Bastian|first3=U.|last4=Fabricius|first4=C.|last5=Kuimov|first5=K.|last6=Lindegren|first6=L.|last7=Makarov|first7=V. V.|last8=Roeser|first8=S.|year=1998}}
3. ^1 2 3 {{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|author1=Samus|first1=N. N.|last2=Durlevich|first2=O. V.|year=2009}}
4. ^1 2 {{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|author1=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}}
5. ^1 {{cite journal|bibcode=1967IAUS...30...57E|title=The Revision of the General Catalogue of Radial Velocities|journal=Determination of Radial Velocities and Their Applications|volume=30|pages=57|author1=Evans|first1=D. S.|year=1967}}
6. ^1 2 3 4 5 {{cite journal|bibcode=1984AcA....34..225O|title=Observational determination of pulsation modes and photometric masses of Cepheid variables|journal=Acta Astronomica |volume=34|pages=225|author1=Opolski|first1=A.|year=1984}}
7. ^1 2 {{cite journal|bibcode=1988Ap&SS.150..223T|title=Absolute and relative amplitudes of variations in radius of classical Cepheids|journal=Astrophysics and Space Science |volume=150|issue=2|pages=223–234|author1=Tsvetkov|first1=Ts. G.|year=1988|doi=10.1007/BF00641718}}
8. ^1 2 {{cite journal|bibcode=1978A&A....62...75P|title=Intrinsic colours and physical properties of Cepheids|journal=Astronomy and Astrophysics|volume=62|pages=75|author1=Pel|first1=J. W.|year=1978}}
}}{{Stars of Crux}} 7 : Crux (constellation)|Classical Cepheid variables|Objects with variable star designations|2MASS objects|Henry Draper Catalogue objects|G-type supergiants|Durchmusterung objects |