R Crucis
{{Short description|Variable star in the constellation Crux}}
{{Starbox begin}}
{{Starbox image
| image = 250px
| caption = A visual band light curve for R Crucis, adapted from Dean et al. (1977)
}}
{{Starbox observe
| epoch = J2000.0
| constell = Crux
| dec = {{DEC|−61|37|44.8570}}
}}
{{Starbox character
| type =
| class = F6-G2Ib-II or F7Ib/II
| u-b =
| variable = δ Cep
}}
{{Starbox astrometry
| radial_v = {{Val|−13.5|3.0}}
| parallax = 1.98
| p_error = 0.54
| absmag_v =
}}
{{Starbox detail
| source =
| mass =
| luminosity =
| temperature = {{Val|5812|22|fmt=commas}}
| rotational_velocity =
| age_myr =
}}
{{Starbox catalog
| names = {{odlist | V=R Cru | CD=−60°4138 | HD=107805 | HIP=60455 | SAO=251878 | AAVSO=1218-61 }}
}}
{{Starbox reference
| Simbad = R+Cru
}}
{{Starbox end}}
R Crucis is a variable star in the southern constellation of Crux. It has a yellow-white hue and is often too faint to see with the naked eye, having an apparent visual magnitude that fluctuates around 6.89. This object is located at a distance of approximately 1,600 light years from the Sun based on parallax, but it is drifting closer with a radial velocity of −13.5 km/s.
This is a Classical Cepheid, or Delta Cephei variable, that ranges in brightness from visual magnitude 6.40 down to 7.23 with a period of 5.82575 days. It is a supergiant star with a stellar classification that varies over each pulsation cycle, giving it a class range of F6-G2Ib-II. The star has a mean radius 44.6 times the radius of the Sun ({{solar radius|44.6}}), but the radius varies by {{solar radius|5}} during each pulsation. It has a near solar metallicity and the atmospheric abundances indicate it is likely past first dredge-up.
A candidate companion star has been detected at an angular separation of {{Val|7.6|ul=arcsecond}}, which corresponds to a projected separation of {{Val|6330|ul=AU|fmt=commas}}. The Hubble WFC3 shows a closer companion at a separation of {{Val|1.9|u=arcsecond}}. The system is a source for X-ray emission but the contributing component is unclear.
References
{{Reflist|colwidth=30em|refs=
{{cite DR2|6054935874793666176}}
{{cite simbad | title=R Cru | access-date=2020-02-14 }}
| title=Hubble Space Telescope Snapshot Survey for Resolved Companions of Galactic Cepheids
| display-authors=1 | last1=Evans | first1=Nancy Remage
| last2=Bond | first2=Howard E. | last3=Schaefer | first3=Gail H.
| last4=Mason | first4=Brian D. | last5=Tingle | first5=Evan
| last6=Karovska | first6=Margarita | last7=Pillitteri | first7=Ignazio
| journal=The Astronomical Journal
| volume=151 | issue=5 | id=129 | pages=14 | date=May 2016
| arxiv=1603.02224 | bibcode=2016AJ....151..129E
| doi=10.3847/0004-6256/151/5/129 | s2cid=119248298 | doi-access=free }}
| last1=Dean | first1=J. F.
| last2=Cousins | first2=A. W. J.
| last3=Bywater | first3=R. A.
| last4=Warren | first4=P. R.
| title=VBI photometry of some southern cepheid and RR Lyrae variables
| journal=Memoirs of the Royal Astronomical Society |date=January 1977
| volume=83 | pages=69–93
| bibcode=1977MmRAS..83...69D
| url=https://ui.adsabs.harvard.edu/abs/1977MmRAS..83...69D | access-date=18 December 2021}}
| title=Spectroscopic studies of southern-hemisphere Cepheids: Three Cepheids in Crux (BG Cru, R Cru, and T Cru)
| display-authors=1 | last1=Usenko | first1=I. A.
| last2=Kniazev | first2=A. Yu. | last3=Berdnikov | first3=L. N.
| last4=Fokin | first4=A. B. | last5=Kravtsov | first5=V. V.
| journal=Astronomy Letters
| volume=40 | issue=7 | pages=435–448 | date=July 2014
| doi=10.1134/S106377371407007X | bibcode=2014AstL...40..435U | s2cid=122521758 }}
| title=The Secret Lives of Cepheids: δ Cep—The Prototype of a New Class of Pulsating X-Ray Variable Stars
| display-authors=1 | last1=Engle | first1=Scott G.
| last2=Guinan | first2=Edward F. | last3=Harper | first3=Graham M.
| last4=Cuntz | first4=Manfred | last5=Remage Evans | first5=Nancy
| last6=Neilson | first6=Hilding R. | last7=Fawzy | first7=Diaa E.
| journal=The Astrophysical Journal
| volume=838 | issue=1 | id=67 | pages=9 | date=March 2017
| doi=10.3847/1538-4357/aa6159 | arxiv=1702.06560
| bibcode=2017ApJ...838...67E | s2cid=118928066 | doi-access=free }}
| title=Validation of the new Hipparcos reduction
| last1=van Leeuwen | first1=F.
| journal=Astronomy and Astrophysics
| volume=474 | issue=2 | pages=653–664 | date=2007
| arxiv=0708.1752 | bibcode=2007A&A...474..653V
| doi=10.1051/0004-6361:20078357 | s2cid=18759600 }}
| title=XHIP: An extended hipparcos compilation
| last1=Anderson | first1=E. | last2=Francis | first2=Ch.
| journal=Astronomy Letters | arxiv=1108.4971
| volume=38 | issue=5 | pages=331 | year=2012
| bibcode=2012AstL...38..331A | doi=10.1134/S1063773712050015 | s2cid=119257644 }}
| last1=Houk | first1=Nancy
| title=Michigan catalogue of two-dimensional spectral types for the HD stars
| location=Ann Arbor, Michigan
| publisher=Department of Astronomy, University of Michigan
| volume=1 | year=1979
| bibcode=1978mcts.book.....H }}
| 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=5.1 | journal=Astronomy Reports
| year=2017 | volume=61 | issue=1 | pages=80–88
| bibcode=2017ARep...61...80S | doi=10.1134/S1063772917010085 | s2cid=125853869 }}
| last1=Moskalik | first1=P. | last2=Gorynya | first2=N. A.
| title=Mean Angular Diameters and Angular Diameter Amplitudes of Bright Cepheids
| journal=Acta Astronomica
| volume=55 | pages=247 | year=2005
| arxiv = astro-ph/0507076 | bibcode=2005AcA....55..247M }}
| title=R Crucis | work=AAVSO Website
| last=Watson | first=Christopher | date=4 January 2010
| publisher=American Association of Variable Star Observers
| url=http://www.aavso.org/vsx/index.php?view=detail.top&oid=10769
| accessdate=12 March 2014 }}
| title=Mean Angular Diameters and Angular Diameter Amplitudes of Bright Cepheids
| last1=Moskalik | first1=P. | last2=Gorynya | first2=N. A.
| journal=Acta Astronomica
| volume=55 | pages=247–260 | date=June 2005
| arxiv=astro-ph/0507076 | bibcode=2005AcA....55..247M }}
}}
{{Stars of Crux}}
{{DEFAULTSORT:R Crucis}}
Category:Classical Cepheid variables