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R Crucis - Wikipedia

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R Crucis
Observation data Epoch J2000.0 Equinox J2000.0
A visual band light curve for R Crucis, adapted from Dean et al. (1977)^[1]
Constellation	Crux
Right ascension	12^h 23^m 37.68840^s^[2]
Declination	−61° 37′ 44.8570″^[2]
Apparent magnitude (V)	6.89^[3]
Characteristics
Spectral type	F6-G2Ib-II^[4] or F7Ib/II^[5]
B−V color index	0.67±0.02^[3]
Variable type	δ Cep^[6]
Astrometry

Radial velocity (R_v)	−13.5±3.0^[3] km/s
Proper motion (μ)	RA: -9.404^[2] mas/yr Dec.: −0.430^[2] mas/yr
Parallax (π)	1.98 ± 0.54 mas^[7]
Distance	approx. 1,600 ly (approx. 500 pc)

Details

Radius	44.6^[8] `R`_☉
Surface gravity (log g)	1.65^[9] cgs
Temperature	5,812±22^[9] K
Metallicity [Fe/H]	+0.06^[9] dex

Other designations
R Cru, CD−60°4138, HD 107805, HIP 60455, SAO 251878^[10]
Database references
SIMBAD	data

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.^[3] This object is located at a distance of approximately 1,600 light years from the Sun based on parallax,^[7] but it is drifting closer with a radial velocity of −13.5 km/s.^[3]

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.^[6] It is a supergiant star with a stellar classification that varies over each pulsation cycle, giving it a class range of F6-G2Ib-II.^[4] The star has a mean radius 44.6 times the radius of the Sun (44.6 R_☉), but the radius varies by 5 R_☉ during each pulsation.^[11] It has a near solar metallicity and the atmospheric abundances indicate it is likely past first dredge-up.^[9]

A candidate companion star has been detected at an angular separation of 7.6″, which corresponds to a projected separation of 6,330 AU. The Hubble WFC3 shows a closer companion at a separation of 1.9″.^[12] The system is a source for X-ray emission but the contributing component is unclear.^[13]

References

^ Dean, J. F.; Cousins, A. W. J.; Bywater, R. A.; Warren, P. R. (January 1977). "VBI photometry of some southern cepheid and RR Lyrae variables". Memoirs of the Royal Astronomical Society. 83: 69–93. Bibcode:1977MmRAS..83...69D. Retrieved 18 December 2021.
^ ^a ^b ^c ^d Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
^ ^a ^b ^c ^d ^e Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters. 38 (5): 331. arXiv:1108.4971. Bibcode:2012AstL...38..331A. doi:10.1134/S1063773712050015. S2CID 119257644.
^ ^a ^b Watson, Christopher (4 January 2010). "R Crucis". AAVSO Website. American Association of Variable Star Observers. Retrieved 12 March 2014.
^ Houk, Nancy (1979). Michigan catalogue of two-dimensional spectral types for the HD stars. Vol. 1. Ann Arbor, Michigan: Department of Astronomy, University of Michigan. Bibcode:1978mcts.book.....H.
^ ^a ^b Samus, N. N.; et al. (2017). "General Catalogue of Variable Stars". Astronomy Reports. 5.1. 61 (1): 80–88. Bibcode:2017ARep...61...80S. doi:10.1134/S1063772917010085. S2CID 125853869.
^ ^a ^b van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. S2CID 18759600.
^ Moskalik, P.; Gorynya, N. A. (2005). "Mean Angular Diameters and Angular Diameter Amplitudes of Bright Cepheids". Acta Astronomica. 55: 247. arXiv:astro-ph/0507076. Bibcode:2005AcA....55..247M.
^ ^a ^b ^c ^d Usenko, I. A.; et al. (July 2014). "Spectroscopic studies of southern-hemisphere Cepheids: Three Cepheids in Crux (BG Cru, R Cru, and T Cru)". Astronomy Letters. 40 (7): 435–448. Bibcode:2014AstL...40..435U. doi:10.1134/S106377371407007X. S2CID 122521758.
^ "R Cru". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2020-02-14.
^ Moskalik, P.; Gorynya, N. A. (June 2005). "Mean Angular Diameters and Angular Diameter Amplitudes of Bright Cepheids". Acta Astronomica. 55: 247–260. arXiv:astro-ph/0507076. Bibcode:2005AcA....55..247M.
^ Evans, Nancy Remage; et al. (May 2016). "Hubble Space Telescope Snapshot Survey for Resolved Companions of Galactic Cepheids". The Astronomical Journal. 151 (5): 14. arXiv:1603.02224. Bibcode:2016AJ....151..129E. doi:10.3847/0004-6256/151/5/129. S2CID 119248298. 129.
^ Engle, Scott G.; et al. (March 2017). "The Secret Lives of Cepheids: δ Cep—The Prototype of a New Class of Pulsating X-Ray Variable Stars". The Astrophysical Journal. 838 (1): 9. arXiv:1702.06560. Bibcode:2017ApJ...838...67E. doi:10.3847/1538-4357/aa6159. S2CID 118928066. 67.

Constellation of Crux

Stars

Bayer	α (Acrux) β (Mimosa) γ (Gacrux) δ (Imai) ε (Ginan) ζ η θ¹ θ² ι λ μ¹ μ²
Variable	R S T V W X BG BH BL BP BU BZ CD CH DL DS DU
HR	4729 4848 4887 4890
HD	106906 108147 (Tupã)
Other	NGC 4349-127 PSR B1259−63/LS 2883 WR 46

Exoplanets	HD 106906 b HD 108147 b

Star clusters	Dragonfish Nebula Jewel Box (κ) NGC 4103 NGC 4349 NGC 4609

Nebulae	Coalsack Nebula Dragonfish Nebula IRAS 12063-6259