R Centauri

For r Centauri, see HD 115310.
R Centauri

The visual band light curve of R Centauri, from AAVSO data[1]
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Centaurus
Right ascension 14h 16m 34.319s[2]
Declination −59° 54′ 49.29″[2]
Apparent magnitude (V) 5.2 - 11.5[3]
Characteristics
Spectral type M5IIe[4] (M4e-M9.5[3])
U−B color index +1.24[5]
B−V color index +2.04[5]
Variable type Mira[3]
Astrometry
Radial velocity (Rv)−19.8[6] km/s
Proper motion (μ) RA: −9.077[2] mas/yr
Dec.: −6.692[2] mas/yr
Parallax (π)1.1082 ± 0.2413 mas[2]
Distanceapprox. 2,900 ly
(approx. 900 pc)
Absolute magnitude (MV)−1.49 (at maximum)[7]
Details
Radius615[8] R☉
Luminosity47,000[4] L☉
Surface gravity (log g)−0.733[8] cgs
Temperature3,450[4] K
Other designations
R Centauri, HR 5326, HD 124601, CP−59°5476, HIP 69754, SAO 241580, GC 19234, CCDM J14166-5955
Database references
SIMBADdata

R Centauri (R Cen) is a Mira variable star in the constellation Centaurus.

The distance to R Centauri as indicated by its Gaia Data Release 3 parallax is about 2,900 light years, but that is considered to be potentially unreliable.[2] The Gaia Data Release 2 parallax was negative and relatively meaningless.[9] The older Hipparcos parallax suggested a distance of about 1,300 light years, but with a wide margin of error.[10] Estimates based on an assumed brightness for the star, adjusted for extinction, give distances as low as 750 light years.[11]

The effective temperature of R Centauri's photosphere has been calculated by different methods to be 2,403 K[8] or 3,450 K.[4] Its luminosity is even more uncertain, depending on assumptions about the distance. At a distance of 384 pc, the bolometric luminosity would be 11,342 L☉,[8] while assuming a larger distance of 640 pc the luminosity would be over 47,000 L☉.[4] In either case, it is a very large star, over 600 R☉.[8]

R Centauri is a Mira variable and its brightness varies from magnitude +5.2 to +11.5 with a period of about 500 days. It used to have an unusual double-peaked light curve, but by 2001 this had reverted to an almost normal single-peaked curve. Prior to 1950 the period was about 550 days, but since then has decreased to about 500 days. A 2016 analysis of ASAS data derived a period of 498.84 days.[12]

It is thought that the unusual behaviour of R Centauri is caused by a flash in the helium shell around its core, which occurs periodically in asymptotic giant branch (AGB) stars as the mass of the helium shell increases with helium from the outer hydrogen shell.[13] It is also an H2O maser source.[14]

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  8. ^ a b c d e Cite error: The named reference mcdonald2017 was invoked but never defined (see the help page).
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  10. ^ Cite error: The named reference van Leeuwen2007 was invoked but never defined (see the help page).
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  14. ^ Cite error: The named reference lepine was invoked but never defined (see the help page).