RR Coronae Borealis

Not to be confused with R Coronae Borealis.

RR Coronae Borealis (RR CrB, HD 140297, HIP 76844) is a M3-type semiregular variable star located in the constellation Corona Borealis with a parallax of 2.93mas being a distance of 341 parsecs (1,110 ly). It varies between magnitudes 7.3 and 8.2 over 60.8 days.^[3] Located around 1228 light-years distant, it shines with a luminosity approximately 2180 times that of the Sun and has a surface temperature of 3309 K.^[6]

RR Coronae Borealis

A light curve for RR Coronae Borealis, plotted from Hipparcos data[1]
Observation data Epoch J2000      Equinox J2000
Constellation	Corona Borealis
Right ascension	15h 41m 26.22899s[2]
Declination	+38° 33′ 26.5958″[2]
Apparent magnitude (V)	7.3 - 8.2[3]
Characteristics
Spectral type	M5III[4] (M3 - M6[3])
Variable type	SRb[3]
Astrometry
Radial velocity (Rv)	-58.39[5] km/s
Proper motion (μ)	RA: 20.24[2] mas/yr Dec.: -32.44[2] mas/yr
Parallax (π)	2.93±0.53 mas[2]
Distance	approx. 1,100 ly (approx. 340 pc)
Details
Luminosity	2,180[6] L☉
Temperature	3,309[6] K
Other designations
RR CrB, BD+39° 2901, HD 140297, HIP 76844, SAO 64848, GC 21108, TYC 3053-1035-1, 2MASS J15412622+3833266
Database references
SIMBAD	data

In 1907 it was announced that Williamina Fleming had discovered that the star, listed then as BD +39° 2901, is a variable star. She had determined that from the examination of 26 photographic plates taken from 1892 to 1907. It was given its variable star designation, RR Coronae Borealis, in 1908.^[7][8][9]