101 Virginis

101 Virginis is a red giant variable star in the Boötes constellation, currently on the asymptotic giant branch.^[4] Its apparent magnitude ranges from 5.74 to 5.9, making it faintly visible to the naked eye under good observing conditions. It was originally catalogued as 101 Virginis by Flamsteed due to an error in the position.^[9][10] John R. Percy found it to be "marginally variable" in 1993.^[11] When it was confirmed as a variable star, it was actually within the border of the constellation Boötes and given the name CY Boötis.^[12]

101 Virginis

Location of CY Boötis (circled)
Observation data Epoch J2000      Equinox J2000
Constellation	Boötes[1]
Right ascension	14h 17m 28.4519s[2]
Declination	+15° 15′ 48.167″[2]
Apparent magnitude (V)	5.74 - 5.90[3]
Characteristics
Evolutionary stage	AGB[4]
Spectral type	M3IIIa[1]
B−V color index	1.678[1]
Variable type	SRb[3]
Astrometry
Radial velocity (Rv)	−11.30[5] km/s
Proper motion (μ)	RA: 14.27[2] mas/yr Dec.: 8.80[2] mas/yr
Parallax (π)	3.3735±0.1766 mas[6]
Distance	970 ± 50 ly (300 ± 20 pc)
Absolute magnitude (MV)	−0.98[1]
Details
Mass	1.2[7] M☉
Radius	76.78[6] R☉
Luminosity	1,078[8] L☉
Surface gravity (log g)	1.35[7] cgs
Temperature	3,682[8] K
Metallicity	−0.31[7]
Other designations
101 Vir, CY Boötis, NSV 6613, AG+15°1445, BD+15°2690, GC 19284, HD 125180, HIP 69829, HR 5352, SAO 100956, PPM 130465, TYC 1469-1456-1, GCRV 8358, GSC 01469-01456, IRAS 14150+1529, 2MASS J14172843+1515478
Database references
SIMBAD	data
Data sources:
Hipparcos Catalogue, Bright Star Catalogue (5th rev. ed.)

The variability is not strongly defined but a primary period of 23 days and a secondary period of 340 days have been reported.^[13]

CY Boo is listed in the Hipparcos catalogue as a "problem binary", a star which was suspected of being multiple but for which the Hipparcos observations did not give a satisfactory solution. Further observations have always shown it to be single.^[14]