S Canis Minoris

S Canis Minoris is a variable star in the equatorial constellation Canis Minor. It has a peak apparent visual magnitude of 6.5, so not normally visible to the naked eye. The star is located at a distance of approximately 1,340 light-years from the Sun based on stellar parallax, and is drifting further away with a radial velocity of about +68 km/s.

S Canis Minoris

The visual band light curve of S Canis Minoris, from AAVSO data[1]
Observation data Epoch J2000      Equinox J2000
Constellation	Canis Minor[2]
Right ascension	07h 32m 43.06942s[3]
Declination	+08° 19′ 05.1975″[3]
Apparent magnitude (V)	6.5 to 13.7[4]
Characteristics
Evolutionary stage	AGB[5]
Spectral type	M7-8e[6]
B−V color index	1.50±0.51[2]
Variable type	Mira variable[7][4]
Astrometry
Radial velocity (Rv)	68.0±4.8[8] km/s
Proper motion (μ)	RA: −10.785 mas/yr[3] Dec.: −12.827 mas/yr[3]
Parallax (π)	2.440±0.098 mas[9]
Distance	1,340 ± 50 ly (410 ± 20 pc)[9]
Details
Radius	378 – 402[9] R☉
Luminosity	6,174+402 −378[9] L☉
Surface gravity (log g)	−0.46 to −0.51[9] cgs
Temperature	2,854 – 2,872[9] K
Metallicity [Fe/H]	+0.39[10] dex
Other designations
S CMi, AAVSO 0727+08, BD+08°1800, HD 59950, HIP 36675, SAO 115591[11]
Database references
SIMBAD	data

In 1856, John Russell Hind discovered that S Canis Minoris is a variable star.^[12] This is an aging red giant star with a stellar classification of M7-8e,^[6] where the 'e' suffix indicates emission lines in the spectrum. It is a Mira-type^[7] long period variable that varies by an amplitude of 4.27 in visual magnitude over a period of 327.77±2.78 d.^[13] Evidence has been found of asymmetry in this star, suggesting a non-spherical shape.^[5] Abundance-wise, it is an oxygen-rich^[14] giant and the emission feature is of the oxygen-rich silicate class as it sheds silicate dust from its atmosphere.^[15] The star is shedding mass at the rate of 4.9×10⁻⁸ M_☉/yr.^[5]