Chi Serpentis

Chi Serpentis (χ Ser, χ Serpentis) is a solitary star^[14] in the Serpens Caput section of the equatorial constellation Serpens. Based upon an annual parallax shift of 14.84 mas as seen from Earth, it is located around 222 light years from the Sun. The star is bright enough to be faintly visible to the naked eye, having an apparent visual magnitude of +5.30.^[3]

Chi Serpentis

A light curve for Chi Serpentis plotted from TESS data[1]
Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Serpens
Right ascension	15h 41m 47.41474s[2]
Declination	+12° 50′ 51.0937″[2]
Apparent magnitude (V)	+5.30[3]
Characteristics
Spectral type	A2 Vp MnEu(Sr)[4]
U−B color index	+0.04[3]
B−V color index	+0.04[3]
Variable type	α2 CVn[5]
Astrometry
Radial velocity (Rv)	+1.90±1.78[6] km/s
Proper motion (μ)	RA: +39.045[2] mas/yr Dec.: −2.923[2] mas/yr
Parallax (π)	14.7221±0.0748 mas[2]
Distance	222 ± 1 ly (67.9 ± 0.3 pc)
Absolute magnitude (MV)	+1.10[7]
Details
Mass	2.11[8] M☉
Radius	2.25[9] R☉
Luminosity	26[10] L☉
Surface gravity (log g)	3.66±0.24[11] cgs
Temperature	9,557±274[11] K
Metallicity [Fe/H]	+0.35±0.13[11] dex
Rotation	1.5948[7] d
Rotational velocity (v sin i)	75[12] km/s
Age	212[8] Myr
Other designations
χ Ser, 20 Ser, BD+13°2982, FK5 3243, HD 140160, HIP 76866, HR 5843, SAO 101683[13]
Database references
SIMBAD	data

In 1966 it was listed as a suspected spectroscopic binary,^[15] but it is believed to be single.^[14] This is a chemically peculiar star Ap star with a stellar classification of A2 Vp MnEu(Sr),^[4] indicating the spectrum shows abnormal excesses of manganese and europium. The star has 2.11 times the mass of the Sun^[8] and about 2.25 times the Sun's radius.^[9] It is radiating 26 times the solar luminosity from its photosphere^[10] at an effective temperature of 9,557 K.^[11] At the age of 212 million years,^[8] it is spinning with a rotation period of 1.6 days.^[15]

Chi Serpentis is classified as an Alpha2 Canum Venaticorum type variable star,^[5] and its magnitude varies by 0.03 with a period of 1.5948 days.^[7] The pattern of variation in the spectrum suggest there are regions of enhanced strontium, chromium, iron, titanium, and magnesium on the surface of the star.^[16] The averaged quadratic field strength of the surface magnetic field is (859.1±712.3)×10⁻⁴ T.^[17]