Lambda Persei

λ Persei, Latinized as Lambda Persei, is a star in the northern constellation of Perseus. It is visible to the naked eye as a faint, white-hued point of light with an apparent visual magnitude of 4.29.^[2] This object is located approximately 422 light years from the Sun based on parallax,^[1] and is drifting further away with a radial velocity of +6 km/s.^[4]

λ Persei in optical light

Lambda Persei

Location of λ Persei (circled)
Observation data Epoch J2000      Equinox J2000
Constellation	Perseus
Right ascension	04h 06m 35.04360s[1]
Declination	50° 21′ 04.5500″[1]
Apparent magnitude (V)	4.29[2]
Characteristics
Spectral type	A0IVn[3]
U−B color index	−0.04[2]
B−V color index	+0.02[2]
Astrometry
Radial velocity (Rv)	+6.1±2.0[4] km/s
Proper motion (μ)	RA: −12.75[1] mas/yr Dec.: −35.60[1] mas/yr
Parallax (π)	7.73±0.22 mas[1]
Distance	420 ± 10 ly (129 ± 4 pc)
Absolute magnitude (MV)	−1.31[5]
Details
Radius	3.1[6] R☉
Luminosity	348[5] L☉
Surface gravity (log g)	4.05[7] cgs
Temperature	10,585[7] K
Metallicity [Fe/H]	+0.01[7] dex
Rotational velocity (v sin i)	196[8] km/s
Age	345[9] Myr
Other designations
λ Per, 47 Persei, BD+49°1101, FK5 1113, GC 4924, HD 25642, HIP 19167, HR 1261, SAO 24412[10]
Database references
SIMBAD	data

This object has a stellar classification of A0IVn,^[3] matching an A-type subgiant star with "nebulous" lines due to rapid rotation. It is spinning with a projected rotational velocity of 196 km/s,^[8] which is giving the star an equatorial bulge that is an estimated 16% larger than the polar radius.^[11] Unusually for a star of this type, spectra show weak emission features among the Hydrogen lines, which may be due to plage regions on the surface caused by an implied magnetic field.^[12] The star is 345^[9] million years old and is radiating 348^[5] times the luminosity of the Sun from its photosphere at an effective temperature of 10,585 K.^[7]

In Chinese astronomy, Lambda Persei is called 積水, Pinyin: Jīshuǐ, meaning Stored Water, because this star is marking itself and stand alone in Stored Water asterism, Stomach mansion (see : Chinese constellation).^[13] This name has also been applied to Omicron Geminorum and was approved by the IAU Working Group on Star Names as the name of that star.^[14]