HD 224801

HD 224801

File:CGAndLightCurve.png A light curve for CG Andromedae (HD 224801), plotted from TESS data.
Observation data Epoch J2000      Equinox J2000
Constellation	Andromeda
Right ascension	Template:RA
Declination	Template:DEC
Apparent magnitude (V)	6.32Template:Snd6.42
Characteristics
Spectral type	A0IIspSiSrHg
Apparent magnitude (B)	6.299
Apparent magnitude (V)	6.347
Apparent magnitude (G)	6.333
Apparent magnitude (J)	6.407
Apparent magnitude (H)	6.506
Apparent magnitude (K)	6.511
U−B Template:Engvar	-0.35
B−V Template:Engvar	-0.0425
Variable type	Alpha² CVn
Astrometry
Radial velocity (Rv)	km/s
Proper motion (μ)	RA: +17.745 mas/yr Dec.: +0.607 mas/yr
Parallax (π)	5.5784±0.0405 mas
Distance	Template:Rnd ± Template:Rnd ly (Template:Rnd ± Template:Rnd pc)
Absolute magnitude (MV)	0.0
Details
Mass	3.4 Template:Solar mass
Radius	2.8 Template:Solar radius
Luminosity	170 Template:Solar luminosity
Surface gravity (log g)	4.12 cgs
Temperature	11,900 K
Metallicity [Fe/H]	0.98 dex
Rotation	3.74 days
Rotational velocity (v sin i)	30 km/s
Age	239 Myr
Metallicity [Fe/H]	{{{metal_fe2}}} dex
Other designations
CG Andromedae, BD+44° 4538, HD 224801, HIP 63, HR 9080, SAO 53568, PPM 42458, TYC 3246-2388-1.
Database references
SIMBAD	data

HD 224801, also known as CG Andromedae, is an Alpha² Canum Venaticorum variable star in the constellation Andromeda. Located approximately away, the star varies between apparent magnitudes 6.32 and 6.42 over a period of approximately 3.74 days.

Spectrum

CG Andromedae is also a chemically peculiar star with a strong magnetic field, or Ap star, with a spectral type A0IIspSiSrHg. This means that it's a bright giant star that shows narrow absorption lines and unusual strong lines of silicium, strontium and mercury. Calcium and manganese lines are weaker than expected instead. Other sources report that the stronger lines are of silicium and europium, thus giving a spectral classification B9pSiEu, which has just a slightly different temperature for the blackbody emission in addition to the different lines.

Variability

CG Andromedae's variability was detected in 1951, and announced by Sanford S. Provin in 1953.

Like in Alpha² Canum Venaticorum variable stars, CG Andromedae shows a variation of luminosity and one in the strength of spectral lines with the same period of approximately 3.74 days. It is thought that this is caused by an inhomogeneous distribution of elements on the surface of the star, which cause an inhomogeneous surface brightness.

A shorter period, slightly longer than 2 hours, with an amplitude of 0.011 magnitudes has been observed in the light curve of CG Andromedae; however, with a temperature of 11,000 K, it lies outside the instability strip of the HR diagram where rapidly oscillating Ap stars are located. Magnetohydrodynamic waves propagating in the star could explain the observed variability.