HD 201772

HD 201772

HD 201772 is the star circled in red
Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Microscopium
Right ascension	21h 13m 03.06827s[1]
Declination	−39° 25′ 29.7097″[1]
Apparent magnitude (V)	5.26[2]
Characteristics
Spectral type	F5 IV-V[3] or F6 V Fe−0.9 CH−0.5[4]
B−V color index	+0.44[2]
Astrometry
Radial velocity (Rv)	−41±1[5] km/s
Proper motion (μ)	RA: +185.855 mas/yr[1] Dec.: −113.449 mas/yr[1]
Parallax (π)	29.2823 ± 0.0827 mas[1]
Distance	111.4 ± 0.3 ly (34.15 ± 0.10 pc)
Absolute magnitude (MV)	+2.66[6]
Details
Mass	1.5[1] M☉
Radius	2.18±0.09[7] R☉
Luminosity	7.83±0.04[1] L☉
Surface gravity (log g)	3.91±0.09[8] cgs
Temperature	6,519±80[9] K
Metallicity [Fe/H]	−0.18±0.03[10] dex
Rotational velocity (v sin i)	10[11] km/s
Age	2.23±0.04 Gyr
Other designations
56 G. Microscopii[12], CD−39°14152, CPD−39°8898, GC 29640, HD 201772, HIP 104738, HR 8104, SAO 212793, LTT 8413[13]
Database references
SIMBAD	data

HD 201772, also known as HR 8104, is a yellowish-white hued star located in the southern constellation Microscopium. It has an apparent magnitude of 5.26,^[2] making it one of the brighter members of this generally faint constellation. The object is located relatively close at a distance of 111 light-years based on Gaia DR3 parallax measurements^[1] but is approaching closer with a heliocentric radial velocity of −41 km/s.^[5] At its current distance, HD 201772's brightness is diminished by 0.11 magnitudes due to interstellar dust.^[14]

The star has been given multiple stellar classifications over the years. It was given the luminosity class of a subgiant and main sequence star (IV/V; IV-V)^[15][3] and a dwarf (V).^[16][17] Most sources generally agree that it is a F5 star. Richard O. Gray and colleagues give HD 201772 a class of F6 V Fe−0.9 CH−0.5, which indicates that it is a F-type main-sequence star with an underabundance of iron and CH molecules in its spectrum.^[4]

It has 1.47 times the mass of the Sun^[18] and an enlarged radius of 2.2 R_☉.^[7] It radiates 7.8 times the luminosity of the Sun from its photosphere at an effective temperature of 6,519 K.^[9] At an age of 2.5 billion years, HD 201722 is currently 1.33 magnitudes above the ZAMS, consistent with a star that is evolving off the main sequence.^[11] The star has an iron abundance 66% that of the Sun,^[10] making it metal deficient. It spins modestly with a projected rotational velocity of 10 km/s.^[11]

HD 201772 is suspected to be a spectroscopic binary consisting of the subgiant described above and an ordinary F6 V star with a mass of 1.31 M_☉.^[19] However, the stars have no separation or an orbital period.^[20] This is because the companion might be a result of spectrum contamination, so HD 201772 is more likely to be a solitary star.^[21]