HD 170773

HD 170773 (HR 6948; 14 G. Coronae Australis) is a solitary star located in the southern constellation Corona Australis. It has an apparent magnitude of 6.22,^[3] placing it near the limit for naked eye visibility, even under ideal conditions. The object is located relatively close at a distance of 120 light-years based on Gaia DR3 parallax measurements^[2] and it is drifting closer with a heliocentric radial velocity of −25.2 km/s.^[7] At its current distance, HD 170773's brightness is diminished by an interstellar extinction of 0.19 magnitudes^[16] and it has an absolute magnitude of +3.38.^[8]

HD 170773

Image of the disk with the REASONS survey[1]
Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Corona Australis
Right ascension	18h 33m 00.91673s[2]
Declination	−39° 53′ 31.2751″[2]
Apparent magnitude (V)	6.22±0.01[3]
Characteristics
Spectral type	F5 V[4][5]
B−V color index	+0.42[6]
Astrometry
Radial velocity (Rv)	−25.2±1.0[7] km/s
Proper motion (μ)	RA: +86.353 mas/yr[2] Dec.: −79.927 mas/yr[2]
Parallax (π)	27.0749±0.03 mas[2]
Distance	120.5 ± 0.1 ly (36.93 ± 0.04 pc)
Absolute magnitude (MV)	+3.38[8]
Details
Mass	1.30[9] M☉
Radius	1.43±0.07[10] R☉
Luminosity	3.62±0.01[2] L☉
Surface gravity (log g)	4.21±0.04[11] cgs
Temperature	6,694±126[12] K
Metallicity [Fe/H]	−0.02±0.04[13] dex
Rotational velocity (v sin i)	67.2±6.2[14] km/s
Age	1.50+1.2 −0.7[11] Gyr
Other designations
14 G. Coronae Australis[15], CD−39°12704, CPD−39°8118, FK5 3470, GC 25304, HD 170773, HIP 90936, HR 6948, SAO 210286, TIC 313723578
Location of HD 170773 on the map (circled)
Database references
SIMBAD	data

HD 170773 has a stellar classification of F5 V,^[4][5] indicating that it is an ordinary F-type main-sequence star that is generating energy via hydrogen fusion at its core. It has also been given a classification of F5 IV, indicating that it is a slightly evolved subgiant that is ceasing hydrogen fusion at its core. It has 1.30 times the mass of the Sun^[9] and 1.43 times the radius of the Sun.^[10] It radiates 3.62 times the luminosity of the Sun^[2] from its photosphere at an effective temperature of 6,694 K,^[12] giving it the typical yellowish-white hue of a F-type star. HD 170773 has a near solar metallicity of [Fe/H] = −0.02^[13] and it is estimated to be 1.5 billion years old.^[11] It spins fairly quickly with a projected rotational velocity of 67.2 km/s.^[14]

The star has a debris disk located 78 AU away and it has a temperature of 43 K.^[17] It was first observed in 1986 by astronomers K. Sakadane and M. Nishida in their survey of Vega-like stars due to the star displaying an infrared excess that could suggest the presence of a circumstellar disk.^[18] However, the actual disk was not discovered until 2004 using the Spitzer Space Telescope.^[19] There might be a second cooler disk surrounding the star, but subsequent observations have not confirmed this.^[17]