HR 7578

HR 7578 (also known as V4200 Sagittarii) is a triple star system in the constellation of Sagittarius. Their combined apparent magnitude is 6.18.^[3] Parallax measurements by the Gaia spacecraft put the system at 46 light-years (14.1 parsecs) away, making this a nearby system.^[2]

HR 7578

A light curve for V4200 Sagittarii, plotted from Hipparcos data[1]
Observation data Epoch J2000      Equinox J2000
Constellation	Sagittarius
Right ascension	19h 54m 17.17.7453s[2]
Declination	−23° 56′ 27.8630″[2]
Apparent magnitude (V)	6.18[3]
Characteristics
Spectral type	K3 V + K3 V[4] + M5[5]
U−B color index	+0.915[6]
B−V color index	+1.045[6]
Variable type	BY Dra[3]
Astrometry
Radial velocity (Rv)	−5.1 ± 0.2[7] km/s
Proper motion (μ)	RA: −124.476±0.067[2] mas/yr Dec.: −410.440±0.043[2] mas/yr
Parallax (π)	70.857±0.019 mas[5]
Distance	46.03 ± 0.01 ly (14.113 ± 0.004 pc)
Orbit[5]
Primary	HR 7578 A
Companion	HR 7578 B
Period (P)	46.81614±0.00003 d
Semi-major axis (a)	0.3054±0.0001 AU
Eccentricity (e)	0.68664±0.00006
Inclination (i)	99.048±0.007°
Longitude of the node (Ω)	111.83±0.01°
Periastron epoch (T)	2455441.0406±0.0003 HJD
Argument of periastron (ω) (secondary)	241.056±0.011°
Semi-amplitude (K1) (primary)	47.79±0.01 km/s
Semi-amplitude (K2) (secondary)	48.63±0.01 km/s
Details
HR 7578 A
Mass	0.87492±0.00032[5] M☉
Radius	0.86±0.04[8] R☉
Luminosity	0.35±0.02[8] L☉
Temperature	4820±200[5] K
Metallicity [Fe/H]	0.28[5] dex
Rotational velocity (v sin i)	2.0[4] km/s
HR 7578 B
Mass	0.85978±0.00029[5] M☉
Radius	0.81±0.04[8] R☉
Luminosity	0.31±0.02[8] L☉
Temperature	4820±200[5] K
Other designations
CD−24° 15668, GJ 770, HD 188088, HIP 97944, HR 7578, SAO 188692
Database references
SIMBAD	data
ARICNS	data

The two main stars of HR 7578 are fairly old, older than the Pleiades but possibly younger than the Hyades.^[7] The stars are between 5×10⁸ and 2×10⁹ years old.^[7] Both are K-type main-sequence stars.^[4] Both stars have a minimum mass of 0.85 ± 0.03 M_☉, and are unusually metal-rich, showing high amounts of cyanide and sodium in their spectra.^[7]

HR 7578 is a BY Draconis variable. This is a class of variable star whose variability comes from starspots on the stars' surfaces. HR 7578 also has a common proper motion companion, 2MASS J19542064−2356398. It is a red dwarf that is at least 580 astronomical units from the central star system.^[3] There is another star that is separated about 40″ away and is 4.4 magnitudes fainter, but is not physically associated with HR 7578.^[8]