HR 7578

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HR 7578
V4200SgrLightCurve.png
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]
PrimaryHR 7578 A
CompanionHR 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☉
Luminosity0.31±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

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] making it very faintly visible to the naked eye of an observer under a dark sky, far from any city. Parallax measurements by the Gaia spacecraft put the system at 46 light-years (14.1 parsecs) away, making this a nearby system. [2]

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]

In 1982, Francis C. Fekel and Willet I. Beavers suggested that HR 7578 might be a variable star, based on their spectroscopic observations. [9] James T. Hooten and Douglas S. Hall confirmed that the star's brightness varies, in 1990. [10] It was given its variable star designation, V4200 Sagittarii, in 1993. [11] 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]

References

  1. ↑ "Light Curve". Hipparcos ESA. ESA. Retrieved 17 February 2022.
  2. 1 2 3 4 5 Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics . 616. A1. arXiv: 1804.09365 . Bibcode: 2018A&A...616A...1G . doi: 10.1051/0004-6361/201833051 . Gaia DR2 record for this source at VizieR.
  3. 1 2 3 4 Chini, R.; Fuhrmann, K.; Barr, A.; Pozo, F.; Westhues, C.; Hodapp, K. (2014). "New visual companions of solar-type stars within 25 pc". Monthly Notices of the Royal Astronomical Society. 437 (1): 879–886. arXiv: 1310.2684 . Bibcode:2014MNRAS.437..879C. doi: 10.1093/mnras/stt1953 . S2CID   118717758.
  4. 1 2 3 Pasquini, L.; Cortés, C.; Lombardi, M.; Monaco, L.; Leão, I. C.; Delabre, B. (2015). "Tachoastrometry: Astrometry with radial velocities". Astronomy & Astrophysics. 574: A76. arXiv: 1412.7075 . Bibcode:2015A&A...574A..76P. doi:10.1051/0004-6361/201424882. S2CID   55059342.
  5. 1 2 3 4 5 6 7 8 Gallenne, A.; Mérand, A.; Kervella, P.; Graczyk, D.; Pietrzyński, G.; Gieren, W.; Pilecki, B. (2023-04-01). "The Araucaria project: High-precision orbital parallaxes and masses of binary stars. I. VLTI/GRAVITY observations of ten double-lined spectroscopic binaries". Astronomy and Astrophysics. 672: A119. arXiv: 2302.12960 . Bibcode:2023A&A...672A.119G. doi:10.1051/0004-6361/202245712. ISSN   0004-6361.
  6. 1 2 Mermilliod, J.-C. (1986). "Compilation of Eggen's UBV data, transformed to UBV (unpublished)". Catalogue of Eggen's UBV Data. Bibcode:1986EgUBV........0M.
  7. 1 2 3 4 Fekel, F. C. Jr.; Beavers, W. I. (1983). "HR 7578 - A K dwarf double-lined spectroscopic binary with peculiar abundances". The Astrophysical Journal. 267: 682. Bibcode:1983ApJ...267..682F. doi:10.1086/160905.
  8. 1 2 3 4 5 Fekel, Francis C.; Henry, Gregory W.; Tomkin, Jocelyn (2017). "New Precision Orbits of Bright Double-lined Spectroscopic Binaries. X. HD 96511, HR 7578, and KZ Andromedae". The Astronomical Journal. 154 (3). 120. Bibcode:2017AJ....154..120F. doi: 10.3847/1538-3881/aa816e .
  9. ↑ Fekel, F. C.; Beavers, W. I. (December 1982). "HR 7578: a Possible Late-Type Eclipsing Binary and/or a BY Draconis Variable". Information Bulletin on Variable Stars. 2243: 1–2. Bibcode:1982IBVS.2243....1F . Retrieved 24 September 2025.
  10. ↑ Hooten, James T.; Hall, Douglas S. (September 1990). "Photometry of 50 Suspected Variable Stars". Astrophysical Journal Supplement. 74: 225–247. Bibcode:1990ApJS...74..225H. doi:10.1086/191497 . Retrieved 24 September 2025.
  11. ↑ Kazarovets, E. V.; Samus, N. N.; Goranskij, V. P. (February 1993). "The 71st Name-List of Variable Stars". Information Bulletin on Variable Stars. 3840: 1–27. Bibcode:1993IBVS.3840....1K . Retrieved 24 September 2025.
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