Astronomy:HR 7578

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Short description: Triple star system in the constellation Sagittarius
HR 7578
250px
A light curve for V4200 Sagittarii, plotted from Hipparcos data[1]
Observation data
Equinox J2000.0]] (ICRS)
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[5] mas
Distance46.03 ± 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 astronomical unit|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
Mass0.87492±0.00032[5] M☉
Radius0.86±0.04[8] R☉
Luminosity0.35±0.02[8] L☉
Temperature4820±200[5] K
Metallicity [Fe/H]0.28[5] dex
Rotational velocity (v sin i)2.0[4] km/s
HR 7578 B
Mass0.85978±0.00029[5] M☉
Radius0.81±0.04[8] R☉
Luminosity0.31±0.02[8] L☉
Temperature4820±200[5] K
Other designations
CD−24° 15668, GJ 770, HD 188088, HIP 97944, HR 7578, SAO 188692
Database references
SIMBADdata
ARICNSdata

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". ESA. https://www.cosmos.esa.int/web/hipparcos/java-tools/light-curve. 
  2. ↑ 2.0 2.1 2.2 2.3 2.4 Brown, A. G. A. (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics 616: A1. doi:10.1051/0004-6361/201833051. Bibcode: 2018A&A...616A...1G.  Gaia DR2 record for this source at VizieR.
  3. ↑ 3.0 3.1 3.2 3.3 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. doi:10.1093/mnras/stt1953. Bibcode: 2014MNRAS.437..879C. 
  4. ↑ 4.0 4.1 4.2 Pasquini, L.; Cortés, C.; Lombardi, M.; Monaco, L.; Leão, I. C.; Delabre, B. (2015). "Tachoastrometry: Astrometry with radial velocities". Astronomy & Astrophysics 574: A76. doi:10.1051/0004-6361/201424882. Bibcode: 2015A&A...574A..76P. 
  5. ↑ 5.0 5.1 5.2 5.3 5.4 5.5 5.6 5.7 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. doi:10.1051/0004-6361/202245712. ISSN 0004-6361. Bibcode: 2023A&A...672A.119G. 
  6. ↑ 6.0 6.1 Mermilliod, J.-C. (1986). "Compilation of Eggen's UBV data, transformed to UBV (unpublished)". Catalogue of Eggen's UBV Data. Bibcode: 1986EgUBV........0M. 
  7. ↑ 7.0 7.1 7.2 7.3 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. doi:10.1086/160905. Bibcode: 1983ApJ...267..682F. 
  8. ↑ 8.0 8.1 8.2 8.3 8.4 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. doi:10.3847/1538-3881/aa816e. Bibcode: 2017AJ....154..120F. 
  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. https://articles.adsabs.harvard.edu/pdf/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. doi:10.1086/191497. Bibcode: 1990ApJS...74..225H. https://articles.adsabs.harvard.edu/pdf/1990ApJS...74..225H. 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. https://articles.adsabs.harvard.edu/pdf/1993IBVS.3840....1K. Retrieved 24 September 2025. 



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