Xi Herculis

Xi Herculis

ξ Herculis in optical light
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Hercules
Right ascension 17h 57m 45.88567s[1]
Declination +29° 14′ 52.3660″[1]
Apparent magnitude (V) 3.70[2]
Characteristics
Spectral type G8 III[3]
U−B color index +0.66[2]
B−V color index +0.93[2]
Astrometry
Radial velocity (Rv)−1.65±0.17[4] km/s
Proper motion (μ) RA: 81.919 mas/yr[1]
Dec.: −18.962 mas/yr[1]
Parallax (π)23.8544 ± 0.1068 mas[1]
Distance136.7 ± 0.6 ly
(41.9 ± 0.2 pc)
Absolute magnitude (MV)+0.62[5]
Details
Mass2.01[6] M☉
Radius9.94±0.09[7] R☉
Luminosity57.2±2.1[7] L☉
Surface gravity (log g)2.87±0.09[8] cgs
Temperature5,032±48[7] K
Metallicity [Fe/H]+0.09±0.04[8] dex
Rotation67[9] d
Rotational velocity (v sin i)2.8[4] km/s
Age2.48[6] Gyr
Other designations
ξ Her, 92 Her, BD+29° 3156, HD 163993, HIP 87933, HR 6703, SAO 85590[10]
Database references
SIMBADdata

Xi Herculis is a solitary[11] star located within the northern constellation of Hercules. The star is visible to the naked eye with an apparent visual magnitude of 3.70.[2] Based upon an annual parallax shift of 23.85 mas as seen from Earth, it is located 137 light years from the Sun.[1] At that distance, the visual magnitude of the star is diminished by an extinction factor of 0.05 due to interstellar dust. It is a suspected member of the Sirius stream of co-moving stars.[12]

A light curve for Xi Herculis, plotted from Hipparcos data[13]

This is an evolved G-type giant star with a stellar classification of G8 III.[3] It is a red clump star, which means it is on the horizontal branch and generating energy through the thermonuclear fusion of hydrogen at its core. The star is emitting X-rays with a luminosity of 3.03×1030 erg s−1 in the 0.3–10 keV band.[9] It has twice[6] the mass of the Sun but, at the age of two and a half billion years,[6] it has expanded to 10 times the Sun's radius. The star is radiating 57 times the solar luminosity from its photosphere at an effective temperature of 5,032 K.[7]

Xi Herculis is a semiregular variable star, oscillating in brightness by 3 hundredths of a magnitude, over a period of 120.8 days.[14]

  1. ^ a b c d e Cite error: The named reference DR3 was invoked but never defined (see the help page).
  2. ^ a b c d Cite error: The named reference Mermilliod1986 was invoked but never defined (see the help page).
  3. ^ a b Cite error: The named reference Morgan1973 was invoked but never defined (see the help page).
  4. ^ a b Cite error: The named reference Massarotti2008 was invoked but never defined (see the help page).
  5. ^ Cite error: The named reference BohmVitense2000 was invoked but never defined (see the help page).
  6. ^ a b c d Cite error: The named reference Luck2015 was invoked but never defined (see the help page).
  7. ^ a b c d Cite error: The named reference baines was invoked but never defined (see the help page).
  8. ^ a b Cite error: The named reference Prugniel2011 was invoked but never defined (see the help page).
  9. ^ a b Cite error: The named reference Gondoin2005 was invoked but never defined (see the help page).
  10. ^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  11. ^ Cite error: The named reference Eggleton2008 was invoked but never defined (see the help page).
  12. ^ Cite error: The named reference aaa430_165 was invoked but never defined (see the help page).
  13. ^ Cite error: The named reference CDS was invoked but never defined (see the help page).
  14. ^ Cite error: The named reference IVSI was invoked but never defined (see the help page).