Epsilon Gruis

Epsilon Gruis
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Grus
Right ascension 22h 48m 33.29833s[1]
Declination −51° 19′ 00.7001″[1]
Apparent magnitude (V) 3.466[2]
Characteristics
Spectral type A2 IVn[3]
B−V color index 0.09[2]
Astrometry
Radial velocity (Rv)−0.4±2.1[4] km/s
Proper motion (μ) RA: +108.43[1] mas/yr
Dec.: −64.83[1] mas/yr
Parallax (π)25.30 ± 0.48 mas[1]
Distance129 ± 2 ly
(39.5 ± 0.7 pc)
Absolute magnitude (MV)+0.52[5]
Details
Mass1.85[6] M☉
Surface gravity (log g)3.47±0.14[6] cgs
Temperature8,685±295[6] K
Metallicity [Fe/H]−0.16[3] dex
Rotational velocity (v sin i)235.1±11.8[5] km/s
Age249[6] Myr
Other designations
ε Gru, CD−51° 13389, FK5 860, GJ 9796, HD 215789, HIP 112623, HR 8675, SAO 247593[7]
Database references
SIMBADdata

ε Gruis, Latinised as Epsilon Gruis, is a blue-white hued star in the southern constellation of Grus. It is visible to the naked eye, having an apparent visual magnitude of 3.5.[2] Based upon an annual parallax shift of 25.30 mas as measured from Earth,[1] it is located around 129 light years from the Sun. The system may be moving closer to the Sun with a radial velocity of about −0.4 km/s.[4]

This is an A-type subgiant of spectral type A2IVn,[3] a star that has used up its core hydrogen and has begun to expand off the main sequence. At the estimated age of 249 million years,[6] it is spinning rapidly with a projected rotational velocity of 235 km/s.[5] This is giving the star an oblate shape with an equatorial bulge that is an estimated 18% larger than the polar radius.[8] The star displays an infrared excess, suggesting the presence of a circumstellar disk of orbiting dust.[9]

Epsilon Gruis is suspected of having a moderately active[10] close companion,[11] which is most likely the source of the weak X-ray emission from these coordinates with a luminosity of 1.3×1028 erg s−1.[10]

  1. ^ a b c d e f Cite error: The named reference vanLeeuwen2007 was invoked but never defined (see the help page).
  2. ^ a b c Cite error: The named reference Hog2000 was invoked but never defined (see the help page).
  3. ^ a b c Cite error: The named reference Gray2006 was invoked but never defined (see the help page).
  4. ^ a b Cite error: The named reference Gontcharov2006 was invoked but never defined (see the help page).
  5. ^ a b c Cite error: The named reference vonEiff2012 was invoked but never defined (see the help page).
  6. ^ a b c d e Cite error: The named reference David2015 was invoked but never defined (see the help page).
  7. ^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  8. ^ Cite error: The named reference belle2012 was invoked but never defined (see the help page).
  9. ^ Cite error: The named reference Ertel2014 was invoked but never defined (see the help page).
  10. ^ a b Cite error: The named reference Schroeder2008 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).