Epsilon Hydri

From Wikipedia, the free encyclopedia
Jump to: navigation, search
ε Hydri
Hydrus constellation map.svg
Red circle.svg

Location of ε Hydri (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Hydrus
Right ascension 02h 39m 35.36121s[1]
Declination −68° 16′ 01.0103″[1]
Apparent magnitude (V) 4.12[2]
Spectral type B9Va[2]
U−B color index -0.14[3]
B−V color index -0.06[3]
Radial velocity (Rv) +13.60[4] km/s
Proper motion (μ) RA: +87.30[1] mas/yr
Dec.: +0.09[1] mas/yr
Parallax (π) 21.48 ± 0.09[1] mas
Distance 151.8 ± 0.6 ly
(46.6 ± 0.2 pc)
Absolute magnitude (MV) 0.78[2]
Mass 2.64[5] M
Radius 2.2[6] R
Luminosity 60[5] L
Surface gravity (log g) 4.33[7] cgs
Temperature 10,970[7] K
Rotational velocity (v sin i) 96[5] km/s
Other designations
FK5 95, GC 3240, HIP 12394, HR 806, HD 16978, SAO 248621
Database references

Epsilon Hydri (ε Hyi) is a class B9V[2] (blue main-sequence) star in the constellation Hydrus. Its apparent magnitude is 4.12[2] and it is approximately 151.8 light years away based on parallax.[1]


  1. ^ a b c d e f Van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653. arXiv:0708.1752Freely accessible. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357.  Vizier catalog entry
  2. ^ a b c d e Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters. 38 (5): 331. arXiv:1108.4971Freely accessible. Bibcode:2012AstL...38..331A. doi:10.1134/S1063773712050015.  Vizier catalog entry
  3. ^ a b Mallama, A. (2014). "Sloan Magnitudes for the Brightest Stars". The Journal of the American Association of Variable Star Observers. 42: 443. Bibcode:2014JAVSO..42..443M. Vizier catalog entry
  4. ^ Gontcharov, G. A. (2006). "Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system". Astronomy Letters. 32 (11): 759. Bibcode:2006AstL...32..759G. doi:10.1134/S1063773706110065. 
  5. ^ a b c Zorec, J.; Royer, F. (2012). "Rotational velocities of A-type stars". Astronomy & Astrophysics. 537: A120. arXiv:1201.2052Freely accessible. Bibcode:2012A&A...537A.120Z. doi:10.1051/0004-6361/201117691.  Vizier catalog entry
  6. ^ Allende Prieto, C.; Lambert, D. L. (1999). "Fundamental parameters of nearby stars from the comparison with evolutionary calculations: Masses, radii and effective temperatures". Astronomy and Astrophysics. 352: 555. arXiv:astro-ph/9911002Freely accessible. Bibcode:1999A&A...352..555A.  Vizier catalog entry
  7. ^ a b David, Trevor J.; Hillenbrand, Lynne A. (2015). "The Ages of Early-Type Stars: Strömgren Photometric Methods Calibrated, Validated, Tested, and Applied to Hosts and Prospective Hosts of Directly Imaged Exoplanets". The Astrophysical Journal. 804 (2): 146. arXiv:1501.03154Freely accessible. Bibcode:2015ApJ...804..146D. doi:10.1088/0004-637X/804/2/146.  Vizier catalog entry