Chi2 Hydrae

For other stars with this Bayer designation, see χ Hydrae
Chi2 Hydrae

A light curve for Chi2 Hydrae, plotted from TESS data[1]
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Hydra
Right ascension 11h 05m 57.57000s[2]
Declination −27° 17′ 16.2727″[2]
Apparent magnitude (V) 5.65 - 5.94[3] (5.85 + 7.57)[4]
Characteristics
Spectral type B8 III-IVe + B8.5 V[5]
U−B color index −0.26[6]
B−V color index −0.06[6]
Variable type Algol (detached)[3]
Astrometry
Radial velocity (Rv)+30.6±0.9[7] km/s
Proper motion (μ) RA: +34.417[2] mas/yr
Dec.: −16.477[2] mas/yr
Parallax (π)4.7616 ± 0.0652 mas[2]
Distance685 ± 9 ly
(210 ± 3 pc)
Orbit[8]
Period (P)2.2677 d
Eccentricity (e)0.00
Periastron epoch (T)2439925.545 JD
Argument of periastron (ω)
(secondary)		0.00°
Semi-amplitude (K1)
(primary)		123.3 km/s
Semi-amplitude (K2)
(secondary)		168.9 km/s
Details[9]
χ Lyr A
Mass3.605±0.078 M☉
Radius4.391±0.039 R☉
Luminosity344[10] L☉
Surface gravity (log g)3.65[11] cgs
Temperature11,750±190 K
Rotational velocity (v sin i)112±10[4] km/s
Age158[4] Myr
χ Lyr B
Mass2.632±0.049 M☉
Radius2.160±0.030 R☉
Luminosity66[10] L☉
Surface gravity (log g)4.23[4] cgs
Temperature11,100±230 K
Rotational velocity (v sin i)60±6[4] km/s
Other designations
χ Lyr, CD−26°8342, HD 96314, HIP 54255, HR 4317, SAO 179522[12]
Database references
SIMBADdata

Chi2 Hydrae, Latinised from χ2 Hydrae, is a binary star system in the equatorial constellation of Hydra. Based upon an annual parallax shift of 4.6 mas as seen from Earth, it is located roughly 685 light years from the Sun. It is visible to the naked eye with a combined apparent visual magnitude of about 5.7.

This is a detached eclipsing binary star system with an orbital period of 2.27 days and an essentially circular orbit having a measured eccentricity of 0.00.[8] The eclipse of the primary by the secondary component reduces the visual magnitude of the system by 0.29, while the eclipse of the secondary diminishes the magnitude by 0.27.[5]

The primary, component A, is a magnitude 5.85 B-type star with a stellar classification of B8 III-IVe,[4] suggesting it may be part way along the path of evolving into a giant star from a subgiant. It has about 3.6 times the mass of the Sun and 4.4 times the Sun's radius,[9] although it may be tidally deformed since its radius is 86%[10] of the Roche radius.[13] With an estimated age of 158 million years, it has a projected rotational velocity of 112 km/s.[4]

Component B is a magnitude 7.57[4] B-type main sequence star with a class of B8.5 V.[5] It has 2.6 times the Sun's mass and 2.16 times the radius of the Sun. The star is filling 60% of its Roche radius.[10]

  1. ^ Cite error: The named reference MAST was invoked but never defined (see the help page).
  2. ^ a b c d e Cite error: The named reference dr3 was invoked but never defined (see the help page).
  3. ^ a b Cite error: The named reference gcvs was invoked but never defined (see the help page).
  4. ^ a b c d e f g h Cite error: The named reference Torres2010 was invoked but never defined (see the help page).
  5. ^ a b c Cite error: The named reference Malkov2006 was invoked but never defined (see the help page).
  6. ^ a b Cite error: The named reference Nicolet1978 was invoked but never defined (see the help page).
  7. ^ Cite error: The named reference deBruijne2012 was invoked but never defined (see the help page).
  8. ^ a b Cite error: The named reference Pourbaix2004 was invoked but never defined (see the help page).
  9. ^ a b Cite error: The named reference Brown2010 was invoked but never defined (see the help page).
  10. ^ a b c d Cite error: The named reference Eker2015 was invoked but never defined (see the help page).
  11. ^ Cite error: The named reference Jordi1997 was invoked but never defined (see the help page).
  12. ^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  13. ^ Cite error: The named reference Pols1997 was invoked but never defined (see the help page).