Beta Hydrae

β Hydrae

A light curve for Beta Hydrae plotted from TESS data[1]
Location of β Hydrae (circled)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Hydra
Right ascension 11h 52m 54.52149s[2]
Declination −33° 54′ 29.2672″[2]
Apparent magnitude (V) 4.29 (combined)[3] (4.67 + 5.47)[4]
Characteristics
Spectral type B9IIIp Si[5] + ?
kB8hB8HeA0VSi[6]
U−B color index −0.34[3]
B−V color index −0.100±0.003[3]
R−I color index −0.08[7]
Variable type α2 CVn[8]
Astrometry
Radial velocity (Rv)−1.0±3.7[3] km/s
Proper motion (μ) RA: −56.56[2] mas/yr
Dec.: +0.19[2] mas/yr
Parallax (π)10.53 ± 0.60 mas[2]
Distance310 ± 20 ly
(95 ± 5 pc)
Absolute magnitude (MV)−0.59[3]
Details
A
Mass3.36±0.15[9] M☉
Radius3.89±0.08[10] R☉
Luminosity257+45
−38[11] L☉
Surface gravity (log g)2.52±0.03[10] cgs
Temperature10,980±110[10] K
Rotation2.35666±0.00002 d[12]
Age178+62
−12[11] Myr
B
Mass~3[13] M☉
Other designations
Beta Hydrae, Beta Hya, HJ 4478AB, β Hya, CD−33°8018, CPD−33°3159, GC 16258, HD 103192, HIP 57936, HR 4552, SAO 202901, PPM 289465, CCDM J11529-3354AB, WDS 11529-3354AB[14]
Database references
SIMBADdata
A
B

Beta Hydrae, Latinized from β Hydrae, is a double star in the equatorial constellation of Hydra.[14] Historically, Beta Hydrae was designated 28 Crateris, but the latter fell out of use when the IAU defined the permanent constellation boundaries in 1930.[15] The system is faintly visible to the naked eye with a combined apparent visual magnitude that ranges around 4.29.[3] It is located at a distance of approximately 310 light years from the Sun based on parallax.

The double nature of this system was first reported by English astronomer John Herschel in 1834.[16] The brighter primary, designated component A, has an average visual magnitude of 4.67, while the secondary, component B, is of magnitude 5.47. As of 2002, the secondary is located at an angular separation of 0.65 arcseconds from the primary, along a position angle of 28.5°.[4]

The brighter component is an α2 Canum Venaticorum variable that changes in brightness with a period of 2.344 days and an amplitude of 0.04 in visual magnitude.[8] It is a magnetic chemically-peculiar star[17] with an average quadratic field strength of (−206±68)×10−4 T.[12] The star is around 178 million years old[11] with 3.4[9] times the mass of the Sun and 3.9[10] times the Sun's radius. On average, it is radiating 257[11] times the luminosity of the Sun from its photosphere at an effective temperature of 10,980 K.[10]

In 1972, M. R. Molnar found a stellar classification of B9IIIp Si for β Hydrae A, showing an abundance anomaly for silicon.[5] R. F. Garrison and R. O. Gray assigned it a class of kB8hB8HeA0VSi in 1994.[6] This notation indicates the Calcium K line matches a star of class B8, the hydrogen lines also match a B8 spectrum, while the helium lines match an A-type main-sequence star of class A0V.[18] They noted that the hydrogen lines have "curious rounded profiles".[6] Later studies list abundance anomalies of silicon, chromium, and strontium.[19]

  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 vanLeeuwen2007 was invoked but never defined (see the help page).
  3. ^ a b c d e f Cite error: The named reference Anderson_Francis_2012 was invoked but never defined (see the help page).
  4. ^ a b Cite error: The named reference Fabricius_et_al_2002 was invoked but never defined (see the help page).
  5. ^ a b Cite error: The named reference Molnar1972 was invoked but never defined (see the help page).
  6. ^ a b c Cite error: The named reference Garrison_Gray_1994 was invoked but never defined (see the help page).
  7. ^ Cite error: The named reference bsc1 was invoked but never defined (see the help page).
  8. ^ a b Cite error: The named reference Samus_et_al_2017 was invoked but never defined (see the help page).
  9. ^ a b Cite error: The named reference aaa334_181 was invoked but never defined (see the help page).
  10. ^ a b c d e Cite error: The named reference Arcos_et_al_2018 was invoked but never defined (see the help page).
  11. ^ a b c d Cite error: The named reference Sikora_et_al_2019 was invoked but never defined (see the help page).
  12. ^ a b Cite error: The named reference Sikora_et_al_2019b was invoked but never defined (see the help page).
  13. ^ Cite error: The named reference kaler was invoked but never defined (see the help page).
  14. ^ a b Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  15. ^ Cite error: The named reference Wagman1987 was invoked but never defined (see the help page).
  16. ^ Cite error: The named reference Mason_et_al_2014 was invoked but never defined (see the help page).
  17. ^ Cite error: The named reference Bychkov_et_al_2003 was invoked but never defined (see the help page).
  18. ^ Cite error: The named reference Gray_Corbally_2009 was invoked but never defined (see the help page).
  19. ^ Cite error: The named reference Mikulášek2007 was invoked but never defined (see the help page).