Phi2 Hydrae

For other stars with this Bayer designation, see φ Hydrae
Phi2 Hydrae
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Hydra
Right ascension 10h 36m 16.65960s[1]
Declination −16° 20′ 39.5778″[1]
Apparent magnitude (V) 6.0943[2]
Characteristics
Spectral type M1 III[3]
U−B color index +1.95[4]
B−V color index +1.64[4]
Variable type SR[5]
Astrometry
Radial velocity (Rv)+15.7±2.9[2] km/s
Proper motion (μ) RA: −29.14[1] mas/yr
Dec.: +2.31[1] mas/yr
Parallax (π)4.31 ± 0.33 mas[1]
Distance760 ± 60 ly
(230 ± 20 pc)
Absolute magnitude (MV)−0.80[6]
Details
Luminosity703[7] L☉
Temperature3,791[7] K
Other designations
φ2 Hya, BD−15°3087, HD 91880, HIP 51905, HR 4156, SAO 156093[8]
Database references
SIMBADdata

Phi2 Hydrae, Latinized from φ2 Hydrae, is a star in the constellation Hydra. It originally received the Flamsteed designation of 1 Crateris before being placed in the Hydra constellation.[9] Based upon an annual parallax shift of 4.31 mas as seen from Earth, it is located roughly 760 light years from the Sun. The star is faintly visible to the naked with an apparent visual magnitude of 6.09.[2] It forms a triangle with the fainter φ1 Hydrae and the brighter φ3 Hydrae, between μ Hydrae and ν Hydrae.

Pulsations[5]
Period
(days) 		Amplitude
(magnitude)
11.0 0.008
110.3 0.012
153.6 0.015

This is an evolved red giant star with a stellar classification of M1 III.[10] It is currently on the asymptotic giant branch,[10] and is a semiregular variable that undergoes changes in luminosity according to three pulsation periods.[5] The star is radiating an estimated 703[7] times the Sun's luminosity from its photosphere at an effective temperature of 3,791 K.[7]

Phi2 Hydrae has a faint visual companion: a magnitude 12.20 star at an angular separation of 3.50 arc seconds along a position angle of 280°, as of 1959.[11]

  1. ^ a b c d e Cite error: The named reference vanLeeuwen2007 was invoked but never defined (see the help page).
  2. ^ a b c Cite error: The named reference deBruijne2012 was invoked but never defined (see the help page).
  3. ^ Cite error: The named reference houk1978 was invoked but never defined (see the help page).
  4. ^ a b Cite error: The named reference Mermilliod1986 was invoked but never defined (see the help page).
  5. ^ a b c Cite error: The named reference tabur2009 was invoked but never defined (see the help page).
  6. ^ Cite error: The named reference Anderson2012 was invoked but never defined (see the help page).
  7. ^ a b c d Cite error: The named reference Mcdonald2012 was invoked but never defined (see the help page).
  8. ^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  9. ^ Cite error: The named reference Wagman1987 was invoked but never defined (see the help page).
  10. ^ a b Cite error: The named reference Eggen1992 was invoked but never defined (see the help page).
  11. ^ Cite error: The named reference WDSC2014 was invoked but never defined (see the help page).