HD 96700

HD 96700 is the Henry Draper Catalogue designation for a star in the equatorial constellation of Hydra. It has an apparent visual magnitude of 6.51,[2] which puts it below the limit that can be seen with the naked eye by a typical observer.[8] (According to the Bortle scale, it is possible for some observers to see it from dark rural skies.) Based upon measurements made by the Hipparcos spacecraft, this star is around 84 light years away from the Sun.[1]

HD 96700
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Hydra
Right ascension 11h 07m 54.42699s[1]
Declination −30° 10′ 28.4381″[1]
Apparent magnitude (V) 6.51[2]
Characteristics
Spectral type G0 V[3]
B−V color index 0.606[2]
Astrometry
Radial velocity (Rv)12.839 ± 0.0105[2] km/s
Proper motion (μ) RA: −505.21[1] mas/yr
Dec.: −131.42[1] mas/yr
Parallax (π)38.98 ± 0.47[1] mas
Distance84 ± 1 ly
(25.7 ± 0.3 pc)
Details
Mass0.96[4] M☉
Radius0.96 or 1.1[5] R☉
Surface gravity (log g)4.36[3] cgs
Temperature5,879[3] K
Metallicity [Fe/H]−0.14[3] dex
Age11.9[6] Gyr
Other designations
CD−29° 8875, GJ 412.2, HD 96700, HIP 54400, HR 4328, SAO 179558.[7]
Database references
SIMBADdata

This is considered a high proper motion star, shifting its position across the celestial sphere at a rate of 0.52 arc seconds per year, along a position angle of 255.21°.[9] It is a member of the thin disk population of stars and is orbiting the galactic core at a mean galactocentric distance of 23.4 kly (7.17 kpc) with an orbital eccentricity 0.16. The inclination of its galactic orbit carries it no more than 950 ly (290 pc) away from the galactic plane.[10]

HD 96700 is a G-type main sequence star with a stellar classification of G0 V.[3] It has a slightly lower mass than the Sun[4] and a lower metallicity.[3] The estimated size is similar to the Sun, ranging from 96% to 110% depending on the method used.[5] The effective temperature of the star's outer atmosphere is 5,879 K,[3] giving it the yellow-hued glow of a G-type star.[11] It appears to be much older than the Sun, with age estimates ranging up to 11.9 billion years.[6]

The survey in 2015 have ruled out the existence of any additional stellar companions at projected distances from 7 to 209 astronomical units.[12]

Planetary system

Two planetary companions have been discovered by the HARP instrument, which measures variations in the star's radial velocity that are presumed to be caused by gravitational perturbations from orbiting objects. The innermost planet, HD 96700 b, is orbiting close to the star at a distance of roughly 0.08 AU with a brief orbital period of 8.13 days. It has at least nine times the mass of the Earth, and so may be a Neptune-like planet. But until astronomers can determine the orbital inclination or directly image the planet, there is no way to know for certain its actual mass.[13]

The second companion, HD 96700 c, is orbiting at roughly the same distance as Mercury from the Sun, with a semimajor axis of 0.42 AU and a period of around 103 days. It may have a relatively high eccentricity of 0.4. This object has at least 13 times the mass of the Earth.[13]

The HD 96700 planetary system[13]
Companion
(in order from star)		 Mass Semimajor axis
(AU)		 Orbital period
(days)		 Eccentricity Inclination Radius
b ≥ 9.03 ± 0.63 M⊕ 0.0774 ± 0.0012 8.1256 ± 0.0013 0.10 ± 0.05 — —
c ≥ 12.76 ± 1.63 M⊕ 0.422 ± 0.007 103.49 ± 0.58 0.37 ± 0.19 — —

References
  1. van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357.
  2. Soubiran, C.; et al. (April 2013), "The catalogue of radial velocity standard stars for Gaia. I. Pre-launch release", Astronomy & Astrophysics, 552: 11, arXiv:1302.1905, Bibcode:2013A&A...552A..64S, doi:10.1051/0004-6361/201220927, A64.
  3. Gray, R. O.; et al. (July 2006), "Contributions to the Nearby Stars (NStars) Project: spectroscopy of stars earlier than M0 within 40 pc-The Southern Sample", The Astronomical Journal, 132 (1): 161–170, arXiv:astro-ph/0603770, Bibcode:2006AJ....132..161G, doi:10.1086/504637.
  4. Santos, N. C.; et al. (August 2013), "SWEET-Cat: A catalogue of parameters for Stars With ExoplanETs. I. New atmospheric parameters and masses for 48 stars with planets", Astronomy & Astrophysics, 556: 11, arXiv:1307.0354, Bibcode:2013A&A...556A.150S, doi:10.1051/0004-6361/201321286, A150.
  5. Pasinetti Fracassini, L. E.; et al. (2001), "Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS) - Third edition - Comments and statistics", Astronomy & Astrophysics, 367: 521–24, arXiv:astro-ph/0012289, Bibcode:2001A&A...367..521P, doi:10.1051/0004-6361:20000451.
  6. Holmberg, J.; Nordström, B.; Andersen, J. (July 2009), "The Geneva-Copenhagen survey of the solar neighbourhood. III. Improved distances, ages, and kinematics", Astronomy and Astrophysics, 501 (3): 941–947, arXiv:0811.3982, Bibcode:2009A&A...501..941H, doi:10.1051/0004-6361/200811191.
  7. "HD 96700". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2015-12-07.
  8. Weaver, Harold F. (October 1947), "The Visibility of Stars Without Optical Aid", Publications of the Astronomical Society of the Pacific, 59 (350): 232, Bibcode:1947PASP...59..232W, doi:10.1086/125956.
  9. Bakos, Gáspár Á.; et al. (July 2002), "Revised Coordinates and Proper Motions of the Stars in the Luyten Half-Second Catalog", The Astrophysical Journal Supplement Series, 141 (1): 187–193, arXiv:astro-ph/0202164, Bibcode:2002ApJS..141..187B, doi:10.1086/340115.
  10. Ibukiyama, A.; Arimoto, N. (November 2002), "HIPPARCOS age-metallicity relation of the solar neighbourhood disc stars", Astronomy and Astrophysics, 394: 927–941, arXiv:astro-ph/0207108, Bibcode:2002A&A...394..927I, doi:10.1051/0004-6361:20021157.
  11. "The Colour of Stars", Australia Telescope, Outreach and Education, Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, archived from the original on March 10, 2012, retrieved 2012-01-16.
  12. Mugrauer, M.; Ginski, C. (12 May 2015). "High-contrast imaging search for stellar and substellar companions of exoplanet host stars". Monthly Notices of the Royal Astronomical Society. 450 (3). doi:10.1093/mnras/stv771. Retrieved 19 June 2020.
  13. Mayor, M.; et al. (September 13, 2011), The HARPS search for southern extra-solar planets XXXIV. Occurrence, mass distribution and orbital properties of super-Earths and Neptune-mass planets, p. 23, arXiv:1109.2497, Bibcode:2011arXiv1109.2497M.
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