Gliese 176

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Gliese 176
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Taurus
Right ascension 04h 42m 55.78s[1]
Declination +18° 57′ 29.40″[1]
Apparent magnitude (V) 9.95
Characteristics
Spectral type M2V[2]
B−V color index 1.523 ± 0.025[1]
Variable type BY Dra
Astrometry
Radial velocity (Rv) 26.4105 ± 0.0004[2] km/s
Proper motion (μ) RA: 656.85 ± 3.81[1] mas/yr
Dec.: -1116.20 ± 2.49[1] mas/yr
Parallax (π) 107.83 ± 2.85[1] mas
Distance 30.2 ± 0.8 ly
(9.3 ± 0.2 pc)
Absolute magnitude (MV) 10.10 ± 0.06[2]
Details
Mass 0.50 ± 0.03[3] M
Luminosity 0.022[2] L
Temperature 3346[3] K
Metallicity [Fe/H] –0.1 ± 0.2[2] dex
Rotation 40.00 ± 0.11[2] days
Rotational velocity (v sin i) ≤0.8[2] km/s
Age 0.56 Gyr
Other designations
HD 285968, HIP 21932, Ross 33
Database references
SIMBAD data
Extrasolar Planets
Encyclopaedia
data

Gliese 176 is a red dwarf in the constellation of Taurus. Based upon parallax measurements from the Hipparcos mission, it is located approximately 30 light-years away.[1] The star is orbited by a Super-Earth.

Planetary system[edit]

A planetary companion to Gliese 176 was announced in 2008.[4] Radial velocity observations with the Hobby-Eberly Telescope (HET) showed a 10.24-day periodicity, which was interpreted as being caused by a planet. With a semi-amplitude of 11.6 m/s, its minimum mass equated to 24.5 Earth masses, or approximately 1.4 Neptune masses.

Observations with the HARPS spectrograph could not confirm the 10.24-day variation.[2] Instead, two other periodicities were detected at 8.78 and 40.0 days, with amplitudes below the HET observational errors. The 40-day variation coincides with the rotational period of the star and is therefore caused by activity, but the shorter-period variation is not explained by activity and is therefore caused by a planet. Its semi-amplitude of 4.1 m/s corresponds to a minimum mass of 8.4 Earth masses, making the planet a Super-Earth.

In an independent study, observations with Keck-HIRES also failed to confirm the 10.24-day signal.[5] An 8.77-day periodicity - corresponding to the planet announced by the HARPS team - was detected to intermediate significance, though it was not deemed significant enough to claim a planetary cause with their data alone.

The Gliese 176 system[2]
Companion
(in order from star)
Mass Semimajor axis
(AU)
Orbital period
(days)
Eccentricity Inclination Radius
b ≥8.4 M 0.066 8.7836 ± 0.0054 0

See also[edit]

References[edit]

  1. ^ a b c d e f g 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. ^ a b c d e f g h i Forveille, T.; et al. (January 2009). "The HARPS search for southern extra-solar planets. XIV. Gl 176b, a super-Earth rather than a Neptune, and at a different period". Astronomy and Astrophysics 493 (2): 645–650. arXiv:0809.0750. Bibcode:2009A&A...493..645F. doi:10.1051/0004-6361:200810557. 
  3. ^ a b Neves, V.; et al. (March 2013). "Metallicity of M dwarfs. III. Planet-metallicity and planet-stellar mass correlations of the HARPS GTO M dwarf sample". Astronomy and Astrophysics 551. arXiv:1212.3372. Bibcode:2013A&A...551A..36N. doi:10.1051/0004-6361/201220574. 
  4. ^ Endl, Michael; Cochran, William D.; Wittenmyer, Robert A.; Boss, Alan P. (February 2008). "An msini = 24 M Planetary Companion to the Nearby M Dwarf GJ 176". The Astrophysical Journal 673 (2): 1165–1168. arXiv:0709.0944. Bibcode:2008ApJ...673.1165E. doi:10.1086/524703. 
  5. ^ Butler, R. Paul; et al. (February 2009). "Nondetection of the Neptune-Mass Planet Reported Around GJ 176". The Astrophysical Journal 691 (2): 1738–1743. Bibcode:2009ApJ...691.1738B. doi:10.1088/0004-637X/691/2/1738. 

Coordinates: Sky map 04h 42m 55.78s, +18° 57′ 29.40″