HD 17156

HD 17156, named Nushagak by the IAU,[7] is a yellow subgiant star approximately 255 light-years away in the constellation of Cassiopeia. The apparent magnitude is 8.17, which means it is not visible to the naked eye but can be seen with good binoculars.[2] A search for a binary companion star using adaptive optics at the MMT Observatory was negative.[8]

HD 17156
Observation data
Epoch J2000      Equinox J2000
Constellation Cassiopeia
Right ascension  02h 49m 44.4867s[1]
Declination +71° 45′ 11.6322″[1]
Apparent magnitude (V) 8.17[2]
Characteristics
Spectral type G0IV[3]
Apparent magnitude (B) 8.76[2]
Apparent magnitude (V) 8.17[2]
Astrometry
Radial velocity (Rv)−3.15 ± 0.20[4] km/s
Proper motion (μ) RA: 90.982±0.064[1] mas/yr
Dec.: −33.197±0.062[1] mas/yr
Parallax (π)12.7776 ± 0.0389[1] mas
Distance255.3 ± 0.8 ly
(78.3 ± 0.2 pc)
Absolute magnitude (MV)3.70
Details
Mass1.275 ± 0.018[5] M☉
Radius1.5007 ± 0.0076[5] R☉
Temperature6079 ± 80[6] K
Metallicity [Fe/H]0.24 ± 0.05[6] dex
Age3.37 +0.20
−0.47[5] Gyr
Other designations
Nushagak, BD+71°171, HIP 13192, SAO 4737, GSC 04321-01320, PPM 5099, TYC 4321-1320-1, AG+71 95 [2]
Database references
SIMBADdata
Extrasolar Planets
Encyclopaedia		data

The star is more massive and larger than our Sun while Its absolute magnitude of 3.70 and spectral type of G0, show that it is both hotter and more luminous. Based on asteroseismic density constraints and stellar isochrones, it was found that the age is 3.37 +0.20
−0.47 billion years making it about two thirds as old as the sun. Spectral observations show that the star is metal-rich.[3][5]

An extrasolar planet, HD 17156 b, was discovered with the radial velocity method in 2007, and subsequently was observed to transit the star. At the time it was the transiting planet with the longest period.[3][9]

Name

The star was given the name Nushagak by the IAU, chosen by United States representatives for the NameExoWorlds content, with the comment that "Nushagak is a regional river near Dilingham, Alaska, which is famous for its wild salmon that sustain local Indigenous communities."[7] HD 17156 b was given the designation Mulchatna, as Mulchatna is a tributary of the Nushagak river.

Planetary system

It is the first star in Cassiopeia around which an orbiting planet was discovered (in 2007) using the radial velocity method. Later observations showed that this planet also transited the star.[9] In February 2008, a second planet, HD 17156 c, was proposed, with a 5:1 mean motion resonance to the inner planet HD 17156 b.[10]

The HD 17156 planetary system[5][11][10]
Companion
(in order from star)		 Mass Semimajor axis
(AU)		 Orbital period
(days)		 Eccentricity Inclination Radius
b 3.235±0.032 MJ 0.16278±0.00076 21.2163979 ± 0.0000159 0.6703+0.0014
−0.0013		 — —
c (unconfirmed) 0.063 MJ 0.481 111.314 0.136 — —
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See also
  • List of stars with extrasolar planets

References
  1. Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
  2. "HD 17156". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2009-05-20.
  3. Fischer, Debra A.; et al. (2007). "Five Intermediate-Period Planets from the N2K Sample". The Astrophysical Journal. 669 (2): 1336–1344. arXiv:0704.1191. Bibcode:2007ApJ...669.1336F. doi:10.1086/521869.
  4. Barbieri, M.; et al. (2009). "Characterization of the HD 17156 planetary system". Astronomy and Astrophysics. 503 (2): 601–612. arXiv:0812.0785. Bibcode:2009A&A...503..601B. doi:10.1051/0004-6361/200811466.
  5. Nutzman, Philip; et al. (2011). "Precise Estimates of the Physical Parameters for the Exoplanet System HD 17156 Enabled by Hubble Space Telescope Fine Guidance Sensor Transit and Asteroseismic Observations". The Astrophysical Journal. 726 (1). 3. arXiv:1011.0440. Bibcode:2011ApJ...726....3N. doi:10.1088/0004-637X/726/1/3.
  6. Winn, Joshua N.; et al. (2009). "The Transit Light Curve Project. X. A Christmas Transit of HD 17156b". The Astrophysical Journal. 693 (1): 794–803. arXiv:0810.4725. Bibcode:2009ApJ...693..794W. doi:10.1088/0004-637X/693/1/794.
  7. "Approved names (§ United States of America)". Name Exo Worlds. IAU. Retrieved 19 December 2019.
  8. Adams, E. R.; et al. (2013). "Adaptive Optics Images. II. 12 Kepler Objects of Interest and 15 Confirmed Transiting Planets". The Astronomical Journal. 146 (1). 9. arXiv:1305.6548. Bibcode:2013AJ....146....9A. doi:10.1088/0004-6256/146/1/9.
  9. Barbieri, M.; et al. (2007). "HD 17156b: A Transiting Planet with a 21.2 Day Period and an Eccentric Orbit". Astronomy and Astrophysics Letters. 476 (2): L13–L16. arXiv:0710.0898. Bibcode:2007A&A...476L..13B. doi:10.1051/0004-6361:20078787.
  10. Short, Donald; et al. (2008). "Orbital Dynamics Of A Possible Second Planet In HD 17156". arXiv:0803.2935. Bibcode:2008arXiv0803.2935S. Cite journal requires |journal= (help)
  11. Bonomo, A. S.; et al. (2017). "The GAPS Programme with HARPS-N at TNG . XIV. Investigating giant planet migration history via improved eccentricity and mass determination for 231 transiting planets". Astronomy and Astrophysics. 602. A107. arXiv:1704.00373. Bibcode:2017A&A...602A.107B. doi:10.1051/0004-6361/201629882.

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