HIP 57274

HIP 57274 is a star in the northern circumpolar constellation of Ursa Major with a system of three planets.[2] It is invisible to the naked eye, having an apparent visual magnitude of 8.96.[2] The distance to this system is 84.4 light years based on stellar parallax, and it is drifting further away with a radial velocity of +30 km/s.[1] The star has a relatively high rate of proper motion, traversing the celestial sphere at the rate of 0.382 arcsecond/year.[6]

HIP 57274
Observation data
Epoch J2000      Equinox J2000
Constellation Ursa Major
Right ascension 11h 44m 40.9643s[1]
Declination +30° 57′ 33.4509″[1]
Apparent magnitude (V) 8.96[2]
Characteristics
Spectral type K5 V[2]
U−B color index +1.06[3]
B−V color index +1.111±0.016[4]
Astrometry
Radial velocity (Rv)+29.76±0.35[1] km/s
Proper motion (μ) RA: −27.069±0.081[1] mas/yr
Dec.: −381.708±0.079[1] mas/yr
Parallax (π)38.6381 ± 0.0499 mas[1]
Distance84.4 ± 0.1 ly
(25.88 ± 0.03 pc)
Absolute magnitude (MV)6.89[2]
Details[2]
Mass0.73±0.05 M☉
Radius0.68±0.03 R☉
Luminosity0.19±0.01 L☉
Surface gravity (log g)4.71±0.1 cgs
Temperature4,640±100 K
Metallicity [Fe/H]+0.09±0.05 dex
Rotation45 d
Rotational velocity (v sin i)0.5±0.5 km/s
Age7.87±5 Gyr
Other designations
BD+31° 2290, Gaia DR2 4021079911593673600, GJ 439, HIP 57274, SAO 62684, LTT 13227, 2MASS J11444095+3057339[5]
Database references
SIMBADdata
ARICNSdata

This is an ordinary K-type main-sequence star with a stellar classification of K5V.[2] It appears to be older than the Sun with an age of roughly eight billion years and is spinning slowly with a projected rotational velocity of under 1 km/s. The star has 73% of the mass of the Sun and 68% of the Sun's radius. The abundance of elements heavier than helium is about the same or slightly higher than in the Sun. The star is radiating just 19% of the luminosity of the Sun from its photosphere at an effective temperature of 4,640 K.

Planetary system

The three exoplanets orbiting HIP 57274 were discovered by the radial velocity method in 2011, all of them having mass significantly greater than the Earth.[2] A 2014 search for planetary transits was unsuccessful.[7] The planetary orbits are possibly highly variable, being strongly affected by mean motion resonances.[8] The most stable region for a hypothetical super-earth within the star's habitable zone would be an orbit inside 0.37–0.56 AU from the host star.[8]

The HIP 57274 planetary system[2][8]
Companion
(in order from star)		 Mass Semimajor axis
(AU)		 Orbital period
(days)		 Eccentricity Inclination Radius
b ≥11.6±1.3 M🜨 0.0713±0.00163 8.1352±0.004 0.187±0.10 — —
c ≥0.41±0.01 MJ 0.1778±0.0041 32.03±0.02 0.05±0.02 — —
d ≥0.53±0.03 MJ 1.007±0.027 431.7±8.5 0.27±0.05 — —

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. Fischer, Debra A.; et al. (2012). "M2K. II. A Triple-planet System Orbiting HIP 57274". The Astrophysical Journal. 745 (1). 21. arXiv:1109.2926. Bibcode:2012ApJ...745...21F. doi:10.1088/0004-637X/745/1/21.
  3. Mermilliod, J.-C. (1986). "Compilation of Eggen's UBV data, transformed to UBV (unpublished)". Catalogue of Eggen's UBV Data. Bibcode:1986EgUBV........0M.
  4. Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015, S2CID 119257644.
  5. "BD+31 2290". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 28 August 2017.
  6. Lépine, Sébastien; Shara, Michael M. (March 2005). "A Catalog of Northern Stars with Annual Proper Motions Larger than 0.15" (LSPM-NORTH Catalog)". The Astronomical Journal. 129 (3): 1483–1522. arXiv:astro-ph/0412070. Bibcode:2005AJ....129.1483L. doi:10.1086/427854. S2CID 2603568.
  7. Kammer, J. A.; et al. (February 2014). "A Spitzer Search for Transits of Radial Velocity Detected Super-Earths". The Astrophysical Journal. 781 (2): 6. arXiv:1310.7952. Bibcode:2014ApJ...781..103K. doi:10.1088/0004-637X/781/2/103. S2CID 37557541. 103.
  8. Elser, S.; et al. (2013), "Super Earths and Dynamical Stability of Planetary Systems: First Parallel GPU Simulations Using GENGA", Monthly Notices of the Royal Astronomical Society, 433 (3): 2194–2205, arXiv:1305.4070, Bibcode:2013MNRAS.433.2194E, doi:10.1093/mnras/stt883
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