Astronomy:HD 121056

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Short description: Star in the constellation Centaurus
HD 121056
Observation data
Equinox J2000.0]] (ICRS)
Constellation Centaurus
Right ascension  13h 53m 52.06131s[1]
Declination −35° 18′ 51.6918″[1]
Apparent magnitude (V) 6.17[2]
Characteristics
Evolutionary stage giant star
Spectral type K0 III[3]
B−V color index 1.01[4]
Astrometry
Radial velocity (Rv)5.60±0.13[1] km/s
Proper motion (μ) RA: −295.304±0.040[1] mas/yr
Dec.: −68.458±0.058[1] mas/yr
Parallax (π)15.6261 ± 0.0418[1] mas
Distance208.7 ± 0.6 ly
(64.0 ± 0.2 pc)
Absolute magnitude (MV)+2.08[5]
Details
Mass1.60±0.18[6] M
Radius5.72[7] R
Luminosity15.8[7] L
Surface gravity (log g)3.261±0.105[2] cgs
Temperature4,867±49[2] K
Metallicity[Mg/H] 0.286±0.05 dex[2]
Metallicity [Fe/H]0.020±0.031[2] dex
Rotational velocity (v sin i)2.38±0.51[2] km/s
Age5.46[7] Gyr
Other designations
CD−34 9223, Gaia DR2 6169943210465504384, GJ 532.1, HD 121056, HIP 67851, HR 5224, TYC 7287-1874-1, 2MASS J13535209-3518517[8]
Database references
SIMBADdata

HD 121056, or HIP 67851, is an aging giant star with a pair of orbiting exoplanets located in the southern constellation of Centaurus. This star is dimly visible to the naked eye with an apparent visual magnitude of 6.17.[2] It is located at a distance of 209 light years from the Sun, based on parallax measurements, and is drifting further away with a radial velocity of 5.6 km/s.[1]

The spectrum of HD 121056 presents as an evolved K-type giant star with a stellar classification of K0 III.[9] It is presently ascending the red-giant branch, having exhausted the supply of hydrogen at its core.[4] The star is about 5.5[7] billion years old and is spinning with a projected rotational velocity of 2.4 km/s. HD 121056’s concentration of heavy elements is similar to the Sun, with a metallicity Fe/H index of 0.020±0.031, although the star is enriched in lighter rock-forming elements like magnesium and aluminum.[2] It has 1.6[6] times the mass of the Sun and has expanded to 5.72 times the Sun's radius.[7] The star is radiating 15.8[7] times the luminosity of the Sun from its enlarged photosphere at an effective temperature of 4,867 K.[2]

Planetary system

In 2014, two planets orbiting HD 121056 were discovered by the radial velocity method,[4] and were confirmed a few months later.[9] The orbits of these planets are stable on astronomical timescales,[10] although the periods are not in orbital resonance.[11] In 2022, the inclination and true mass of HD 121056 c were measured via astrometry.[12]

The planetary system configuration is favorable for direct imaging of exoplanets in the near future, being included in the top ten easiest targets in 2018.[13]

The HD 121056 planetary system[12]
Companion
(in order from star)
Mass Semimajor axis
(AU)
Orbital period
(days)
Eccentricity Inclination Radius
b ≥ 1.568+0.071
−0.072
 MJ
0.482+0.009−0.010 88.9±0.1 0.063+0.031−0.032
c 6.937+2.045−0.518 MJ 6.032+0.651−0.362 3,923.7+617.5−330.2 0.356+0.112−0.085 89.863+28.378−24.730°

References

  1. 1.0 1.1 1.2 1.3 1.4 1.5 Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940  Gaia DR3 record for this source at VizieR.
  2. 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 Hojjatpanah, S. et al. (2019). "Catalog for the ESPRESSO blind radial velocity exoplanet survey". Astronomy & Astrophysics 629: A80. doi:10.1051/0004-6361/201834729. Bibcode2019A&A...629A..80H. 
  3. Houk, N.; Swift, C. (1999). "Michigan catalogue of two-dimensional spectral types for the HD Stars". Michigan Spectral Survey 5. Bibcode1999MSS...C05....0H. 
  4. 4.0 4.1 4.2 Jones, M. I. et al. (2015). "A planetary system and a highly eccentric brown dwarf around the giant stars HIP 67851 and HIP 97233". Astronomy & Astrophysics 573: A3. doi:10.1051/0004-6361/201424771. Bibcode2015A&A...573A...3J. 
  5. Anderson, E.; Francis, Ch. (2012-05-01). "XHIP: An extended hipparcos compilation". Astronomy Letters 38 (5): 331–346. doi:10.1134/S1063773712050015. ISSN 1063-7737. Bibcode2012AstL...38..331A. 
  6. 6.0 6.1 Sousa, S. G. et al. (2018). "SWEET-Cat updated". Astronomy & Astrophysics 620: A58. doi:10.1051/0004-6361/201833350. Bibcode2018A&A...620A..58S. 
  7. 7.0 7.1 7.2 7.3 7.4 7.5 Soto, M. G. et al. (2021). "SPECIES. II. Stellar parameters of the EXPRESS giant star sample". Astronomy and Astrophysics 647: A157. doi:10.1051/0004-6361/202039357. Bibcode2021A&A...647A.157S. 
  8. "HD 121056". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=HD+121056. 
  9. 9.0 9.1 Wittenmyer, Robert A. et al. (2015). "The Pan-Pacific Planet Search. Ii. Confirmation of a Two-Planet System Around Hd 121056". The Astrophysical Journal 800 (1): 74. doi:10.1088/0004-637X/800/1/74. Bibcode2015ApJ...800...74W. 
  10. Kane, Stephen R. et al. (2019). "Predicting multiple planet stability and habitable zone companions in the TESS era". Monthly Notices of the Royal Astronomical Society 485 (4): 4703–4725. doi:10.1093/mnras/stz345. Bibcode2019MNRAS.485.4703A. 
  11. Saillenfest, M. et al. (2019). "Secular spin-axis dynamics of exoplanets". Astronomy & Astrophysics 623: A4. doi:10.1051/0004-6361/201834344. Bibcode2019A&A...623A...4S. 
  12. 12.0 12.1 Feng, Fabo et al. (August 2022). "3D Selection of 167 Substellar Companions to Nearby Stars". The Astrophysical Journal Supplement Series 262 (21): 21. doi:10.3847/1538-4365/ac7e57. Bibcode2022ApJS..262...21F. 
  13. Martinache, Frantz; Ireland, Michael J. (2018). "Kernel-nulling for a robust direct interferometric detection of extrasolar planets". Astronomy & Astrophysics 619: A87. doi:10.1051/0004-6361/201832847. Bibcode2018A&A...619A..87M. 

Coordinates: Sky map 13h 53m 52.0610s, −35° 18′ 51.6809″