Astronomy:HD 145457
| Observation data Equinox J2000.0]] (ICRS) | |
|---|---|
| Constellation | Corona Borealis[1] |
| Right ascension | 16h 10m 03.91440s[2] |
| Declination | +26° 44′ 33.8932″[2] |
| Apparent magnitude (V) | 6.57[1] |
| Characteristics | |
| Evolutionary stage | red clump[3] |
| Spectral type | K0 III[4] |
| B−V color index | +1.037±0.005[1] |
| Astrometry | |
| Radial velocity (Rv) | −3.25±0.12[2] km/s |
| Proper motion (μ) | RA: −18.354[2] mas/yr Dec.: +36.856[2] mas/yr |
| Parallax (π) | 7.3867 ± 0.0153[2] mas |
| Distance | 441.5 ± 0.9 ly (135.4 ± 0.3 pc) |
| Absolute magnitude (MV) | 1.09[1] |
| Details | |
| Mass | 1.57±0.46[5] M☉ |
| Radius | 10.49+0.13 −0.41[6] R☉ |
| Luminosity | 49.97±0.27[6] L☉ |
| Surface gravity (log g) | 2.72±0.11[5] cgs |
| Temperature | 4,738+95 −28[6] K |
| Metallicity [Fe/H] | −0.177[7] dex |
| Age | 5.2[7] Gyr |
| Other designations | |
| Database references | |
| SIMBAD | data |
HD 145457 is a star located in the northern constellation of Corona Borealis (The Northern Crown) at a distance of around 442 light-years from the Sun,[2] as determined through parallax measurements. It has been formally named Kamuy by the IAU,[9] after a spiritual or divine being in Ainu mythology. With an apparent magnitude of 6.57,[10] it is barely visible to the unaided eye on dark nights clear of light pollution. It is drifting closer to the Sun with a radial velocity of −3.2 km/s.[2]
HD 145457 is an aging giant star with a stellar classification of K0 III[4] that has cooled and expanded off the main sequence after exhausting its core hydrogen supply. With the assumption that it is a helium-burning object, the properties of HD 145457 can be derived by comparison with evolutionary tracks.[3] With an age of 5.2 billion years old,[7] it is around 1.57 times as massive as the Sun[5] and has swollen to around 10 times its diameter. It is radiating 50 times the luminosity of the Sun from its enlarged photosphere at an effective temperature of 4,738 K.[6]
It is a lithium-rich giant, unusual since lithium is rapidly destroyed once a star becomes a red giant. One explanation for the excess lithium in these stars has been a recent engulfment of a planet, but it is now thought more likely to be due to nucleosynthesis in the star. It is generally assumed that these lithium-rich giants are members of the red clump, core helium burning stars at the cool end of the horizontal branch.[11]
Planetary system
HD 145457 has an exoplanetary companion called HD 145457 b discovered in 2010. 2.9 times as massive as Jupiter, it orbits about every 176 days with an orbital eccentricity of 0.112±3.1. Its semimajor axis is 0.76 AU. HD 145457 b was discovered by precise Doppler measurements with the Subaru Telescope.[10]
As part of the IAU NameExoWorlds project in 2019, HD 145457 b has been formally named Chura. The name was selected by Japan. Chura is a word in the Ryukyuan/Okinawan language meaning natural beauty.[9]
| Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (days) |
Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| b | ≥2.794+0.132 −0.117 MJ |
0.762±0.001 | 176.13+0.18 −0.20 |
0.111+0.039 −0.040 |
— | — |
References
- ↑ 1.0 1.1 1.2 1.3 Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters 38 (5): 331. doi:10.1134/S1063773712050015. Bibcode: 2012AstL...38..331A XHIP record for this object at VizieR.
- ↑ 2.0 2.1 2.2 2.3 2.4 2.5 2.6 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.
- ↑ 3.0 3.1 Kumar, Yerra Bharat; Reddy, Bacham E.; Lambert, David L. (2011). "Origin of Lithium Enrichment in K Giants". The Astrophysical Journal 730 (1): L12. doi:10.1088/2041-8205/730/1/L12. Bibcode: 2011ApJ...730L..12K.
- ↑ 4.0 4.1 Heard, John Frederick (1956). "The radial velocities, spectral classes and photographic magnitudes of 1041 late-type stars". Publications of the David Dunlap Observatory (University of Toronto, Toronto, Canada: University of Toronto Press) 2 (4): 107–143. Bibcode: 1956PDDO....2..107H.
- ↑ 5.0 5.1 5.2 Feuillet, Diane K. et al. (2016). "Determining Ages of APOGEE Giants with Known Distances". The Astrophysical Journal 817 (1): 40. doi:10.3847/0004-637X/817/1/40. Bibcode: 2016ApJ...817...40F.
- ↑ 6.0 6.1 6.2 6.3 Brown, A. G. A. (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics 616: A1. doi:10.1051/0004-6361/201833051. Bibcode: 2018A&A...616A...1G. Gaia DR2 record for this source at VizieR.
- ↑ 7.0 7.1 7.2 Ting, Yuan-Sen; Rix, Hans-Walter (2019). "The Vertical Motion History of Disk Stars throughout the Galaxy". The Astrophysical Journal 878 (1): 21. doi:10.3847/1538-4357/ab1ea5. Bibcode: 2019ApJ...878...21T.
- ↑ "HD 145457". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=HD+145457.
- ↑ 9.0 9.1 "Japan" (in en). IAU. http://www.nameexoworlds.iau.org/japan.
- ↑ 10.0 10.1 Sato, Bun'ei et al. (2010). "Substellar Companions to Evolved Intermediate-Mass Stars: HD 145457 and HD 180314". Publications of the Astronomical Society of Japan 62 (4): 1063–69. doi:10.1093/pasj/62.4.1063. Bibcode: 2010PASJ...62.1063S.
- ↑ Holanda, N.; Drake, N. A.; Pereira, C. B. (2020). "HD 150382: A Lithium-rich Star at the Early-AGB Stage?". The Astronomical Journal 159 (1): 9. doi:10.3847/1538-3881/ab5528. Bibcode: 2020AJ....159....9H.
- ↑ Teng, Huan-Yu et al. (December 2023). "Revisiting planetary systems in the Okayama Planet Search Program: A new long-period planet, RV astrometry joint analysis, and a multiplicity-metallicity trend around evolved stars". Publications of the Astronomical Society of Japan 75 (6): 1030–1071. doi:10.1093/pasj/psad056. Bibcode: 2023PASJ...75.1030T.
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