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,[1] as determined through parallax measurements. It has been formally named Kamuy by the IAU,[8] after a spiritual or divine being in Ainu mythology. With an apparent magnitude of 6.57,[9] 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.[1]
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Corona Borealis |
| Right ascension | 16h 10m 03.91440s[1] |
| Declination | +26° 44′ 33.8932″[1] |
| Apparent magnitude (V) | 6.57[2] |
| Characteristics | |
| Evolutionary stage | Giant[3] |
| Spectral type | K0 III[4] |
| B−V color index | +1.037±0.005[2] |
| Astrometry | |
| Radial velocity (Rv) | −3.25±0.12[1] km/s |
| Proper motion (μ) | RA: −18.354 mas/yr[1] Dec.: +36.856 mas/yr[1] |
| Parallax (π) | 7.3867 ± 0.0153 mas[1] |
| Distance | 441.5 ± 0.9 ly (135.4 ± 0.3 pc) |
| Absolute magnitude (MV) | 1.09[2] |
| Details | |
| Mass | 1.57±0.46[3] M☉ |
| Radius | 10.49+0.13 −0.41[5] R☉ |
| Luminosity | 49.97±0.27[5] L☉ |
| Surface gravity (log g) | 2.72±0.11[3] cgs |
| Temperature | 4,738+95 −28[5] K |
| Metallicity [Fe/H] | −0.177[6] dex |
| Age | 5.2[6] Gyr |
| Other designations | |
| Database references | |
| SIMBAD | data |
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.[10] With an age of 5.2 billion years old,[6] it is around 1.57 times as massive as the Sun[3] 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.[5]
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
editHD 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.[9]
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.[8]
| 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
edit- ^ a b c d e f g Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
- ^ a b c 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.
- ^ a b c d Feuillet, Diane K.; et al. (2016). "Determining Ages of APOGEE Giants with Known Distances". The Astrophysical Journal. 817 (1): 40. arXiv:1511.04088. Bibcode:2016ApJ...817...40F. doi:10.3847/0004-637X/817/1/40. S2CID 118675933.
- ^ a b Heard, John Frederick (1956). "The radial velocities, spectral classes and photographic magnitudes of 1041 late-type stars". Publications of the David Dunlap Observatory. 2 (4). University of Toronto, Toronto, Canada: University of Toronto Press: 107–143. Bibcode:1956PDDO....2..107H.
- ^ a b c d 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.
- ^ a b c Ting, Yuan-Sen; Rix, Hans-Walter (2019). "The Vertical Motion History of Disk Stars throughout the Galaxy". The Astrophysical Journal. 878 (1): 21. arXiv:1808.03278. Bibcode:2019ApJ...878...21T. doi:10.3847/1538-4357/ab1ea5. S2CID 119211560.
- ^ "HD 145457". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2020-02-04.
- ^ a b "Japan". NameExoworlds. IAU. Retrieved 2019-12-30.
- ^ a b 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. arXiv:1005.2860. Bibcode:2010PASJ...62.1063S. doi:10.1093/pasj/62.4.1063. S2CID 119113950.
- ^ Kumar, Yerra Bharat; Reddy, Bacham E.; Lambert, David L. (2011). "Origin of Lithium Enrichment in K Giants". The Astrophysical Journal. 730 (1): L12. arXiv:1102.2299. Bibcode:2011ApJ...730L..12K. doi:10.1088/2041-8205/730/1/L12. S2CID 118383042.
- ^ 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. Bibcode:2020AJ....159....9H. doi:10.3847/1538-3881/ab5528.
- ^ Teng, Huan-Yu; Sato, Bun'ei; 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. arXiv:2308.05343. Bibcode:2023PASJ...75.1030T. doi:10.1093/pasj/psad056.