BD+20 2457

BD+20°2457
Observation data; Epoch J2000.0 Equinox J2000.0
Constellation	Leo
Right ascension	10h 16m 44.8635s
Declination	+19° 53′ 28.974″
Apparent magnitude (V)	9.75
Characteristics
Spectral type	K2II
B−V color index	1.18
Variable type	none
Astrometry
Proper motion (μ)	RA: –35.20 mas/yr ; Dec.: –31.70 mas/yr
Parallax (π)	5.00 ± 3.33 mas
Distance	650 ± 330 ly ; (200 ± 100 pc)
Details
Mass	2.8 ± 1.5 M☉
Radius	49 R☉
Luminosity	624 L☉
Surface gravity (log g)	2.5 cgs
Temperature	4127 ± 17 K
Metallicity	–1.00 ± 0.07
Other designations
	PPM 127264
Database references
SIMBAD	data
Exoplanet Archive	data

BD+20°2457 is a 10th magnitude K-type bright giant star located between 320 and 980 light years away in the constellation of Leo. This star is very metal-poor, containing only 10% as enriched with elements heavier than hydrogen and helium as our sun, almost classifying this as a population II star. On June 10, 2009, two planets were announced to be orbiting the star, with minimum masses 21.4 and 12.5 times the mass of Jupiter and orbital periods of 380 and 622 days for the inner and outer planets respectively.^[1] A dynamical analysis reveals that the proposed system is unstable on astronomically-short timescales and so the suggested planetary configuration is unlikely to be correct: further data is needed to determine a physically-plausible explanation for the radial velocity variations.^[2]

References

^ ^a ^b ^c ^d Niedzielski, A.; et al. (2009). "Substellar-mass Companions to the K-dwarf BD+14 4559 and the K-giants HD 240210 and BD+20 2457". The Astrophysical Journal. 707 (1): 768–777. arXiv:0906.1804. Bibcode:2009ApJ...707..768N. doi:10.1088/0004-637X/707/1/768.
^ Horner, J.; Wittenmyer, R. A.; Hinse, T. C.; Marshall, J. P. (2014). "A dynamical investigation of the proposed BD +20 2457 system". Monthly Notices of the Royal Astronomical Society. 439 (1): 1176–1181. arXiv:1401.2793. Bibcode:2014MNRAS.439.1176H. doi:10.1093/mnras/stu081.

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[Niedzielski2009-1] Niedzielski, A.; et al. (2009). "Substellar-mass Companions to the K-dwarf BD+14 4559 and the K-giants HD 240210 and BD+20 2457". The Astrophysical Journal. 707 (1): 768–777. arXiv:0906.1804. Bibcode:2009ApJ...707..768N. doi:10.1088/0004-637X/707/1/768.

[Horner2014-2] Horner, J.; Wittenmyer, R. A.; Hinse, T. C.; Marshall, J. P. (2014). "A dynamical investigation of the proposed BD +20 2457 system". Monthly Notices of the Royal Astronomical Society. 439 (1): 1176–1181. arXiv:1401.2793. Bibcode:2014MNRAS.439.1176H. doi:10.1093/mnras/stu081.

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