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HD 134606
Observation data; Epoch J2000 Equinox J2000
Constellation	Apus
Right ascension	15h 15m 15.04464s
Declination	−70° 31′ 10.6449″
Apparent magnitude (V)	6.86
Characteristics
Spectral type	G6 IV
B−V color index	0.740±0.001
Astrometry
Radial velocity (Rv)	+1.94±0.12 km/s
Proper motion (μ)	RA: −177.871 mas/yr ; Dec.: −164.709 mas/yr
Parallax (π)	37.3020 ± 0.0182 mas
Distance	87.44 ± 0.04 ly ; (26.81 ± 0.01 pc)
Absolute magnitude (MV)	4.74
Details
Mass	1.046+0.070; −0.059 M☉
Radius	1.158+0.039; −0.036 R☉
Luminosity	1.161+0.071; −0.049 L☉
Surface gravity (log g)	4.330+0.044; −0.041 cgs
Temperature	5,576+86; −85 K
Metallicity [Fe/H]	+0.343+0.081; −0.084 dex
Rotation	42.0±3.9 d
Age	7.3+3.6; −3.4 Gyr
Other designations
	CD−70° 1258, GC 20455, HD 134606, HIP 74653, SAO 257257, LTT 6064, 2MASS J15151504-7031105
Database references
SIMBAD	data

HD 134606 is a yellow-hued star with a planetary system, positioned in the southern constellation of Apus. It is below the nominal limit for visibility with the naked eye, having an apparent visual magnitude of 6.86.^[2] Based upon an annual parallax shift of 37.3 mas, it is located 87.44 light-years away. The star appears to be moving further from the Earth with a heliocentric radial velocity of +1.9 km/s.^[1]

This is an evolving G-type subgiant star with a stellar classification of G6 IV^[3] and is not considered active, having a chromospheric activity index of −5.04.^[6] It has about the same^[7] mass as the Sun but is 25% more luminous.^[2] The photosphere is radiating energy at an effective temperature of 5,614 K.^[7] It has a higher than solar metallicity – a term astronomers use to describe the abundance of elements other than hydrogen and helium.^[7]

There is a companion star of spectral type M3V at a separation of ~1500 AU, designated L 72-1.^[8]^[4] This companion presents a bimodal distribution of the Gaia DR3 G-band light-curve, indicating that it is a close binary.^[9]

Planetary system

The discovery of a planetary system orbiting HD 134606 was announced in 2011 following an eight-year survey carried out at the La Silla Observatory in Chile. The detection was made via the radial velocity method using the HARPS instrument. Applying a Keplerian fit to the data suggests the presence of three planets in moderately eccentric orbits.^[10] None of the planetary orbits displays a mean motion resonance with the others.^[11]

The system was updated by a 2024 study, which confirmed the three previously reported planets, though with a longer period for planet d, and detected two new ones. While all five planets are very likely to be real, the study advises caution regarding planet f due to the similarity of its period to the lunar cycle. The five planets range from super-Earth to super-Neptune mass, and the outermost, HD 134606 d, is a small gas giant orbiting within the habitable zone that may be a candidate for future space-based direct imaging missions. A long-period radial velocity trend was also detected, suggesting the presence of a distant sixth substellar companion of some kind.^[4]

The HD 134606 planetary system^[4]
Companion (in order from star)	Mass	Semimajor axis (AU)	Orbital period (days)	Eccentricity	Inclination	Radius
e	≥2.34+0.35 −0.34 $M$ _🜨	0.0527+0.0011 −0.0012	4.3203+0.00051 −0.00047	0.2+0.14 −0.13	—	—
b	≥9.09+0.64 −0.63 $M$ _🜨	0.1046+0.0023 −0.0024	12.089+0.0016 −0.0015	0.092+0.054 −0.053	—	—
f	≥5.63+0.72 −0.69 $M$ _🜨	0.1784+0.0039 −0.0041	26.915±0.016	0.081+0.1 −0.059	—	—
c	≥11.31+1.0 −0.99 $M$ _🜨	0.3007+0.0066 −0.0069	58.883+0.041 −0.039	0.055+0.062 −0.04	—	—
d	≥44.8±2.9 $M$ _🜨	1.941+0.043 −0.046	966.5+5.3 −6.9	0.092±0.045	—	—

References

^ ^a ^b ^c ^d ^e ^f 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 ^d ^e 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 Gray, R. O.; et al. (July 2006). "Contributions to the Nearby Stars (NStars) Project: spectroscopy of stars earlier than M0 within 40 pc-The Southern Sample". The Astronomical Journal. 132 (1): 161–170. arXiv:astro-ph/0603770. Bibcode:2006AJ....132..161G. doi:10.1086/504637. S2CID 119476992.
^ ^a ^b ^c ^d Li, Zhexing; Kane, Stephen R.; Brandt, Timothy D.; Fetherolf, Tara; Robertson, Paul; Zhao, Jinglin; Dalba, Paul A.; Wittenmyer, Robert A.; Butler, R. Paul (April 2024). "Revised Architecture and Two New Super-Earths in the HD 134606 Planetary System". The Astronomical Journal. 167 (4): 155. arXiv:2401.17415. Bibcode:2024AJ....167..155L. doi:10.3847/1538-3881/ad2461.
^ "HD 134606". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved October 20, 2018.
^ Jenkins, J. S.; et al. (October 2006), "An activity catalogue of southern stars", Monthly Notices of the Royal Astronomical Society, 372 (1): 163–173, arXiv:astro-ph/0607336, Bibcode:2006MNRAS.372..163J, doi:10.1111/j.1365-2966.2006.10811.x, S2CID 17524675.
^ ^a ^b ^c Tsantaki, M.; et al. (July 2013). "Deriving precise parameters for cool solar-type stars. Optimizing the iron line list". Astronomy & Astrophysics. 555: A150. arXiv:1304.6639. Bibcode:2013A&A...555A.150T. doi:10.1051/0004-6361/201321103. S2CID 118388752.
^ "L 72-1". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 1 February 2024.
^ González-Payo, J.; Caballero, J. A.; Gorgas, J.; Cortés-Contreras, M.; Gálvez-Ortiz, M.-C.; Cifuentes, C. (2024-07-29). "Multiplicity of stars with planets in the solar neighbourhood". arXiv:2407.20138 [astro-ph.SR].
^ Mayor, M.; Marmier, M.; Lovis, C.; Udry, S.; Ségransan, D.; Pepe, F.; Benz, W.; Bertaux, J.-L.; Bouchy, F.; Dumusque, X.; Lo Curto, G.; Mordasini, C.; Queloz, D.; Santos, N. C. (September 13, 2011), The HARPS search for southern extra-solar planets XXXIV. Occurrence, mass distribution and orbital properties of super-Earths and Neptune-mass planets, arXiv:1109.2497
^ Giuppone, C. A.; et al. (December 2013), "A semi-empirical stability criterion for real planetary systems with eccentric orbits", Monthly Notices of the Royal Astronomical Society, 436 (4): 3547–3556, arXiv:1309.6861, Bibcode:2013MNRAS.436.3547G, doi:10.1093/mnras/stt1831