HD 154857

HD 154857

Observation data Epoch J2000      Equinox J2000
Constellation	Ara
Right ascension	17^h 11^m 15.72180^s[1]
Declination	−56° 40′ 50.8706″[1]
Apparent magnitude (V)	7.25[2]
Characteristics
Spectral type	G5IV-V[3]
B−V color index	0.699±0.001[2]
Variable type	Constant[4]
Astrometry
Radial velocity (Rv)	+28.06±0.15[1] km/s
Proper motion (μ)	RA: 87.585[1] mas/yr Dec.: −55.891[1] mas/yr
Parallax (π)	15.7321 ± 0.0385 mas[1]
Distance	207.3 ± 0.5 ly (63.6 ± 0.2 pc)
Absolute magnitude (MV)	3.07[3]
Details
Mass	1.718+0.03 −0.022[5] M☉
Radius	2.1±0.1[4] R☉
Luminosity	4.4±0.3[4] L☉
Surface gravity (log g)	3.83±0.03[4] cgs
Temperature	5,740±46[4] K
Metallicity [Fe/H]	−0.26±0.01[6] dex
Rotational velocity (v sin i)	1.44±0.50[7] km/s
Age	5.8±0.5[4] Gyr
Other designations
CD−56° 6717, CPD−56° 8059, GC 23146, HD 154857, HIP 84069, SAO 244491, PPM 345752, TYC 8735-1682-1, GSC 08735-01682[8]
Database references
SIMBAD	data

HD 154857 is a star with two exoplanetary companions in the southern constellation of Ara. It is too dim to be visible with the naked eye having an apparent visual magnitude of 7.25.[2] The star is located at a distance of 207 light years from the Sun based on parallax measurements, and is drifting further away with a radial velocity of +28 km/s.[1]

This is a G-type star with a stellar classification of G5IV-V.[3] The absolute magnitude of this star is two magnitudes above the main sequence, which suggests that the star is evolving toward the subgiant stage.[3] It is a metal-poor thin disk star[9] approximately six billion years old and is chromopherically quiet although not in a Maunder Minimum state.[4] The star is larger, more massive, and more luminous than the Sun. It is spinning with a projected rotational velocity of 1.4 km/s.[7]

Planetary system

The discovery of one confirmed and one unconfirmed Jovian exoplanet was reported in 2004[3] and 2007[10] respectively. The former planet HD 154857 b has mass >1.8 times that of Jupiter. It orbits the star 20% further than Earth-Sun distance, taking 409 days with 47% eccentricity. The additional object (HD 154857 c) was confirmed as a planetary companion in January 2014.[5]

The HD 154857 planetary system[5]

Companion (in order from star)	Mass	Semimajor axis (AU)	Orbital period (days)	Eccentricity	Inclination	Radius
b	≥ 2.24±0.05 MJ	1.291±0.008	408.6±0.5	0.06±0.05	—	—
c	≥ 2.58±0.16 MJ	5.36±0.09	3,452±105	0.06±0.05	—	—

See also

• List of extrasolar planets

References

1. 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.
2. 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.
3. McCarthy, Chris; et al. (2004). "Multiple Companions to HD 154857 and HD 160691". The Astrophysical Journal. 617 (1): 575–579. arXiv:astro-ph/0409335. Bibcode:2004ApJ...617..575M. doi:10.1086/425214. S2CID 119446133.
4. Bonfanti, A.; Ortolani, S.; Nascimbeni, V. (2016). "Age consistency between exoplanet hosts and field stars". Astronomy & Astrophysics. 585: 14. arXiv:1511.01744. Bibcode:2016A&A...585A...5B. doi:10.1051/0004-6361/201527297. S2CID 53971692. A5.
5. Wittenmyer, Robert A.; et al. (March 2014). "The Anglo-Australian Planet Search. XXIII. Two New Jupiter Analogs". The Astrophysical Journal. 783 (2): 9. arXiv:1401.5525. Bibcode:2014ApJ...783..103W. doi:10.1088/0004-637X/783/2/103. S2CID 14082923. 103.
6. Sousa, S. G.; et al. (November 2018). "SWEET-Cat updated. New homogenous spectroscopic parameters". Astronomy & Astrophysics. 620: 13. arXiv:1810.08108. Bibcode:2018A&A...620A..58S. doi:10.1051/0004-6361/201833350. S2CID 119374557. A58.
7. Butler, R. P.; et al. (December 2006). "Catalog of Nearby Exoplanets". The Astrophysical Journal. 646 (1): 505–522. arXiv:astro-ph/0607493. Bibcode:2006ApJ...646..505B. doi:10.1086/504701. S2CID 119067572.
8. "HD 154857". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2021-10-10.
9. Gonzalez, Guillermo (October 2009). "Stars with planets and the thick disc". Monthly Notices of the Royal Astronomical Society: Letters. 399 (1): L103 – L107. Bibcode:2009MNRAS.399L.103G. doi:10.1111/j.1745-3933.2009.00734.x.
10. O'Toole, Simon J.; et al. (2007). "New Planets around Three G Dwarfs". The Astrophysical Journal. 660 (2): 1636–1641. arXiv:astro-ph/0702213. Bibcode:2007ApJ...660.1636O. doi:10.1086/513563. S2CID 118958847.

External links

• "HD 154857". Extrasolar Planets Encyclopaedia. Archived from the original on July 2, 2007. Retrieved 2008-07-21.
• http://planetquest.jpl.nasa.gov