HIP 79431

HIP 79431 is a red dwarf star with a planetary companion in the constellation Scorpius. It has the proper name Sharjah, as selected in the NameExoWorlds campaign by United Arab Emirates, during the 100th anniversary of the IAU. Sharjah is the cultural capital of United Arab Emirates.^[11][12] The star has an apparent visual magnitude of 11.34,^[2] which is far too faint to be visible to the naked eye. Based on parallax measurements, this system is located at a distance of 47.4 light-years from the Sun. It is drifting closer with a radial velocity of −5 km/s.^[4]

HIP 79431 / Sharjah

Observation data Epoch J2000.0      Equinox J2000.0
Constellation	Scorpius
Right ascension	16h 12m 41.780s[1]
Declination	−18° 52′ 31.81″[1]
Apparent magnitude (V)	11.34[2]
Characteristics
Spectral type	M3V[3]
Apparent magnitude (B)	12.826[2]
Apparent magnitude (R)	10.46[2]
Apparent magnitude (I)	9.370[2]
Apparent magnitude (J)	7.555±0.026[2]
Apparent magnitude (H)	6.855±0.044[2]
Apparent magnitude (K)	6.589±0.018[2]
B−V color index	1.486±0.011[2]
V−R color index	0.88[2]
R−I color index	1.09[2]
Astrometry
Radial velocity (Rv)	−4.66±0.28[4] km/s
Proper motion (μ)	RA: 35.707 mas/yr[1] Dec.: −214.050 mas/yr[1]
Parallax (π)	68.7833 ± 0.1217 mas[1]
Distance	47.42 ± 0.08 ly (14.54 ± 0.03 pc)
Absolute magnitude (MV)	10.55[2]
Details
Mass	0.49±0.05 M☉[5] 0.445 M☉[6] 0.466[7] M☉
Radius	0.54±0.02 R☉[8] 0.391 R☉[6] 0.442[7] R☉
Surface gravity (log g)	4.86 cgs[6] 4.815[7] cgs
Temperature	3,689±20[9] K
Metallicity [Fe/H]	+0.46±0.17[9] dex
Other designations
Sharjah, HIP 79431, LP 804-27, NLTT 42226[10]
Database references
SIMBAD	data
Exoplanet Archive	data
ARICNS	data

This is an M-type main-sequence star with a stellar classification of M3V.^[3] This star is smaller, cooler, dimmer, and less massive than the Sun, but the estimated metal content is 2.5 times as much as the Sun. The level of chromospheric activity does not appear to be unusually high for a star of this class.^[9]

In 2010, a superjovian exoplanetary companion was discovered using the radial-velocity method. It is orbiting at a distance of 0.36 AU from the host star with a period of 0.3 years and an eccentricity (ovalness) of 0.29. Since the inclination of the orbit is unknown, only a lower bound on the mass can be determined. It has at least 2.1 times the mass of Jupiter.^[5]

The HIP 79431 planetary system^[5]

Companion (in order from star)	Mass	Semimajor axis (AU)	Orbital period (days)	Eccentricity	Inclination	Radius
b / Barajeel	≥2.1 MJ	0.36	111.7 ± 0.7	0.29 ± 0.02	—	—

See also

• Gliese 179
• 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. 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.
4. Terrien, Ryan C.; et al. (March 2015). "M Dwarf Luminosity, Radius, and α-enrichment from I-band Spectral Features". The Astrophysical Journal Letters. 802 (1): 6. arXiv:1503.01776. Bibcode:2015ApJ...802L..10T. doi:10.1088/2041-8205/802/1/L10. S2CID 118497562. L10.
5. Apps, Kevin; et al. (2010). "M2K: I. A Jupiter-Mass Planet Orbiting the M3V Star HIP 79431". Publications of the Astronomical Society of the Pacific. 122 (888): 156–161. arXiv:1001.1174. Bibcode:2010PASP..122..156A. doi:10.1086/651058. S2CID 119186731.
6. Doyle, L.; et al. (October 2018). "Investigating the rotational phase of stellar flares on M dwarfs using K2 short cadence data". Monthly Notices of the Royal Astronomical Society. 480 (2): 2153–2164. arXiv:1807.08592. Bibcode:2018MNRAS.480.2153D. doi:10.1093/mnras/sty1963.
7. Tsuji, Takashi; Nakajima, Tadashi (October 2014). "Near-infrared spectroscopy of M dwarfs. I. CO molecule as an abundance indicator of carbon†". Publications of the Astronomical Society of Japan. 66 (5): 26. arXiv:1407.5829. Bibcode:2014PASJ...66...98T. doi:10.1093/pasj/psu078. 98.
8. Stassun, Keivan G.; et al. (2016). "Accurate Empirical Radii and Masses of Planets and Their Host Stars with Gaia Parallaxes". The Astronomical Journal. 153 (3): 136. arXiv:1609.04389. Bibcode:2017AJ....153..136S. doi:10.3847/1538-3881/aa5df3. S2CID 119219062.
9. Rojas-Ayala, Bárbara; et al. (April 2012), "Metallicity and Temperature Indicators in M Dwarf K-band Spectra: Testing New and Updated Calibrations with Observations of 133 Solar Neighborhood M Dwarfs", The Astrophysical Journal, 748 (2): 93, arXiv:1112.4567, Bibcode:2012ApJ...748...93R, doi:10.1088/0004-637X/748/2/93, S2CID 41902340
10. "LP 804-27". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2021-11-13.
11. "Approved names". NameExoworlds. Retrieved 2020-01-02.
12. "International Astronomical Union | IAU". www.iau.org. Retrieved 2020-01-02.