Rho Indi

ρ Indi, Latinised as Rho Indi (also HR 8701 or HD 216437), is a yellow-hued star in the constellation Indus. With an apparent visual magnitude of +6.05[2] it is, barely, a naked eye star, not visible in the northern hemisphere outside the tropics. Based upon an annual parallax shift of 37.46 mas, it is located 87 light-years (27 parsecs) from the Sun. The star is moving closer to the Sun with a radial velocity of −2 km/s.[1]

ρ Indi
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Indus
Right ascension 22h 54m 39.482s[1]
Declination –70° 04′ 25.35″[1]
Apparent magnitude (V) +6.05[2]
Characteristics
Spectral type G1 V Fe+0.3[3]
U−B color index +0.22[4]
B−V color index +0.66[4]
Astrometry
Radial velocity (Rv)−2.29±0.12[1] km/s
Proper motion (μ) RA: −43.140[1] mas/yr
Dec.: +72.728[1] mas/yr
Parallax (π)37.4641 ± 0.0253 mas[1]
Distance87.06 ± 0.06 ly
(26.69 ± 0.02 pc)
Absolute magnitude (MV)+3.90[5]
Details[6]
Mass1.317±0.083 M☉
Radius1.456±0.024 R☉
Luminosity2.24 L☉
Surface gravity (log g)4.23 cgs
Temperature5,849 K
Metallicity [Fe/H]0.18 dex
Rotation26.7 d[7]
Rotational velocity (v sin i)3.1 km/s
Age4.6+1.0
−0.4 Gyr
Other designations
ρ Ind, CPD–70°2971, FK5 865, HR 8701, HD 216437, HIP 113137, SAO 258084.
Database references
SIMBADdata
Exoplanet Archivedata
Extrasolar Planets
Encyclopaedia		data

Properties

The stellar classification of Rho Indi is G1 V Fe+0.3,[3] which indicates it is a G-type main-sequence star with a mild overabundance of iron in its outer atmosphere. However, Houk and Cowley (1975) classified it as G2.5 IV,[8] suggesting it is instead a somewhat more evolved subgiant star. It has an estimated 1.32 times the mass of the Sun and 1.46 times the Sun's radius. The star is radiating about 2.24 times the Sun's luminosity from its photosphere at an effective temperature of 5,849 K. It is around 4.6 billion years old and is spinning with a leisurely projected rotational velocity of 3.1 km/s.[6]

Planetary system

On September 17, 2002, this star was found to have a planetary companion, designated Rho Indi b.[9] The discovery was made by measuring variations in the host star's radial velocity, thereby indicating the presence of a perturbing object. Based upon the data, the object is orbiting the host star with a period of about 3.7 years at an eccentricity of 0.32. The semimajor axis for this orbit is around 2.5 times the distance from the Earth to the Sun. Since the inclination of the orbit to the line-of-sight was initially unknown, only a lower bound on the planet's mass could be determined. It has at least 2.3 times Jupiter's mass.[9] In 2023, the inclination and true mass of Rho Indi b were determined via astrometry.[10]

The Rho Indi planetary system[10]
Companion
(in order from star)		 Mass Semimajor axis
(AU)		 Orbital period
(years)		 Eccentricity Inclination Radius
b 3.88±0.73 MJ 2.501+0.036
−0.037		 3.658±0.034 0.318±0.028 35.0+10.0
−6.1 or 145.0+6.1
−10.0°		 —

See also
  • Tau1 Gruis, a star with a separate exoplanet discovery by the same team

References
  1. 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.
  2. Ducati, J. R. (2002). "VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system". CDS/ADC Collection of Electronic Catalogues. 2237. Bibcode:2002yCat.2237....0D.
  3. Gray, R. O.; Corbally, C. J.; Garrison, R. F.; McFadden, M. T.; Bubar, E. J.; McGahee, C. E.; O'Donoghue, A. A.; Knox, E. R. (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. Mermilliod, J.-C. (1986). "Compilation of Eggen's UBV data, transformed to UBV (unpublished)". Catalogue of Eggen's UBV Data. Bibcode:1986EgUBV........0M.
  5. 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.
  6. Valenti, Jeff A.; Fischer, Debra A. (2005). "Spectroscopic Properties of Cool Stars (SPOCS). I. 1040 F, G, and K Dwarfs from Keck, Lick, and AAT Planet Search Programs". The Astrophysical Journal Supplement Series. 159 (1): 141–166. Bibcode:2005ApJS..159..141V. doi:10.1086/430500.
  7. Mayor, M.; et al. (2004). "The CORALIE survey for southern extra-solar planets XII. Orbital solutions for 16 extra-solar planets discovered with CORALIE". Astronomy and Astrophysics. 415 (1): 391–402. arXiv:astro-ph/0310316. Bibcode:2004A&A...415..391M. doi:10.1051/0004-6361:20034250. S2CID 5233877.
  8. Houk, N.; Cowley, A. P. (1975). Michigan catalogue of two-dimensional spectral types for the HD stars. Vol. 1. Ann Arbor, Michigan: Dept. of Astronomy, University of Michigan. Bibcode:1975mcts.book.....H.
  9. Jones, Hugh R. A.; et al. (2002). "Extrasolar planets around HD 196050, HD 216437 and HD 160691". Monthly Notices of the Royal Astronomical Society. 337 (4): 1170–1178. arXiv:astro-ph/0206216. Bibcode:2002MNRAS.337.1170J. doi:10.1046/j.1365-8711.2002.05787.x. S2CID 119520409.
  10. Xiao, Guang-Yao; Liu, Yu-Juan; et al. (May 2023). "The Masses of a Sample of Radial-Velocity Exoplanets with Astrometric Measurements". Research in Astronomy and Astrophysics. 23 (5): 055022. arXiv:2303.12409. Bibcode:2023RAA....23e5022X. doi:10.1088/1674-4527/accb7e.
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