Iota Sagittarii

Iota Sagittarii
Diagram showing star positions and boundaries of the Sagittarius constellation and its surroundings


Location of ι Sagittarii (circled)

Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Sagittarius
Right ascension 19h 55m 15.69691s[1]
Declination −41° 52′ 05.8388″[1]
Apparent magnitude (V) +4.118[2]
Characteristics
Spectral type K0 II-III[3]
U−B color index +0.911[2]
B−V color index +1.084[2]
Astrometry
Radial velocity (Rv)+35.8[3] km/s
Proper motion (μ) RA: +22.61[1] mas/yr
Dec.: +51.40[1] mas/yr
Parallax (π)17.94 ± 0.21[1] mas
Distance182 ± 2 ly
(55.7 ± 0.7 pc)
Details
Mass1.40[3] M☉
Radius14[4] R☉
Luminosity87[3] L☉
Surface gravity (log g)1.89[5] cgs
Temperature4,594±41[3] K
Metallicity [Fe/H]−0.26[5] dex
Age4.74[3] Gyr
Other designations
ι Sgr, CPD−42° 8944, FK5 1520, HD 188114, HIP 98032, HR 7581, SAO 229927[6]
Database references
SIMBADdata

Iota Sagittarii (Iota Sgr, ι Sagittarii, ι Sgr) is a star in the zodiac constellation of Sagittarius. With an apparent visual magnitude of +4.118, it is bright enough to be viewed with the naked eye.[2] Based upon an annual parallax shift of 17.94 mas as seen from Earth,[1] this star is located 182 light years from the Sun. It is moving away from the Earth with a radial velocity of +35.8 km/s.[3]

This is a probable astrometric binary,[7] based upon proper motion data collected during the Hipparcos mission.[8] The visible component shows the spectrum of an evolved K-type giant or bright giant star with a stellar classification of K0 II-III.[3] The measured angular diameter, after correction for limb darkening, is 2.32±0.02 mas.[9] At an estimated distance of this star, this yields a physical size of about 14 times the radius of the Sun.[4] It has 1.4[3] times the mass of the Sun and is radiating 87[3] times the Sun's luminosity from its photosphere at an effective temperature of about 4,594 K.[3]

References

  1. 1 2 3 4 5 6 van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, Bibcode:2007A&A...474..653V, arXiv:0708.1752 Freely accessible, doi:10.1051/0004-6361:20078357.
  2. 1 2 3 4 Cousins, A. W. J. (1973), "Revised zero points and UBV photometry of stars in the Harvard E and F regions", Memoirs of the Royal Astronomical Society, 77: 223–236, Bibcode:1973MmRAS..77..223C.
  3. 1 2 3 4 5 6 7 8 9 10 11 Luck, R. Earle (2015), "Abundances in the Local Region. I. G and K Giants", The Astronomical Journal, 150 (3): 88, Bibcode:2015AJ....150...88L, doi:10.1088/0004-6256/150/3/88.
  4. 1 2 Lang, Kenneth R. (2006), Astrophysical formulae, Astronomy and astrophysics library, 1 (3rd ed.), Birkhäuser, ISBN 3-540-29692-1. The radius (R*) is given by:
  5. 1 2 Soubiran, C.; Le Campion, J.-F.; Cayrel de Strobel, G.; Caillo, A. (June 2010), "The PASTEL catalogue of stellar parameters", Astronomy and Astrophysics, 515: A111, Bibcode:2010A&A...515A.111S, arXiv:1004.1069 Freely accessible, doi:10.1051/0004-6361/201014247.
  6. ↑ "iot Sgr". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-07-07.
  7. ↑ Eggleton, P. P.; Tokovinin, A. A. (September 2008), "A catalogue of multiplicity among bright stellar systems", Monthly Notices of the Royal Astronomical Society, 389 (2): 869–879, Bibcode:2008MNRAS.389..869E, arXiv:0806.2878 Freely accessible, doi:10.1111/j.1365-2966.2008.13596.x.
  8. ↑ Frankowski, A.; et al. (March 2007), "Proper-motion binaries in the Hipparcos catalogue. Comparison with radial velocity data", Astronomy and Astrophysics, 464 (1): 377–392, Bibcode:2007A&A...464..377F, arXiv:astro-ph/0612449 Freely accessible, doi:10.1051/0004-6361:20065526.
  9. ↑ Richichi, A.; et al. (February 2005), "CHARM2: An updated Catalog of High Angular Resolution Measurements", Astronomy and Astrophysics, 431 (2): 773–777, Bibcode:2005A&A...431..773R, doi:10.1051/0004-6361:20042039.
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