Astronomy:Iota Sagittarii
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| Observation data 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 |
| Distance | 182 ± 2 ly (55.7 ± 0.7 pc) |
| Absolute magnitude (MV) | +0.39[4] |
| Details | |
| Mass | 1.40[3] M☉ |
| Radius | 15[5] R☉ |
| Luminosity | 87[3] L☉ |
| Surface gravity (log g) | 1.89[6] cgs |
| Temperature | 4,594±41[3] K |
| Metallicity [Fe/H] | −0.26[6] dex |
| Age | 4.74[3] Gyr |
| Other designations | |
| Database references | |
| SIMBAD | data |
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 an astrometric binary,[8] based upon proper motion data collected during the Hipparcos mission.[9] The primary 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.[10] At an estimated distance of this star, this yields a physical size of about 15 times the radius of the Sun.[5] It has 1.4[3] times the mass of the Sun and is radiating 87[3] times the Sun's luminosity from its enlarged photosphere at an effective temperature of about 4,594 K.[3]
The companion star was directly observed for the first time in 2014 with the SPHERE instrument on the Very Large Telescope. It is separated from the primary star by 0.24″ and is more than 4,000 times fainter than it.[11] This is an M-type red dwarf star with an estimated mass of 0.36 M☉.[12]
References
- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics 474 (2): 653–664, doi:10.1051/0004-6361:20078357, Bibcode: 2007A&A...474..653V.
- ↑ 2.0 2.1 2.2 2.3 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.
- ↑ 3.00 3.01 3.02 3.03 3.04 3.05 3.06 3.07 3.08 3.09 3.10 Luck, R. Earle (2015), "Abundances in the Local Region. I. G and K Giants", The Astronomical Journal 150 (3): 88, doi:10.1088/0004-6256/150/3/88, Bibcode: 2015AJ....150...88L.
- ↑ Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters 38 (5): 331, doi:10.1134/S1063773712050015, Bibcode: 2012AstL...38..331A.
- ↑ 5.0 5.1 Stassun, Keivan G. et al. (2019), "The Revised TESS Input Catalog and Candidate Target List", The Astronomical Journal 158 (4): 138, doi:10.3847/1538-3881/ab3467, Bibcode: 2019AJ....158..138S.
- ↑ 6.0 6.1 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, doi:10.1051/0004-6361/201014247, Bibcode: 2010A&A...515A.111S.
- ↑ "iot Sgr". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=iot+Sgr.
- ↑ 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, doi:10.1111/j.1365-2966.2008.13596.x, Bibcode: 2008MNRAS.389..869E.
- ↑ 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, doi:10.1051/0004-6361:20065526, Bibcode: 2007A&A...464..377F.
- ↑ Richichi, A. et al. (February 2005), "CHARM2: An updated Catalog of High Angular Resolution Measurements", Astronomy and Astrophysics 431 (2): 773–777, doi:10.1051/0004-6361:20042039, Bibcode: 2005A&A...431..773R.
- ↑ "The very faint companion star to Iota Sagitarii seen with SPHERE". ESO. 4 June 2014. https://www.eso.org/public/images/eso1417i/.
- ↑ Claudi, R. et al. (2016). "First science with SPHERE". Memorie della Societa Astronomica Italiana 87: 132. Bibcode: 2016MmSAI..87..132C.
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