Chi1 Sagittarii

Chi¹ Sagittarii (χ¹ Sagittarii) is a binary star^[6] system in the zodiac constellation of Sagittarius. The pair have a combined apparent visual magnitude of +5.03,^[2] which is bright enough to be seen with the naked eye. Based upon an annual parallax shift of 12.95 mas as seen from Earth,^[1] it is located around 252 light years from the Sun. It is advancing through space in the general direction of the Earth with a radial velocity of −43.4 km/s.^[4]

For other stars with this Bayer designation, see χ Sagittarii.

Chi¹ Sagittarii

Location of χ1 Sagittari (circled)
Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Sagittarius
Right ascension	19h 25m 16.49013s[1]
Declination	−24° 30′ 30.8599″[1]
Apparent magnitude (V)	+5.03[2]
Characteristics
Spectral type	A3/5 IV/V[3]
B−V color index	+0.23[2]
Astrometry
Radial velocity (Rv)	−43.4±1.6[4] km/s
Proper motion (μ)	RA: +61.63[1] mas/yr Dec.: −50.66[1] mas/yr
Parallax (π)	12.95 ± 0.50 mas[1]
Distance	252 ± 10 ly (77 ± 3 pc)
Absolute magnitude (MV)	+0.59[5]
Orbit[6]
Period (P)	5.72 yr
Semi-major axis (a)	0.069″
Eccentricity (e)	0.710
Inclination (i)	97.3°
Longitude of the node (Ω)	259.0°
Periastron epoch (T)	1984.29
Argument of periastron (ω) (secondary)	10.7°
Details
Chi1 Sgr A
Mass	1.64[7] M☉
Luminosity	42.9[8] L☉
Surface gravity (log g)	4.15[7] cgs
Temperature	7,859±267[7] K
Rotational velocity (v sin i)	54[9] km/s
Age	393[7] Myr
Other designations
Chi1 Sgr, 47 Sgr, CPD−24° 6721, HD 182369, HIP 95477, HR 7362, SAO 188101, WDS J19253-2431[10]
Database references
SIMBAD	data

This is a visual binary with an orbital period of 5.72 years, an eccentricity of 0.710, and an angular semimajor axis of 69 mas. The primary, component A, is an A-type star showing a mixed spectrum that matches a stellar classification of A3/5 IV/V.^[3] Helmut Abt classified it as an Am star with a spectral type of kA5hF0VmF0.^[11] This notation indicates it has the calcium K-lines of an A5 star, and the hydrogen and metal lines of an F0 star. It is around 393^[7] million years old and is spinning with a projected rotational velocity of 54 km/s.^[9] The star has an estimated 1.6^[7] times the mass of the Sun and is radiating 42.9^[8] times the Sun's luminosity from its photosphere at an effective temperature of 7,859 K.^[7]

References

1. van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357, S2CID 18759600.
2. Nicolet, B. (1978), "Photoelectric photometric Catalogue of homogeneous measurements in the UBV System", Astronomy and Astrophysics Supplement Series, 34: 1–49, Bibcode:1978A&AS...34....1N.
3. Houk, Nancy; Smith-Moore, M. (1978), Michigan catalogue of two-dimensional spectral types for the HD stars, vol. 4, Ann Arbor: Dept. of Astronomy, University of Michigan, Bibcode:1988mcts.book.....H.
4. Kharchenko, N. V.; et al. (2007), "Astrophysical supplements to the ASCC-2.5: Ia. Radial velocities of ˜55000 stars and mean radial velocities of 516 Galactic open clusters and associations", Astronomische Nachrichten, 328 (9): 889–896, arXiv:0705.0878, Bibcode:2007AN....328..889K, doi:10.1002/asna.200710776, S2CID 119323941.
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. "Sixth Catalog of Orbits of Visual Binary Stars". United States Naval Observatory. April 25, 2016. Archived from the original on 1 August 2017. Retrieved 20 June 2017.
7. David, Trevor J.; Hillenbrand, Lynne A. (2015), "The Ages of Early-Type Stars: Strömgren Photometric Methods Calibrated, Validated, Tested, and Applied to Hosts and Prospective Hosts of Directly Imaged Exoplanets", The Astrophysical Journal, 804 (2): 146, arXiv:1501.03154, Bibcode:2015ApJ...804..146D, doi:10.1088/0004-637X/804/2/146, S2CID 33401607.
8. McDonald, I.; et al. (2012), "Fundamental Parameters and Infrared Excesses of Hipparcos Stars", Monthly Notices of the Royal Astronomical Society, 427 (1): 343–57, arXiv:1208.2037, Bibcode:2012MNRAS.427..343M, doi:10.1111/j.1365-2966.2012.21873.x, S2CID 118665352.
9. Royer, F.; et al. (February 2007), "Rotational velocities of A-type stars. III. Velocity distributions", Astronomy and Astrophysics, 463 (2): 671–682, arXiv:astro-ph/0610785, Bibcode:2007A&A...463..671R, doi:10.1051/0004-6361:20065224, S2CID 18475298.
10. "chi01 Sgr". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-07-05.{{cite web}}: CS1 maint: postscript (link)
11. Abt, H. A. (March 1981), "Visual multiples. VII - MK classifications", Astrophysical Journal Supplement Series, 45: 437–456, Bibcode:1981ApJS...45..437A, doi:10.1086/190719.