Xi1 Sagittarii

Xi¹ Sagittarii (ξ¹ Sagittarii) is a solitary,^[11] blue-white hued star in the zodiac constellation of Sagittarius. It is visible to the naked eye with an apparent visual magnitude of +5.06.^[2] Based upon a small annual parallax shift of 1.58 mas as seen from Earth,^[1] this system is located roughly 2,100 light years from the Sun.

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

Xi¹ Sagittarii

Location of ξ1 Sagittarii (circled)
Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Sagittarius
Right ascension	18h 57m 20.47670s[1]
Declination	−20° 39′ 22.8539″[1]
Apparent magnitude (V)	+5.06[2]
Characteristics
Spectral type	B9/A0 Ib[3]
U−B color index	−0.14[2]
B−V color index	+0.12[2]
Astrometry
Proper motion (μ)	RA: −1.46[1] mas/yr Dec.: −5.75[1] mas/yr
Parallax (π)	1.58 ± 0.26 mas[1]
Distance	approx. 2,100 ly (approx. 600 pc)
Absolute magnitude (MV)	−3.92[4]
Details
Mass	7.8±0.1[5] M☉
Radius	15[6] R☉
Luminosity	2,753[7] L☉
Surface gravity (log g)	2.3[8] cgs
Temperature	9,400[8] K
Metallicity [Fe/H]	−0.20[8] dex
Rotational velocity (v sin i)	10[9] km/s
Age	39.8±4.9[5] Myr
Other designations
ξ1 Sgr, 36 Sgr, BD−20° 5339, HD 175687, HIP 93057, HR 7145, SAO 187498[10]
Database references
SIMBAD	data

This is a massive supergiant star^[6] with a stellar classification of B9/A0 Ib.^[3] With an estimated 7.8^[5] times the mass of the Sun and an age of about 40^[5] million years it has depleted the hydrogen at its core, causing it to expand to about 15 times the Sun's radius.^[6] It is radiating 2,753^[7] times the Sun's luminosity from its photosphere at an effective temperature of about 9,400 K.^[8]

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. Fernie, J. D. (1983), "New UBVRI photometry for 900 supergiants", Astrophysical Journal Supplement Series, 52: 7, Bibcode:1983ApJS...52....7F, doi:10.1086/190856.
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. 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.
5. Tetzlaff, N.; et al. (January 2011), "A catalogue of young runaway Hipparcos stars within 3 kpc from the Sun", Monthly Notices of the Royal Astronomical Society, 410 (1): 190–200, arXiv:1007.4883, Bibcode:2011MNRAS.410..190T, doi:10.1111/j.1365-2966.2010.17434.x, S2CID 118629873.
6. Venn, Kim A. (August 1995), "Atmospheric Parameters and LTE Abundances for 22 Galactic, A-Type Supergiants", Astrophysical Journal Supplement, 99: 659, Bibcode:1995ApJS...99..659V, doi:10.1086/192201.
7. 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.
8. 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, arXiv:1004.1069, Bibcode:2010A&A...515A.111S, doi:10.1051/0004-6361/201014247, S2CID 118362423.
9. Royer, F.; et al. (January 2012), "Rotational velocities of A-type stars. I. Measurement of v sin i in the southern hemisphere", Astronomy and Astrophysics, 381 (1): 105–121, arXiv:astro-ph/0110490, Bibcode:2002A&A...381..105R, doi:10.1051/0004-6361:20011422, S2CID 13133418.
10. "ksi01 Sgr". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-07-05.
11. 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, arXiv:0806.2878, Bibcode:2008MNRAS.389..869E, doi:10.1111/j.1365-2966.2008.13596.x, S2CID 14878976.