Y Sagittarii

Y Sagittarii

A light curve for Y Sagittarii, plotted from Hipparcos data[1]
Observation data Epoch J2000      Equinox J2000
Constellation	Sagittarius
Right ascension	18^h 21^m 22.98643^s[2]
Declination	−18° 51′ 36.0018″[2]
Apparent magnitude (V)	5.76[3]
Characteristics
Spectral type	F8 II[4]
B−V color index	0.67±0.02[3]
Variable type	Cepheid variable[4]
Astrometry
Radial velocity (Rv)	−1.4±2.3[3] km/s
Proper motion (μ)	RA: −3.12[2] mas/yr Dec.: −7.12[2] mas/yr
Parallax (π)	2.13 ± 0.29 mas[5]
Distance	approx. 1,500 ly (approx. 470 pc)
Absolute magnitude (MV)	−2.06[3]
Details
Surface gravity (log g)	1.80[4] cgs
Temperature	5,967±26[4] K
Age	330[6] Myr
Other designations
57 G. Sgr, Y Sgr, BD−18° 4926, HD 168608, HIP 89968, HR 6863[7]
Database references
SIMBAD	data

Y Sagittarii is a variable star in the constellation of Sagittarius. It is a Cepheid variable with an apparent magnitude that ranges around +5.77. The measure of its parallax by Hubble Space Telescope puts Y Sagittarii to 1,293 light-years away from the Solar System.

The brightness ranges in Y Sagittarii's apparent magnitude varies from +5.25 and +6.24 in a period of 5.7736 days. The spectral type of this star is F8II, while the effective temperature is 5370 K. It has a radius 50 times larger than the Sun, while its projected rotational velocity of 16 km / s and it has an estimated mass six times that of the Sun. The star's metal content is similar to Sun, with an index of metallicity [Fe / H] = +0.05. For other metals tested, it shows some overabundance of copper, zinc, yttrium and sodium; the level of the elements is almost double that of the Sun ([Na / H] = +0.27).[8]

There is evidence that Y Sagittarii may be a spectroscopic binary. It has been suggested that the orbital period for the system is on the order of 10,000 to 12,000 days. However, subsequent studies assume eccentricity zero for orbit, and they have failed to find a convincing orbital solution. Instead, it appears to be a distant visual companion.[9]

References

1. "Light Curve". Hipparcos ESA. ESA. Retrieved 17 February 2022.
2. 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.
3. 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.
4. Usenko, I. A.; et al. (July 2013), "Spectroscopic studies of southern-hemisphere Cepheids: Six objects in Centaurus (V Cen, V737 Cen) and Sagittarius (BB Sgr, W Sgr, X Sgr, Y Sgr)", Astronomy Letters, 39 (7): 432–445, Bibcode:2013AstL...39..432U, doi:10.1134/S1063773713070074, S2CID 121213614.
5. Benedict, G. Fritz; et al. (January 2017), "Astrometry with Hubble Space Telescope Fine Guidance Sensors—A Review", Publications of the Astronomical Society of the Pacific, 129 (971): 012001, arXiv:1610.05176, Bibcode:2017PASP..129a2001B, doi:10.1088/1538-3873/129/971/012001, S2CID 118432032.
6. "HIP 89968", Wolfram Alpha, retrieved 2012-09-17.
7. "V* Y Sgr". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2012-09-17.
8. J., Duncan (August 2013), "Changes in the spectrographic elements of Y Sagittarii", Astrophysical Journal, 56: 340–341, Bibcode:1922ApJ....56..340D, doi:10.1086/142708.
9. Evans, Nancy Remage; et al. (December 2020), "Hubble Space Telescope Snapshot Survey for Resolved Companions of Galactic Cepheids: Final Results", The Astrophysical Journal, 905 (1): 34, arXiv:2010.07996, Bibcode:2020ApJ...905...81E, doi:10.3847/1538-4357/abc1f1, S2CID 223953710, 81.