Astronomy:Delta Sagittae

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Short description: Binary star system in the constellation Sagitta
δ Sagittae
Location of δ Sagittae (circled)
Observation data
Equinox J2000.0]] (ICRS)
Constellation Sagitta
Right ascension  19h 47m 23.26653s[1]
Declination +18° 32′ 03.5203″[1]
Apparent magnitude (V) +3.82[2](3.91[3]/ 6.64)[4]
Characteristics
Evolutionary stage AGB + main sequence[5]
Spectral type M2II + B9.5V[4]
U−B color index +0.98[6]
B−V color index +1.40[6]
Variable type LB?[7]
Astrometry
Radial velocity (Rv)2.5 ± 0.9[8] km/s
Proper motion (μ) RA: -6.514[1] mas/yr
Dec.: 0.849[1] mas/yr
Parallax (π)5.9674 ± 0.2597[9] mas
Distance550 ± 20 ly
(168 ± 7 pc)
Absolute magnitude (MV)−2.58[10]
Orbit[11]
Period (P)3,703.7±1.5 days
Semi-major axis (a)(5.50±0.04)×108 km[lower-alpha 1]
Eccentricity (e)0.441±0.005
Inclination (i)40°
Longitude of the node (Ω)170.2[4]°
Periastron epoch (T)1979.93[4]
Argument of periastron (ω)
(secondary)		263.9±1.0°
Details
δ Sge A
Mass3.8[11] M☉
Radius180±25[11] R☉
Luminosity3,162[4] L☉
Surface gravity (log g)0.74±0.10[5] cgs
Temperature3,660±170[12] K
δ Sge B
Mass3.611[13] M☉
Radius3.3 – 4.7[13] R☉
Luminosity63[4] L☉
Temperature10,000[4] K
Other designations
δ Sagittae, 7 Sagittae, BD+18 4240, CCDM J19474+1832AB, FK5 743, GC 27391, HD 187076, HIP 97365, HR 7536, IDS 19429+1817 AB, PPM 136976, SAO 105259, WDS J19474+1832AB
Database references
SIMBADdata

Delta Sagittae (Delta Sge, δ Sagittae, δ Sge) is a binary star in the constellation of Sagitta, with an apparent magnitude of +3.68. The primary component is a red M-type bright giant, and the secondary is a B-type main-sequence star.[2] It is approximately 430 light years from Earth, based on its Gaia Data Release 2 parallax.[1]

A visual band light curve for Delta Sagittae, plotted from data published by Tabur et al. (2009)[14]

Delta Sagittae is a spectroscopic binary with a composite spectrum, meaning that light from both stars can be detected. It has an orbital period of about 10 years and an eccentricity of about 0.44.[4] It is also a variable star, with its brightness changing between a maximum of magnitude 3.75 and a minimum of 3.83 in an unpredictable way.[7]

Naming

In Chinese, 左旗 (Zuǒ Qí), meaning Left Flag, refers to an asterism consisting of δ Sagittae, α Sagittae, β Sagittae, ζ Sagittae, γ Sagittae, 13 Sagittae, 11 Sagittae, 14 Sagittae and ρ Aquilae. Consequently, the Chinese name for δ Sagittae itself is 左旗三 (Zuǒ Qí sān, English: the Third Star of Left Flag.)[15]

Notes

  1. ↑ calculated from a sin i divided by the sine of inclination.

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 Brown, A. G. A. (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics 616: A1. doi:10.1051/0004-6361/201833051. Bibcode: 2018A&A...616A...1G.  Gaia DR2 record for this source at VizieR.
  2. ↑ 2.0 2.1 "* del Sge". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=%2A+del+Sge. 
  3. ↑ Calculated from subtracting magnitudes.
  4. ↑ 4.0 4.1 4.2 4.3 4.4 4.5 4.6 4.7 Eaton, Joel A.; Hartkopf, William I.; McAlister, Harold A.; Mason, Brian D. (1995). "Winds and accretion in delta Sagittae". Astronomical Journal 109 (4): 1856–1866. doi:10.1086/117412. Bibcode: 1995AJ....109.1856E. 
  5. ↑ 5.0 5.1 Schröder, K.-P.; Cuntz, M. (2007). "A critical test of empirical mass loss formulas applied to individual giants and supergiants". Astronomy and Astrophysics 465 (2): 593–601. doi:10.1051/0004-6361:20066633. Bibcode: 2007A&A...465..593S. 
  6. ↑ 6.0 6.1 Mermilliod, J.-C. (1986). "Compilation of Eggen's UBV data, transformed to UBV (unpublished)". Catalogue of Eggen's UBV Data. Bibcode: 1986EgUBV........0M. http://cdsads.u-strasbg.fr/cgi-bin/nph-bib_query?1986EgUBV........0M&db_key=AST&nosetcookie=1. 
  7. ↑ 7.0 7.1 Samus, N. N. et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S 1: B/GCVS. Bibcode: 2009yCat....102025S. 
  8. ↑ Wilson, Ralph Elmer (1953). "General catalogue of stellar radial velocities". Carnegie Institute Washington D.C. Publication. Bibcode: 1953GCRV..C......0W. 
  9. ↑ Brown, A. G. A. (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics 649: A1. doi:10.1051/0004-6361/202039657. Bibcode: 2021A&A...649A...1G.  Gaia EDR3 record for this source at VizieR.
  10. ↑ Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters 38 (5): 331, doi:10.1134/S1063773712050015, Bibcode: 2012AstL...38..331A. 
  11. ↑ 11.0 11.1 11.2 Pugh, T.; Gray, David F.; Griffin, R. F. (2015). "The orbit and variations of δ Sagittae" (in en). Monthly Notices of the Royal Astronomical Society 454 (3): 2344–2352. doi:10.1093/mnras/stv2003. ISSN 0035-8711. Bibcode: 2015MNRAS.454.2344P. 
  12. ↑ Messineo, M.; Brown, A. G. A. (2019). "A Catalog of Known Galactic K-M Stars of Class I Candidate Red Supergiants in Gaia DR2". The Astronomical Journal 158 (1): 20. doi:10.3847/1538-3881/ab1cbd. Bibcode: 2019AJ....158...20M. 
  13. ↑ 13.0 13.1 Eggleton, Peter P.; Yakut, Kadri (2017). "Models for 60 double-lined binaries containing giants". Monthly Notices of the Royal Astronomical Society 468 (3): 3533–3556. doi:10.1093/mnras/stx598. 
  14. ↑ Tabur, V.; Bedding, T. R.; Kiss, L. L.; Moon, T. T.; Szeidl, B.; Kjeldsen, H. (December 2009). "Long-term photometry and periods for 261 nearby pulsating M giants". Monthly Notices of the Royal Astronomical Society 400 (4): 1945–1961. doi:10.1111/j.1365-2966.2009.15588.x. Bibcode: 2009MNRAS.400.1945T. 
  15. ↑ (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 3 日
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