Sigma Aquilae
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Aquila[1] |
| Right ascension | 19h 39m 11.642s[2] |
| Declination | +05° 23′ 51.98″[2] |
| Apparent magnitude (V) | +5.17[3] |
| Characteristics | |
| Spectral type | B3 V + B3 V:[4] |
| U−B color index | −0.60[3] |
| B−V color index | +0.03[3] |
| Variable type | β Lyr[5] |
| Astrometry | |
| Radial velocity (Rv) | −4.8±0.9[6] km/s |
| Proper motion (μ) | RA: +4.528 mas/yr[2] Dec.: −4.507 mas/yr[2] |
| Parallax (π) | 4.1557±0.0775 mas[2] |
| Distance | 780 ± 10 ly (241 ± 4 pc) |
| Absolute magnitude (MV) | −1.69[1] |
| Orbit[7] | |
| Primary | σ Aql A |
| Companion | σ Aql B |
| Period (P) | 1.95028±0.00002 d |
| Semi-major axis (a) | 14.3 R☉ |
| Eccentricity (e) | 0 |
| Inclination (i) | 71.97° |
| Periastron epoch (T) | 2459809.625±0.004 HJD |
| Semi-amplitude (K1) (primary) | 156.2±2.9 km/s |
| Semi-amplitude (K2) (secondary) | 196.7±3.1 km/s |
| Details | |
| σ Aql A | |
| Mass | 5.8±0.1[7] M☉ |
| Radius | 3.7[7] R☉ |
| Luminosity | 1,862[8] L☉ |
| Temperature | 18,493[8] K |
| Rotational velocity (v sin i) | 36.1±8.9[9] km/s |
| Age | 140[10] Myr |
| σ Aql B | |
| Mass | 4.6±0.1[7] M☉ |
| Radius | 3.3[7] R☉ |
| Luminosity | 524[8] L☉ |
| Temperature | 15,848[8] K |
| Rotational velocity (v sin i) | 120[4] km/s |
| Other designations | |
| σ Aquilae, σ Aql, 44 Aquilae, BD+05 4225, GC 27185, HD 185507, HIP 96665, HR 7474, SAO 124903, PPM 168338, WDS J19392+0524A[11] | |
| Database references | |
| SIMBAD | data |
Sigma Aquilae is an eclipsing binary star system in the equatorial constellation of Aquila. Its name is a Bayer designation that is Latinized from σ Aquilae, and abbreviated Sigma Aql or σ Aql. The baseline apparent visual magnitude of the pair is +5.17,[3] which, according to the Bortle Dark-Sky Scale, is bright enough to be seen with the naked eye from suburban skies. Because of the Earth's orbit about the Sun, this system has an annual parallax shift of 4.16 mas.[2] This provides a distance estimate of approximately 780 light-years (240 parsecs). The system is drifting closer to the Sun with a radial velocity of −5 km/s.[6]
Sigma Aquilae is a double-lined[13] spectroscopic binary system consisting of two intermediate-mass B-type main sequence stars; each has a stellar classification of B3 V.[4] They are detached components,[10] which means the two stars are sufficiently distant from each other that neither fills its Roche lobe. Their close, circular orbit has a period of 1.95 days with a semimajor axis of 14.3 times the radius of the Sun.[7]
Because the orbital plane lies close to the line of sight with the Earth, they form an eclipsing binary system.[5] The two components are each distorted by the gravity of the other star, and their shapes mean that the magnitude of the star system varies constantly even outside of the eclipses, an arrangement known as a Beta Lyrae variable. The brightness of the pair decreases during each eclipse, which occurs with a frequency determined by their orbital period of 1.95028 days. During the eclipse of the primary component the magnitude decreases by 0.20 to a net of 5.37; the eclipse of the secondary component results in a magnitude decrease of 0.10 to a net of 5.27.[14]
The primary component has 5.8 times the mass of the Sun and 3.7 times the Sun's radius.[7] It is radiating 1,862 times the luminosity of the Sun from its photosphere at an effective temperature of 18,493 K.[8] The smaller secondary has 4.6 times the mass, 3.3 times the radius,[7] and 524 times the luminosity of the Sun. Its outer atmosphere has an effective temperature of 15,848 K.[8] This star has a high rate of spin, showing a projected rotational velocity of 120 km/s.[4]
References
- ^ a b 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.
- ^ a b c d e Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
- ^ a b c d 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.
- ^ a b c d Levato, H. (January 1975), "Rotational velocities and spectral types for a sample of binary systems", Astronomy and Astrophysics Supplement Series, 19: 91–99, Bibcode:1975A&AS...19...91L.
- ^ a b Lefèvre, L.; et al. (November 2009), "A systematic study of variability among OB-stars based on HIPPARCOS photometry", Astronomy and Astrophysics, 507 (2): 1141–1201, Bibcode:2009A&A...507.1141L, doi:10.1051/0004-6361/200912304.
- ^ a b Wilson, Ralph Elmer (1953), "General catalogue of stellar radial velocities", Carnegie Institute Washington D.C. Publication, Carnegie Institution of Washington, Bibcode:1953GCRV..C......0W.
- ^ a b c d e f g h Quadri, U.; et al. (June 2023), "Spectroscopic and Photometric Study of the Eclipsing Binary Star sigma Aquilae", The Journal of the American Association of Variable Star Observers, 51 (1): 59, Bibcode:2023JAVSO..51...59Q.
- ^ a b c d e f Malkov, O. Yu. (December 2007), "Mass-luminosity relation of intermediate-mass stars", Monthly Notices of the Royal Astronomical Society, 382 (3): 1073–1086, Bibcode:2007MNRAS.382.1073M, doi:10.1111/j.1365-2966.2007.12086.x.
- ^ Tetzlaff, N.; Neuhäuser, R.; Hohle, M. M. (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.
- ^ a b Pan, Kaike; et al. (July 1998), "Orbital circularization in detached binaries with early-type primaries", Astronomy and Astrophysics, 335: 179–182, Bibcode:1998A&A...335..179P.
- ^ "* sig Aql", SIMBAD, Centre de données astronomiques de Strasbourg, retrieved 2012-07-20.
- ^ "Light Curve", Hipparcos ESA, ESA, retrieved 17 February 2022.
- ^ van Rensbergen, W.; et al. (February 2006), "Evolution of interacting binaries with a B type primary at birth", Astronomy and Astrophysics, 446 (3): 1071–1079, Bibcode:2006A&A...446.1071V, doi:10.1051/0004-6361:20053543
- ^ Zasche, P.; et al. (August 2009), "A Catalog of Visual Double and Multiple Stars With Eclipsing Components", The Astronomical Journal, 138 (2): 664–679, arXiv:0907.5172, Bibcode:2009AJ....138..664Z, doi:10.1088/0004-6256/138/2/664, S2CID 17089387.