Epoch J2000.0 Equinox J2000.0 (ICRS)
|Right ascension||21h 17m 55.07506s|
|Declination||+34° 53′ 48.8289″|
|Apparent magnitude (V)||4.43|
|Spectral type||B2 Vne|
|U−B color index||−0.82|
|B−V color index||−0.11|
|Radial velocity (Rv)||±0.59−1.93 km/s|
|Proper motion (μ)||RA: +10.03 mas/yr
Dec.: +6.49 mas/yr
|Parallax (π)||5.08 ± 0.55 mas|
|Distance||approx. 640 ly
(approx. 200 pc)
|Luminosity (bolometric)||7,305 L☉|
|Surface gravity (log g)||±0.103.30 cgs|
|Rotational velocity (v sin i)||±24230 km/s|
Upsilon Cygni (υ Cyg) is a star in the northern constellation of Cygnus. It is visible to the naked eye, having an apparent visual magnitude of 4.43. Based upon an annual parallax shift of 5.08 mas, it lies at a distance of roughly 640 light years from the Sun.
This is a B-type main sequence star with a stellar classification of B2 Vne. The 'e' suffix indicates this is a Be star, which means it is a rapidly rotating star surrounded by an orbiting gaseous disk. It has a high projected rotational velocity of about 230 km/s, which accounts for the nebulous appearance of its lines as indicated by the 'n' suffix. The emission region of its disk has a radius of ±0.04 AU. 0.20 The star itself is being viewed generally "pole-on", as ascertained by the lack of absorption features from the disk.
Upsilon Cygni holds 9.3 times the mass of the Sun and is 4.7 times the Sun's radius. The rapid rotation is giving the star an oblate shape with an equatorial bulge that is 18% wider than the polar radius. It is radiating 7,305 times the solar luminosity from its outer atmosphere at an effective temperature of 22,000 K.
The star shows variations in luminosity, including short term non-radial pulsations with periods of 2.95 and 2.6 per day, as well as random outbursts occurring up to every few years. The latter may be associated with mass-loss episodes. There is suspicion this is a spectroscopic binary, but no companion has been detected via speckle interferometry. Measured variations in radial velocity may be caused by a companion having an orbital period of about 11.4 years.
- van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv: , Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357.
- 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.
- Murphy, R. E. (November 1969), "A spectroscopic investigation of visual binaries with B-type primaries.", Astronomical Journal, 74: 1082−1094, Bibcode:1969AJ.....74.1082M, doi:10.1086/110908.
- Becker, Juliette C.; et al. (April 2015), "Extracting Radial Velocities of A- and B-type Stars from Echelle Spectrograph Calibration Spectra", The Astrophysical Journal Supplement Series, 217 (2): 13, arXiv: , Bibcode:2015ApJS..217...29B, doi:10.1088/0067-0049/217/2/29, 29.
- Hohle, M. M.; et al. (April 2010), "Masses and luminosities of O- and B-type stars and red supergiants", Astronomische Nachrichten, 331 (4): 349, arXiv: , Bibcode:2010AN....331..349H, doi:10.1002/asna.200911355.
- Rivinius, Thomas; et al. (2013), "Classical Be stars. Rapidly rotating B stars with viscous Keplerian decretion disks", The Astronomy and Astrophysics Review, 21: 69, arXiv: , Bibcode:2013A&ARv..21...69R, doi:10.1007/s00159-013-0069-0.
- Neiner, C.; et al. (July 2005), "Rotation, pulsations and outbursts in the Be star υ Cygni (HD 202904)", Astronomy and Astrophysics, 437 (1): 257−272, Bibcode:2005A&A...437..257N, doi:10.1051/0004-6361:20041901.
- 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: , Bibcode:2011MNRAS.410..190T, doi:10.1111/j.1365-2966.2010.17434.x.
- "ups Cyg -- Be Star", SIMBAD Astronomical Database, Centre de Données astronomiques de Strasbourg, retrieved 2017-02-21.
- Peters, G. J. (February 1979), "An analysis of the far-ultraviolet spectra of the pole-on Be stars Upsilon Cygni and MU Centauri", Astrophysical Journal Supplement Series, 39: 175−193, Bibcode:1979ApJS...39..175P, doi:10.1086/190570.