Upsilon Cygni
 A light curve for Upsilon Cygni. The main figure, plotted from Hipparcos data,[1] shows the long-term variability, and the inset figure, plotted from TESS data,[2] shows the short-term variability. | |
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Cygnus |
| Right ascension | 21h 17m 55.08585s[3] |
| Declination | +34° 53′ 48.7255″[3] |
| Apparent magnitude (V) | 4.43[4] |
| Characteristics | |
| Spectral type | B2 Vne[5] |
| U−B color index | −0.82[4] |
| B−V color index | −0.11[4] |
| Astrometry | |
| Radial velocity (Rv) | −1.93±0.59[6] km/s |
| Proper motion (μ) | RA: +5.667[3] mas/yr Dec.: −5.601[3] mas/yr |
| Parallax (π) | 5.0120±0.1891 mas[3] |
| Distance | 650 ± 20 ly (200 ± 8 pc) |
| Absolute magnitude (MV) | −2.03[7] |
| Details | |
| Mass | 9.25±0.52[8] M☉ |
| Radius | 4.7[9] R☉ |
| Luminosity (bolometric) | 7,305[8] L☉ |
| Surface gravity (log g) | 3.30±0.10[10] cgs |
| Temperature | 22,000[8] K |
| Metallicity [Fe/H] | −0.36[7] dex |
| Rotational velocity (v sin i) | 230±24[6] km/s |
| Age | 17.0±2.8[11] Myr |
| Other designations | |
| υ Cyg, 66 Cygni, BD+34°4371, FK5 1559, HD 202904, HIP 105138, HR 8146, SAO 71173[12] | |
| Database references | |
| SIMBAD | data |
Upsilon Cygni is a star in the northern constellation of Cygnus. Its name is a Bayer designation that is Latinized from υ Cygni, and abbreviated Upsilon Cyg or υ Cyg. It is visible to the naked eye, having an apparent visual magnitude of 4.43. Based upon an annual parallax shift of 5.0 mas, it lies at a distance of roughly 650 light years from the Sun.
This is a B-type main sequence star with a stellar classification of B2 Vne.[5] 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,[6] 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 0.20±0.04 AU.[9] The star itself is being viewed generally "pole-on", as ascertained by the lack of absorption features from the disk.[13]
Upsilon Cygni holds 9.3[8] times the mass of the Sun and is 4.7[9] 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.[10] It is radiating 7,305[8] times the solar luminosity from its outer atmosphere at an effective temperature of 22,000 K.[8]
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.[10] Several stars appear close to it in the sky, but they are likely optical companions.[14]
References
[edit]- ^ "/ftp/cats/more/HIP/cdroms/cats". Centre de Données astronomiques de Strasbourg. Strasbourg astronomical Data Center. Retrieved 15 October 2022.
- ^ "MAST: Barbara A. Mikulski Archive for Space Telescopes". Space Telescope Science Institute. Retrieved 8 December 2021.
- ^ 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 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 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.
- ^ a b c 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:1503.03874, Bibcode:2015ApJS..217...29B, doi:10.1088/0067-0049/217/2/29, S2CID 33968873, 29.
- ^ 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 f 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:1003.2335, Bibcode:2010AN....331..349H, doi:10.1002/asna.200911355, S2CID 111387483.
- ^ a b c 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:1310.3962, Bibcode:2013A&ARv..21...69R, doi:10.1007/s00159-013-0069-0, S2CID 118652497.
- ^ a b c 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:1007.4883, Bibcode:2011MNRAS.410..190T, doi:10.1111/j.1365-2966.2010.17434.x, S2CID 118629873.
- ^ "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.
- ^ Hutter, D. J.; Tycner, C.; Zavala, R. T.; Benson, J. A.; Hummel, C. A.; Zirm, H. (2021). "Surveying the Bright Stars by Optical Interferometry. III. A Magnitude-limited Multiplicity Survey of Classical Be Stars". The Astrophysical Journal Supplement Series. 257 (2): 69. arXiv:2109.06839. Bibcode:2021ApJS..257...69H. doi:10.3847/1538-4365/ac23cb. S2CID 237503492.