Astronomy:Upsilon Cygni
250px 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 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[3] mas |
| 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 | |
| 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
- ↑ "/ftp/cats/more/HIP/cdroms/cats". Strasbourg astronomical Data Center. https://cdsarc.cds.unistra.fr/viz-bin/ftp-index?/ftp/cats/more/HIP/cdroms/cats.
- ↑ "MAST: Barbara A. Mikulski Archive for Space Telescopes". Space Telescope Science Institute. https://mast.stsci.edu/portal/Mashup/Clients/Mast/Portal.html.
- ↑ 3.0 3.1 3.2 3.3 3.4 Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940 Gaia DR3 record for this source at VizieR.
- ↑ 4.0 4.1 4.2 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.
- ↑ 5.0 5.1 Murphy, R. E. (November 1969), "A spectroscopic investigation of visual binaries with B-type primaries.", Astronomical Journal 74: 1082–1094, doi:10.1086/110908, Bibcode: 1969AJ.....74.1082M.
- ↑ 6.0 6.1 6.2 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, doi:10.1088/0067-0049/217/2/29, 29, Bibcode: 2015ApJS..217...29B.
- ↑ 7.0 7.1 Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters 38 (5): 331, doi:10.1134/S1063773712050015, Bibcode: 2012AstL...38..331A.
- ↑ 8.0 8.1 8.2 8.3 8.4 8.5 Hohle, M. M. et al. (April 2010), "Masses and luminosities of O- and B-type stars and red supergiants", Astronomische Nachrichten 331 (4): 349, doi:10.1002/asna.200911355, Bibcode: 2010AN....331..349H.
- ↑ 9.0 9.1 9.2 Rivinius, Thomas et al. (2013), "Classical Be stars. Rapidly rotating B stars with viscous Keplerian decretion disks", The Astronomy and Astrophysics Review 21: 69, doi:10.1007/s00159-013-0069-0, Bibcode: 2013A&ARv..21...69R.
- ↑ 10.0 10.1 10.2 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, doi:10.1051/0004-6361:20041901, Bibcode: 2005A&A...437..257N.
- ↑ 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, doi:10.1111/j.1365-2966.2010.17434.x, Bibcode: 2011MNRAS.410..190T.
- ↑ "ups Cyg -- Be Star", SIMBAD Astronomical Database (Centre de Données astronomiques de Strasbourg), http://simbad.u-strasbg.fr/simbad/sim-id?Ident=ups+Cyg, 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, doi:10.1086/190570, Bibcode: 1979ApJS...39..175P.
- ↑ 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. doi:10.3847/1538-4365/ac23cb. Bibcode: 2021ApJS..257...69H.
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