9 Cephei

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9 Cephei
Cepheus constellation map.svg
Red circle.svg
Location of 9 Cephei (circled)
Observation data
Epoch J2000.0       Equinox J2000.0
Constellation Cepheus
Right ascension 21h 37m 55.22469s [1]
Declination +62° 04′ 54.9825″ [1]
Apparent magnitude  (V)4.69 - 4.78 [2]
Characteristics
Spectral type B2 Ib [3]
U−B color index −0.54 [4]
B−V color index +0.30 [4]
Variable type α Cyg [2]
Astrometry
Radial velocity (Rv)−13.50 ± 0.8 [5] km/s
Proper motion (μ)RA: −1.64 ± 0.17 [1] mas/yr
Dec.: −3.02 ± 0.16 [1] mas/yr
Parallax (π)0.48±0.14  mas [1]
Distance 950 [6]   pc
Absolute magnitude  (MV)−6.44 [3]
Details
Searle et al 2008 [3]
Mass 21  M☉
Radius 39.8  R☉
Luminosity 151,000  L☉
Surface gravity (log g)2.50  cgs
Temperature 18,000  K
Rotational velocity (v sin i)73 km/s
Markova & Puls 2008 [7]
Mass 12  M☉
Radius 32  R☉
Luminosity129,000  L☉
Surface gravity (log g)2.50  cgs
Temperature 19,200  K
Rotational velocity (v sin i)45 km/s
Other designations
9  Cephei, V337  Cephei, HD  206165, HR  8279, HIP  106801, BD+61°2169, 2MASS  J21375521+6204548, GSC  04253-02243
Database references
SIMBAD data

9 Cephei (9 Cep), also known as V337 Cephei, is a variable star in the constellation Cepheus. It is visible to the naked eye.

A light curve for V337 Cephei, plotted from TESS data V337CepLightCurve.png
A light curve for V337 Cephei, plotted from TESS data

In 1967, Graham Hill announced his discovery that 9 Cephei is a variable star. [9] 9 Cephei was given the name V337 Cephei and classified as an α Cygni variable in 1979. [10] It varies irregularly between magnitude 4.69 and 4.78. [2] A study of the Hipparcos satellite photometry showed an amplitude of 0.56 magnitudes, but could find no periodicity. [11]

9 Cephei is considered to be a member of the Cepheus OB2 stellar association, a scattering of massive bright stars around a thousand parsecs away in the southern part of the constellation Cepheus. [3]

Calculations of the physical properties of 9 Cephei vary considerably even from broadly similar observational data. Modelling using the non-LTE line-blanketed CMFGEN atmospheric code gives a temperature of 18,000 K, radius of 40 R☉, luminosity of 151,000 L☉, and mass of 21 M☉. [3] Calculations using the FASTWIND model give gives a temperature of 19,200 K, radius of 32 R☉, luminosity of 129,000 L☉, and mass of 12 M☉. [7]

References

  1. 1 2 3 4 5 van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv: 0708.1752 . Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. S2CID   18759600. Vizier catalog entry
  2. 1 2 3 Samus, N. N.; Durlevich, O. V.; 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. Bibcode:2009yCat....102025S.
  3. 1 2 3 4 5 Searle, S. C.; Prinja, R. K.; Massa, D.; Ryans, R. (2008). "Quantitative studies of the optical and UV spectra of Galactic early B supergiants. I. Fundamental parameters". Astronomy and Astrophysics. 481 (3): 777. arXiv: 0801.4289 . Bibcode:2008A&A...481..777S. doi:10.1051/0004-6361:20077125. S2CID   1552752.
  4. 1 2 Ducati, J. R. (2002). "VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system". CDS/ADC Collection of Electronic Catalogues. 2237. Bibcode:2002yCat.2237....0D.
  5. ↑ Gontcharov, G. A. (2006). "Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system". Astronomy Letters. 32 (11): 759–771. arXiv: 1606.08053 . Bibcode:2006AstL...32..759G. doi:10.1134/S1063773706110065. S2CID   119231169.
  6. ↑ Pan, K.; Federman, S. R.; Cunha, K.; Smith, V. V.; Welty, D. E. (2004). "Cloud Structure and Physical Conditions in Star-forming Regions from Optical Observations. I. Data and Component Structure". The Astrophysical Journal Supplement Series. 151 (2): 313. arXiv: astro-ph/0312095 . Bibcode:2004ApJS..151..313P. doi:10.1086/381805. S2CID   17367021.
  7. 1 2 Markova, N.; Puls, J. (2008). "Bright OB stars in the Galaxy. IV. Stellar and wind parameters of early to late B supergiants". Astronomy and Astrophysics. 478 (3): 823. arXiv: 0711.1110 . Bibcode:2008A&A...478..823M. doi:10.1051/0004-6361:20077919. S2CID   14510634.
  8. ↑ "MAST: Barbara A. Mikulski Archive for Space Telescopes". Space Telescope Science Institute. Retrieved 23 April 2023.
  9. ↑ Hill, Graham (August 1967). "Some New Variables in Nearby Associations and Galactic Clusters". Astrophysical Journal Supplement. 14: 301–306. Bibcode:1967ApJS...14..301H. doi:10.1086/190157 . Retrieved 22 January 2025.
  10. ↑ Kholopov, P. N.; Kukarkina, N. P.; Perova, N. B. (1979). "64th Name-List of Variable Stars". Information Bulletin on Variable Stars. 1581: 1. Bibcode:1979IBVS.1581....1K.
  11. ↑ Lefèvre, L.; Marchenko, S. V.; Moffat, A. F. J.; Acker, A. (2009). "A systematic study of variability among OB-stars based on HIPPARCOS photometry". Astronomy and Astrophysics. 507 (2): 1141. Bibcode:2009A&A...507.1141L. doi: 10.1051/0004-6361/200912304 .
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