9 Cephei

9 Cephei (9 Cep), also known as V337 Cephei, is a variable star in the constellation Cepheus.

A light curve for V337 Cephei, plotted from TESS data^[8]

9 Cephei

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☉
Luminosity	129,000 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 was given the name V337 Cephei and classified as an α Cygni variable in 1967.^[9] 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.^[10]

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. 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. 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. 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. 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. 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. 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.
10. 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.