S Normae
 
| |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Norma |
| Right ascension | 16h 18m 51.8325s[1] |
| Declination | −57° 53′ 59.244″[1] |
| Apparent magnitude (V) | 6.394[2] (6.12 - 6.77[3]) |
| Characteristics | |
| Spectral type | F8-G0Ib[3] + B9.5V[4] |
| U−B color index | +0.66[5] |
| B−V color index | +1.00[5] |
| Variable type | δ Cepheid[3] |
| Astrometry | |
| Radial velocity (Rv) | 5.83[6] km/s |
| Proper motion (μ) | RA: 0.07[1] mas/yr Dec.: 0.04[1] mas/yr |
| Parallax (π) | 1.16 ± 0.76[1] mas |
| Distance | 924[2] pc |
| Absolute magnitude (MV) | -4.02[4] |
| Orbit[4] | |
| Period (P) | 8,660 yr |
| Semi-major axis (a) | 794 AU |
| Details[4] | |
| Mass | 6.3 M☉ |
| Radius | 65.6[2] R☉ |
| Luminosity | 2,800 L☉ |
| Temperature | 6,350 K |
| Metallicity | +0.10[7] |
| companion | |
| Mass | 2.4 M☉ |
| Age | 80[8] Myr |
| Other designations | |
| Database references | |
| SIMBAD | data |
S Normae (S Nor) is a yellow supergiant variable star in the constellation Norma. It is the brightest member of the open cluster NGC 6087.
S Normae is a Classical Cepheid variable with a visual magnitude range of 6.12 to 6.77 and a period of 9.75411 days. The spectral type varies during the pulsation cycle from F8 to G0.[3]
S Normae is a spectroscopic binary, although it the companion has now been resolved using the Hubble Space Telescope Wide Field Camera 3. The separation was 0.90" in April 2011, corresponding to 817 AU. This gives the rare opportunity for a direct determination of the mass of a Cepheid variable star and confirmation of other properties. It is a supergiant that is 6.3 times as massive as the Sun and 2,800 times as luminous. The companion a 2.4 M☉ blue-white main sequence star of spectral type B9.5.[4] There is a more distant 10th magnitude companion at 30", unsurprising in the centre of an open cluster.
References
- 1 2 3 4 5 Van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics 474 (2): 653. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357.
- 1 2 3 Moskalik, P.; Gorynya, N. A. (2005). "Mean Angular Diameters and Angular Diameter Amplitudes of Bright Cepheids". Acta Astronomica 55: 247. arXiv:astro-ph/0507076. Bibcode:2005AcA....55..247M.
- 1 2 3 4 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.
- 1 2 3 4 5 Evans, Nancy Remage; Bond, Howard E.; Schaefer, Gail H.; Mason, Brian D.; Karovska, Margarita; Tingle, Evan (2013). "Binary Cepheids: Separations and Mass Ratios in 5M ⊙ Binaries". Astronomical Journal 146 (4): 93, 10 pp. arXiv:1307.7123v1. Bibcode:2013AJ....146...93R. doi:10.1088/0004-6256/146/4/93.
- 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.
- ↑ Mermilliod, J. C.; Mayor, M.; Udry, S. (2008). "Red giants in open clusters. XIV. Mean radial velocities for 1309 stars and 166 open clusters". Astronomy and Astrophysics 485: 303. Bibcode:2008A&A...485..303M. doi:10.1051/0004-6361:200809664.
- ↑ Klagyivik, P.; Szabados, L. (2009). "Observational studies of Cepheid amplitudes. I. Period-amplitude relationships for Galactic Cepheids and interrelation of amplitudes". Astronomy and Astrophysics 504 (3): 959. arXiv:0908.3561. Bibcode:2009A&A...504..959K. doi:10.1051/0004-6361/200811464.
- ↑ Netopil, M.; Paunzen, E.; Heiter, U.; Soubiran, C. (2016). "On the metallicity of open clusters. III. Homogenised sample". Astronomy & Astrophysics 585: A150. arXiv:1511.08884. Bibcode:2016A&A...585A.150N. doi:10.1051/0004-6361/201526370.
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