Phi Cassiopeiae

φ Cassiopeiae
Location of φ Cassiopeiae (circled)
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Cassiopeia
A
Right ascension 01h 20m 04.917s[1]
Declination +58° 13′ 53.80″[1]
Apparent magnitude (V) +5.11[2]
C
Right ascension 01h 19m 51.737s[1]
Declination +58° 11′ 29.32″[1]
Apparent magnitude (V) +7.08[2]
Characteristics
A
Spectral type F0Ia[2]
U−B color index +0.49[3]
B−V color index +0.68[3]
C
Spectral type B6Ib[2]
U−B color index −0.37[3]
B−V color index +0.41[3]
Astrometry
A
Radial velocity (Rv)−28.39[4] km/s
Proper motion (μ) RA: −0.59[1] mas/yr
Dec.: −1.59[1] mas/yr
Parallax (π)0.27 ± 0.32[1] mas
Distance2300 ly
(710 pc)
Absolute magnitude (MV)−8.76[5]
C
Radial velocity (Rv)−28.50[6] km/s
Proper motion (μ) RA: −0.46[1] mas/yr
Dec.: −0.79[1] mas/yr
Parallax (π)0.61 ± 0.66[1] mas
Distanceapprox. 5,000 ly
(approx. 2,000 pc) ly
Absolute magnitude (MV)−6.5[7]
Details
A
Mass6.3[8] M☉
Radius263[8] R☉
Luminosity170,000[8] L☉
Surface gravity (log g)1.0[5] cgs
Temperature7,341[5] K
Metallicity-0.24[5]
Rotational velocity (v sin i)23[9] km/s
Age20[10] Myr
C
Mass21[7] M☉
Radius53[7] R☉
Luminosity83,000[11] L☉
Surface gravity (log g)2.05[11] cgs
Temperature15,500[11] K
Rotational velocity (v sin i)35[11] km/s
Other designations
34 Cassiopeiae, HR 382, CCDM J01200+5813, ADS 1073
A: HD 7927, HIP 6242, BD+57°260, SAO 22191, GC 1594
C: HD 7902, HIP 6229, BD+57°257, SAO 22187, GC 1590, NSV 466
Database references
SIMBADdata

Phi Cassiopeiae (φ Cas, φ Cassiopeiae) is a star in the constellation Cassiopeia. φ Cassiopeiae is a multiple star with a combined apparent magnitude of +4.95. The two brightest components are A and C, sometimes called φ1 and φ2 Cas. φ Cas A is an F0 bright supergiant of magnitude 4.95 and φ Cas C is a 7.08 magnitude B6 supergiant at 134".

System

φ1 and φ2 Cassiopeiae are the two brightest star in the field of open cluster NGC 457.

φ Cassiopeiae appears among the stars of the open cluster NGC 457, which is at 2,400pc, but it is uncertain whether it is a member of the cluster.[10] φ Cas is generally treated as having five component stars, designated A to E in order of distance from the brightest star. The two components A and C are the brightest and the only two supergiant members of NGC 457; they are sometimes referred to as φ1 and φ1 Cassiopeiae.[12] Component B is a 12th magnitude star 49" from φ1. Components D and E and both 10th magnitude B-type main sequence stars in NGC 457, with component E only 42" from φ2. Another three components are sometimes listed as components of the multiple system, although this is somewhat arbitrary with dozens of members of NGC 457 being found within a few arc-minutes.[13]

The two supergiants share a similar space motion to the other stars in the cluster, but their evolutionary status and brightness makes them unlikely members.[8]

Properties

φ1 is a very bright yellow supergiant. Its absolute magnitude is comparable to some yellow hypergiants but it does not show the level of mass loss and instability that would qualify it as a hypergiant itself. Various model atmospheres all give a temperature around 7,300K, a low surface gravity, a radius around 250 R☉, and a luminosity well over 100,000 L☉. More uncertain is the mass, which would be expected to have been well over 25 M☉ initially, but much less now. Different authors have published values from 6 M☉ to 17 M☉.[8][14]

φ2 is a relatively typical B class supergiant, 83,000 times the luminosity of the sun. It is a suspected variable and a suspected spectroscopic binary.[15]

See also

References

  1. 1 2 3 4 5 6 7 8 9 10 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.
  2. 1 2 3 4 Eggleton, P. P.; Tokovinin, A. A. (2008). "A catalogue of multiplicity among bright stellar systems". Monthly Notices of the Royal Astronomical Society. 389 (2): 869. arXiv:0806.2878. Bibcode:2008MNRAS.389..869E. doi:10.1111/j.1365-2966.2008.13596.x.
  3. 1 2 3 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.
  4. ↑ 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. CiteSeerX 10.1.1.30.7545. doi:10.1051/0004-6361:200809664.
  5. 1 2 3 4 Kovtyukh, V. V.; Gorlova, N.; Belik, S. I. (2012). "Accurate luminosities from the oxygen 7771-4 a triplet and the fundamental parameters of F-G supergiants". Monthly Notices of the Royal Astronomical Society. 423 (4): 3268. arXiv:1204.4115v1. Bibcode:2012MNRAS.423.3268K. doi:10.1111/j.1365-2966.2012.21117.x.
  6. ↑ Kharchenko, N. V.; Scholz, R.-D.; Piskunov, A. E.; Röser, S.; Schilbach, E. (2007). "Astrophysical supplements to the ASCC-2.5: Ia. Radial velocities of ˜55000 stars and mean radial velocities of 516 Galactic open clusters and associations". Astronomische Nachrichten. 328 (9): 889. arXiv:0705.0878. Bibcode:2007AN....328..889K. doi:10.1002/asna.200710776.
  7. 1 2 3 Leitherer, C.; Wolf, B. (1984). "Early-type stars in OB associations in the infrared. I Extinction law and IR excesses". Astronomy and Astrophysics. 132: 151. Bibcode:1984A&A...132..151L.
  8. 1 2 3 4 5 Rosenzweig, P.; Anderson, L. (1993). "A determination of the basic atmospheric parameters of Phi Cassiopeiae". The Astrophysical Journal. 411: 207. Bibcode:1993ApJ...411..207R. doi:10.1086/172820.
  9. ↑ Evans, Christopher J.; Howarth, Ian D. (2003). "Characteristics and classification of A-type supergiants in the Small Magellanic Cloud". Monthly Notices of the Royal Astronomical Society. 345 (4): 1223. arXiv:astro-ph/0308125. Bibcode:2003MNRAS.345.1223E. doi:10.1046/j.1365-2966.2003.07038.x.
  10. 1 2 Zhang, X. B.; Luo, C. Q.; Fu, J. N. (2012). "B-Type Variables in the Young Open Cluster Ngc 457". The Astronomical Journal. 144 (3): 86. Bibcode:2012AJ....144...86Z. doi:10.1088/0004-6256/144/3/86.
  11. 1 2 3 4 McErlean, N. D.; Lennon, D. J.; Dufton, P. L. (1999). "Galactic B-supergiants: A non-LTE model atmosphere analysis to estimate atmospheric parameters and chemical compositions". Astronomy and Astrophysics. 349: 553. Bibcode:1999A&A...349..553M.
  12. ↑ Mark Bratton (15 September 2011). The Complete Guide to the Herschel Objects: Sir William Herschel's Star Clusters, Nebulae and Galaxies. Cambridge University Press. pp. 583–. ISBN 978-0-521-76892-4.
  13. ↑ Dommanget, J.; Nys, O. (1994). "Catalogue des composantes d'etoiles doubles et multiples (CCDM) premiere edition - Catalogue of the components of double and multiple stars (CCDM) first edition". Com. de l'Observ. Royal de Belgique. 115: 1. Bibcode:1994CoORB.115....1D.
  14. ↑ Arellano Ferro, A.; Parrao, L.; Giridhar, S. (1988). "Comments on the variability and physical parameters of the F supergiant Phi Cassiopeiae". Astronomical Society of the Pacific. 100: 993. Bibcode:1988PASP..100..993A. doi:10.1086/132261.
  15. ↑ Mayer, Pavel; Hanna, Magdy A.; Wolf, Marek; Chochol, Drahos (1998). "Radial velocities of six early-type evolved stars". Astrophysics and Space Science. 262 (2): 163. Bibcode:1994CoSka..24...65M. doi:10.1023/A:1001840718226.
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