Phi Cassiopeiae

φ Cassiopeiae


Location of φ Cassiopeiae (circled)

Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Cassiopeia
φ1
Right ascension 01h 20m 04.917s[1]
Declination +58° 13′ 53.80″[1]
Apparent magnitude (V) +5.11[2]
φ2
Right ascension 01h 19m 51.737s[1]
Declination +58° 11′ 29.32″[1]
Apparent magnitude (V) +7.08[2]
Characteristics
φ1
Spectral type F0Ia[2]
U−B color index +0.49[3]
B−V color index +0.68[3]
φ2
Spectral type B6Ib[2]
U−B color index −0.37[3]
B−V color index +0.41[3]
Astrometry
φ1
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]
φ2
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
φ1
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
φ2
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
φ1: HD 7927, HIP 6242, BD+57°260, SAO 22191, GC 1594
φ2: 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 binary star with an apparent magnitude of +4.95. φ1 Cas is an F0Ia bright supergiant of magnitude 4.95 and φ2 is a 7.08 magnitude B6 supergiant at 134" distance.

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 unclear whether either star is a member of the cluster.[10] The two components φ1 and φ1 are the brightest two stars in the cluster and the only probable supergiant members. They are listed as components A and C of a multiple star system, with component B being 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 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.[12]

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][13]

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.[14]

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:0708.1752Freely accessible. 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:0806.2878Freely accessible. 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. 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:1204.4115v1Freely accessible. 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:0705.0878Freely accessible. 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/0308125Freely accessible. 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. ↑ 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.
  13. ↑ 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.
  14. ↑ 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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