PZ Cassiopeiae

PZ Cassiopeiae is a red supergiant star located in the Cassiopeia constellation, and a semi-regular variable star.

PZ Cassiopeiae

PZ Cassiopeiae is the bright star towards upper right in this WISE infrared image.
Observation data
Epoch J2000      Equinox J2000
Constellation Cassiopeia
Right ascension 23h 44m 03.28104s[1]
Declination +61° 47′ 22.1823″[1]
Apparent magnitude (V) 8.90[2] (8.2 - 10.2[3])
Characteristics
Evolutionary stage Red supergiant
Spectral type M3Ia[4]
U−B color index +1.32[2]
B−V color index +2.58[2]
Variable type SRc[5] + Cepheid[6]
Astrometry
Radial velocity (Rv)–45.68 ± 0.68[7] km/s
Proper motion (μ) RA: −4.15[1] mas/yr
Dec.: −3.55[1] mas/yr
Parallax (π)0.356 ± 0.026[8] mas
Distance2,810+220
−190[8] pc
Absolute magnitude (MV)−7.89[9]
Details
Radius1,062[10] R☉
Luminosity229,000[11] L☉
Surface gravity (log g)−0.5[9] cgs
Temperature3,605±170[10] K
Age8 – 10[8] Myr
Other designations
PZ Cas, IRC +60417, HIP 117078, BD+60°2613, RAFGL 3138
Database references
SIMBADdata

Characteristics

PZ Cassiopeiae is a luminous red supergiant star, one of the largest stars currently known with a radius over 1,000 times the Sun's radius (R☉), and also one of most luminous of its type, around 200,000 times more luminous than the Sun (L☉). It is likely to be part of the Cas OB5 stellar association although apparently much younger than the other stars in the association.[8] The star is losing mass at around 2.6×10−5 M☉ and has also once been described as a hypergiant.[12][13]

Its distance from Earth was initially estimated to be around 7,800 light-years (2.4 kiloparsecs). Subsequent studies of the star using the water masers that surround it have allowed to refine both the distance and the parameters of this star, deriving an accurate parallax of 0.356±0.026 mas, corresponding to a distance of 9,160 light-years (2.81 kiloparsecs), that translates a luminosity for it around 229,000 L☉, and an initial mass of 20 to 25 times that of the Sun. These parameters are all similar to those estimated for the red hypergiant VY Canis Majoris.[8][11]

A less reliable Gaia Data Release 2 parallax of 0.42±0.09 mas gives the star a luminosity below 180,000 L☉ with a corresponding radius of 1,062 R☉.[10]

PZ Cas is a slow semi-regular variable star with the period quoted as 925 days in the General Catalogue of Variable Stars,[14] although periods of 850 and 3,195 days have been derived.[5][3] The visual range is approximate magnitude 8-10, large for this type of variable.[3]

Supergiant or AGB star

PZ Cas has traditionally been treated as a massive supergiant, comparable to others such as VY CMa, but there is some evidence that it is a possible less massive O-rich S- or SC-type Asymptotic Giant Branch (AGB) or post-AGB star. It shows enrichment of Zr and Ba, but not Li as would be expected for a true supergiant.[15]

Companion

PZ Cas has a Cepheid variable companion, a 13th magnitude star 12" away.[6]

See also

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.
  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.
  3. Kiss, L. L.; Szabó, G. M.; Bedding, T. R. (2006). "Variability in red supergiant stars: Pulsations, long secondary periods and convection noise". Monthly Notices of the Royal Astronomical Society. 372 (4): 1721–1734. arXiv:astro-ph/0608438. Bibcode:2006MNRAS.372.1721K. doi:10.1111/j.1365-2966.2006.10973.x. S2CID 5203133.
  4. Keenan, Philip C.; McNeil, Raymond C. (1989). "The Perkins catalog of revised MK types for the cooler stars". Astrophysical Journal Supplement Series. 71: 245. Bibcode:1989ApJS...71..245K. doi:10.1086/191373.
  5. Le Squeren, A. M.; Sivagnanam, P.; Dennefeld, M.; David, P. (1992). "A Complete Survey of OH / Infrared Objects from the IRAS LRS Sources Within a Domain of the Color Diagram". Astronomy and Astrophysics. 254: 133. Bibcode:1992A&A...254..133L.
  6. Mason, Brian D.; Wycoff, Gary L.; Hartkopf, William I.; Douglass, Geoffrey G.; Worley, Charles E. (2001). "The 2001 US Naval Observatory Double Star CD-ROM. I. The Washington Double Star Catalog". The Astronomical Journal. 122 (6): 3466. Bibcode:2001AJ....122.3466M. doi:10.1086/323920.
  7. Famaey, B.; Jorissen, A.; Luri, X.; Mayor, M.; Udry, S.; Dejonghe, H.; Turon, C. (2005). "Local kinematics of K and M giants from CORAVEL/Hipparcos/Tycho-2 data. Revisiting the concept of superclusters". Astronomy and Astrophysics. 430: 165. arXiv:astro-ph/0409579. Bibcode:2005A&A...430..165F. doi:10.1051/0004-6361:20041272. S2CID 17804304.
  8. Kusuno, K.; Asaki, Y.; Imai, H.; Oyama, T. (2013). "Distance and Proper Motion Measurement of the Red Supergiant, Pz Cas, in Very Long Baseline Interferometry H2O Maser Astrometry". The Astrophysical Journal. 774 (2): 107. arXiv:1308.3580. Bibcode:2013ApJ...774..107K. doi:10.1088/0004-637X/774/2/107. S2CID 118867155.
  9. Levesque, E. M.; Massey, P.; Olsen, K. A. G.; Plez, B.; Josselin, E.; Maeder, A.; Meynet, G. (2005). "The Effective Temperature Scale of Galactic Red Supergiants: Cool, but Not as Cool as We Thought". The Astrophysical Journal. 628 (2): 973–985. arXiv:astro-ph/0504337. Bibcode:2005ApJ...628..973L. doi:10.1086/430901. S2CID 15109583.
  10. Messineo, M.; Brown, A. G. A. (2019). "A Catalog of Known Galactic K-M Stars of Class I Candidate Red Supergiants in Gaia DR2". The Astronomical Journal. 158 (1): 20. arXiv:1905.03744. Bibcode:2019AJ....158...20M. doi:10.3847/1538-3881/ab1cbd. S2CID 148571616.
  11. Davies, Ben; Beasor, Emma R. (March 2020). "The 'red supergiant problem': the upper luminosity boundary of Type II supernova progenitors". MNRAS. 493 (1): 468–476. arXiv:2001.06020. Bibcode:2020MNRAS.493..468D. doi:10.1093/mnras/staa174. S2CID 210714093.
  12. Mauron, N.; Josselin, E. (2011). "The mass-loss rates of red supergiants and the de Jager prescription". Astronomy and Astrophysics. 526: A156. arXiv:1010.5369. Bibcode:2011A&A...526A.156M. doi:10.1051/0004-6361/201013993. S2CID 119276502.
  13. Stickland, D. J. (1985). "IRAS observations of the cool galactic hypergiants". The Observatory. 105: 229. Bibcode:1985Obs...105..229S.
  14. 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.
  15. García-Hernández, D. A.; García-Lario, P.; Plez, B.; Manchado, A.; d'Antona, F.; Lub, J.; Habing, H. (2007). "Lithium and zirconium abundances in massive Galactic O-rich AGB stars". Astronomy and Astrophysics. 462 (2): 711. arXiv:astro-ph/0609106. Bibcode:2007A&A...462..711G. doi:10.1051/0004-6361:20065785. S2CID 16016698.
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