PZ Cassiopeiae
 Location of PZ Cas | |
| 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 | |
| Spectral type | M3I[4] |
| U−B color index | +1.32[2] |
| B−V color index | +2.58[2] |
| Variable type | SRc[5] |
| Astrometry | |
| Radial velocity (Rv) | -45.68 ± 0.68[6] km/s |
| Proper motion (μ) | RA: −4.15[1] mas/yr Dec.: −3.55[1] mas/yr |
| Parallax (π) | 0.356 ± 0.026 mas[7] |
| Distance | 2,810+220 −190[7] pc |
| Absolute magnitude (MV) | −7.89[4] |
| Details | |
| Radius | 1,190 (-1,940)[4] R☉ |
| Luminosity | 240,000–270,000[7] L☉ |
| Surface gravity (log g) | −0.5[4] cgs |
| Temperature | 3,600[4] K |
| Age | 8 – 10[7] Myr |
| Other designations | |
| Database references | |
| SIMBAD | data |
PZ Cassiopeiae is a red supergiant star located in the Cassiopeia constellation, and a semi-regular variable star.
Characteristics
PZ Cas is an extreme luminous red supergiant star, one of the largest stars currently known with estimates at 1,190–1,940 times the Sun's radius. Its distance from Earth was initially estimated to be around 7800 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 a distance of 9,160 light-years (2.81 kiloparsecs) that translates into a luminosity for it of between 240,000 and 270,000 times the Sun's luminosity, a radius 1,260–1,340 the solar one, and an initial mass 25 times that of the Sun. These parameters are all similar to those estimated for the red hypergiant VY Canis Majoris. It is likely to be part of the Cas OB5 stellar association although apparently much younger than the other stars in the association.[7]
PZ Cas is a slow semi-regular variable star with the period quoted as 925 days in the General Catalogue of Variable Stars,[8] 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 less massive 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.[9]
Companion
PZ Cas has a companion, a 13th magnitude star 12" away.[10]
References
- ^ a b c d 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.
- ^ a b c 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.
- ^ a b c 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. arXiv:astro-ph/0608438. Bibcode:2006MNRAS.372.1721K. doi:10.1111/j.1365-2966.2006.10973.x.
{{cite journal}}: CS1 maint: unflagged free DOI (link) - ^ a b c d e 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. arXiv:astro-ph/0504337. Bibcode:2005ApJ...628..973L. doi:10.1086/430901.
- ^ a b 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.
- ^ 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.
- ^ a b c d e 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.
- ^ 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.
- ^ 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.
- ^ 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.
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