Astronomy:Theta Cassiopeiae

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Short description: Star in the constellation Cassiopeia
Theta Cassiopeiae
Cassiopeia IAU.svg
Red circle.svg
Location of θ Cassiopeiae (circled)
Observation data
Equinox J2000.0]] (ICRS)
Constellation Cassiopeia
Right ascension  01h 11m 06.16225s[1]
Declination +55° 08′ 59.6472″[1]
Apparent magnitude (V) 4.334[2]
Characteristics
Spectral type A7 V[3]
U−B color index +0.130[2]
B−V color index +0.170[2]
Variable type Suspected δ Sct[4]
Astrometry
Radial velocity (Rv)2.5±0.6[5] km/s
Proper motion (μ) RA: +226.77[1] mas/yr
Dec.: −18.75[1] mas/yr
Parallax (π)24.42 ± 0.24[1] mas
Distance134 ± 1 ly
(41.0 ± 0.4 pc)
Absolute magnitude (MV)+1.28[6]
Details[7]
Mass1.83 M☉
Radius2.6[8] R☉
Surface gravity (log g)4.03±0.14 cgs
Temperature8,202±279 K
Rotational velocity (v sin i)103[9] km/s
Age650 Myr
Other designations
Marfak, θ Cas, 33 Cassiopeiae, BD+54°236, HD 6961, HIP 5542, HR 343, SAO 22070[10]
Database references
SIMBADdata

Theta Cassiopeiae or θ Cassiopeiae is a solitary[3] star in the northern constellation of Cassiopeia. It shares the traditional name Marfak /ˈmɑːrfæk/ with μ Cassiopeiae, positioned less than half a degree to the WSW,[11] which is derived from the Arabic term Al Marfik or Al Mirfaq (المرفق), meaning "the elbow".[12] At an apparent visual magnitude of 4.3,[2] Theta Cassiopeiae is visible to the naked eye. Based upon an annual parallax shift of 24.42 mas,[1] it is located about 134 light years from the Sun. It has a total annual proper motion of 0.227 arcseconds per year,[13] and is slowly drifting further away from the Sun with a radial velocity of 2.5 km/s.[5]

In Chinese, 閣道 (Gé Dào), meaning Flying Corridor, refers to an asterism consisting of θ Cassiopeiae, ι Cassiopeiae, ε Cassiopeiae, δ Cassiopeiae, ν Cassiopeiae and ο Cassiopeiae.[14] Consequently, θ Cassiopeiae itself is known as 閣道四 (Gé Dào sì, English: the Fourth Star of Flying Corridor.)[15]

This is an A-type main sequence star with a stellar classification of A7 V.[3] The measured angular diameter of this star is 0.58±0.02 mas,[16] which, at the estimated distance of this star, yields a physical size of about 2.6 times the radius of the Sun.[8] It is about 650[7] million years in age and is spinning with a projected rotational velocity of 103 km/s.[9] This is a candidate Vega-type system, which means it displays an infrared excess suggesting it has an orbiting debris disk.[17] It is a suspected Delta Scuti variable.[4]

The star appears to be a member of a leading tidal tail of the Hyades cluster.[18]

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics 474 (2): 653–664, doi:10.1051/0004-6361:20078357, Bibcode: 2007A&A...474..653V. 
  2. ↑ 2.0 2.1 2.2 2.3 Oja, T. (August 1991), "UBV photometry of stars whose positions are accurately known. VI", Astronomy and Astrophysics Supplement Series 89 (2): 415–419, Bibcode: 1991A&AS...89..415O. 
  3. ↑ 3.0 3.1 3.2 Eggleton, P. P.; Tokovinin, A. A. (September 2008), "A catalogue of multiplicity among bright stellar systems", Monthly Notices of the Royal Astronomical Society 389 (2): 869–879, doi:10.1111/j.1365-2966.2008.13596.x, Bibcode: 2008MNRAS.389..869E. 
  4. ↑ 4.0 4.1 Frolov, M. S. (April 1970), "List of Probable Delta Scuti Stars", Information Bulletin on Variable Stars 427: 1, Bibcode: 1970IBVS..427....1F. 
  5. ↑ 5.0 5.1 de Bruijne, J. H. J.; Eilers, A.-C. (October 2012), "Radial velocities for the HIPPARCOS-Gaia Hundred-Thousand-Proper-Motion project", Astronomy & Astrophysics 546: 14, doi:10.1051/0004-6361/201219219, A61, Bibcode: 2012A&A...546A..61D. 
  6. ↑ Eggen, Olin J. (July 1998), "The Age Range of Hyades Stars", The Astronomical Journal 116 (1): 284–292, doi:10.1086/300413, Bibcode: 1998AJ....116..284E. 
  7. ↑ 7.0 7.1 David, Trevor J.; Hillenbrand, Lynne A. (2015), "The Ages of Early-Type Stars: Strömgren Photometric Methods Calibrated, Validated, Tested, and Applied to Hosts and Prospective Hosts of Directly Imaged Exoplanets", The Astrophysical Journal 804 (2): 146, doi:10.1088/0004-637X/804/2/146, Bibcode: 2015ApJ...804..146D. 
  8. ↑ 8.0 8.1 Lang, Kenneth R. (2006), Astrophysical formulae, Astronomy and astrophysics library, 1 (3rd ed.), Birkhäuser, ISBN 3-540-29692-1, https://books.google.com/books?id=OvTjLcQ4MCQC&pg=PA41.  The radius (R*) is given by:
    [math]\displaystyle{ \begin{align} 2\cdot R_* & = \frac{(41.0\cdot 0.58\cdot 10^{-3})\ \text{AU}}{0.0046491\ \text{AU}/R_{\bigodot}} \\ & \approx 5.1\cdot R_{\bigodot} \end{align} }[/math]
  9. ↑ 9.0 9.1 Royer, F. et al. (February 2007), "Rotational velocities of A-type stars. III. Velocity distributions", Astronomy and Astrophysics 463 (2): 671–682, doi:10.1051/0004-6361:20065224, Bibcode: 2007A&A...463..671R. 
  10. ↑ "* tet Cas". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=%2A+tet+Cas. 
  11. ↑ Sinnott, Roger W.; Perryman, Michael A. C. (1997), Millennium Star Atlas, 1, Sky Publishing Corporation and the European Space Agency, p. 64, ISBN 0-933346-84-0. 
  12. ↑ Allen, R. H. (1963), Star Names: Their Lore and Meaning (Reprint ed.), New York: Dover Publications Inc., p. 148, ISBN 0-486-21079-0, https://archive.org/details/starnamestheirlo00alle/page/148, retrieved 2010-12-12 
  13. ↑ Lépine, Sébastien; Shara, Michael M. (March 2005), "A Catalog of Northern Stars with Annual Proper Motions Larger than 0.15" (LSPM-NORTH Catalog)", The Astronomical Journal 129 (3): 1483–1522, doi:10.1086/427854, Bibcode: 2005AJ....129.1483L. 
  14. ↑ (in Chinese) 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, ISBN:978-986-7332-25-7.
  15. ↑ (in Chinese) 香港太空館 - 研究資源 - 亮星中英對照表 , Hong Kong Space Museum. Accessed on line November 23, 2010.
  16. ↑ Richichi, A. et al. (February 2005), "CHARM2: An updated Catalog of High Angular Resolution Measurements", Astronomy and Astrophysics 431 (2): 773–777, doi:10.1051/0004-6361:20042039, Bibcode: 2005A&A...431..773R. 
  17. ↑ Song, Inseok et al. (January 2001), "Ages of A-Type Vega-like Stars from uvbyβ Photometry", The Astrophysical Journal 546 (1): 352–357, doi:10.1086/318269, Bibcode: 2001ApJ...546..352S. 
  18. ↑ Röser, Siegfried et al. (January 2019), "Hyades tidal tails revealed by Gaia DR2", Astronomy & Astrophysics 621: 5, doi:10.1051/0004-6361/201834608, L2, Bibcode: 2019A&A...621L...2R. 

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