Theta Cassiopeiae

From Wikipedia, the free encyclopedia
Jump to navigation Jump to search

Theta Cassiopeiae
Diagram showing star positions and boundaries of the Reticulum constellation and its surroundings
Cercle rouge 100%.svg
Location of θ Cassiopeiae (circled)
Observation data
Epoch J2000.0      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 Ret, 33 Cassiopeiae, BD+54° 236, HD 6961, HIP 5542, HR 343, SAO 22070.[10]
Database references
SIMBADdata

Theta Cassiopeiae (θ Cas, θ Cassiopeiae) is a solitary[3] star in the northern constellation of Cassiopeia. It shares the traditional name Marfak /ˈmɑːrfæk/ with μ Cassiopeiae to the southeast, which is derived from the Arabic term Al Marfik or Al Mirfaq (المرفق), meaning "the elbow".[11] At an apparent visual magnitude of 4.3,[2] it 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.[12]

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.[13] Consequently, θ Cassiopeiae itself is known as 閣道四 (Gé Dào sì, English: the Fourth Star of Flying Corridor.)[14]

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,[15] 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.[16] It is a suspected Delta Scuti variable.[4]

References[edit]

  1. ^ a b c d e f 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.
  2. ^ a b c d 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. ^ a b c 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, arXiv:0806.2878, Bibcode:2008MNRAS.389..869E, doi:10.1111/j.1365-2966.2008.13596.x.
  4. ^ a b Frolov, M. S. (April 1970), "List of Probable Delta Scuti Stars", Information Bulletin on Variable Stars, 427: 1, Bibcode:1970IBVS..427....1F.
  5. ^ 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, arXiv:1208.3048, Bibcode:2012A&A...546A..61D, doi:10.1051/0004-6361/201219219, A61.
  6. ^ Eggen, Olin J. (July 1998), "The Age Range of Hyades Stars", The Astronomical Journal, 116 (1): 284–292, Bibcode:1998AJ....116..284E, doi:10.1086/300413.
  7. ^ a b 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, arXiv:1501.03154, Bibcode:2015ApJ...804..146D, doi:10.1088/0004-637X/804/2/146.
  8. ^ a b Lang, Kenneth R. (2006), Astrophysical formulae, Astronomy and astrophysics library, 1 (3rd ed.), Birkhäuser, ISBN 3-540-29692-1. The radius (R*) is given by:
  9. ^ a b Royer, F.; et al. (February 2007), "Rotational velocities of A-type stars. III. Velocity distributions", Astronomy and Astrophysics, 463 (2): 671–682, arXiv:astro-ph/0610785, Bibcode:2007A&A...463..671R, doi:10.1051/0004-6361:20065224.
  10. ^ "* tet Cas". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-02-16.
  11. ^ Allen, R. H. (1963), Star Names: Their Lore and Meaning (Reprint ed.), New York: Dover Publications Inc., p. 148, ISBN 0-486-21079-0, retrieved 2010-12-12
  12. ^ 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, arXiv:astro-ph/0412070, Bibcode:2005AJ....129.1483L, doi:10.1086/427854.
  13. ^ (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.
  14. ^ (in Chinese) 香港太空館 - 研究資源 - 亮星中英對照表 Archived 2011-01-30 at the Wayback Machine, Hong Kong Space Museum. Accessed on line November 23, 2010.
  15. ^ Richichi, A.; et al. (February 2005), "CHARM2: An updated Catalog of High Angular Resolution Measurements", Astronomy and Astrophysics, 431 (2): 773–777, Bibcode:2005A&A...431..773R, doi:10.1051/0004-6361:20042039.
  16. ^ Song, Inseok; et al. (January 2001), "Ages of A-Type Vega-like Stars from uvbyβ Photometry", The Astrophysical Journal, 546 (1): 352–357, arXiv:astro-ph/0010102, Bibcode:2001ApJ...546..352S, doi:10.1086/318269.

External links[edit]