Zeta Cassiopeiae

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Star
ζ Cassiopeiae
AladinLite
Observation
dates equinox :  J2000.0 , epoch : J2000.0
Constellation Cassiopeia
Right ascension 0 h 36 m 58.28 s
declination + 53 ° 53 ′ 48.9 ″
Apparent brightness 3.66 likes
Typing
B − V color index −0.20 
U − B color index −0.87 
R − I index −0.21 
Spectral class B2 IV
Variable star type slowly pulsating
B star 
Astrometry
Radial velocity −0.2 ± 0.1 km / s
parallax 5.50 ± 0.16  mas
distance 590 ± 20  ly
182 ± 6  pc  
Visual absolute brightness M vis −2.6 mag
Proper movement 
Rec. Share: 17.38 ± 0.13  mas / a
Dec. portion: −9.86 ± 0.11  mas / a
Physical Properties
Dimensions 8 - 9  M ☉
radius 5.4  R ☉
Luminosity

≈ 5,000  L ☉

Effective temperature 20 750 ± 200  K
Metallicity [Fe / H] −0.01
Rotation time 5.370 447 ± 0.000 078 d
Age 20 mill.  A
Other names
and catalog entries
Bayer name ζ Cassiopeiae
Flamsteed name 17 Cassiopeiae
Bonn survey BD + 53 ° 105
Bright Star Catalog HR 153 [1]
Henry Draper Catalog HD 3360 [2]
Hipparcos catalog HIP 2920 [3]
SAO catalog SAO 21566 [4]
Tycho catalog TYC 3654-2132-1 [5]
2MASS catalog 2MASS J00365827 + 5353486 [6]
Other names FK5 17; GSC 03654-02132; NSV 225; Gaia DR2 418001477266591744

ζ Cassiopeiae ( Zeta Cassiopeiae , short ζ Cas ; IAU - name Fulu ) is a star in the constellation Kassiopeia . The star has an apparent magnitude of 3.66 mag and is about 600 light years away from us.

ζ Cas is a star of the spectral class B2 IV (or IV – V) and has a mass of 8 - 9 M ⊙ . The rotation period could be measured very precisely with the help of the International Ultraviolet Explorer (IUE) to 5.370 447 ± 0.000 078 days. The inclination of the axis of rotation in relation to our line of sight i , the projected rotation speed v sin i and the true rotation speed at the equator v are, according to Coralie Neiner et al. (2003) i = 18 ± 4 °, v sin i = 17 ± 3 km / s and v = 55 ± 28 km / s or according to Maryline Briquet et al. (2016) i = 30 ± 1 °, v sin i = 20 ± 3 km / s and v = 40 ± 7.5 km / s. With the above rotation period, the star radius is ≈ 6 R ⊙ in the first case or ≈ 4 R ⊙ in the second case . Apart from that, the radius of 5.4 R ⊙ was calculated using theoretical models (based on IUE observation data).

In 2003 the presence of a weak dipolar magnetic field of B pol = 335  +120−65 G (in a later study B pol ≈ 100 - 150 G) detected. The magnetic field has a strong inclination towards the axis of rotation of almost 80 ° and influences the discharge of the stellar wind . The wind particles escape at the magnetic poles and settle in a disk at the magnetic equator. Shock fronts are presumably formed over the magnetic poles by winds flowing out and falling back again. The annual mass loss due to the stellar wind is (depending on the determination method ) 10 −9.7 or 10 −11 M ⊙ . Observations with the NARVAL spectropolarimeter have shown that ζ Cas does not rotate differentially , but that a “rigid” rotation is forced by the magnetic field.

ζ Cas is weakly changeable and belongs to the slowly pulsating B-stars (outdated 53-Persei-stars ). Here, ζ Cas in the instability strip in the HR diagram is on the border with the β-Cephei stars . The brightness fluctuates by less than 0.004 mag (in the ubvyβ system). The star pulsates nonradially with a period of 1.56 days.

On June 30, 2017, the name Fulu was added to the IAU's official list of star names.

Web links

Individual evidence

  1. ^ A b c Floor van Leeuwen: Hipparcos, the New Reduction . VizieR data catalog I / 311 (published electronically). 2008, bibcode : 2008yCat.1311 .... 0V . VizieR catalog entry .
  2. ↑ a b c d Dorrit Hoffleit, Wayne H. Warren Jr .: Bright Star Catalog, 5th Revised Ed. VizieR data catalog V / 50 (published electronically). 1995, bibcode : 1995yCat.5050 .... 0H . VizieR catalog entry .
  3. ^ A b William W. Morgan , Philip C. Keenan : Spectral classification . In: Annual Review of Astronomy and Astrophysics . Vol. 11, 1973, p. 33, bibcode : 1973ARA & A..11 ... 29M , doi: 10.1146 / annurev.aa.11.090173.000333 .
  4. ↑ George A. Gontcharov: Pulkovo radial velocities for 35493 HIP stars . VizieR data catalog III / 252 (published electronically). 2007, bibcode : 2007yCat.3252 .... 0G . VizieR catalog entry .
  5. ↑ Derived from parallax ( π = 5.50 ± 0.16 mas, van Leeuwen 2007).
  6. ↑ Calculated from the apparent brightness m V and parallax π (in arc seconds) according to m V - 5 ∙ lg (1 / π) + 5 .
  7. ↑ a b c d e f g h i j Coralie Neiner et al. : Discovery of a magnetic field in the Slowly Pulsating B star ζ Cassiopeiae . In: Astronomy and Astrophysics , Vol. 406, 2003, pp. 1019, 1023, 1029, bibcode : 2003A & A ... 406.1019N , doi: 10.1051 / 0004-6361: 20030742 .
  8. ↑ a b c Maria-Fernanda Nieva, Norbert Przybilla: Present-day cosmic abundances. A comprehensive study of nearby early B-type stars and implications for stellar and Galactic evolution and interstellar dust models . In: Astronomy & Astrophysics , Vol. 539, 2012, Art.-ID A143, P. 9, bibcode : 2012A & A ... 539A.143N , doi: 10.1051 / 0004-6361 / 201118158 , arxiv : 1203.5787 .
  9. ↑ a b c d Lidia Oskinova et al. : Early magnetic B-type stars: X-ray emission and wind properties . In: Monthly Notices of the Royal Astronomical Society . Vol. 416, Ausg. 2, 2011, pp. 1468-1469, bibcode : 2011MNRAS.416.1456O , doi: 10.1111 / j.1365-2966.2011.19143.x , arxiv : 1106.0508 .
  10. ↑ Mina Koleva, Alexander Vazdekis: Atmospheric parameters of stars for UV models . VizieR data catalog J / A + A / 538 / A143 (published electronically). 2012, bibcode : 2011yCat..35380143K . VizieR catalog entry .
  11. ↑ a b c d e Maryline Briquet et al. : Weak magnetic field, solid-envelope rotation, and wave-induced N-enrichment in the SPB star ζ Cassiopeiae . In: Astronomy & Astrophysics , Vol. 587, 2016, Art.-ID A126, pp. 1, 7, 8, bibcode : 2016A & A ... 587A.126B , doi: 10.1051 / 0004-6361 / 201527751 , arxiv : 1601.04517 .
  12. ^ A b Myron A. Smith, David A. Bohlender: Variations of the ultraviolet resonance lines of the B2 IV-V star ζ Cassiopeiae . In: Astronomy and Astrophysics , Vol. 466, Ausg. 2, 2007, p. 675. bibcode : 2007A & A ... 466..675S , doi: 10.1051 / 0004-6361: 20066639 , arxiv : astro-ph / 0702461 .
  13. ↑ Hamid Sadsaoud et al. : Photometric and spectroscopic observations of the 53 Persei type stars: ζ Cassiopeiae . In: Astronomy and Astrophysics , Vol. 287, 1994, pp. 510, 515, bibcode : 1994A & A ... 287..509S .
  14. ↑ list