Beta 2 Capricorni
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Double star β 2 Capricorni |
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| β 2 cap in the constellation "Capricorn" | |||||||||||||||||||
| AladinLite | |||||||||||||||||||
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Observation dates equinox : J2000.0 , epoch : J2000.0 |
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| Constellation | Capricorn | ||||||||||||||||||
| Right ascension | 20 h 20 m 46.55 s | ||||||||||||||||||
| declination | -14 ° 47 ′ 5.6 ″ | ||||||||||||||||||
| Apparent brightness | 6.09 mag | ||||||||||||||||||
| Typing | |||||||||||||||||||
| B − V color index | −0.02 | ||||||||||||||||||
| Spectral class | B9 / A0 III / IV | ||||||||||||||||||
| Astrometry | |||||||||||||||||||
| Radial velocity | (−17.6 ± 1.8) km / s | ||||||||||||||||||
| parallax | (9.61 ± 0.90) mas | ||||||||||||||||||
| distance | (339 ± 32) ly (104 ± 10) pc |
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| Proper movement | |||||||||||||||||||
| Rec. Share: | (44.06 ± 1.01) mas / a | ||||||||||||||||||
| Dec. portion: | (−1.66 ± 0.98) mas / a | ||||||||||||||||||
| Physical Properties | |||||||||||||||||||
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Other names and catalog entries |
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Beta 2 Capricorni (β 2 Cap) is the weaker component of the visual binary star Beta Capricorni in the constellation Capricorn . It has an apparent magnitude of 6.1 mag and its distance is approximately 340 light years .
Beta 2 Capricorni is a spectroscopic binary star. The main star is a white giant or sub-giant with five times the mass and 30 times the luminosity of the Sun, which is orbited by a white star about 40 times weaker with three times the solar mass in about 200 years.
Beta 2 is together with the star Beta 1 Capricorni also with the proper name "Dabih" (from Arabic سعد الذابح, DMG saʿd aḏ-ḏābiḥ 'luck (star) of the slaughterer'). To distinguish it from this, it is also called "Dabih Minor". According to the “IAU Catalog of Star Names” of the Working Group on Star Names (WGSN) of the IAU for the standardization of star names, the name in the form “Dabih” was only assigned to the lighter Beta 1 Capricorni in 2016 .
Scientific research
The main star of Beta 2 Capricorni is a peculiar star that is counted among the mercury-manganese stars due to the appearance of certain spectral lines in its spectrum . These blue-white stars with a spectral class of a “late B” are characterized by exceptionally low values of the projected equatorial rotation speed v ∙ sin i , a low value of only about 1.2 km / s was found for Beta 2 Capricorni.
The light from the star was examined spectroscopically in the ultraviolet range and in the visible range for the abundance of different elements. Compared to the sun, a significantly reduced occurrence of He, C, O, Mg, Al and Sc was found, while the abundance of the elements Ga, Sr, Y, Pr, Nd, Ho, Tm, Pt, Au at several hundred up to several thousand times the frequency of which is on the sun, with Hg the relative frequency is even several ten thousand times that of the sun and the absolute frequency is around 1 ppm that of hydrogen . In addition, a surface temperature of the star of about 10,650 K was derived.
A further investigation essentially confirmed the previous results and also showed a low frequency for N as well as a significantly higher relative frequency for Ce, Sm, Yb and Tl compared to the sun. Bi also occurs in a relative frequency on Beta 2 Capricorni, which is 5 orders of magnitude higher than on the Sun.
Individual evidence
- ↑ a b c d e VizieR: Hipparcos, the New Reduction (van Leeuwen, 2007) - The Astrometric Catalog
- ↑ VizieR: Michigan Catalog of HD stars, Vol.4 (Houk +, 1988)
- ↑ VizieR: General Catalog of Stellar Radial Velocities (Wilson, 1953)
- ↑ VizieR: Multiple star catalog (MSC) (Tokovinin 1997–1999)
- ^ VizieR: Catalog of Stellar Diameters (CADARS) (Pasinetti-Fracassini + 2001)
- ↑ Bulletin of the IAU Working Group on Star Names, No. 2. IAU Division C Education, Outreach and Heritage, 2016, iau.org (PDF; 158 kB).
- ↑ O. Kochukhov, V. Makaganiuk, N. Piskunov, SV Jeffers, CM Johns-Krull, CU Keller, M. Rodenhuis, F. Snik, HC Stempels, JA Valenti: Are there tangled magnetic fields on HgMn stars? In: Astronomy & Astrophysics. Vol. 554, A61, 2013, doi: 10.1051 / 0004-6361 / 201321467 , pp. 1–12, ( bibcode : 2013A & A ... 554A..61K ).
- ↑ KC Smith, MM Dworetsky : Elemental abundances in normal late-B and HgMn stars from co-added IUE spectra. I. Iron-peak elements. In: Astronomy & Astrophysics. Vol. 274, 1993, pp. 335-355 ( bibcode : 1993A & A ... 274..335S ).
- ^ SJ Adelmann: Elemental abundance analyzes with DAO Spectrograms - XII. The mercury-manganese stars HR 4072A and 7775 and the metallic-lined star HR 4072B. In: Monthly Notices of the Royal Astronomical Society. Vol. 266, 1994, doi: 10.1093 / mnras / 266.1.97 , pp. 97-113 ( bibcode : 1994MNRAS.266 ... 97A ).
- Jump up ↑ GM Wahlgren, L. Dolk, G. Kalus, S. Johansson, U. Litzén, DS Leckrone: An optical region elemental abundance analysis of the HgMn type star HR 7775. In: The Astrophysical Journal. Vol. 539, 2000, doi: 10.1086 / 309239 , pp. 908-927 ( bibcode : 2000ApJ ... 539..908W ).
- ↑ GM Wahlgren, T. Brage, JC Brandt, J. Fleming, S. Johansson, DS Leckrone, CR Proffitt, J. Reader, CJ Sansonetti: The Bismuth Abundance in the HgMn Stars χ Lupi and HR 7775 and Improved Atomic Data for Selected Transitions of Bi I, Bi II, and Bi III. In: The Astrophysical Journal. Vol. 551, 2001, doi: 10.1086 / 320063 , pp. 520-535 ( bibcode : 2001ApJ ... 551..520W ).