BPM 37093

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Star
BPM 37093
AladinLite
Observation
dates equinox :  J2000.0 , epoch : J2000.0
Constellation centaur
Right ascension 12 h 38 m 49.78 s
declination -49 ° 48 ′ 0.2 ″
Apparent brightness 14.0 mag
Typing
B − V color index (+0.18) 
Spectral class DA4.2
Variable star type ZZA 
Astrometry
Radial velocity (−21.1 ± 8.6) km / s
parallax 67.52 ± 0.04  mas
distance 48.28 ± 0.03  ly
14.81 ± 0.01  pc
Proper movement 
Rec. Share: (−557.23 ± 0.07)  mas / a
Dec. portion: (−74.09 ± 0.05)  mas / a
Physical Properties
Dimensions 1.1  M ☉
radius 0.0029  R ☉
Luminosity

0.0006  L ☉

Effective temperature 11730 ± 350  K
Other names
and catalog entries
Gliese catalog FY 2095 [1]
2MASS catalog 2MASS J12384981-4948001 [2]
Other names V886 Centauri • WG 22 • LHS 2594 • WD 1236-495

BPM 37093 is a mutable white dwarf in the constellation Centaur .

The star is about 15  parsecs away and was discovered by Kanaan Kepler, Nitta, and Winget in 1992. It is an unusually massive specimen of the ZZ-Ceti star type and is one of the so-called DAV (pulsating white dwarfs with a hydrogen atmosphere). It was established in 1992 that it does indeed pulsate weakly.

Inside, it consists of carbon and oxygen, which were created in the three-alpha process (atomic reaction in the prehistory of the star).

As early as the 1960s, it was predicted that the coldest such stars could have a crystalline structure inside. The star deserves special attention because it was the first to detect a crystalline core using astroseismological methods. The evaluation of brightness measurements (including by means of the Whole Earth Telescope (WET) network of several telescopes and by Hubble and Magellan, among others, in 1998 and 1999 and 2003) suggested that BPM 37093 is 90% crystalline. The oscillation modes and their frequencies identified using the luminosity curves measured with telescopes are compared with models of the star. Periodicities are found in the luminosity curves by means of Fourier transformation . A prominent frequency, for example, has a period of 625 seconds. The crystalline core can not execute certain vibrations due to its shear modulus , or it hinders or reflects them. Its size can be deduced from this.

A further evaluation of the brightness data in 2004 showed a crystalline proportion between 32 and 82%.

The crystalline structure is probably body-centered cubic and consists of atomic nuclei surrounded by an electron gas . This cannot be compared with the cubic crystalline diamond , nonetheless the star became popular as the "diamond star" because of this crystallinity. The star's density is about 6000 tons per cubic centimeter. The crystalline mass of BPM 37093 is estimated to be greater than 5 · 10 29 kg.

Web links

Individual evidence

  1. ↑ a b c d e f g WG 22. In: SIMBAD . Center de Données astronomiques de Strasbourg , accessed February 2, 2019 .
  2. ↑ V0886 Cen. In: VSX. AAVSO , accessed February 2, 2019 .
  3. ↑ http://wet.physics.iastate.edu/xcov17/bpm/obsinstr.html XCov 17 Observing Instructions for BPM 37093, University of Delaware website on the Whole Earth Telescope project, accessed on Mar 18, 2019
  4. ↑ https://www.researchgate.net/publication/234206089_The_discovery_of_a_new_DAV_star_using_IUE_temperature_determination A. Kanaan, SO Kepler, O. Giovannini, M. Diaz: The discovery of a new DAV star using IUE temperature determination , in Astrophysical Journal Letters 390, # 2 ( May 10, 1992), pages L89-L91
  5. ↑ S. Metcalfe, T; Montgomery, Michael; Kanaan, A .: Testing White Dwarf Crystallization Theory with Asteroseismology of the Massive Pulsating DA Star BPM 37093 , in The Astrophysical Journal 605 (2), February 2004, accessed Mar 18, 2019
  6. ↑ http://www.astro.umontreal.ca/~fontaine/phy6761/bpm37093.pdf P. Brassard, G. Fontaine: Asteroseismology of the Crystallized ZZ Ceti Star BPM 37093: a Different View in The Astrophysical Journal 622, pages 572 -576, March 20, 2005, accessed March 18, 2019
  7. ↑ https://www.researchgate.net/publication/234434506_Crystallization_of_carbon-oxygen_mixtures_in_white_dwarfs JL Barrat, JP Hansen, R. Mochkovitch: Crystallization of carbon-oxygen mixtures in white dwarfs , in Astronomy and Astrophysics 199 (1988), pages L15 – L18, Retrieved on Mar 18, 2019