The discovery of a 685 second orbital period from the X-ray source 4U 1820 - 30 in the globular cluster NGC 6624
| Autor: | W. Priedhorsky, Luigi Stella, Nicholas E. White |
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| Rok vydání: | 1987 |
| Předmět: |
Physics
Stellar rotation White dwarf Astronomy Astronomy and Astrophysics Astrophysics Orbital period Neutron star Star cluster Space and Planetary Science Globular cluster Binary star Astrophysics::Solar and Stellar Astrophysics Astrophysics::Earth and Planetary Astrophysics Stellar evolution Astrophysics::Galaxy Astrophysics |
| Zdroj: | The Astrophysical Journal. 312:L17 |
| ISSN: | 1538-4357 0004-637X |
| DOI: | 10.1086/184811 |
| Popis: | The discovery of a coherent 685 s periodicity in the X-ray source 4U 1820 -30, which is located in the globular cluster NGC 6624, is reported. The modulation has a peak-to-peak amplitude of up to 3 percent and was independently detected in three observations by the EXOSAT Observatory. This period is unlikely to represent the rotation of a neutron star, because accretion torques should cause it to change by at least 10 s/yr, but observations constrain any change to less than 0.4 s/yr. The period is thus identified as the orbital period of 4U 1820 - 30, the first to be found for a globular cluster X-ray source and the shortest yet identified for any binary system. In this compact system the mass-losing star is probably a low-mass (0.055 solar mass) helium white dwarf. 37 references. |
| Databáze: | OpenAIRE |
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