Correlated Timing and Spectral Variations of the Soft X-Ray Transient Aquila X-1 : Evidence for an Atoll Classification
Based on Rossi X-Ray Timing Explorer data, we discuss the classification of the soft X-ray transient Aquila X-1 in the Z/atoll scheme and the relation of its kilohertz quasi-periodic oscillations (kHz QPOs) properties to the X-ray colors. The color-color diagram shows one elongated ("banana&quo...
| Autores: | , , , |
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| Tipo de recurso: | artículo |
| Estado: | Versión publicada |
| Fecha de publicación: | 2000 |
| País: | Argentina |
| Institución: | Universidad Nacional de La Plata |
| Repositorio: | SEDICI (UNLP) |
| Idioma: | inglés |
| OAI Identifier: | oai:sedici.unlp.edu.ar:10915/127256 |
| Acceso en línea: | http://sedici.unlp.edu.ar/handle/10915/127256 |
| Access Level: | acceso abierto |
| Palabra clave: | Astronomía Ciencias Astronómicas accretion, accretion disks stars : individual (Aquila X-1) stars : neutron X-rays : stars |
| Sumario: | Based on Rossi X-Ray Timing Explorer data, we discuss the classification of the soft X-ray transient Aquila X-1 in the Z/atoll scheme and the relation of its kilohertz quasi-periodic oscillations (kHz QPOs) properties to the X-ray colors. The color-color diagram shows one elongated ("banana") structure and several "islands" of data points. The power spectra of the island are best represented by a broken power law whereas those of the banana by a power law below ~1 Hz plus an exponentially cutoff component at intermediate frequencies (30-60 Hz). The parameters of these two components change in correlation with the position of the source in the color-color diagram. Based on the pattern that the source shows in the color-color diagram and its aperiodic variability, we conclude that Aquila X-1 is an atoll source. We have also investigated the possible correlation between the frequency of the kHz QPOs and the position of the source in the color-color diagram. The complexity seen in the frequency versus count rate diagram is reduced to a single track when the frequency is plotted against hard or soft color. |
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