2013/01/04 by Federico García, Guobao Zhang, Mariano Méndez · 1 citation
Earth and Planetary Sciences · Physics and Astronomy · #Astrophysical Phenomena and Observations #High-pressure geophysics and materials #Pulsars and Gravitational Waves Research #astro-ph.HE
paper · pdf · doi:10.1093/mnras/sts583
7 pages, 6 figures, accepted for publication in MNRAS
openalex publication_date 2013/01/04 · arxiv created 2013/01/06 · arxiv updated 2013/01/24 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/01
We analysed the complete set of bursts from the neutron star low-mass X-ray binary 4U 1820−30 detected with the Rossi X-ray Timing Explorer (RXTE). We found that all are photospheric radius expansion bursts, and have similar duration, peak flux and fluence. From the analysis of time-resolved spectra during the cooling phase of the bursts, we found that the relation between the bolometric flux and the temperature is very different from the canonical F ∝ T4 relation which is expected if the apparent emitting area on the surface of the neutron star remains constant. The flux–temperature relation can be fitted using a broken power law, with indices ν1 = 2.0 ± 0.3 and ν2 = 5.72 ± 0.06. The departure from the F ∝ T4 relation during the cooling phase of the X-ray bursts in 4U 1820−30 could be due to changes in the emitting area of the neutron star while the atmosphere cools down, variations in the colour-correction factor due to chemical evolution, or the presence of a source of heat, e.g. residual hydrogen nuclear burning, playing an important role when the burst emission ceases.