An enigmatic hump around 30 keV in Suzaku spectra of Aquila X-1 in the Hard State
| Autor: | Kubota, Megu, Tamagawa, Toru, Makishima, Kazuo, Nakano, Toshio, Iwakiri, Wataru, Sugizaki, Mutsumi, Ko, Ono |
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| Rok vydání: | 2019 |
| Předmět: | |
| Zdroj: | Publ. Astron. Soc. Japan (2019) 00 (0), 1-13 |
| Druh dokumentu: | Working Paper |
| DOI: | 10.1093/pasj/psy148 |
| Popis: | The typical accreting neutron star, Aquila X-1, was observed with Suzaku seven times in the decay phase of an outburst in 2007 September-October. Among them, the second to the fourth observations were performed 10 to 22 days after the outburst peak, when the source was in the hard state with a luminosity of 2x10^36 erg/sec. A unified spectral model for this type of objects approximately reproduced the 0.8--100~keV spectra obtained in these 3 observations. However, the spectra all exhibited an enigmatic hump-like excess around 30 keV, above the hard X-ray continuum which is interpreted as arising via Comptonization. The excess feature was confirmed to be significant against statistical and systematic uncertainties. It was successfully represented by a Gaussian centered at ~32 keV, with a width (sigma) of ~6 keV and an equivalent width of ~8.6 keV. Alternatively, the feature can also be explained by a recombination edge model, that produces a quasi-continuum above an edge energy of ~27 keV with an electron temperature of ~11 keV and an equivalent width of ~6.3 keV. These results are discussed in the context of atomic features of heavy elements synthesized via rapid-proton capture process during thermonuclear flashes. Comment: 13 pages, 7 figures, submitted to PASJ |
| Databáze: | arXiv |
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