Suzaku Observations of Hercules X-1 : Measurements of the Two Cyclotron Harmonics
| Autor: | Enoto, Teruaki, Makishima, Kazuo, Terada, Yukikatsu, Mihara, Tatehiro, Nakazawa, Kazuhiro, Ueda, Tsuyoshi, Dotani, Tadayasu, Kokubun, Motohide, Nagase, Fumiaki, Naik, Sachindra, Suzuki, Motoko, Nakajima, Motoki, Takahashi, Hiromitsu |
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| Rok vydání: | 2007 |
| Předmět: | |
| Druh dokumentu: | Working Paper |
| DOI: | 10.1093/pasj/60.sp1.S57 |
| Popis: | The accretion-powered pulsar Her X-1 was observed with Suzaku twice in its main-on state, on 2005 October 5-6 and 2006 March 29-30, for a net exposure of 30.5 ks and 34.4 ks, respectively. In the 2005 and 2006 observations, the source was detected at an average 10-30 keV intensity of 290 mCrab and 230 mCrab, respectively. The intrinsic pulse period was measured on both occasions at 1.23776 s by HXD-PIN, after barycentric and binary corrections. The pulse phase-averaged spectra in the energy range above 10 keV are well fitted by ``Negative and Positive power-law times EXponential (NPEX)'' model, multiplied by a fundamental cyclotron resonance scattering feature at ~36 keV which appears very significantly in the HXD-PIN data. The resonance profiles were reproduced successfully by the Lorentzian type scattering cross section, rather than by a Gaussian type alternative. The pulse phase-averaged HXD-GSO data, covering 50-120 keV, are featureless. However, in a differential spectrum between the pulse-decay phase and off-pulse phase, the second harmonic cyclotron resonance was detected in the GSO data at ~73 keV, with a depth of 1.6_-0.7^+0.9. This makes Her X-1 a 6th pulsar with established second harmonic resonance. Implications of these results are briefly discussed. Comment: 22 pages, 10 figures, accepted for publication in PASJ |
| Databáze: | arXiv |
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