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The Vela X-1 pulse-averaged spectrum as observed by BeppoSAX
Astrophysics · Submitted 19 Nov 1997
abstract compiled · 2026-09-23 · no language-model review
The authors' main claim We interpreted this feature as a cyclotron resonance, corresponding to a neutron star surface magnetic strength of 4.9 x 10^12 Gauss.
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The abstract, sentence by sentence
We report on the 20 ksec observation of Vela X-1 performed by BeppoSAX on 1996 July 14 during its Science Verification Phase. We observed the source in two intensity states, characterized by a change in luminosity of a factor ~ 2, and a change in absorption of a factor ~ 10. The single Narrow Field Instrument pulse-averaged spectra are well fit by a power law with significantly different indices. This is in agreement with the observed changes of slope in the wide-band spectrum: a first change of slope at ~ 10 keV, and a second one at ~ 35 keV. To mimic this behaviour we used a double power law modified by an exponential cutoff --- the so-called NPEX model --- to fit the whole 2-100 keV continuum. This functional is able to adequately describe the data, expecially the low intensity state. We found an absorption-like feature at ~ 57 keV, very well visible in the ratio performed with the Crab spectrum. We interpreted this feature as a cyclotron resonance, corresponding to a neutron star surface magnetic strength of 4.9 x 10^12 Gauss. The BeppoSAX data do not require the presence of a cyclotron resonance at ~ 27 keV as found in earlier works.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | We report on the 20 ksec observation of Vela X-1 performed by BeppoSAX on 1996 July 14 during its Science Verification Phase. | method 0.51 | 0.94 | 0.02 | asserted 0.99 |
| s1 | We observed the source in two intensity states, characterized by a change in luminosity of a factor ~ 2, and a change in absorption of a factor ~ 10. | result 0.88 | 0.96 | 0.07 | asserted 1.00 |
| s2 | The single Narrow Field Instrument pulse-averaged spectra are well fit by a power law with significantly different indices. | result 1.00 | 0.93 | 0.09 | asserted 1.00 |
| s3 | This is in agreement with the observed changes of slope in the wide-band spectrum: a first change of slope at ~ 10 keV, and a second one at ~ 35 keV. | result 0.79 | 0.80 | 0.09 | asserted 0.70 |
| s4 | To mimic this behaviour we used a double power law modified by an exponential cutoff --- the so-called NPEX model --- to fit the whole 2-100 keV continuum. | method 0.99 | 0.93 | 0.07 | asserted 0.98 |
| s5 | This functional is able to adequately describe the data, expecially the low intensity state. | result 0.86 | 0.78 | 0.08 | asserted 0.99 |
| s6 | We found an absorption-like feature at ~ 57 keV, very well visible in the ratio performed with the Crab spectrum. | result 1.00 | 0.96 | 0.12 | asserted 1.00 |
| s7 | We interpreted this feature as a cyclotron resonance, corresponding to a neutron star surface magnetic strength of 4.9 x 10^12 Gauss. | interpretation 1.00 | 0.93 | 0.41 | asserted 0.88 |
| s8 | The BeppoSAX data do not require the presence of a cyclotron resonance at ~ 27 keV as found in earlier works. | result 0.95 | 0.86 | 0.17 | asserted 0.99 |
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Original abstract
We report on the 20 ksec observation of Vela X-1 performed by BeppoSAX on 1996 July 14 during its Science Verification Phase. We observed the source in two intensity states, characterized by a change in luminosity of a factor ~ 2, and a change in absorption of a factor ~ 10. The single Narrow Field Instrument pulse-averaged spectra are well fit by a power law with significantly different indices. This is in agreement with the observed changes of slope in the wide-band spectrum: a first change of slope at ~ 10 keV, and a second one at ~ 35 keV. To mimic this behaviour we used a double power law modified by an exponential cutoff --- the so-called NPEX model --- to fit the whole 2-100 keV continuum. This functional is able to adequately describe the data, expecially the low intensity state. We found an absorption-like feature at ~ 57 keV, very well visible in the ratio performed with the Crab spectrum. We interpreted this feature as a cyclotron resonance, corresponding to a neutron star surface magnetic strength of 4.9 x 10^12 Gauss. The BeppoSAX data do not require the presence of a cyclotron resonance at ~ 27 keV as found in earlier works.
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