The Vela X-1 pulse-averaged spectrum as observed by BeppoSAX

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dc.creatorOrlandini, M.
dc.creatorFiume, D. Dal
dc.creatorFrontera, F.
dc.creatorCusumano, G.
dc.creatorDel Sordo, S.
dc.creatorGiarrusso, S.
dc.creatorPiraino, S.
dc.creatorSegreto, A.
dc.creatorGuainazzi, M.
dc.creatorPiro, L.
dc.date1997-11-19
dc.date.accessioned2026-07-07T02:25:10Z
dc.date.available2026-07-07T02:25:10Z
dc.descriptionWe 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.
dc.description6 pages, 4 PostScript figures. Uses l-aa.sty. Accepted for publication in Astronomy & Astrophysics, Main Journal
dc.identifierhttps://arxiv.org/abs/astro-ph/9711215
dc.identifierhttp://arxiv.org/abs/astro-ph/9711215
dc.identifier.urihttp://salesiana.dossiersoluciones.com/handle/123456789/11825
dc.subjectAstrophysics
dc.titleThe Vela X-1 pulse-averaged spectrum as observed by BeppoSAX
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