X-ray observations during a Her X-1 anomalous low-state

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dc.creatorParmar, A. N.
dc.creatorOosterbroek, T.
dc.creatorFiume, D. Dal
dc.creatorOrlandini, M.
dc.creatorSantangelo, A.
dc.creatorSegreto, A.
dc.creatorDel Sordo, S.
dc.date1999-09-02
dc.date.accessioned2026-07-07T02:33:01Z
dc.date.available2026-07-07T02:33:01Z
dc.descriptionResults of a 1999 July 8-10 BeppoSAX observation during an anomalous low-state of Her X-1 are presented. The standard on-state power-law and blackbody continuum model is excluded at high confidence unless partial covering is included. This gives a power-law photon index of 0.63 +/- 0.02 and implies that 0.28 +/- 0.03 of the flux undergoes additional absorption of (27 +/- 7) 10^22 atom/cm2. 11% of the observed 0.1-10 keV flux is from the 0.068 +/- 0.015 keV blackbody. 1.237747(2) s pulses with a semi-amplitude of 2.1 +/- 0.8% are detected at >99.5% confidence and confirmed by RXTE measurements. This implies that Her X-1 underwent substantial spin-down close to the start of the anomalous low-state. The spectral and temporal changes are similar to those recently reported from 4U1626-67. These may result from a strongly warped disk that produces a spin-down torque. The X-ray source is then mostly viewed through the inner regions of the accretion disk. A similar mechanism could be responsible for the Her X-1 anomalous low-states. Shadowing by such an unusually warped disk could produce observable effects in the optical and UV emission from the companion star.
dc.description4 pages. To appear in A&AL
dc.identifierhttps://arxiv.org/abs/astro-ph/9909039
dc.identifierhttp://arxiv.org/abs/astro-ph/9909039
dc.identifier.urihttp://salesiana.dossiersoluciones.com/handle/123456789/14679
dc.subjectAstrophysics
dc.titleX-ray observations during a Her X-1 anomalous low-state
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