Simultaneous BeppoSAX and Rossi X-ray Timing Explorer observations of 4U1812-12

Abstract

4U1812-12 is a faint persistent and weakly variable neutron star X-ray binary. It was observed by BeppoSAX between April 20th and 21st, 2000 in a hard spectral state with a bolometric luminosity of ~2x10^36 ergs/s. Its broad band energy spectrum is characterized by the presence of a hard X-ray tail extending above ~100 keV. It can be represented as the sum of a dominant hard Comptonized component (electron temperature of ~36 keV and optical depth ~3) and a weak soft component. The latter component which can be fitted with a blackbody of about 0.6 keV and equivalent radius of ~2 km is likely to originate from the neutron star surface. We also report on the first measurement of the power density spectrum of the source rapid X-ray variability, as recorded during a simultaneous snapshot observation performed by the Rossi X-ray Timing Explorer. As expected for a neutron star system in such hard spectral state, its power density spectrum is characterized by the presence of a ~0.7 Hz low frequency quasi-periodic oscillation together with three broad noise components, one of which extends above ~200 Hz.

6 pages, 3 figures, accepted for publication in A&A

References in corpus (7)

• A Unified Description of the Timing Features of Accreting X-ray Binaries
• A multi-Lorentzian timing study of the atoll sources 4U 0614+09 and 4U 1728-34
• The broad band X-ray/hard X-ray spectra of accreting neutron stars
• The X-ray spectrum of the atoll source 4U 1608-52
• A peculiar spectral state transition of 4U1705--44: when an Atoll looks like a Z
• Correlated timing and spectral behavior of 4U 1705-44
• Spectral Properties of a Sample of Low Luminosity Type I X-ray Bursters

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