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Astron. Astrophys. 360, L35-L38 (2000)

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Letter to the Editor

Detection of a broad iron emission line and sub-millisecond quasiperiodic oscillations from the type I X-ray burster 4U 1728-34 in a high state

S. Piraino 1, A. Santangelo 1 and P. Kaaret 2

1 IFCAI/CNR, Via Ugo La Malfa 153, 90146 Palermo, Italy
2 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA

Received 25 May 2000 / Accepted 24 July 2000


We report results from simultaneous RossiXTE and BeppoSAX observations of the neutron-star x-ray binary and type I X-ray burster 4U 1728-34. The source was found in a high luminosity state, [FORMULA], and quasiperiodic oscillations were detected at [FORMULA] Hz, the highest frequency ever observed from this source. The x-ray spectrum shows a broad, [FORMULA] keV, iron [FORMULA] fluorescence line. We discuss interpretations of the broad line and the quasiperiodic oscillations and how future simultaneous spectral and timing observations can be used to test these interpretations and, potentially, to estimate the mass of the compact object.

Key words: accretion, accretion disks – stars: individual: – stars: neutron – X-rays: stars

Send offprint requests to: Philip Kaaret (pkaaret@cfa.harvard.edu)

© European Southern Observatory (ESO) 2000

Online publication: August 23, 2000