ﻻ يوجد ملخص باللغة العربية
We have observed the millisecond X-ray pulsar SAX J1808.4-3658 on three occasions during its 2000 outburst with the BeppoSAX satellite. The source was highly variable and erratic during this outburst, and by coincidence we obtained data only during times when the source had very low luminosities. During our observations, we detected four faint sources. The source closest to the position of SAX J1808.4-3658 is still ~1.6 away. This source can only be identified with SAX J1808.4-3658 if we assume that the BeppoSAX positional reconstruction is not completely understood. We also reanalyzed a BeppoSAX observation taken in March 1999 when the source was in quiescence and during which the source was thought to have been detected (Stella et al. 2000). Based on the similarities (position and luminosity) of this source with the above mentioned source ~1.6 away from SAX J1808.4-3658, it is possible that they are the same source. If this source is not the millisecond pulsar, then during all BeppoSAX observations of SAX J1808.4-3658 (the 2000 outburst ones and the 1999 quiescent one), the millisecond pulsar was not detected. A reanalysis of the ASCA quiescent data of SAX J1808.4-3658 (Dotani, Asai, & Wijnands 2000) confirms that during this observation the source was securely detected in quiescence. We discuss our results for SAX J1808.4-3658 in the context of the quiescent properties of low-mass X-ray binary transients.
We report the discovery of phase shifts between X-ray pulses at different energies in the newly discovered millisecond (ms) X-ray pulsar SAX J1808.4-3658. The results show that low-energy pulses lag high-energy pulses by as much as $sim$0.2 ms (or $s
aims: We obtained phase-resolved spectroscopy of the accreting millisecond X-ray pulsar SAX J1808.4-3658 during its outburst in 2008 to find a signature of the donor star, constrain its radial velocity semi-amplitude (K_2), and derive estimates on th
In this paper we present a coherent timing analysis of the 401 Hz pulsations of the accreting millisecond X-ray pulsar SAX J1808.4-3658 during its 2019 outburst. Using observations collected with the Neutron Star Interior Composition Explorer (NICER)
We report the detection of a possible gamma-ray counterpart of the accreting millisecond pulsar SAX J1808.4-3658. The analysis of ~6 years of data from the Large Area Telescope on board the Fermi Gamma-ray Space Telescope (Fermi-LAT) within a region
We analysed Rossi X-ray Timing Explorer observations of the accretion-powered 401 Hz pulsar SAX J1808.4-3658, in order to precisely determine the source distance. While the fluences for the five transient outbursts observed from 1996 were constant to