Intermittent millisecond X-ray pulsations from the neutron-star X-ray transient SAX J1748.9-2021 in the globular cluster NGC 6440

Abstract

We report on intermittent X-ray pulsations with a frequency of 442.36 Hz from the neutron-star X-ray binary SAX J1748.9--2021 in the globular cluster NGC 6440. The pulsations were seen during both 2001 and 2005 outbursts of the source, but only intermittently, appearing and disappearing on timescales of hundreds of seconds. We find a suggestive relation between the occurrence of type-I X-ray bursts and the appearance of the pulsations but the relation is not strict. This behavior is very similar to that of the intermittent accreting millisecond X-ray pulsar HETE J1900.1--2455. The reason for the intermittence of the pulsations remains unclear. However it is now evident that a strict division between pulsating and non-pulsating does not exist. By studying the Doppler shift of the pulsation frequency we determine an orbit with a period of 8.7 hrs and an projected semi major axis of 0.39 lightsec. The companion star might be a main--sequence or a slightly evolved star with a mass of $\sim$1 $M_{\odot }$. Therefore, SAX J1748.9--2021 has a longer period and may have a more massive companion star than all the other accreting millisecond X-ray pulsars except for Aql X-1.

5 pages, 4 figures, Accepted by ApJL - Uses emulateapj.cls - New figure added: "Pulse frequency as a function of orbital phase". Figure 4 has changed. Text has been rewritten as to fit the 4 pages limit

References in corpus (22)

• Evolutionary tracks and isochrones for low- and intermediate-mass stars: from 0.15 to 7 M_sun, and from Z=0.0004 to 0.03
• Calibration of the Rossi X-ray Timing Explorer Proportional Counter Array
• Jets in neutron star X-ray binaries: a comparison with black holes
• Magnetic Screening in Accreting Neutron Stars
• Discovery of coherent millisecond X-ray pulsations in Aql X-1
• The Disk-Magnetosphere Interaction in the Accretion-Powered Millisecond Pulsar SAX J1808.4-3658
• Chandra Observation of the Globular Cluster NGC 6440 and the Nature of Cluster X-ray Luminosity Functions
• Absolute Timing of the Crab Pulsar with RXTE
• Discovery of the Millisecond X-Ray Pulsar HETE J1900.1-2455
• Intermittent pulsations in an accretion-powered millisecond pulsar
• Identification of the optical and quiescent counterparts to the bright X-ray transient in NGC 6440
• The Orbital Light Curve of Aquila X-1
• Ages and metallicities of star clusters: new calibrations and diagnostic diagrams from visible integrated spectra
• Millihertz Oscillation Frequency Drift Predicts the Occurrence of Type I X-ray Bursts
• Why is it Difficult to Detect a Millisecond Pulsar in Neutron Star X-ray Binaries?
• Studies of orbital parameters and pulse profile of the accreting millisecond pulsar XTE J1807-294
• Discovery of 442-Hz Pulsations from an X-ray Source in the Globular Cluster NGC 6440
• Revised orbital parameters of the accreting millisecond pulsar SAX J1808.4-3658
• Discovery of X-Ray Burst Oscillations from a Neutron-Star X-Ray Transient in the Globular Cluster NGC 6440
• Is the Lack of Pulsations in Low Mass X-Ray Binaries due to Comptonizing Coronae?
• The X-Ray Binary X2127+119 in M15: Evidence for a Very-Low-Mass, Stripped-Giant Companion
• Correlations between X-ray Spectral and Timing Characteristics in Cyg X-2

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