IXAE observations of the X-ray pulsar XTE J1946+274

Abstract

Abstract.We report results from two observations of the transient binary X-ray pulsar XTE J1946+274 with the Indian X-ray Astronomy Experiment (IXAE) made in September 18-30 1999 and June 28-July 7 2000. The pulsar has a ∼80 days orbital period during which the X-ray intensity varies almost sinusoidally between intensity levels of 5 and 50 mCrab. The mid-time of the two observations with the IXAE are separated by an orbital phase of 0.56 and were in the decaying and rising parts of its orbital modulation, respectively. During both the observations, strong pulsations with 15.8 s period are detected in the 2-6 and 6-18 keV energy bands of IXAE. The pulse profiles in both the observations are double peaked and identical with a similar pulse fractions of ∼30% in the two energy bands. The pulse periods and its local derivatives are obtained from the IXAE observations. The known pulse period history shows small deviations from an otherwise nearly constant spin-up trend of the pulsar since its discovery. If the measured local period derivatives are a sum of a nearly constant spin-up of the pulsar and effect of its orbital motion, it suggests that the orbit of this Be X-ray binary is eccentric. The RXTE-ASM light curve shows a continuous detection of 10 orbital modulation of the source since its discovery.

The Transient Accreting X-Ray Pulsar Xte J1946+274: Stability of X-Ray Properties at Low Flux and Updated Orbital Solution

“…The 2010 RXTE and Suzaku pulse profiles of XTE J1946+274 are double-peaked with a deep and a shallow minimum that show weak energy dependence of the depths (Figure 3). This structure is strongly similar to what has been observed by Wilson et al (2003) and Paul et al (2001) during the 1998 outburst with other instruments at different luminosities. The source even shows a double-peaked profile during quiescence as observed by Chandra (Özbey Arabacı et al 2014).…”

BeppoSAX observations of XTE J1946+274

“…Several weaker outbursts followed the first one from 1998 to 2001 (Campana et al 1999;Paul et al 2001;Wilson et al 2003). Similar behaviour has been also observed in other Be systems (see for example Caballero et al 2013).…”

“…The two peaks are separated by about half a phase, and, therefore, likely represent two emission components with roughly orthogonal beam patterns. Paul et al (2001) suggested that the two peaks might be related to the emission from the two poles of the neutron star not diametrically positioned to each other. On the other hand, the pulse profile evolution, and in particular the ∼ 180…”

Class transitions and two component accretion flow in GRS 1915+105

“…Similarly, 0.1 s time resolution in the Medium mode restricts the observation of QPOs up to 5 Hz only, while the 1 s resolution restricts the reporting of QPOs up to 0.5 Hz only. Nevertheless, the light curves are clear enough and the identification of the specific class can be done without ambiguity (e.g., Naik et al 2001Naik et al , 2002bPaul et al 2001). It is to be noted that (a) the counts in the high energy bin could be very low and the s φ suffers from low number statistics; and (b) the slope itself is known to vary in the 2−18 keV range, especially, the spectrum becomes harder above 10−12 keV in the hard state.…”