Aperiodic variability study of the accreting millisecond pulsar IGR - PowerPoint PPT Presentation

Aperiodic variability study of the accreting millisecond pulsar IGR J17511-3057 Maithili Kalamkar Diego Altamirano Michiel van der Klis University of Amsterdam Black hole variability 2010, University of Southampton 1

a. Introduction to the source IGR J17511-3057 Discovered on September 12 th 2009 by INTEGRAL AMP with spin frequency 244.8 Hz Exhibited type-I x-ray bursts Orbital period 207.4 minutes Companion star mass estimate 0.13 solar mass Distance estimate 6.87 kpc Fig. 1. Low Mass X-ray Binary Black hole variability 2010, University of Southampton 2

b. Colo(u)r analysis The hard and soft colors correlate with the intensity during the entire outburst Similar to AMPs - XTE J1807-294 and XTE J1751-305 In other sources, hard color does not correlate with intensity Fig. 2. Intensity, hard and soft colours. Each point corresponds to one observation Hard color = 9.7-16/6.0- 9.7 keV, Soft colour = 3.5-6/2-3.5 keV Black hole variability 2010, University of Southampton 3

b. Colo(u)r analysis Source appears to be an atoll in the Extreme Island State Fig. 3. Color-color Diagram of IGR J17511-3057 and a typical atoll source. Hard color = 9.7-16/6.0-9.7 keV, Soft colour = 3.5-6/2-3.5 keV Black hole variability 2010, University of Southampton 4

c. Aperiodic variability RXTE - PCA data Fourier analysis of Event mode in 2 16 keV energy range – Fig. 4. Power spectrum of group3 with fit and power spectrum in a typical extreme island state Black hole variability 2010, University of Southampton 5

c. Aperiodic variability Not all power spectra resemble the power spectrum expected in the Extreme Island State observed in other sources Fig. 5. Power spectrum of group1 with fit and power spectrum in a typical Lower Left Banana branch Black hole variability 2010, University of Southampton 6

e. Identification of features Fig. 6. Frequency-frequency correlations as seen in LMXBs Black hole variability 2010, University of Southampton 7

e. Implications If the high frequency features are kHz QPOs, then kHz QPOs in Extreme Island State (one exception, 4U 1728-34; Migliari et al.2003) ● Measured differences Δν are 112 ± 13, 144.9 ± 18.4 and 104.2 ± 15 respectively ; ● inconsistent with the spin frequency ν s of 244.8 Hz ( ν s < 400 Hz) but close to ν s /2 instead as is the case seen in fast rotators ( ν s > 400 Hz) ; Miller et al. 1998 Fig.7 Ratio of measurements of Δν/ν s vs. ν s Mendez , Belloni et al. 2007, Altamirano et. al 2010 Black hole variability 2010, University of Southampton 8

Thank You Black hole variability 2010, University of Southampton 9