1 / 16

Timing and Spectral Properties of Neutron Star Low-Mass X-ray Binaries

Timing and Spectral Properties of Neutron Star Low-Mass X-ray Binaries. Sudip Bhattacharyya Department of Astronomy and Astrophysics Tata Institute of Fundamental Research. Different types of NS LMXBs. van der Klis (2006).

yana
Download Presentation

Timing and Spectral Properties of Neutron Star Low-Mass X-ray Binaries

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Timing and Spectral Properties of Neutron Star Low-Mass X-ray Binaries Sudip Bhattacharyya Department of Astronomy and Astrophysics Tata Institute of Fundamental Research

  2. Different types of NS LMXBs van der Klis (2006) Atoll and Z sources are identified by their tracks in the colour-colour diagrams (CDs) and hardness-intensity diagrams (HIDs). Soft colour: background –subtracted count rate ratio in two softer energy bands. Hard colour: background-subtracted count rate ratio in two harder energy bands. Typical Rossi X-ray Timing Explorer (RXTE) proportional counter array (PCA) energy bands: 2.21-3.45, 3.45-5.12, 5.12-8.46, 8.46-18.15 (all in keV).

  3. Different types of NS LMXBs van der Klis (2006)

  4. Energy spectrum of NS LMXBs Two emission components: accretion disk and NS surface: each of them can emit blackbody; each of them can be partially or fully covered with Comptonizing corona. No spectral model uniquely fits the data. NS LBXB XB 1254-690: an example with RXTE PCA data Model χν2(dof) Model χν2(dof) diskbb+comptt 1.95(30) diskbb+powerlaw 1.95(32) diskbb+cutoffpl 1.97(31) diskbb+bknpower 0.52(30) comptt+bbody 1.50(30) powerlaw+bbody 2.24(32) cutoffpl+bbody 1.65(31) bknpower+bbody 2.39(30) diskbb+bbody 2.75(32) comptt+comptt 0.91(28) powerlaw+comptt 0.95(30)cutoffpl+comptt 0.91(29) bknpower+comptt 0.54(28) powerlaw+powerlaw 32.31(32) cutoffpl+powerlaw 2.33(31) bknpower+powerlaw 3.47(30) cutoffpl+cutoffpl 1.54(30) bknpower+cutoffpl 0.53(29) bknpower+bknpower 3.73(28) Mukherjee and Bhattacharyya (2011)

  5. NS LBXB XB 1254-690: an example with RXTE PCA data Mukherjee and Bhattacharyya (2011)

  6. Accreting pulsars

  7. Kilohertz quasi-periodic oscillations (kHz QPOs) This observationally robust timing feature have been detected from many neutron star LMXBs. According to almost all the models, the uniquely high kHz QPO frequencies are either the following accretion disk frequencies, or the beating or resonances among them, or with the neutron star spin frequency spin. KHz QPOs often appear in a pair in the power spectrum, in the 200-1200 Hz frequency range. Fourier Transform  : Orbital frequency r : Radial epicyclic frequency  : Vertical epicyclic frequency - r : Periastron precession frequency -  : Nodal or `Lense-Thirring’ precession frequency Power spectrum is the Fourier transform of the intensity vs. time curve.

  8. Kilohertz quasi-periodic oscillations (kHz QPOs) Accretion disk frequencies: Miller et al. (1998) So when the correct model is identified, kHz QPOs can be used to measure the neutron star parameters M and J. Such a constraint on the neutron star mass-radius space is possible, if one of the kHz QPO frequencies is , and the corresponding radial distance r is greater than or equal to the neutron star and the ISCO radius. Apart from neutron star parameter measurement, KHz QPOs can be useful to study the matter flow in strong gravity region, and to test a law of gravitation. For example, the general relativistic `Lense-Thirring’ precision (frequency:  - ) has not yet been detected with certainty in any system.

  9. KHz QPO quality factor vs. frequency: a signature of innermost stable circular orbit (ISCO)? Barret et al.

  10. Spectral origin of kHz QPO: Comptonized component? Gilfanov et al. (2003)

  11. Z sources: • Horizontal Branch Oscillations (HBO) : 15-60 Hz • Normal Branch Oscillations (NBO) : about 6 Hz • Flaring Branch Oscillations (FBO) : about 10 Hz

  12. Atoll sources: • Upper Banana (UB): < 1 Hz power law noise (VLFN) • Lower Banana (LB): 10 Hz BLN • Lower Left Banana (LLB): Twin kHz QPO • Island State (IS): Dominant BLN, becoming stronger and lower frequency as flux decreases

  13. Power spectra in different states

  14. Correlations among various timing features Van der Klis (2006)

  15. ASTROSAT(India’s proposed multiwavelength astronomy space mission) In its time, only ASTROSAT will have the capability to study kHz QPOs. First detection and study of fast timing features in hard X-rays.

  16. ASTROSAT(India’s proposed multiwavelength astronomy space mission) In its time, only ASTROSAT will have the capability to study kHz QPOs. First detection and study of fast timing features in hard X-rays. Thank you!

More Related