Spectral Properties of Anomalous X-ray Pulsars

We examine the spectra of the persistent emission from anomalous X-ray pulsars (AXPs) and their variation with the spin-down rate ˙ . Based on an accretion-powered model, the influences of both the magnetic field and the mass accretion rate on the spectral properties of AXPs are addressed. We then investigate the relation between the spectral property of AXPs and mass accretion rate ˙ M. The result shows that there exists a linear correlation between the photon index and the mass accretion rate: the spectral hardness increases with increasing ˙ M. A possible emission mechanism for the explanation of the spectral properties of AXPs is also discussed.

[1]  Heinz-Ulrich Schmitt,et al.  Results and perspectives , 2005, Belligerent Reprisals.

[2]  K. Cheng,et al.  A Two-Temperature Supernova Fallback Disk Model for Anomalous X-ray Pulsars , 2002 .

[3]  F. Özel.  Surface Emission Properties of Strongly Magnetic Neutron Stars , 2001 .

[4]  L. Stella,et al.  Proton Cyclotron Features in Thermal Spectra of Ultramagnetized Neutron Stars , 2001, astro-ph/0103316.

[5]  N. White,et al.  Correlations between Spectral Properties and Spin-down Rate in Soft Gamma-Ray Repeaters and Anomalous X-Ray Pulsars , 2001, astro-ph/0102375.

[6]  E. Liang,et al.  Monte Carlo Simulations of Thermal-Nonthermal Radiation from a Neutron Star Magnetospheric Accretion Shell , 2000, astro-ph/0010268.

[7]  M. Alpar.  On Young Neutron Stars as Propellers and Accretors with Conventional Magnetic Fields , 2000, astro-ph/0005211.

[8]  Murakami,et al.  Timing Noise in SGR 1806–20 , 2000, The Astrophysical journal.

[9]  T. Dotani,et al.  Study of the Long-Term Stability of Two Anomalous X-Ray Pulsars, 4U 0142+61 and 1E 1048.1–5937, with ASCA , 2000, astro-ph/0002220.

[10]  J. Higdon,et al.  Nature versus Nurture: The Origin of Soft Gamma-Ray Repeaters and Anomalous X-Ray Pulsars , 1999, astro-ph/9912207.

[11]  L. Hernquist,et al.  An Accretion Model for Anomalous X-Ray Pulsars , 1999, astro-ph/9912137.

[12]  Chakrabarty,et al.  Precision Timing of Two Anomalous X-Ray Pulsars , 1999, The Astrophysical journal.

[13]  A. Harding,et al.  Magnetar Spin-Down , 1999, The Astrophysical journal.

[14]  C. Kouveliotou,et al.  Variable Spin-Down in the Soft Gamma Repeater SGR 1900+14 and Correlations with Burst Activity , 1999, astro-ph/9907173.

[15]  G. Vasisht,et al.  On the Spin History of the X-Ray Pulsar in Kes 73: Further Evidence for an Ultramagnetized Neutron Star , 1999, astro-ph/9906122.

[16]  L. Stella,et al.  Further Evidence that 1RXS J170849.0–400910 Is an Anomalous X-Ray Pulsar , 1999, astro-ph/9904212.

[17]  N. Kawai,et al.  Accurate Position of SGR 1900+14 by Bursts and Changes in Pulse Period and Folded Pulse Profile with ASCA , 1999 .

[18]  K. Hurley,et al.  UvA-DARE ( Digital Academic Repository ) ASCA discovery of an x-ray pulsar in the error box of SGR 1900 + 14 , 1998 .

[19]  Kristen Menou,et al.  Black Hole and Neutron Star Transients in Quiescence , 1998, astro-ph/9810323.

[20]  K. Torii,et al.  Discovery of an 11-s X-Ray Pulsar in the Galactic-Plane Section of the Scorpius Constellation , 1997 .

[21]  J. Heyl,et al.  Powering Anomalous X-Ray Pulsars by Neutron Star Cooling , 1997, astro-ph/9708179.

[22]  G. Vasisht,et al.  Kes 73: A Young Supernova Remnant with an X-Ray-bright, Radio-quiet Central Source , 1997, astro-ph/9706057.

[23]  T. Mihara,et al.  The Spin-down Rate and X-Ray Flux of 1E 1048.1–5937 , 1997 .

[24]  Christopher Thompson,et al.  The Soft Gamma Repeaters as Very Strongly Magnetized Neutron Stars. II. Quiescent Neutrino, X-Ray, and Alfvén Wave Emission , 1996 .

[25]  L. Angelini,et al.  The Spectrum of the 8.7 s X-ray Pulsar 4U 0142+61 , 1996 .

[26]  K. Koyama,et al.  The spectrum and pulses of 1E 2259+586 from ASCA and BBXRT observations , 1995 .

[27]  S. Mereghetti,et al.  The Very low mass X-ray binary pulsars: A New class of sources? , 1995 .

[28]  S. Kulkarni,et al.  Characteristics of the persistent emission of SGR 1806-20 , 1994 .

[29]  J. Cannizzo,et al.  The Disk Accretion of a Tidally Disrupted Star onto a Massive Black Hole , 1990 .

[30]  A. Fabian.  Slowly Rotating Neutron Stars and Transient X-ray Sources , 1975 .

[31]  M. Greco.  Results and Perspectives in Particle Physics , 1994 .