Linearly polarized X-ray flares following short gamma-ray bursts

Soft X-ray flares were detected following the short-duration gamma-ray burst GRB 050724. The temporal properties of the flares suggest that they are likely due to the late-time activity of the central engine. We argue that if short GRBs are generated through compact star mergers, as is supported by the recent observations, the jet powering the late X-ray flares must be launched via magnetic processes rather than via neutrino-antineutrino annihilations. As a result, the X-ray flares following short GRBs are expected to be linearly polarized. The argument may also apply to the X-ray flares following long GRBs. Future observations with the upcoming X-ray polarimeters will test this prediction.

[1]  M. Rees,et al.  Poynting Jets from Black Holes and Cosmological Gamma-Ray Bursts , 1996, astro-ph/9609065.

[2]  M. Feroci,et al.  Probing the environment in gamma-ray bursts : The case of an X-ray precursor, afterglow late onset, and wind versus constant density profile in GRB 011121 and GRB 011211 , 2004 .

[3]  Merging White Dwarf/Black Hole Binaries and Gamma-Ray Bursts , 1998, astro-ph/9808094.

[4]  Tsvi Piran,et al.  Astrophysics: refreshed shocks from a γ-ray burst , 2003, Nature.

[5]  Bing Zhang,et al.  An Analysis of Gamma-Ray Burst Spectral Break Models , 2002 .

[6]  Y. Z. Fan,et al.  Late internal‐shock model for bright X‐ray flares in gamma‐ray burst afterglows and GRB 011121 , 2005 .

[7]  Bing Zhang,et al.  γ‐ray burst internal shocks with magnetization , 2004 .

[8]  D. Wei,et al.  The very early afterglow powered by, ultra-relativistic mildly magnetized outflows , 2004, astro-ph/0405392.

[9]  Chris L. Fryer,et al.  Hyperaccreting Black Holes and Gamma-Ray Bursts , 1998, astro-ph/9807028.

[10]  M. Livio,et al.  Nucleosynthesis, neutrino bursts and γ-rays from coalescing neutron stars , 1989, Nature.

[11]  C. I. O. Technology.,et al.  Polarization of Prompt Gamma-Ray Burst Emission: Evidence for Electromagnetically Dominated Outflow , 2003, astro-ph/0305410.

[12]  N. Produit,et al.  POLAR, a compact detector for gamma-ray bursts photon polarization measurements , 2005 .

[13]  Jonathan Granot.  The Most Probable Cause for the High Gamma-Ray Polarization in GRB 021206 , 2003 .

[14]  M. Rees,et al.  Steep Slopes and Preferred Breaks in Gamma-Ray Burst Spectra: The Role of Photospheres and Comptonization , 1999 .

[15]  J. Bloom,et al.  The Spatial Distribution of Coalescing Neutron Star Binaries , 1998, astro-ph/9805222.

[16]  T. Piran,et al.  Merging neutron stars. 1. Initial results for coalescence of noncorotating systems , 1994, astro-ph/9401032.

[17]  Martin C. Weisskopf,et al.  Calibration of the Stellar X-Ray Polarimeter , 1997, Optics & Photonics.

[18]  M. M. Kasliwal,et al.  The afterglow of GRB 050709 and the nature of the short-hard γ-ray bursts , 2005, Nature.

[19]  S. Rosswog,et al.  Mergers of Neutron Star-Black Hole Binaries with Small Mass Ratios: Nucleosynthesis, Gamma-Ray Bursts, and Electromagnetic Transients , 2005, astro-ph/0508138.

[20]  Tsvi Piran,et al.  The Variable Light Curve of GRB 030329: The Case for Refreshed Shocks , 2003 .

[21]  Jesper Sollerman,et al.  The optical afterglow of the short γ-ray burst GRB 050709 , 2005, Nature.

[22]  Evolution of a neutrino-cooled disc in gamma-ray bursts , 2004, astro-ph/0406362.

[23]  R. Blandford,et al.  Electromagnetic extraction of energy from Kerr black holes , 1977 .

[24]  T. Piran,et al.  Astronomy & Astrophysics manuscript no. (will be inserted by hand later) The Luminosity and Redshift Distributions of Short-Duration , 2004 .

[25]  N. Gehrels,et al.  Bright X-ray Flares in Gamma-Ray Burst Afterglows , 2005, Science.

[26]  T. Piran,et al.  Gamma-ray bursts as the death throes of massive binary stars , 1992, astro-ph/9204001.

[27]  P. Giommi,et al.  A short γ-ray burst apparently associated with an elliptical galaxy at redshift z = 0.225 , 2005, Nature.

[28]  General Relativistic Magnetohydrodynamic Simulations of Collapsars , 2004, astro-ph/0404152.

[29]  Boulder,et al.  Accretion of Low Angular Momentum Material onto Black Holes: Two-dimensional Magnetohydrodynamic Case , 2003 .

[30]  Chris L. Fryer,et al.  To be submitted to The Astrophysical Journal Formation Rates of Black Hole Accretion Disk Gamma-Ray Bursts , 1999 .

[31]  Bing Zhang,et al.  Accepted for publication in The Astrophysical Journal Preprint typeset using L ATEX style emulateapj GAMMA-RAY BURSTS WITH CONTINUOUS ENERGY INJECTION AND THEIR AFTERGLOW SIGNATURE , 2001 .

[32]  C. Thompson.  A Model of gamma-ray bursts , 1994 .

[33]  T. Piran,et al.  Accretion Models of Gamma-Ray Bursts , 2001, astro-ph/0103360.

[34]  Bing Zhang,et al.  Optical afterglows of short Gamma-ray Bursts and GRB 040924 , 2005 .

[35]  Bohdan Paczynski,et al.  Cosmological gamma-ray bursts , 1991 .

[36]  Melvyn B. Davies,et al.  High-resolution calculations of merging neutron stars - III. Gamma-ray bursts , 2003, astro-ph/0306418.

[37]  A. Panaitescu,et al.  Afterglow Emission from Naked Gamma-Ray Bursts , 2000, astro-ph/0006317.

[38]  J.-L. Atteia,et al.  Discovery of the short γ-ray burst GRB 050709 , 2005, Nature.

[39]  PROMPT MERGERS OF NEUTRON STARS WITH BLACK HOLES , 2005, astro-ph/0505094.

[40]  V. Usov.  On the nature of nonthermal radiation from cosmological gamma-ray bursters , 1993, astro-ph/9312024.