Unveiling soft gamma-ray repeaters with INTEGRAL |
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Authors: | Diego Götz Sandro Mereghetti Kevin Hurley |
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Institution: | (1) CEA-Service d’Astrophysique, Orme des Merisiers, Bat. 709, 91191 Gif-sur-Yvette, France;(2) INAF—Istituto di Astrofisica Spaziale e Fisica Cosmica, Milano, Italy;(3) Space Sciences Laboratory, University of California at Berkeley, Berkeley, CA, USA |
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Abstract: | Thanks to INTEGRAL’s long exposures of the Galactic Plane, the two brightest Soft Gamma-Ray Repeaters, SGR 1806-20 and SGR
1900+14, have been monitored and studied in detail for the first time at hard-X/soft gamma rays.
This has produced a wealth of new scientific results, which we will review here. Since SGR 1806-20 was particularly active
during the last two years, more than 300 short bursts have been observed with INTEGRAL and their characteristics have been
studied with unprecedented sensitivity in the 15–200 keV range. A hardness-intensity anticorrelation within the bursts has
been discovered and the overall Number-Intensity distribution of the bursts has been determined. In addition, a particularly
active state, during which 100 bursts were emitted in 10 minutes, has been observed on October 5 2004, indicating that the
source activity was rapidly increasing. This eventually led to the Giant Flare of December 27th 2004, for which a possible
soft gamma-ray (>80 keV) early afterglow has been detected.
The deep observations allowed us to discover the persistent emission in hard X-rays (20–150 keV) from 1806-20 and 1900+14,
the latter being in a quiescent state, and to directly compare the spectral characteristics of all Magnetars (two SGRs and
three Anomalous X-ray Pulsars) detected with INTEGRAL.
D.G. acknowledges the French Space Agency (CNES) for financial support. Based on observations with INTEGRAL, an ESA project
with instruments and the science data centre funded by ESA member states (especially the PI countries: Denmark, France, Germany,
Italy, Switzerland, Spain), Czech Republic and Poland, and with the participation of Russia and the USA. ISGRI has been realized
and maintained in flight by CEA-Saclay/DAPNIA with the support of CNES. K.H. is grateful for support under NASA’s INTEGRAL
U.S. Guest Investigator program, Grants NAG5-13738 and NNG05GG35G. |
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Keywords: | Gamma-rays: observations Pulsars: individual SGR 1806-20 SGR 1900+14 Pulsars: general |
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