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Title: A CHALLENGING VIEW OF THE 2015 SUMMER V404 CYG OUTBURST AT HIGH ENERGY WITH INTEGRAL /SPI: THE FINALE

Abstract

During its strong outburst of 2015 June/July, the X-ray transient V404 Cygni (=GS2023+338) was observed up to a level of 50 Crab in the hard X-ray domain. We focus here on a particularly intense episode preceeding a definitive decline of the source activity. We benefit from large signal-to-noise ratios to investigate the source spectral variability, on a timescale of five minutes. A hardness–intensity study of three broad bands reveals clearly different behaviors at low and high energy (below and above ∼100 keV). In particular, on two occasions, the source intensity varies by a factor of 3–4 in amplitude while keeping the same spectral shape. On the other hand, at the end of the major flare, the emission presents a clear anticorrelation between flux and hardness. These behaviors strongly suggest the presence of two spectral components related to emission processes varying in a largely independent way. The first component ( E < 100–150 keV) is classically identified with a Comptonizing thermal electron population, and requires either an unusual seed photon population or a specific geometry with strong absorbing/reflecting material. The second component is modeled by a cutoff power-law, which could correspond to a second hotter Comptonizing population or another mechanism (synchrotron,more » non-thermal Comptonization...). In the framework of such a model, hardness–intensity and flux–flux diagrams clearly demonstrate that the source evolution follows a well-organized underlying scheme. They reveal unique information about the hard X-ray emission processes and connections between them.« less

Authors:
; ;  [1]
  1. Université Toulouse, UPS-OMP, CNRS, IRAP, 9 Avenue Roche, BP 44346, F-31028 Toulouse (France)
Publication Date:
OSTI Identifier:
22663977
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 834; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; AMPLITUDES; BLACK HOLES; CRABS; EMISSION; EVOLUTION; HARD X RADIATION; KEV RANGE; NOISE; SIGNAL-TO-NOISE RATIO; SIMULATION; TRANSIENTS

Citation Formats

Jourdain, Elisabeth, Roques, Jean-Pierre, and Rodi, James. A CHALLENGING VIEW OF THE 2015 SUMMER V404 CYG OUTBURST AT HIGH ENERGY WITH INTEGRAL /SPI: THE FINALE. United States: N. p., 2017. Web. doi:10.3847/1538-4357/834/2/130.
Jourdain, Elisabeth, Roques, Jean-Pierre, & Rodi, James. A CHALLENGING VIEW OF THE 2015 SUMMER V404 CYG OUTBURST AT HIGH ENERGY WITH INTEGRAL /SPI: THE FINALE. United States. doi:10.3847/1538-4357/834/2/130.
Jourdain, Elisabeth, Roques, Jean-Pierre, and Rodi, James. Tue . "A CHALLENGING VIEW OF THE 2015 SUMMER V404 CYG OUTBURST AT HIGH ENERGY WITH INTEGRAL /SPI: THE FINALE". United States. doi:10.3847/1538-4357/834/2/130.
@article{osti_22663977,
title = {A CHALLENGING VIEW OF THE 2015 SUMMER V404 CYG OUTBURST AT HIGH ENERGY WITH INTEGRAL /SPI: THE FINALE},
author = {Jourdain, Elisabeth and Roques, Jean-Pierre and Rodi, James},
abstractNote = {During its strong outburst of 2015 June/July, the X-ray transient V404 Cygni (=GS2023+338) was observed up to a level of 50 Crab in the hard X-ray domain. We focus here on a particularly intense episode preceeding a definitive decline of the source activity. We benefit from large signal-to-noise ratios to investigate the source spectral variability, on a timescale of five minutes. A hardness–intensity study of three broad bands reveals clearly different behaviors at low and high energy (below and above ∼100 keV). In particular, on two occasions, the source intensity varies by a factor of 3–4 in amplitude while keeping the same spectral shape. On the other hand, at the end of the major flare, the emission presents a clear anticorrelation between flux and hardness. These behaviors strongly suggest the presence of two spectral components related to emission processes varying in a largely independent way. The first component ( E < 100–150 keV) is classically identified with a Comptonizing thermal electron population, and requires either an unusual seed photon population or a specific geometry with strong absorbing/reflecting material. The second component is modeled by a cutoff power-law, which could correspond to a second hotter Comptonizing population or another mechanism (synchrotron, non-thermal Comptonization...). In the framework of such a model, hardness–intensity and flux–flux diagrams clearly demonstrate that the source evolution follows a well-organized underlying scheme. They reveal unique information about the hard X-ray emission processes and connections between them.},
doi = {10.3847/1538-4357/834/2/130},
journal = {Astrophysical Journal},
number = 2,
volume = 834,
place = {United States},
year = {Tue Jan 10 00:00:00 EST 2017},
month = {Tue Jan 10 00:00:00 EST 2017}
}