A dataset provided by the European Space Agency

Proposal ID 0220151
Obs ID 02201510001
Title Spectral variability of NGC 5548 - pivoting or two components?
Download Data Associated to the proposal https://isla.esac.esa.int/tap/download/bundle?format=ascii_curl&product_id=prop_id:0220151
DOI https://doi.org/10.57780/esa-rrmhx3s
Author McHardy
Abstract It has been known for many years that the X-ray spectral indices ofSeyfert galaxies in the 2-10 keV band become steeper as the fluxincreases. Recently we, and others, have defined the shape of theflux/spectral index relationship very precisely and, in particular, itis noted that the spectral index reaches an asymptotic level at highfluxes.There are two main possible explanations for this relationship. Thefirst possibility is that the spectrum could consist of twocomponents, a relatively hard component of approximately constantflux, and a soft component of variable flux. The second possibilityis that there is intrinsic spectral variability in the component whichdominates the X-ray flux, such that the spectrum does becomeintrinsically softer at high fluxes, perhaps pivoting about some highenergy (100keV).Determining which possibility is actually the case has importantimplications for the physics of the high energy emission regionand is the main aim of the present proposal. Integral is ideallysuited to this programme.
Publications
Temporal Coverage 2004-06-14T18:56:01Z / 2004-06-17T09:18:16Z
Version 1.0
Mission Description The INTEGRAL (International Gamma-Ray Astrophysics Laboratory) mission, launched by the European Space Agency (ESA) on October 17, 2002, was designed to study high-energy phenomena in the universe. INTEGRAL was operating until february 2025 and it was equipped with three high-energy instruments: the Imager on Board the INTEGRAL Satellite (IBIS), the Spectrometer on INTEGRAL (SPI), and the JEM-X (Joint European Monitor for X-rays). Its Optical Monitoring Camera (OMC) provided optical V-band magnitude measurements, complementing the high-energy observations.
Creator Contact https://www.cosmos.esa.int/web/integral/helpdesk
Date Published 2026-03-05T13:05:52Z
Keywords INTEGRAL gamma-ray data, ESA INTEGRAL mission dataset, gamma-ray astronomy observations, high-energy astrophysics data, IBIS imaging data, SPI spectrometer data, JEM-X X-ray monitoring data, OMC optical monitoring data, coded mask telescope observations, gamma-ray spectroscopy dataset, MeV astrophysics data, keV–MeV photon observations, gamma-ray burst observations dataset, black hole gamma-ray data, neutron star high-energy observations, positron annihilation 511 keV line data, Galactic Center gamma-ray emission dataset, supernova nucleosynthesis gamma-ray lines, active galactic nuclei high-energy data, transient astrophysical source monitoring, calibrated photon event lists, gamma-ray light curves, high-energy spectra data, sky maps gamma-ray, time-series astrophysical observations, long-term gamma-ray monitoring dataset
Publisher And Registrant European Space Agency
Credit Guidelines European Space Agency, McHardy, 2026, 'Spectral variability of NGC 5548 - pivoting or two components?', 1.0, European Space Agency, https://doi.org/10.57780/esa-rrmhx3s