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تسجيل مستخدم جديدXMM-Newton discovery of a sharp spectral feature at ~7 keV in the Narrow-Line Seyfert 1 galaxy 1H 0707-495
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Th. Boller
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We report the first detection of a sharp spectral feature in a Narrow-Line Seyfert 1 galaxy. Using XMM-Newton we have observed 1H0707-495 and find a drop in flux by a factor of more than 2 at a rest-frame energy of ~7 keV without any detectable narrow Fe K alpha line emission. The energy of this feature suggests a connection with the neutral iron K photoelectric edge, but the lack of any obvious absorption in the spectrum at lower energies makes the interpretation challenging. We explore two alternative explanations for this unusual spectral feature: (i) partial covering absorption by clouds of neutral material and (ii) ionised disc reflection with lines and edges from different ionisation stages of iron blurred together by relativistic effects. We note that both models require an iron overabundance to explain the depth of the feature. The X-ray light curve shows strong and rapid variability, changing by a factor of four during the observation. The source displays modest spectral variability which is uncorrelated with flux.
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The ultra-soft narrow-line Seyfert 1 galaxy 1H 0707-495 is a well-known and highly variable active galactic nucleus (AGN), with a complex, steep X-ray spectrum, and has been studied extensively with XMM-Newton. 1H 0707-495 was observed with the exten
ded ROentgen Survey with an Imaging Telescope Array (eROSITA) aboard the Spectrum-Roentgen-Gamma (SRG) mission on October 11, 2019, for about 60,000 seconds as one of the first calibration and pointed verification phase (CalPV) observations. The eROSITA light curves show significant variability in the form of a flux decrease by a factor of 58 with a 1 sigma error confidence interval between 31 and 235. This variability is primarily in the soft band, and is much less extreme in the hard band. No strong ultraviolet variability has been detected in simultaneous XMM-Newton Optical Monitor observations. The UV emission is about 10^44 erg s^-1, close to the Eddington limit. 1H 0707-495 entered the lowest hard flux state seen in 20 years of XMM-Newton observations. In the eROSITA All-Sky Survey (eRASS) observations taken in April 2020, the X-ray light curve is still more variable in the ultra-soft band, but with increased soft and hard band count rates more similar to previously observed flux states. A model including relativistic reflection and a variable partial covering absorber is able to fit the spectra and provides a possible explanation for the extreme light-curve behaviour. The absorber is probably ionised and therefore more transparent to soft X-rays. This leaks soft X-rays in varying amounts, leading to large-amplitude soft-X-ray variability.
Since the discovery of the first broad iron-K line in 1995 from the Seyfert Galaxy MCG--6-30-15, broad iron-K lines have been found in several other Seyfert galaxies, from accreting stellar mass black holes and even from accreting neutron stars. The
iron-K line is prominent in the reflection spectrum created by the hard X-ray continuum irradiating dense accreting matter. Relativistic distortion of the line makes it sensitive to the strong gravity and spin of the black hole. The accompanying iron-L line emission should be detectable when the iron abundance is high. Here we report the first discovery of both iron-K and L emission, using XMM-Newton observations of the Narrow-Line Seyfert 1 Galaxy 1H0707-495. The bright Fe-L emission has enabled us, for the first time, to detect a reverberation lag of 30 s between the direct X-ray continuum and its reflection from matter falling into the hole. The observed reverberation timescale is comparable to the light-crossing time of the innermost radii around a supermassive black hole. The combination of spectral and timing data on 1H0707-495 provides strong evidence that we are witnessing emission from matter within a gravitational radius, or a fraction of a light-minute, from the event horizon of a rapidly-spinning, massive black hole.
We present results from the spectral analysis of a long XMM-Newton observation of the radio-loud NLS1 galaxy PKS0558-504. The source is highly variable, on all sampled time scales. We did not observe any absorption features in either the soft or hard
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